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UBC Theses and Dissertations

Environmental effects on the sliding friction behaviour of diamond on glass Nelson, Bradford Charles 1977

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E N V I R O N M E N T A L E F F E C T S ON THE S L I D I N G F R I C T I O N B E H A V I O U R OF D IAMOND ON G L A S S b y BRADFORD C H A R L E S N E L S O N B . E n g . , M c M a s t e r U n i v e r s i t y , H a m i l t o n , O n t a r i o , 1 9 7 4 A T H E S I S S U B M I T T E D I N P A R T I A L F U L F I L M E N T OF THE R E Q U I R E M E N T S FOR THE DEGREE OF M A S T E R OF A P P L I E D S C I E N C E THE F A C U L T Y OF G R A D U A T E S T U D I E S i n t h e D e p a r t m e n t o f M e c h a n i c a l E n g i n e e r i n g We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE U N I V E R S I T Y OF B R I T I S H C O L U M B I A A u g u s t , 1 9 7 7 < T ) B r a d f o r d C h a r l e s N e l s o n , 1 9 7 7 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . B r a d f o r d C h a r l e s N e l s o n Department o f M e c h a n i c a l E n g i n e e r i n g The U n i v e r s i t y of B r i t i s h C o l u m b i a V a n c o u v e r , B.C. Date i i A B S T R A C T C e r t a i n s u r f a c e - a c t i v e m e d i a c a n c o n s i d e r a b l y i n f l u e n c e t h e f l o w a n d f r a c t u r e p r o p e r t i e s o f t h e . s o l i d s t h e y w e t . T h e e f f e c t s o f v a r i o u s l u b r i c a t i n g m e d i a o n t h e s l i d i n g f r i c t i o n b e h a v i o u r o f d i a m o n d o n s o d a - l i m e g l a s s w e r e s t u d i e d i n t h e p r e s e n t r e s e a r c h . A n e x p e r i m e n t a l a p p a r a t u s w a s c o n s t r u c t e d t o s l i d e a h e m i s p h e r i c a l d i a m o n d l i n e a r l y a n d a t c o n s t a n t s p e e d a c r o s s t h e s u r f a c e o f a C o r n i n g t y p e 2 9 4 7 s o d a - l i m e g l a s s m i c r o s l i d e a n d t o m e a s u r e t h e r e s u l t a n t f r i c t i o n f o r c e . T e s t s w e r e c o n d u c t e d i n a v a r i e t y o f l i q u i d a n d g a s e o u s m e d i a a t s l i d i n g s p e e d s r a n g i n g f r o m 0 . 0 0 1 c m / s e c t o 0 . 4 c m / s e c . A s a b a s e f o r c o m p a r i s o n i n i t i a l t e s t s w e r e c o n d u c t e d i n a h i g h v a c u u m — 8 a t 4 x 1 0 t o r r . T h e r e s u l t s s h o w e d t h a t a l l t h e m e d i a e n h a n c e d m a t e r i a l d i s p l a c e m e n t f r o m t h a t o b s e r v e d i n h i g h v a c u u m . I n a d d i t i o n , t h e f r i c t i o n f o r c e w a s o b s e r v e d t o r i s e w i t h d i s p l a c e d m a t e r i a l . A s i m p l e t h e o r y w a s u s e d t o p r e d i c t w i t h r e a s o n a b l e a g r e e m e n t t h e r e s u l t s o b t a i n e d i n i n v a c u u m a n d a i r o n l y . T h e g r e a t e s t i n c r e a s e i n d i s p l a c e d m a t e r i a l w a s o b s e r v e d i n h e p t y l a l c o h o l . S c a n n i n g e l e c t r o n m i c r o g r a p h s o f t h e f r i c t i o n t r a c k s s u g g e s t t h a t h e p t y l ; a l c o h o l s o f t e n e d t h e s u r f a c e o f t h e g l a s s . T h i s i s i n a g r e e m e n t w i t h p r e v i o u s w o r k . i i i T A B L E OF CONTENTS P a g e C H A P T E R I 1 .1 I n t r o d u c t i o n 1 1 . 2 H i s t o r i c a l B a c k g r o u n d 3 C H A P T E R I I 2 . 1 F r i c t i o n T h e o r y 8 2 . 2 P l o u g h i n g T e r m 11 2 . 3 S h e a r i n g T e r m 17 C H A P T E R I I I 3 . 1 E x p e r i m e n t a l O b j e c t i v e 20 3 . 2 A p p a r a t u s 20 3 . 2 . 1 G e n e r a l D e s c r i p t i o n 2 0 3 . 2 . 2 D i a m o n d S l i d e r A s s e m b l y 22 3 . 2 . 3 S p e c i m e n A s s e m b l y 25 3 . 2 . 4 A c t u a t o r S y s t e m 26 3 . 2 . 5 A c t u a t o r P l a t f o r m 29 3 . 2 . 6 V a c u u m S y s t e m 30 3 . 3 I n s t r u m e n t a t i o n 31 3 . 4 M e a s u r e m e n t o f C r o s s - s e c t i o n a l A r e a 32 3 . 5 T h e D i a m o n d 33 3 . 6 S p e c i m e n s 34 i v Page 3.7 E x p e r i m e n t a l P r o c e e d u r e 36 3 . 7 . 1 P r e - t e s t I n v e s t i g a t i o n 36 3 . 7 . 2 Env i ronmen t P r e p a r a t i o n 37 3 . 7 . 3 I n s t r u m e n t P r e p a r a t i o n 38 3 . 7 . 4 T e s t i n g 39 3 . 7 . 5 T a l y s u r f A n a l y s i s 39 CHAPTER IV 4 .1 R e s u l t s and A n a l y s i s 40 4 . 1 . 1 F r i c t i o n F o r c e 40 4 . 1 . 2 Compar i son to Theory 56 4 . 1 . 3 D i s p l a c e d A r e a 59 CHAPTER V 5.1 D i s c u s s i o n 64 5.2 C o n c l u s i o n s 71 5 .3 S u g g e s t i o n s f o r F u t u r e R e s e a r c h 73 BIBLIOGRAPHY 75 A p p e n d i x I CALIBRATION OF SLIDER ARM 78 A p p e n d i x I I MICROSLIDE GLASS COMPOSITION 80 A p p e n d i x I I I VELOCITY MEASUREMENT 81 A p p e n d i x IV TEMPERATURE MEASUREMENT 8 4 ; A p p e n d i x V PROPERTIES OF LIQUID MEDIA 8 7 A p p e n d i x VI INDENTATION HARDNESS OF MICROSLIDES 89 A p p e n d i x V I I CURVE FITTING ANALYSIS 91 • V L I S T OF T A B L E S P a g e T A B L E I. R e s u l t s o f C u r v e F i t t i n g A n a l y s i s . . . E q u a t i o n s o f B e s t F i t C u r v e s 57 T A B L E I I . C o m p a r i s o n o f T h e o r e t i c a l a n d E x p e r i m e n t a l R e s u l t s 60 T A B L E A . I . I C a l i b r a t i o n o f S l i d e r A r m D e f l e c t i o n w i t h L o a d 79 v i LIST OF FIGURES F i g u r e Page 1 Arrangement of Diamond S l i d e r on the G l a s s S u r f a c e 9 2 Diagram of Diamond P y r a m i d Hardness Tes t 13 3 Geometry of Diamond S l i d e r and F r i c t i o n T r a c k 14 4 G e n e r a l Arrangement o f E x p e r i m e n t a l A p p a r a t u s 21 5 Arrangement of Diamond S l i d e r and Specimen A s s e m b l i e s 23 6 Diagram . o f Diamond S l i d e r Assembly 24 7 Diagram .. of Specimen Assembly 2 7 8 S c h e m a t i c o f H y d r a u l i c System 28 9 S t r a i n Gauge System 28 10 S c a n n i n g E l e c t r o n M i c r o g r a p h s o f Diamond 35 11 (a) Recorded F r i c t i o n F o r c e . . . H i g h Vacuum 41 11 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . H i g h Vacuum 4,1; 11 (c) Recorded F r i c t i o n T r a c k P r o f i l e . . . H i g h Vacuum 41 11 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . H i g h Vacuum 41 12 (a) Recorded F r i c t i o n F o r c e . . . N i t r o g e n 42 12 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . N i t r o g e n 42 12 (c) Recorded F r i c t i o n T r a c k P r o f i l e . . . N i t r o g e n 42, 12 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . N i t r o g e n 42" 13 (a) Recorded F r i c t i o n F o r c e . . . A i r 43-' 13 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . A i r 43 13 (c) Recorded F r i c t i o n T r a c k P r o f i l e . . . A i r 43 13 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . A i r 43 v i i L I S T OF F I G U R E S ( c o n t . ) F i g u r e P a g e 14 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . W a t e r 44 14 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . • W a t e r 44 14 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . W a t e r 44. 14 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . W a t e r 44 15 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . C a p r o i c A c i d 4'5-15 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . C a p r o i c A c i d 4'5 15 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . C a p r o i c A c i d 45 15 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . C a p r o i c A c i d 45-16 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . O l e i c A c i d 4,6 16 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . • O l e i c A c i d 46 16 ( c ) R e c o r d e d - F r i c t i o n T r a c k P r o f i l e . . . O l e i c A c i d 4 6 16 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . O l e i c A c i d 46 17 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . H e x a n e 47 17 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . • H e x a n e 47 17 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . • H e x a n e 4 7 17 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . H e x a n e '47 18 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . H e p t a n e 4 8 18 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . H e p t a n e 48" 18 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . H e p t a n e 48 18 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . H e p t a n e 48 19 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . M e t h a n o l 4 9 19 ( b ) F r i c t i o n . F o r c e v e r s u s l V e l q c . i t y . . ..Me t h a h o 1- 49 19 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . M e t h a n o l 49 19 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . .Me t h a n o 1 49 v i i i L I S T OF F I G U R E S ( c o n t . ) F i g u r e P a g e 2 0 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . P r o p a n o l 50 20 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . P r o p a n o l 50 20 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . P r o p a n o l 5 0 20 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . P r o p a n o l 50 21 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . H e p t a n o l 51 21 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . H e p t a n o l 51 21 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . H e p t a n o l 51 21 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . H e p t a n o 1 51 22 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . D e c a n o l 52 22 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . D e c a n o l 52 22 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . D e c a n o l 52 22 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . D e c a n o l 52 23 E f f e c t o f E n v i r o n m e n t o n F r i c t i o n F o r c e 53 24 E f f e c t o f E n v i r o n m e n t o n D i s p l a c e d A r e a 54 25 E f f e c t o f E n v i r o n m e n t o n t h e E x t e n t o f R a i s e d 62 E d g e M a t e r i a l 26 S c a n n i n g E l e c t r o n M i c r o g r a p h s o f F r i c t i o n T r a c k s 67 27 C o m p a r i s o n o f P r e s e n t R e s u l t s t o P r e v i o u s W o r k 69 28 R e v i s e d D i a m o n d S l i d e r A s s e m b l y 74 A . I . I . S e t - u p F o r C a l i b r a t i o n o f S l i d e r A r m 79 A . I I I . l . C i r c u i t u s e d f o r V e l o c i t y M e a s u r e m e n t 82 A . I I I . 2 . V e l o c i t y C a l i b r a t i o n C u r v e 8 3 A . I V . l . T h e r m i s t o r C i r c u i t 8 6; A . I V . 2 . T e m p e r a t u r e C a l i b r a t i o n C u r v e . \ 8;6'. i x LIST OF SYMBOLS Symbol U n i t s A c r o s s - s e c t i o n a l or d i s p l a c e d a r ea of „ c r- . . , 2 f r i c t i o n t r a c k mm A^ h o r i z o n t a l l y p r o j e c t e d a r e a of c o n t a c t 2 of moving s l i d e r on s o l i d s u r f a c e mm A^ h o r i z o n t a l l y p r o j e c t e d a r ea of ha rdness 2 i n d e n t a t i o n mm Ap c r o s s - s e c t i o n a l a r e a o f r a i s e d edge 2 m a t e r i a l mm a apex a n g l e o f DPH t e s t e r degrees b w i d t h of f r i c t i o n t r a c k mm d average l e n g t h of d i a g o n a l o f DPH i n d e n t a t i o n mm f g e n e r a l pa ramete r F f r i c t i o n f o r c e kg F^ r e s i s t a n c e to e l a s t i c d i s p l a c e m e n t of m a t e r i a l kg F^ r e s i s t a n c e to p l a s t i c d i s p l a c e m e n t of m a t e r i a l kg~ F^ r e s i s t a n c e to s h e a r i n g of m a t e r i a l kg F^ r e s i s t a n c e to s h e a r i n g of s u r f a c e f i l m kg g g e n e r a l " p a r a m e t e r h maximum depth of p e n e t r a t i o n of s l i d e r i n t o the s u r f a c e of the s o l i d mm K c o n t a c t c o n s t a n t ( d i m e n s i o n l e s s ) L no rma l l o a d used i n DPH t e s t kg N no rma l l o a d a c t i n g on moving s l i d e r kg P p l o u g h i n g r e s i s t a n c e f o r c e k-g, X S y m b o l U n i t s 2 p m e a n f l o w p r e s s u r e kg/mm m 2 p g s t a t i c m e a n p r e s s u r e kg/mm r g e n e r a l p a r a m e t e r R r a d i u s o f s l i d e r mm s g e n e r a l p a r a m e t e r S s h e a r i n g r e s i s t a n c e f o r c e k g V v e l o c i t y o f s l i d e r c m / s e c x g e n e r a l p a r a m e t e r X g e n e r a l p a r a m e t e r y g e n e r a l p a r a m e t e r Y g e n e r a l p a r a m e t e r A = g e n e r a l p a r a m e t e r B g e n e r a l p a r a m e t e r 2 A s h e a r s t r e n g t h o f s o l i d kg/mm n n u m b e r o f c a r b o n a t o m s i n m o l e c u l a r c h a i n x i ACKNOWLEDGEMENT The e x p e r i m e n t a l p a r t of t h i s program was c a r r i e d out i n the T r i b o l o g y L a b o r a t o r y of the Depar tment of M e c h a n i c a l E n g i n e e r i n g a t The U n i v e r s i t y of B r i t i s h C o l u m b i a . The au tho r w i s h e s to thank M r . E r n i e Jones f o r h i s h e l p i n c o n s t r u c t i n g the a p p a r a t u s and f o r h i s c o n s t a n t s u p p o r t , M r . John Wiebe f o r h i s t e c h n i c a l a s s i s t a n c e and to those of the Depar tments of M e c h a n i c a l E n g i n e e r i n g and M e t a l l u r g y who o f f e r e d t h e i r e f f o r t s to a s s i s t i n t h i s w o r k . S p e c i a l thanks a re due to D r . C. A . B r o c k l e y f o r h i s a d v i c e and encouragement t h roughou t the p rog ram. F i n a n c i a l a s s i s t a n c e was r e c e i v e d t h r o u g h the N a t i o n a l R e s e a r c h C o u n c i l of Canada under g r a n t number 67-1065 and i s g r a t e f u l l y a c k n o w l e d g e d . 1 C H A P T E R I 1 .1 I n t r o d u c t i o n T h e f r i c t i o n a n d m a t e r i a l f l o w b e h a v i o u r o f r u b b i n g s o l i d s c a n b e s t r o n g l y i n f l u e n c e d b y t h e p r e s e n c e o f a l i q u i d e n v i r o n m e n t . A l u b r i c a n t m a y c o m p l e t e l y s e p a r a t e t h e r u b b i n g s u r f a c e s ( i . e . h y d r o d y n a m i c l u b r i c a t i o n ) o r i t may o n l y b e a f i l m w i t h m o l e c u l a r d i m e n s i o n s a n d h e n c e i n t e r f e r e w i t h t h e a d h e s i o n o f d i s c r e t e c o n t a c t a r e a s ( i . e . b o u n d a r y l u b r i c a t i o n ) . I n t h e f o r m e r c a s e m a t e r i a l w e a r i s g r e a t l y r e d u c e d a n d f r i c t i o n a l r e s i s t a n c e i s e f f e c t i v e l y d e p e n d e n t o n t h e v i s c o s i t y o f t h e l u b r i c a n t . I n t h e l a t t e r c a s e b o t h f r i c t i o n a l r e s i s t a n c e a n d w e a r a r e r e d u c e d f r o m t h e d r y f r i c t i o n c a s e i n w h i c h no l u b r i c a n t i s p r e s e n t . A t h i r d a n d m o r e r e c e n t l y c o n s i d e r e d e f f e c t o f l u b r i c a n t s i s t h e m a n n e r i n w h i c h t h e y c a n s o m e t i m e s r e d u c e a s o l i d s r e s i s t a n c e t o p l a s t i c d e f o r m a t i o n a n d m a t e r i a l f l o w . F o r s l i d i n g f r i c t i o n t h a t i n v o l v e s t h e d e s t r u c t i o n o f c o n t a c t i n g s u r f a c e a s p e r i t i e s o r t h e p l o u g h i n g a w a y o f b u l k s o l i d , t h i s t h i r d e f f e c t c c a n h a v e c o n s i d e r a b l e i n f l u e n c e o n t h e f r i c t i o n b e h a v i o u r . T h i s p h e n o m e n o n i s k n o w n a s t h e R e h b i n d e r e f f e c t , n a m e d a f t e r t h e R u s s i a n s c i e n t i s t who f i r s t o b s e r v e d i t . S i n c e R e h b i n d e r ' s o b s e r v a t i o n s i n 1 9 2 8 t h e r e h a s b e e n g r o w i n g i n t e r e s t i n R e h b i n d e r e f f e c t s . I f t h e m e c h a n i s m 2 o f t h e p h e n o m e n o n c a n b e d e t e r m i n e d i t may b e p o s s i b l e t o u t i l i z e i t t o i m p r o v e p r o c e s s e f f i c i e n c y i n o p e r a t i o n s i n v o l v i n g m a t e r i a l r e m o v a l o r d e s t r u c t i o n s u c h a s a b r a s i o n , c o m m i n u t i o n a n d r o c k d r i l l i n g . B u t p r a c t i c a l u t i l i z a t i o n o f R e h b i n d e r e f f e c t s i s s e v e r e l y h a m p e r e d b y t h e l a c k o f q u a n t i t a t i v e i n f o r m a t i o n . A t t h e p r e s e n t t i m e t h e r e i s g e n e r a l a g r e e m e n t t h a t t h e e f f e c t i s o n e o f l o w e r i n g a s o l i d ' s r e s i s t a n c e t o p l a s t i c f l o w h e n c e r e d u c i n g i t s m i c r o h a r d n e s s . B u t t h e e x t e n t o f t h e e f f e c t v a r i e s w i t h d i f f e r e n t s o l i d s a n d l i q u i d e n v i r o n m e n t s . S t u d y h a s s h o w n t h a t w a t e r a f f e c t s i o n i c s o l i d s b u t n o t m e t a l s [ 5 ] . I t h a s a l s o b e e n s h o w n t h a t c e r t a i n s u r f a c e a c t i v e i o n s d e c r e a s e m i c r o h a r d n e s s i n MgO b u t h a v e t h e r e v e r s e e f f e c t o n C a F ^ [ 6 , 7 ] . C l e a r l y m o r e q u a n t i t a t i v e s t u d y i s n e c e s s a r y t o f u l l y u n d e r s t a n d R e h b i n d e r e f f e c t s . T h e p r o b l e m i n s t u d y i n g a l u b r i c a n t ' s i n f l u e n c e o n f r i c t i o n b e h a v i o u r i s t o i s o l a t e t h e p h y s i c o - c h e m i c a l e f f e c t s , a s R e h b i n d e r c a l l e d ; t h e m , f r o m t h e l u b r i c a t i o n e f f e c t s . T h e c o m p l e t e e l i m i n a t i o n o f b o u n d a r y l u b r i c a t i o n i s n o t p h y s i c a l l y p o s s i b l e w h e n a l u b r i c a t i n g m e d i u m i s p r e s e n t d u r i n g s l i d i n g , b u t i t s p r o p o r t i o n a l i n f l u e n c e c a n b e r e d u c e d w h e n a p e n e t r a t i n g s l i d e r i s u s e d t o 3 p e r m a n e n t l y d i s p l a c e t h e s o l i d s u r f a c e . A d i a m o n d s l i d e r w i t h a r a d i u s a b o u t 25 t i m e s s m a l l e r t h a n u s e d b y o t h e r w o r k e r s i n p r e v i o u s s t u d i e s w a s u s e d i n t h i s w o r k t o r e d u c e t h e i n f l u e n c e o f l u b r i c a t i o n e f f e c t s . A v a r i e t y o f l i q u i d m e d i a w e r e u s e d i n t h e p r e s e n t w o r k a n d s l i d i n g t e s t s w e r e c a r r i e d o u t i n a d r y ( h i g h v a c u u m ) e n v i r o n m e n t t o p r o v i d e a b a s e r e f e r e n c e f o r t h e t e s t s c o n d u c t e d i n l i q u i d m e d i a . 1 . 2 H i s t o r i c a l B a c k g r o u n d F r i c t i o n s t u d i e s d a t i n g b a c k a s l a t e a s t h e e x p e r i m e n t s o f T h o m a s E d i s o n [ 1 ] h a v e d e m o n s t r a t e d t h a t c e r t a i n l u b r i c a t i n g m e d i a i n f l u e n c e f r i c t i o n b e h a v i o u r b y a f f e c t i n g t h e s u r f a c e p r o p e r t i e s o f t h e r u b b i n g s o l i d s . E d i s o n o b s e r v e d c h a n g e s i n t h e f r i c t i o n o f r u b b i n g m e t a l s u r f a c e s i n e l e c t r o l y t e s a t d i f f e r e n t i n t e r f a c i a l p o t e n t i a l s . I n 1 9 2 8 R e h b i n d e r [ 2 ] c o n d u c t e d s e v e r a l e x p e r i m e n t s t o d e t e r m i n e t h e m e c h a n i s m s o f t h i s p h e n o m e n o n . He o b s e r v e d t h a t t h e e f f e c t o f a n e l e c t r o l y t e r e g a r d l e s s o f i t s c h a r g e w a s t o r e d u c e t h e m i c r o h a r d n e s s o f t h e s o l i d s u r f a c e . e n h a n c ed R e h b i n d e r n o t e d t h a t t h e t h e m a t e r i a l d i s p l a c e m e n t s u r f a c e a c t i v e b y a m e c h a n i s m m e d i a a p a r t 4 f r o m t h e commonly o b s e r v e d e f f e c t s of b o u n d a r y l u b r i c a t i o n . B oundary l u b r i c a t i o n i s t h e t e n d e n c y of an a d s o r b a t e to . i n t e r f e r e m a r k e d l y w i t h t h e a d h e s i o n of t h e s o l i d s a t t h e i r r e g i o n s of i n t i m a t e c o n t a c t . An i n c r e a s e i n t h e c h a i n l e n g t h of t h e a c t i v e s p e c i e s g e n e r a l l y r e s u l t s i n a d e c r e a s e i n t h e r e s i s t a n c e to t a n g e n t i a l m o t i o n ( t h e f r i c t i o n f o r c e ) and a r e d u c t i o n i n t h e s u r f a c e damage. R e h b i n d e r p r o p o s e d t h e f o l l o w i n g e x p l a n a t i o n f o r th e r e d u c t i o n i n s u r f a c e h a r d n e s s " I n p r o c e s s e s f o r m e c h a n i c a l d e s t r u c t i o n a r e g i o n of i n c r e a s e d c r a c k f o r m a t i o n i s c r e a t e d i n t h e de f o r m e d l a y e r s a d j o i n i n g t h e s u r f a c e of d e s t r u c t i o n f o r m i n g a p r e d e s t r u c t i o n zone. The s u r f a c e a c t i v e medium p e n e t r a t e s t h e embryo m i c r o c r a c k s i n t h i s zone. I n c r e a s i n g t h e a f f i n i t y of t h i s l i q u i d f o r t h e s u r f a c e of t h e s o l i d c o n s i d e r a b l y f a c i l i t a t e s t h e d e f o r m a t i o n and d e s t r u c t i o n by s o f t e n i n g t h e s o l i d i n t h e zone of i n c r e a s e d c r a c k f o r m a t i o n . Thus t h e h a r d n e s s or s t r e n g t h of t h e deformed body i s d e c r e a s e d by t h e i n f l u e n c e of t h e medium." I t was h i s f e e l i n g t h a t t h e phenomenon c o u l d be u t i l i z e d to improve t h e e f f i c i e n c i e s of m i n i n g , m a c h i n i n g and g r i n d i n g p r o c e s s e s . T h e r e i s e v i d e n c e , i n f a c t , t h a t R e h b i n d e r e f f e c t s have been u s e d s u c c e s s f u l l y f o r many y e a r s i n t h e U.S.S.R. to i n c r e a s e t h e e f f i c i e n c y of r o c k - d r i l l i n g o p e r a t i o n s [3,4] . c r e e p of In t h e i r s t u d y of R e h b i n d e r e f f e c t s on i n d e n t a t i o n s o l i d s , W e s t b r o o k and J o r g e n s e n [5] o b s e r v e d 5 t h a t a d s o r b e d w a t e r v a p o u r l o w e r e d t h e i n d e n t a t i o n h a r d n e s s o f A l ^ f r o m t h a t o f i t s ' c l e a n ' s u r f a c e v a l u e b y u p t o 2 0 % . T h e i r s t u d y o n a b r o a d r a n g e o f s o l i d s u r f a c e s s h o w e d t h a t w a t e r d i d n o t a f f e c t m e t a l s o r c o m p o u n d s w h o s e b o n d i n g i s m e t a l l i c , b u t d i d a f f e c t c o v a l e n t c r y s t a l s a n d s o l i d s o f c o m p l e t e l y i o n i c n a t u r e . W e s t w o o d , G o l d h e i m a n d L y e [ 6 , 7 ] s t u d i e d R e h b i n d e r e f f e c t s i n C a F ^ a n d MgO a n d d e m o n s t r a t e d t h a t a d s o r b e d s u r f a c e a c t i v e i o n s o r m o l e c u l e s e n h a n c e d d i s l o c a t i o n m o b i l i t y a n d t h e r e f o r e d e c r e a s e d t h e m i c r o h a r d n e s s o f M g O , b u t h a d t h e r e v e r s e e f f e c t o n C a F ^ . F r o m t h e s e r e s u l t s t h e y p o s t u l a t e d t h a t t h e e f f e c t s i n i o n i c s o l i d s a r e a s s o c i a t e d w i t h c h a n g e s i n t h e s t a t e o f i o n i z a t i o n o f n e a r s u r f a c e d e f e c t s a n d d i s l o c a t i o n s . . One c o n c l u s i o n d r a w n f r o m t h e e x t e n s i v e l i t e r a t u r e i s t h a t t h e w e a r r a t e o f a s o l i d s u r f a c e i s d e p e n d e n t u p o n t h e m e c h a n i s m b y w h i c h t h e m a t e r i a l i s r e m o v e d i n a p a r t i c u l a r p r o c e s s . I n a f u r t h e r s e r i e s o f p a p e r s c o n c e r n -i n g R e h b i n d e r e f f e c t s [ 8 , 9 , 1 0 , 1 1 , 1 2 ] , W e s t w o o d a n d h i s c o l l e a g u e s d e t e r m i n e d t h a t m a t e r i a l r e m o v a l b y b r i t t l e f r a c t u r e w a s r e d u c e d b y s u r f a c e s o f t e n i n g a g e n t s . T h e r e s u l t s o f t h e i r i n v e s t i g a t i o n s o n MgO, A l ^ O ^ , CaF^ a n d s o d a - l i m e ( s . l . ) g l a s s r e v e a l e d t h a t m a x i m u m d r i l l i n g r a t e c o i n c i d e d w i t h m a x i m u m s u r f a c e h a r d n e s s . I t w a s c o n c l u d e d t h a t a 6 r e d u c t i o n i n t h e s u r f a c e h a r d n e s s w o u l d e f f e c t i v e l y r e d u c e t h e d r i l l i n g e f f i c i e n c y b e c a u s e t h e c u t t i n g e n e r g y o f t h e b i t w o u l d b e d i s s i p a t e d i n p a r t b y p l a s t i c f l o w i n s t e a d o f b e i n g u s e d p r i m a r i l y t o c r e a t e t h e n e c e s s a r y b r i t t l e c h i p s c o n s i d e r e d t o c o n t r o l c h i p b e h a v i o u r . B u t W i e d e r h o r n a n d R o b e r t s [ 1 3 ] a p p l i e d t h e f i n d i n g s o f W e s t w o o d a n d h i s a s s o c i a t e s t o t h e a b r a s i v e w e a r o f g l a s s a n d f o u n d t h a t m a x i m u m a b r a s i v e w e a r d i d n o t o c c u r i n t h e s a m e m e d i a a s m a x i m u m d r i l l i n g r a t e . C l o s e e x a m i n a t i o n o f t h e a b r a d e d s u r f a c e s a n d c u t t i n g s l e d t h e m t o o b s e r v e t h a t m a t e r i a l h a d b e e n r e m o v e d b y b o t h a p l o u g h i n g p r o c e s s i n w h i c h b u l k m a t e r i a l h a d b e e n p u s h e d a w a y f r o m i h f r o n t o f a n a b r a d i n g p a r t i c l e , a n d b y b r i t t l e f r a c t u r e i n w h i c h m a t e r i a l w a s d e f o r m e d e l a s t i c a l l y t o t h e p o i n t o f f a i l u r e a n d c h i p s w e r e e j e c t e d . T h e y c o n c l u d e d t h a t p l o u g h i n g a s s u m e d a g r e a t e r i m p o r t a n c e i n a b r a s i o n a n d t h a t a r e d u c t i o n r a t h e r t h a n a n i n c r e a s e i n h a r d n e s s e n h a n c e d t h e w e a r r a t e . I t h a s b e e n t h e o r i z e d t h a t m a t e r i a l r e m o v a l i n d o w n - h o l e d r i l l i n g o c c u r s b y p l a s t i c f l o w r a t h e r t h a n b y b r i t t l e f r a c t u r e [ 1 4 , 1 5 , 1 6 , 1 7 , 1 8 , 1 9 , 2 0 ] . G n i r k a n d C h e a t h a m [ 1 5 ] s h o w e d t h a t r o c k e x h i b i t s a m a c r o s c o p i c t r a n s i t i o n f r o m p r e d o m i n a n t l y b r i t t l e t o p r e d o m i n a n t l y d u c t i l e b e h a v i o u r a t c o n f i n i n g p r e s s u r e s v a r y i n g f r o m 7 a b o u t 5 0 0 t o 1 , 0 0 0 p s i . T h e s e i n - s i t u c o n f i n i n g p r e s s u r e s a r e v e r y common i n m o d e r a t e l y d e e p b o r e h o l e s . F r o m t h i s i t i s a p p a r e n t t h a t a s t u d y o f R e h b i n d e r e f f e c t s f r o m a r o c k d r i l l i n g p o i n t o f v i e w s h o u l d f o c u s o n p l o u g h i n g . W e s t w o o d e t a l [ 1 2 ] a n d N a d e a u [ 2 1 ] d e m o n s t r a t e d t h a t s . l . g l a s s e x h i b i t s R e h b i n d e r e f f e c t s . B o t h s t u d i e s r e v e a l e d t h a t m a t e r i a l r e m o v a l w a s g e n e r a l l y b y b r i t t l e f r a c t u r e . N a d e a u s h o w e d t h a t t h e d r i l l i n g r a t e o f a n i n d u s t r i a l d i a m o n d c o r e d r i l l b i t i n g l a s s w a s 60 p e r c e n t h i g h e r i n a s o l u t i o n o f ^ h e p t y l a l c o h o l t h a n i n w a t e r . He a l s o n o t e d t h a t d r i l l i n g i n h e p t a n o l p r o d u c e d l a r g e r c h i p s t h a n ^ d r i l l i n g i n w a t e r . To c o n t i n u e t h e s t u d y o f R e h b i n d e r e f f e c t s i n s . l . g l a s s i t i s n e c e s s a r y t o e x a m i n e t h e i n f l u e n c e o f t h e e f f e c t s o n t h e p l o u g h i n g b e h a v i o u r i n t h i s m a t e r i a l . G l a s s s u r f a c e s h a v e b e e n o b s e r v e d t o p l o u g h i n a p l a s t i c m a n n e r f o r s l i d e r p e n e t r a t i o n s n o t e x c e e d i n g a b o u t 1 m i c r o n [ 2 2 ] s o t h i s b e h a v i o u r i s r e p r o d u c e d i n t h e p r e s e n t w o r k . 8 CHAPTER I I 2 .1 F r i c t i o n Theory The ar rangement of a h e m i s p h e r i c a l s l i d e r and the s u r f a c e i n t o w h i c h i t c u t s i s shown i n F i g . 1. T h i s i s t y p i c a l of a sys tem t h a t w i l l e x h i b i t a t a n g e n t i a l r e s i s t a n c e ' F ' to s l i d i n g m o t i o n . Under a c o n s t a n t no rma l l o a d ' N ' s u f f i c i e n t to s t r e s s the s o f t e r m a t e r i a l beyond i t s y i e l d p o i n t [23] the hemisphere s i n k s i n t o the s o f t e r m a t e r i a l u n t i l the a r e a of c o n t a c t i s s u f f i c i e n t to suppo r t the a p p l i e d l o a d . As i t moves the s l i d e r w i l l cu t a g roove or f r i c t i o n t r a c k i n the s o f t e r m a t e r i a l . I t i s g e n e r a l l y a c c e p t e d t h a t the f r i c t i o n a l r e s i s t a n c e to s l i d i n g m o t i o n r e s u l t s from a complex d i s s i p a t i o n of energy caused by the d i s r u p t i o n of f r i c t i o n a l bonds . The t o t a l f r i c t i o n f o r c e i s the sum of a l l t he se r e s i s t a n c e s a r e l a t i o n s h i p t h a t K r a g e l s k i i [24] g i v e s as V F = F + F + F + F L 1 2 3 4 where F^ and a re the r e s i s t a n c e s to e l a s t i c and to p l a s t i c d i s p l a c e m e n t of the m a t e r i a l and F^ and F^ a r e the r e s i s t a n c e s due to the s h e a r i n g of the m a t e r i a l and the s h e a r i n g of the s u r f a c e f i l m . The t o t a l f o r c e w i l l t h e r e -f o r e be g r e a t l y i n f l u e n c e d by the p r o p e r t i e s of the s o l i d s S I D E V I EW F R O N T A L C R O S S - S E C T I O N F i g . 1 A r r a n g e m e n t o f D i a m o n d S l i d e r o n t h e G l a s s S u r f a c e a n d l u b r i c a t i n g m e d i a i n v o l v e d . M o r e s i m p l y s t a t e d t h e f r i c t i o n a l r e s i s t a n c e may b e e x p r e s s e d a s t h e sum o f t w o t e r m s , o n e o f w h i c h r e p r e s e n t s t h e p l o u g h i n g a n d t h e o t h e r t h e s h e a r i n g p r o c e s s . T h i s i s t h e r e l a t i o n s h i p g i v e n b y B o w d e n a n d T a b o r [ 2 3 ] F = P + S ( 1 ) C l e a r l y t h e r e i s n o w a y t h a t r e s i s t a n c e t o m o t i o n c a u s e d b y d i s p l a c e m e n t o f m a t e r i a l b y p l o u g h i n g c a n b e s e p a r a t e d . f r o m t h a t r e s u l t i n g f r o m t h e b r e a k i n g o f t h e m o l e c u l a r b o n d s t h a t f o r m b e t w e e n t h e r u b b i n g s u r f a c e s . A n a d d i t i o n a l d i f f i c u l t y i n s o l v i n g f o r t h e f r i c t i o n f o r c e i n t h i s m a n n e r i s t h a t t h e a c t u a l v o l u m e o f d e f o r m e d m a t e r i a l i s n o t k n o w n , b e c a u s e t h i s c o m p r i s e s n o t o n l y t h e m a t e r i a l w i t h i n t h e c r o s s - s e c t i o n o f t h e g r o o v e b u t a l s o s ome o f t h e s u r r o u n d i n g a r e a . S e v e r a l s i m p l i f y i n g a s s u m p t i o n s , h o w e v e r , a l l o w t h e d e r i v a t i o n o f a n a p p r o x i m a t e e x p r e s s i o n f o r t h e f r i c t i o n f o r c e . T h e a s s u m p t i o n s m a d e h e r e a r e t h o s e m a d e b y B o w d e n a n d T a b o r i n t h e d e v e l o p m e n t o f t h e i r g e n e r a l e x p r e s s i o n f o r f r i c t i o n f o r c e . T h e a s s u m p t i o n s a r e t h a t t h e s l i d e r e x p e r i e n c e s no d e f o r m a t i o n d u r i n g s l i d i n g a n d t h a t t h e d i s p l a c e d a r e a o f t h e f r i c t i o n t r a c k c o n f o r m s t o t h e p r o f i l e o f t h e s l i d e r . D i a m o n d h a s a n i n d e n t a t i o n 2 h a r d n e s s o f a p p r o x i m a t e l y 1 0 , 0 0 0 kg/mm ' [ 2 5 ] w h e r e a s 2 t h e h a r d n e s s o f s . l . g l a s s i s a b o u t 5 0 0 kg/mm . T h e 11 d e f o r m a t i o n o f t h e d i a m o n d w h e n p r e s s e d i n t o t h e g l a s s w i l l t h e r e f o r e b e s l i g h t c o m p a r e d t o t h a t e x p e r i e n c e d b y t h e g l a s s a n d h e n c e may b e a s s u m e d n e g l i g i b l e f o r t h e p r e s e n t w o r k . F u r t h e r i t i s c o n s i d e r e d t h a t t h e m a t e r i a l i s d i s p l a c e d p e r m a n e n t l y f r o m t h e f r o n t o f t h e s l i d e r b y p l a s t i c f l o w . A l l m a t e r i a l d e f o r m a t i o n i s t h e r e f o r e a s s u m e d t o b e p e r m a n e n t a n d f r e e o f d i s c o n t i n u i t i e s . E x p r e s s i o n s f o r ' S ' a n d ' P ' a r e d e r i v e d s e p a r a t e l y . 2 . 2 P l o u g h i n g T e r m P d e n o t e s t h e f o r c e r e q u i r e d t o p e r m a n e n t l y d i s p l a c e t h e s o f t e r m a t e r i a l f r o m t h e f r o n t o f t h e s l i d e r . I t i s e q u a l t o t h e c r o s s - s e c t i o n a l a r e a o f t h e f r i c t i o n t r a c k ' A ' m u l t i p l i e d b y t h e m e a n f l o w p r e s s u r e ' p ' r e q u i r e d t o d i s p l a c e t h e m a t e r i a l . T h e n P = A p ( 2 ) c m T h e m e a n f l o w p r e s s u r e i s d e p e n d e n t o n t h e r a t e o f m a t e r i a l f l o w a n d i s i n d e p e n d e n t o f t h e g e o m e t r y o f t h e s l i d e r . F o r s t a t i c i n d e n t a t i o n s w h e r e t h e o n l y m o t i o n i s t h e p e n e t r a t i o n o f t h e s l i d e r i n t o t h e s o l i d s u r f a c e , p i s m a p p r o x i m a t e l y t h e m e a n p r e s s u r e p g d e t e r m i n e d f r o m i n d e n t a t i o n t e s t s [ 2 6 ] , T h e s o f t e r m a t e r i a l f l o w s p l a s t i c a l l y u p t h e s i d e s o f t h e i n d e n t e r a s s h o w n i n F i g . 2 a s t h e i n d e n t e r s i n k s i n t o t h e s o l i d . S i n k i n g c o n t i n u e s u n t i l t h e h o r i z o n t a l l y p r o j e c t e d a r e a 'A.^.' o f t h e i n d e n t a t i o n i s s u f f i c i e n t t o s u p p o r t t h e n o r m a l l o a d ' L ' . T h e m e a n f l o w p r e s s u r e f o r t h i s ' s t a t i c ' c a s e i s t h e r e f o r e P s = J l ( 3 ) A-r B o w d e n a n d T a b o r [ 2 7 ] h a v e s h o w n t h a t f o r f u l l y p l a s t i c i n d e n t a t i o n s p « 3 a ( 4 ) S w h e r e a ' i s t h e y i e l d s t r e n g t h o f t h e m a t e r i a l . I t h a s b e e n s h o w n t h a t w h e n a s l i d e r i s i n m o t i o n , t h e f l o w p r e s s u r e r e q u i r e d t o d i s p l a c e t h e s u r f a c e m a t e r i a l i n c r e a s e s t o a n u l t i m a t e v a l u e t h a t i s a b o u t t h r e e t i m e s t h e s t a t i c v a l u e [ 2 8 ] a s t h e r e s u l t o f t h e r a t e o f e n e r g y d i s s i p a t i o n i n t h e m a t e r i a l . T h u s d u r i n g s l i d i n g Pm = 3 P s ( 5 ) T h e p l o u g h i n g t e r m d e p e n d s o n t h e g e o m e t r y o f t h e s l i d e r . F o r a m o v i n g h e m i s p h e r e t h e a r e a d i s p l a c e d may b e a p p r o x i m a t e d f r o m g e o m e t r i c a l c o n s i d e r a t i o n s . R e f e r r i n g t o F i g . 3 t h i s a p p r o x i m a t e r e l a t i o n s h i p i s LOAD L RAISED MATERIAL PROJECTED AREA OF INDENTATION = ( d COSJ- ) F i g . 2 Diagram; o f Diamond P y r a m i d Hardness Tes t 14 F i g . 3 G e o m e t r y o f D i a m o n d S l i d e r a n d F r i c t i o n T r a c k 15 bh c A = — (6) 2 where b i s the w i d t h of the f r i c t i o n t r a c k and h i s the maximum d e p t h of p e n e t r a t i o n . The same r e l a t i o n s h i p h o l d s i n t h i s dynamic case as i n e x p r e s s i o n ( 3 ) . The h o r i z o n t a l l y p r o j e c t e d a r e a 'A 1 of the s l i d e r grows u n t i l H i t s u p p o r t s the no rma l l o a d ' N ' . The f l o w p r e s s u r e r e q u i r e d to d i s p l a c e the m a t e r i a l i s the dynamic v a l u e g i v e n by e x p r e s s i o n ( 5 ) . Hence A - N H " ? (7) m a d i f f i c u l t y a r i s e s here i n r e l a t i n g the a r e a A to the H geometry of the moving h e m i s p h e r e . On ly a p o r t i o n of the h o r i z o n t a l l y p r o j e c t e d a r e a of the p e n e t r a t i n g p a r t of the s l i d e r w i l l a c t u a l l y c o n t a c t the s o f t e r m a t e r i a l [ 2 9 ] . D e n o t i n g ' K ' as the p o r t i o n of a c t u a l c i r c l e of c o n t a c t , we have (!) (8) K i s a v a l u e between 0 .5 and 1 .0 . In the case of a A „ = K I T r l s t a t i o n a r y i n d e n t e r the f u l l c i r c l e of c o n t a c t would be s u p p o r t i n g the i n d e n t e r and K would be e q u a l to 1 .0 . But f o r s l i d i n g where t h e r e i s no m a t e r i a l b u i l d - u p b e f o r e the s l i d e r , or e l a s t i c r e c o v e r y of compressed m a t e r i a l i n the swept t r a c k beh ind the s l i d e r , K = 0 . 5 . However , e v e n t h o u g h o n e s i m p l i f i c a t i o n i n t h i s f o r m u l a t i o m l i s t h e a b s e n c e o f e l a s t i c r e c o v e r y , i t i s e x p e c t e d t h a t t h e r e w o u l d b e a w a v e o f p u s h e d up m a t e r i a l a h e a d o f t h e s l i d e r s i n c e t h i s i s c o m m o n l y o b s e r v e d i n t h e p l o u g h i n g o f p l a s t i c m a t e r i a l s [ 3 0 ] . T h e r e f o r e t h e r e a l v a l u e o f K w i l l b e c l o s e t o 0 . 5 . K i s a c o m p l e x f u n c t i o n o f t h e g e o m e t r y o f t h e s l i d e r a n d t h e m a t e r i a l p r o p e r t i e s o f t h e s o f t e r s o l i d a n d t h e r e f o r e o n l y a n e s t i m a t e d v a l u e w i l l b e u s e d . A v a l u e o f 0 . 6 i s u s e d i n t h i s w o r k . E q u a t i n g e x p r e s s i o n s ( 7 ) a n d ( 8 ) g i v e s b ( 9 ) a n d f r o m g e o m e t r i c a l c o n s i d e r a t i o n s h ( 1 0 ) 8R w h e r e R i s t h e r a d i u s o f t h e s l i d e r . S u b s t i t u t i n g ( 9 ) i n t o ( 1 0 ) g i v e s h N ( I D 2 u p KR S u b s t i t u t i n g ( 9 ) a n d ( 1 1 ) i n t o ( 6 ) g i v e s 1 . 5 A c 2R ( 1 2 ) p l o u g h i n g We c a n n o w g e t t h e g e n e r a l e x p r e s s i o n f o r t h e f o r c e b y s u b s t i t u t i n g ( 1 2 ) i n t o ( 2 ) 2 R p ^ \ T C K r m 1 . 5 ( 1 3 ) F r o m t h i s e q u a t i o n i t i s a p p a r e n t t h a t r e d u c i n g t h e h a r d n e s s w i l l r e s u l t i n a n i n c r e a s e i n t h e p l o u g h i n g f o r c e . F r o m e x p r e s s i o n ( 1 2 ) we s e e t h a t a r e d u c t i o n i n t h e h a r d n e s s w i l l a l s o r e s u l t i n a n i n c r e a s e i n t h e c r o s s - s e c t i o n a l a r e a o f t h e f r i c t i o n t r a c k . 2 . 3 S h e a r i n g T e r m A l t h o u g h t h e i n t e r e s t i n t h i s s t u d y i s s p e c i f i c a l l y t h e p l o u g h i n g b e h a v i o u r , t h e r e i s n o w a y t o e l i m a t e t h e s h e a r i n g c o m p o n e n t o f t h e t o t a l f r i c t i o n f o r c e . B o w d e n a n d T a b o r s u g g e s t e d t h a t a s p a d e s h a p e d s l i d e r w i t h a n e g l i g i b l e c o n t a c t a r e a t a n g e n t i a l t o t h e d i r e c t i o n o f m o t i o n w o u l d e s s e n t i a l l y e l i m i n a t e t h e s h e a r i n g r e s i s t a n c e [ 2 3 ] . T h i s i s n o t o b s e r v e d i n p r a c t i c e h o w e v e r b e c a u s e t h e r e i s a l w a y s s l i d i n g c o n t a c t b e t w e e n t h e s u r f a c e s a n d h e n c e t h e r e s u l t a n t b o n d s r e q u i r e e n e r g y t o b e s h e a r e d . T h e s h e a r i n g c o m p o n e n t o f f r i c t i o n f o r c e i s t h e f o r c e n e e d e d t o b r e a k t h e b o n d s t h a t f o r m o v e r t h e a r e a o f c o n t a c t . I t i s e q u a l t o t h e a r e a o f c o n t a c t t a n g e n t i a l t o t h e m o t i o n ' A 1 t i m e s t h e s h e a r s t r e n g t h ' A " ' o f t h e H s o f t e r m a t e r i a l s i n c e i t i s m o r e a p t t o s h e a r . S = A R A ( 1 4 ) f r o m e x p r e s s i o n ( 7 ) we g e t S = NX: ( 1 5 ) Pin I n t h e p r e s e n c e o f l u b r i c a n t s t h e r e a l a r e a o f c o n t a c t w i l l b e d i s t u r b e d t h u s r e d u c i n g t h i s s h e a r c o m p o n e n t . F e w e r b o n d s w i l l b e f o r m e d d u e t o t h e i n t e r f e r e n c e o f t h e m e d i u m a n d h e n c e l e s s e n e r g y w i l l b e n e e d e d t o s h e a r t h o s e b o n d s t h a t do f o r m . T h e f i n a l e x p r e s s i o n f o r t h e f r i c t i o n . ' * f o r c e r e s u l t i n g f r o m t h e p l o u g h i n g o f a p l a s t i c m a t e r i a l w i t h a h a r d h e m i s p h e r i c a l s l i d e r i s 1 . 5 F = 1 ( N \ + NX ( 1 6 ) 2 R p ^ \TTK J P m T h e t h e o r y s u g g e s t s t h a t i n c r e a s i n g t h e s l i d e r r a d i u s w o u l d r e d u c e t h e p l o u g h i n g r e s i s t a n c e . A n e x t r e m e e x a m p l e o f ' ; t h i s w o u l d b e a f l a t s l i d e r . F r i c t i o n a l r e s i s t a n c e w o u l d b e d u e o n l y t o t h e s h e a r i n g o f a d h e s i v e b o n d s . I n a c t u a l f a c t t h e r e i s a l w a y s s ome m u t u a l p e n e t r a t i o n o f m i c r o s c o p i c a s p e r i t i e s b e t w e e n t w o f l a t s u r f a c e s so t h e p l o u g h i n g t e r m c a n n e v e r b e c o m p l e t e l y e l i m i n a t e d . To s t u d y p l o u g h i n g b e h a v i o u r t h e p l o u g h i n g t e r m m u s t b e m a d e a s l a r g e a s p o s s i b l e a n d so t h e r a d i u s o f t h e s l i d e r m u s t b e s u f f i c i e n t l y s m a l l . T h e s h e a r i n g f o r c e i s d e p e n d e n t o n l y o n t h e r e a l t a n g e n t i a l a r e a o f c o n t a c t a n d n o t o n t h e r a d i u s o f t h e s l i d e r h e n c e i t s v a l u e w i l l r e m a i n r e l a t i v e l y c o n s t a n t . T h i s i s a m a n i f e s t a t i o n o f ' A m o n t o n ' s L a w ' t h a t f r i c t i o n i s i n d e p e n d e n t o f t h e a p p a r e n t a r e a o f c o n t a c t . C H A P T E R I I I 3 . 1 E x p e r i m e n t a l O b j e c t i v e T h e o b j e c t i v e o f t h e p r e s e n t e x p e r i m e n t s w a s t o s t u d y t h e f r i c t i o n b e h a v i o u r o f a s i n g l e i n d u s t r i a l d i a m o n d s l i d i n g o n t h e s u r f a c e o f a f l a t s o d a - l i m e g l a s s s p e c i m e n i m m e r s e d i n v a r i o u s e n v i r o n m e n t a l m e d i a . T h e f r i c t i o n b e h a v i o u r o b s e r v e d i n t h e p r e s e n c e o f e a c h e n v i r o n m e n t w a s c o m p a r e d t o t h a t o b b s e r v e d i n h i g h v a c u u m . 3 . 2 A p p a r a t u s 3 . 2 . 1 G e n e r a l D e s c r i p t i o n t h i s w o r k w e r e e s s e n t i a l l y t h e s a m e a s t h o s e u s e d b y G r e e n [ 3 1 ] f o r t h e s t u d y o f s l i d i n g f r i c t i o n . T h e a p p a r a t u s w a s s e t up a s s h o w n i n F i g . 4 . i n v e s t i g a t i o n w e r e t h e n o r m a l f o r c e ' N ' a p p l i e d t o t h e d i a m o n d , t h e s l i d i n g v e l o c i t y ' V ' a n d t h e e n v i r o n m e n t i n w h i c h s l i d i n g t o o k p l a c e . T h e m e a s u r e d v a r i a b l e s w e r e t h e t a n g e n t i a l f r i c t i o n f o r c e ' F ' a n d t h e d i s p l a c e d c r o s s - s e c t i o n a l a r e a ' A ' o f t h e f r i c t i o n t r a c k s . T h e a c t u a t o r a n d h i g h v a c u u m s y s t e m s u s e d f o r T h e p a r a m e t e r s t h a t w e r e c o n t r o l l e d i n t h i s c A t m o s p h e r e - f r e e t e s t s w e r e c o n d u c t e d i n a h i g h c h a m b e r a t 4 x 1 0 8 t o r r a n d r o o m t e m p e r a t u r e . v a c u u m F o r c o n v e n i e n c e t e s t s i n v o l v i n g l i q u i d m e d i a w e r e a l s o c a r r i e d o u t w i t h i n t h e c h a m b e r a t a t m o s p h e r i c p r e s s u r e w i t h t h e c h a m b e r c a p r e m o v e d a n d t h e : s p e c i m e n a n d d i a m o n d s l i d e r a s s e m b l i e s e n c l o s e d w i t h i n a l e a k - p r o o f c o n t a i n e r . T h e d i a m o n d s l i d e r m o t i o n a n d p l a c e m e n t w e r e a c h i e v e d b y u s i n g a s y s t e m o f h y d r a u l i c c y l i n d e r s m o u n t e d o n a n a d j u s t a b l e p l a t f o r m . L i n e a l s l i d i n g m o t i o n w a s t r a n s m i t t e d t o t h e s l i d e r t h r o u g h a 1 i n c h d i a m e t e r s t e e l s h a f t . A c t u a l s l i d i n g w a s d o n e b y a d i a m o n d - t i p p e d d r e s s i n g t o o l m o u n t e d t o t h e s h a f t b y a l i n k a g e . T h e d i a m o n d s l i d e r a s s e m b l y i s s h o w n i n F i g . 5 . 3 . 2 . 2 D i a m o n d S l i d e r A s s e m b l y T h e a s s e m b l y s h o w n s c h e m a t i c a l l y i n F i g . 6 w a s d e s i g n e d t o a p p l y a c o n s t a n t d o w n w a r d n o r m a l f o r c e t o a s i n g l e s u r f a c e - s e t i n d u s t r i a l d i a m o n d , a n d t o m e a s u r e t h e f r i c t i o n a l r e s i s t a n c e t o s l i d i n g o v e r a C o r n i n g t y p e 2 9 4 7 s o d a - l i m e g l a s s m i c r o s c o p e s l i d e . T h e n o r m a l f o r c e w a s a p p l i e d d i r e c t l y a b o v e t h e t i p ^ o f t h e s l i d e r b y t h e p l a c e m e n t o f a s t e e l w e i g h t o n t h e l o a d t r a y . T h e s l i d e r a r m w a s b a l a n c e d f o r a n o - l o a d c o n d i t i o n b y a c o u n t e r w e i g h t . T h e a p p l i e d n o r m a l l o a d w a s t h e n s i m p l y t h e w e i g h t a d d e d t o t h e l o a d t r a y . P r e t e s t i n g w i t h t h e s l i d e r m o u n t e d r i g i d l y t o t h e m a i n s h a f t r e v e a l e d t h a t t h e s h a f t t r a n s m i t t e d l o w F i g . 6 D i a g r a m o f D i a m o n d S l i d e r A s s e m b l y a m p l i t u d e h i g h f r e q u e n c y l a t e r a l v i b r a t i o n s t o t h e d i a m o n d . P r e s u m a b l y t h e s e w e r e i n d u c e d b y e x t e r i o r r o o m d i s t u r b a n c e s . T h e s l i d e r a r m w a s t h e r e f o r e m o u n t e d o n a t u r r e n t c a p a b l e o f b o t h h o r i z o n t a l a n d v e r t i c a l r o t a t i o n . S u b s e q u e n t s l i d i n g t e s t s s h o w e d t h a t t r a c k i n g w a s s t r a i g h t a n d f r e e f r o m i n d u c e d v i b r a t i o n s . A n i n c l i n e d r a m p w a s d e s i g n e d t o l o w e r t h e d i a m o n d s m o o t h l y o n t o t h e g l a s s s u r f a c e i n o r d e r t o r e d u c e t h e i n i t i a l i m p a c t b e t w e e n t h e d i a m o n d a n d t h e s p e c i m e n . P r e v i o u s l y t h e d i a m o n d w a s s i m p l y p l a c e d o n t h e g l a s s p r i o r t o s l i d i n g . A n i n i t i a l p e r i o d o f v e r y i r r e g u l a r s c r a t c h i n g o f e a c h f r i c t i o n t r a c k w a s o b s e r v e d t h e r e b y c o m p l i c a t i n g t h e f r i c t i o n b e h a v i o u r . T h e r a m p a l l o w e d a s m o o t h t r a n s i t i o n t o s l i d i n g a n d i r r e g u l a r r u n - i n w a s e l i m i n a t e d . T h e d i a m o n d w a s l i f t e d f r o m t h e g l a s s a t t h e e n d o f e a c h lh c m . s c r a t c h b y r a i s i n g t h e m a i n s h a f t . T h u s t h e d i a m o n d w a s r e s e t i n t h e s t a r t i n g p o s i t i o n o n t h e r a m p w i t h n o f u r t h e r c o n t a c t w i t h t h e g l a s s . 3 . 2 . 3 S p e c i m e n A s s e m b l y A n a s s e m b l y w a s n e e d e d t o h o l d a m i c r o s c o p e s l i d e f i r m l y i n p l a c e d u r i n g s c r a t c h i n g , t o r e t a i n a l i q u i d m e d i u m , a n d t o p e r m i t l a t e r a l r e p o s i t i o n i n g f o r s u b s e q u e n t s c r a t c h e s . E a c h s p e c i m e n w a s s c r a t c h e d n i n e t i m e s w i t h s c r a t c h e s s p a c e d a t h i n . i n t e r v a l s w i t h t h e o u t e r m o s t s c r a t c h e s % i n . f r o m t h e e n d s o f t h e s l i d e . T h e s p e c i m e n a s s e m b l y i s s h o w n s c h e m a t i c a l l y i n F i g . 7 . A s p e c i m e n w a s c l a m p e d a l o n g i t s f r o n t a n d r e a r e d g e s b y f i x i n g a n a d j u s t a b l e m e t a l b r a c i n g p l a t e i n p l a c e a g a i n s t t h e f r o n t e d g e o f t h e s l i d e . T h e c l a m p w a s c o n t a i n e d w i t h i n a 1 i n . d e e p r e c t a n g u l a r d i s h . T h e d i s h w a s m o u n t e d o n a t r o l l e y t h a t l a t e r a l l y t r a v e r s e d t h e v a c u u m c h a m b e r a l o n g a g r o o v e d t r a c k . T h e t r o l l e y w a s f i t t e d w i t h a t o o t h e d r a c k a n d w a s m a n i p u l a t e d b y a n a r m f i t t e d w i t h a m a t c h i n g r a c k . T h i s c l a m p a r m w a s h a n d o p e r a t e d f r o m o u t s i d e t h e v a c u u m c h a m b e r t t h r o u g h a l i n e a r m e c h a n i c a l l i n k i n t h e s i d e c h a m b e r p o r t . T h e c l a m p c o u l d b e m a n e u v e r e d t o m o v e t h e t r o l l e y t o a d e s i r e d s i t e a n d t h e n f i x i t f i r m l y i n p l a c e f o r t e s t i n g . 3 . 2 . 4 A c t u a t o r S y s t e m T h e a c t u a t o r s y s t e m s h o w n s c h e m a t i c a l l y i n F i g . 8 a l l o w e d c o m p l e t e c o n t r o l o f t h e s l i d e r a s s e m b l y f r o m o u t -s i d e t h e v a c u u m c h a m b e r . A n o i l d r i v e n B i m b a h y d r a u l i c c y l i n d e r p r o v i d e d t h e u n i f o r m s l i d i n g m o t i o n . T h e r a t e o f d i s p l a c e m e n t w a s c o n t r o l l e d b y m e t e r i n g t h e f l o w o f o i l t o t h e h y d r a u l i c c y l i n d e r w i t h a N u p r o m i c r o v a l v e e q u i p p e d w i t h a v e r n i e r m e t e r i n g d i a l f o r v e l o c i t y s e l e c t i o n . S l i d i n g v e l o c i t i e s r a n g e d f r o m 0 . 0 0 1 t o 0 . 4 c m / s e c . F i g . 7 D i a g r a m . o f S p e c i m e n A s s e m b l y A C C U M U L A T O R JSZ ( ^ ^ ) PUMP CONTROL BOX -c 3 A C T U A T O R a . b, c-, d , e , . S T A R T - S T O P . B Y P A S S . R A T E CONTROL .MODE .BLOW-DOWN A C T U A T O R F i g . 8.; S c h e m a t i c o f H y d r a u l i c S y s t e m A C T I V E GAUGES SW ITCH 120 120 1201 120' i R E F E R E N C E GAUGES B R I D G E A M P L I F I E R Q -•A - *C CHART RECORDER F i g . 9 S t r a i n G a u g e S y s t e m O i l w a s s u p p l i e d b y a p r e s s u r i z e d a c c u m u l a t o r w h i c h p r o v i d e d a p u l s a t i o n f r e e s o u r c e o f c o n s t a n t p r e s s u r e t h r o u g h o u t e a c h s c r a t c h . T h e a c c u m u l a t o r p r e s s u r e w a s m a i n t a i n e d a t 1 , 0 0 0 p s i s o t h a t a n y i r r e g u l a r i t i e s i n t h e s c r a t c h i n g f o r c e w o u l d n o t a f f e c t t h e s l i d i n g v e l o c i t y . 3 . 2 . 5 A c t u a t o r P l a t f o r m T h e p l a t f o r m s u p p o r t e d t h e h y d r a u l i c c y l i n d e r a n d t h e m a i n s h a f t a n d h a d a l i m i t e d a b i l i t y t o t i l t . T h i s m o t i o n w a s p r o d u c e d b y a s e c o n d h y d r a u l i c c y l i n d e r m o u n t e d v e r t i c a l l y t o t h e e n d o f t h e p l a t f o r m . T h e h o r i z o n t a l p o s i t i o n o f t h e p l a t f o r m w a s i n d i c a t e d b y a S t a r r e t d i a l g a u g e f i x e d t o t h e s t a t i o n a r y s u p p o r t b a s e . T h e m a i n s h a f t e n t e r e d t h e v a c u u m c h a m b e r t h r o u g h a p o r t m o d i f i e d w i t h a m e c h a n i c a l f e e d t h r o u g h u n i t ( a b e l l o w s ) o f 4 i n c h d i a m e t e r a n d 6 i n c h l i n e a r d i s p l a c e m e n t . T h e d e g r e e o f p l a t f o r m t i l t w a s r e s t r i c t e d b y t h e l i m i t e d v e r t i c a l m o v e m e n t o f t h e b e l l o w s . T h e p l a t f o r m w a s m o u n t e d t o a m a c h i n e t a b l e t h a t a l l o w e d x a n d y m o v e m e n t f o r p o s i t i o n i n g t h e s h a f t w i t h r e s p e c t t o t h e c h a m b e r p o r t . T h e m a c h i n e t a b l e w a s f i x e d t o a r i g i d s u p p o r t b a s e w h i c h w a s a n c h o r e d t o t h e c o n c r e t e f l o o r . 30 3 . 2 . 6 V a c u u m S y s t e m T h e h i g h v a c u u m s y s t e m u s e d i n t h i s w o r k w a s — 8 a T T S B - 2 0 0 a l l m e t a l u n i t c a p a b l e o f r e a c h i n g 4 x 1 0 t o r r i n t h r e e h o u r s . H i g h e r v a c u u m s r e q u i r i n g h i g h t e m p e r a t u r e b a k e ' o u t w e r e n o t p o s s i b l e s i n c e b a k e o u t w o u l d h a v e d a m a g e d t h e s t r a i n g a u g e s m o u n t e d w i t h i n t h e c h a m b e r . T h e b e l l j a r u s e d w a s 8 i n c h e s h i g h a n d 12 i n c h e s i n d i a m e t e r a n d w a s e n t e r e d f r o m t h e t o p w h e n t h e l i d w a s r e m o v e d . T h e b e l l j a r c o n t a i n e d a 4 i n c h w i d e b y 1 i n c h t h i c k w o r k s u p p o r t p l a t f o r m o n w h i c h t h e s p e c i m e n t r o l l e y w a s f a s t e n e d . T h i s p l a t f o r m w a s w e l d e d t o t h e i n n e r f l a n g e a t t h e c h a m b e r b a s e . B e l o w t h e b e l l j a r w a s t h e p u m p i n g s e c t i o n o f t h e b a s e w e l l a s s e m b l y . R o u g h p u m p i n g w a s a c c o m p l i s h e d b y t w o c r y o g e n i c s o r p t i o n p u m p s t h a t u s e d L N 2 a s a c o o l a n t a n d h i g h l y p o r o u s s y n t h e t i c z e o l i t e m o l e c u l a r s i e v e s a s t h e s o r b a n t . T h e s e - 3 p u m p s p r o d u c e d a v a c u u m i n t h e o r d e r o f 1 0 t o r r . T h e u s e o f t h e s e p u m p s e l i m i n a t e d t h e p o s s i b i l i t y o f s p e c i m e n s u r f a c e c o n t a m i n a t i o n d u e t o b a c k s t r e a r n i n g o f p u m p i n g o i l s t h a t c a n o c c u r w h e n u s i n g d i f f e r e n t i a l p u m p s t h a t e m p l o y h e a v y o i l s a s t h e p u m p i n g f l u i d . H i g h v a c u u m w a s p r o d u c e d b y u s i n g t i t a n i u m g e t t e r p u m p i n g a n d i o n p u m p i n g . P r e s s u r e w a s m a i n t a i n e d b y m o n i t o r i n g t h e i o n pump c u r r e n t o n a m e t e r s c a l e d i n t o r r u n i t s . S i n c e i n a n y p r o d u c e d v a c u u m t h e r e a r e r e s i d u a l g a s e s , a q u a d r a - p o l e t y p e r e s i d u a l g a s a n a l y z e r ( R G A ) w a s u s e d t o d e t e r m i n e t h e c o m p o s i t i o n a n d r e s p e c t i v e p a r t i a l p r e s s u r e s o f t h o s e g a s e s . T h e RGA h a d a m a s s - 1 4 r a n g e o f 1 - 2 5 0 amu a n d a s e n s i t i v i t y o f 1 x 1 0 t o r r p a r t i a l p r e s s u r e f o r N ^ . I t w a s d e s i r e d t o c o n d u c t a s e t o f t e s t s i n a n i t r o g e n a t m o s p h e r e a t s t a n d a r d p r e s s u r e s o t h e v a c u u m c h a m b e r w a s f i t t e d w i t h a N u p r o a i r i n l e t v a l v e t o b l e e d d r y b o t t l e d n i t r o g e n i n t o t h e c h a m b e r i n a v a c u u m s t a t e u n t i l a t m o s p h e r i c p r e s s u r e w a s i n d i c a t e d o n t h e . b o t t l v a l v e p r e s s u r e m e t e r . 3 . 3 I n s t r u m e n t a t i o n A s e c t i o n o f t h e v e r t i c a l b e a m o n t h e s l i d e r a r m w a s m a c h i n e d t o a t h i n r e c t a n g u l a r c r o s s - s e c t i o n t o i n c r e a s e i t s r e l a t i v e f l e x i b i l i t y w i t h r e s p e c t t o t h e r i g i d i t y o f t h e r e s t o f t h e a s s e m b l y . T h u s t h e s l i d e r a r m b e h a v e d e s s e n t i a l l y a s a c a n t i l e v e r e d e l a s t i c b e a m w i t h a n e n d l o a d ( t h e f r i c t i o n f o r c e ) a p p l i e d t a n g e n t i a l l y t o i t s a x i s . 1 2 0 ohm s t r a i n g a u g e s w e r e c e m e n t e d t o e a c h f a c e o f t h e m a c h i n e d s e c t i o n t o m e a s u r e t h e f o r c e . T h e s t r a i n g a u g e s w e r e u s e d i i i c o n j u n c t i o n w i t h E l l i s m o d e l BAM - 1 b r i d g e a m p l i f i e r . E l e c t r i c a l 32 f e e d f r o m t h e c h a m b e r w a s a c h i e v e d b y a d u a l r o d m e d i u m c u r r e n t e l e c t r i c a l f e e d t h r o u g h u n i t . T h e a c t i v e g a u g e s m a d e u p t w o a r m s o f t h e b r i d g e a n d w e r e a r r a n g e d f o r t e m p e r a t u r e c o m p e n s a t i o n . T h e c a l i b r a t e d o u t p u t w a s m o n i t o r e d d u r i n g a s e r i e s o f v a c u u m p u m p - d o w n s b u t n o u n b a l a n c e o c c u r r e d . T h i s r e s u l t c o n f i r m e d t h a t l o w p r e s s u r e w o u l d n o t a f f e c t t h e o u t p u t d u r i n g t e s t s . T h e c a l i b r a t i o n o f t h e s l i d e r a r m i s g i v e n i n A p p e n d i x I. T h e o u t p u t f r o m t h e b r i d g e a m p l i f i e r w a s f e d t o o n e c h a n n e l o f a B r u s h s t r i p c h a r t r e c o r d e r t o d i s p l a y f r i c t i o n f o r c e o n a t i m e b a s e t h r o u g h o u t e a c h t e s t . A dummy g a u g e w i t h a c o n s t a n t r e f e r e n c e s t r a i n w a s c o n s t r u c t e d a n d c o n n e c t e d t h r o u g h a s w i t c h t o t h e BAM t o d e t e c t a n y DC d r i f t d u r i n g t e s t i n g . T h e a c t o f m o u n t i n g s t r a i n g a u g e s u s u a l l y r e s u l t s i n a p e r m a n e n t r e s i s t a n c e d i f f e r e n t i a l s o t h e dummy g a u g e c o n s i s t e d o f a n o t h e r p a i r o f 1 2 0 ohm s t r a i n g a u g e s m o u n t e d t o a b l o c k o f m i l d s t e e l k e p t o u t s i d e t h e c h a m b e r . T h e r e s i s t a n c e d i f f e r e n t i a l w a s c h e c k e d b e f o r e a n d a f t e r e a c h t e s t f o r a n y c h a n g e . T h e c i r c u i t r y f o r t h i s s y s t e m i s s h o w n i n F i g . 9 . 3 . 4 M e a s u r e m e n t o f C r o s s - S e c t i o n a l A r e a F r i c t i o n t r a c k s w e r e s h a l l o w w i t h p e n e t r a t i o n d e p t h s i n t h e o r d e r o f 0 . 7 m i c r o n s , b u t t h e y w e r e l a r g e w i t h r e s p e c t t o t h e t r a c k w a l l r i d g e s . T h u s a T a l y s u r f -<', 4 s u r f a c e p r o f i l o m e t e r was w e l l s u i t e d to t r a c i n g the c r o s s -s e c t i o n a l p r o f i l e s . I n v e s t i g a t i o n s showed t h a t a f t e r an i n i t i a l r u n - i n l e n g t h of a few m i l l i m e t e r s , a s c r a t c h tended to have a u n i f o r m and r e p r o d u c e a b l e p r o f i l e w i t h l e s s than 1 p e r c e n t v a r i a t i o n . T h e r e f o r e a s i n g l e p r o f i l e was r e c o r d e d f o r each s c r a t c h . P r o f i l e s were d i s p l a y e d on a s t r i p c h a r t . Depth m a g n i f i c a t i o n was u s u a l l y 10 ,000 t imes and w i d t h m a g n i f i c a t i o n v a r i e d w i t h the t r a c k i n g speed of the p i c k up . The c h a r t - r e c o r d e d p r o f i l e s were then t r a c e d w i t h a p l a n i m e t e r and t h i s a r ea v a l u e was c o n v e r t e d to r e a l a r e a . 3 .5 The Diamond The o b j e c t i n s e l e c t i n g the diamond used was to o b t a i n a diamond r e p r e s e n t a t i v e of the k i n d used i n s u r f a c e - s e t i n d u s t r i a l r o t a r y b i t s . These tend to be i n f e r i o r s t o n e s w i t h e i t h e r no c l e a v a g e p r o p e r t i e s or v e r y i r r e g u l a r i l y o r i e n t e d f a c i a l p l a n e s [ 3 2 ] . C u t t i n g f r i c t i o n b e h a v i o r u s i n g c r y s t a l l i n e s t ones w i t h r e g u l a r c l e a v e d f a c e s i s dependent on the o r i e n t a t i o n of the diamond w i t h r e s p e c t to the c u t t i n g d i r e c t i o n [ 3 3 ] . The g e o m e t r i c a l shape of i n d u s t r i a l diamonds used i n s u r f a c e - s e t diamond b i t s i s not s p e c i f i c a l l y 34 c o n t r o l l e d . G e n e r a l l y , h o w e v e r , t h e d i a m o n d s t e n d t o b e r o u n d e d . A b a l l - r o l l e d i n d u s t r i a l d i a m o n d w i t h a r o u g h l y s p h e r i c a l t i p o f a p p r o x i m a t e l y 0 . 0 5 mm r a d i u s w a s u s e d . T h e r a d i u s w a s d e t e r m i n e d f r o m s c a n n i n g e l e c t r o n m i c r o g r a p h s o f t h e f r o n t a l p r o j e c t e d a r e a o f t h e d i a m o n d . T h e d i a m o n d t i p i s s h o w n i n F i g . 1 0 i n v i e w s t a k e n d i r e c t l y o n , a n d a t r i g h t a n g l e s t o t h e s l i d i n g d i r e c t i o n . 3 . 6 S p e c i m e n s M i c r o s c o p e s l i d e s o f s o d a - l i m e g l a s s w e r e s e l e c t e d f o r t h i s s t u d y b e c a u s e o f t h e i r c o n s i s t e n t s u r f a c e a n d m a t e r i a l p r o p e r t i e s . T h e d e c i s i o n t o u s e m i c r o s l i d e s r e s u l t e d f r o m e a r l y w o r k u s i n g f l o a t - p l a t e g l a s s s e c t i o n s . T h e s e w e r e u n s a t i s f a c t o r y b e c a u s e r e g a r d l e s s o f t h e l o a d u s e d , s u r f a c e s t r e s s e s c a u s e d a t i m e d e p e n d e n t g r o w t h o f c r a c k s a n d f i s s u r e s w h i c h r e s u l t e d i n t h e c r e a t i o n a n d e j e c t i o n o f l a r g e c h i p s . T h i s c o m p l i c a t e d t h e e v a l u a t i o n o f t h e r e a l d i s p l a c e d a r e a . C o r n i n g t y p e 2 9 4 7 s . l . g l a s s m i c r o s l i d e s w e r e c h o s e n b e c a u s e t h e y c a m e v a p o u r d e g r e a s e d a n d s e a l e d a g a i n s t a t m o s p h e r i c c o n t a m i n a t i o n . S l i d e s c a m e p a c k e d f a c e t o f a c e a n d f o r c e w a s n e e d e d t o s e p a r a t e t h e m . S l i d e s w e r e ( i ) F r o n t a l P r o f i l e m a g n i f i e d 385 X R - 0 .05 mm ( i i ) R a d i u s of C u t t i n g A s p e r i t y ( i i i ) S ide P r o f i l e m a g n i f i e d 385 X C u t t i n g Face on L e f t S i d e of M i c r o g r a p h F i g . 10 S c a n n i n g E l e c t r o n M i c r o g r a p h s o f Diamond i n s t a l l e d d i r e c t l y f r o m t h e c a r t o n w i t h t h e r e c e n t l y e x p o s e d s u r f a c e f a c e u p . D e t a i l s o f t h e c h e m i c a l c o m -p o s i t i o n o f t h e g l a s s i s g i v e n i n A p p e n d i x I I . 3 . 7 E x p e r i m e n t a l P r o c e e d u r e 3 . T.l P r e - t e s t I n v e s t i g a t i o n T e s t s w e r e c o n d u c t e d t o d e t e r m i n e t h e n o r m a l l o a d a n d s l i d i n g v e l o c i t i e s t h a t w o u l d b e s t d i s p l a y t h e p l o u g h i n g f r i c t i o n b e h a v i o u r . L o a d s i n e x c e s s o f 2 5 0 gm t e n d e d t o c r e a t e u n e v e n s u r f a c e d a m a g e i n t h e f o r m o f e l l i p t i c a l g o u g e s , c r a c k s , a n d t r a c k - w a l l d e b r i s . T h e h i g h e r t h e l o a d t h e m o r e e x t e n s i v e w a s t h i s d a m a g e . T h e l o a d w a s r e d u c e d t o 1 5 0 gm t o o b t a i n t h e t y p e o f f l o w b e h a v i o u r r e p o r t e d i n t h e l i t e r a t u r e . T h e r e s u l t a n t s c r a t c h e s w e r e t o o s h a l l o w t o o b s e r v e w e l l w i t h t h e T a l y s u r f , b u t b y r a i s i n g t h e l o a d a n o t h e r 50 gm t h i s p r o b l e m w a s o v e r -c o m e . T h e s c r a t c h e s p r o d u c e d a l s o s h o w e d e v i d e n c e o f b u i l t - u p e d g e s i n d i c a t i v e o f f l o w b e h a v i o u r . H e n c e a n o r m a l l o a d o f 2 0 0 gm w a s f o u n d m o s t s u i t a b l e f o r t h e p r e s e n t wo r k . T e s t s r e v e a l e d t h a t f r i c t i o n b e h a v i o u r c h a n g e d m o s t n o t i c e a b l y a t t h e l o w e r e n d o f t h e v e l o c i t y r a n g e . C o n v e n i e n t m e t e r s e t t i n g s w e r e c h o s e n t o a l l o w f o r a 37 g r e a t e r c o n c e n t r a t i o n o f t e s t v e l o c i t i e s i n t h e l o w e r r a n g e . T h e v e l o c i t i e s w e r e 0 . 0 0 1 , 0 . 0 1 8 , 0 . 0 4 4 , 0 . 0 9 4 , 0 . 1 2 5 , 0 . 1 6 8 , 0 . 2 5 a n d 0 . 4 c m / s e c . V e l o c i t y w a s m o n i t o r e d b y m e a n s o f a s l i d i n g c o n t a c t o n a c o i l o f r e s i s t a n c e w i r e . T h e m e t a l s l i d e r w a s f i x e d t o t h e m a i n s h a f t a n d t h e DC o u t p u t w a s f e d t o t h e s e c o n d c h a n n e l o f a B r u s h r e c o r d e r . T h e c i r c u i t a n d c a l i b r a t i o n o f t h e v e l o c i t y m e t e r a r e g i v e n i n A p p e n d i x I I I . A t e m p e r a t u r e p r o b e w a s i n s t a l l e d i n t h e c h a m b e r i n t h e r m a l c o n t a c t w i t h t h e s p e c i m e n t o d e t e r m i n e i f a n y t e m p e r a t u r e v a r i a t i o n r e s u l t e d f r o m p u m p - d o w n . T e m p e r a t u r e r e m a i n e d a t r o o m t e m p e r a t u r e t h r o u g h o u t . T h e c i r c u i t a n d c a l i b r a t i o n o f t h e t h e r m i s t o r i s p r e s e n t e d i n A p p e n d i x I V . 3 . 7 . 2 E n v i r o n m e n t P r e p a r a t i o n L i q u i d e n v i r o n m e n t s w e r e p r e p a r e d b y p o u r i n g t h e m e d i u m d i r e c t l y i n t o t h e p r e - c l e a n e d s p e c i m e n d i s h u n t i l t h e l i q u i d l e v e l w a s a b o u t h'lnch a b o v e t h e s u r f a c e o f t h e s p e c i m e n . T h i s a s s u r e d c o m p l e t e c o v e r a g e o f t h e s o l i d d u r i n g s l i d i n g . T h e v o l u m e o f l i q u i d u s e d a l s o r e d u c e d e f f e c t s i n d u c e d b y t h e a b s o r b t i o n o f w a t e r v a p o u r f r o m t h e a i r p a r t i c u l a r i l y o f c o n c e r n w h e n u s i n g t h e s h o r t c h a i n l e n g t h a l c o h o l s [ 1 3 ] . T h e s p e c i m e n a n d d i a m o n d w e r e l e f t t o s o a k f o r 3 0 m i n u t e s p r i o r t o t e s t i n g t o a l l o w a d e q u a t e a d s o r p t i o n o f t h e s u r f a c e a c t i v e s p e c i e s i n t h e m e d i u m o n t o 38 b o t h s u r f a c e s . A f t e r t e s t i n g w a s c o m p l e t e d o n a s p e c i m e n i t w a s r e m o v e d f o r T a l y s u r f a n a l y s i s a n d t h e s p e c i m e n d i s h w a s d r a i n e d a n d c l e a n e d i n a l t e r n a t i n g r i n s e s o f e t h y l a l c o h o l a n d a c e t o n e . T h e d i s h w a s t h e n i m m e r s e d i n a n u l t r a - s o n i c c l e a n -i n g t a n k c o n t a i n i n g a h o t w a t e r a n d d e t e r g e n t s o l u t i o n f o r a 30 m i n u t e b a t h . T h i s w a s f o l l o w e d b y a l e n g t h y r i n s e i n c l e a n b o i l i n g w a t e r a n d t h e d i s h w a s t h e n a l l o w e d t o a i r d r y . T h i s c l e a n i n g s e q u e n c e r e d u c e d t h e p o s s i b i l i t y o f c o n t a m i n a t i o n f r o m a p r e v i o u s l y u s e d e n v i r o n m e n t . L a b o r a t o r y g r a d e m e d i a w e r e u s e d d i r e c t l y f r o m s e a l e d a n d l a b e l l e d b o t t l e s . T h e p r o p e r t i e s o f t h e s e l i q u i d s a r e g i v e n i n A p p e n d i x V . 3 . 7 . 3 I n s t r u m e n t P r e p a r a t i o n A l l e l e c t r o n i c i n s t r u m e n t a t i o n w a s s w i t c h e d o n 30 m i n u t e s b e f o r e u s e t o a l l o w f o r t h e i n i t i a l w a r m - u p d r i f t . T h e BAM w a s b a l a n c e d a n d c a l i b r a t e d a g a i n s t ' s l i d e r a r m d e f l e c t i o n t o d e t e r m i n e t h e g a i n . T h e B r u s h r e c o r d e r w a s t h e n c o n n e c t e d a n d i t s g a i n c o n t r o l s w e r e a d j u s t e d f o r c o n v e n i e n c e t o d i s p l a y a k n o w n u n i t o f f o r c e p e r c h a r t d i v i s i o n . T h e r e f e r e n c e s t r a i n w a s t h e n d e t e r m i n e d b y s w i t c h i n g t o t h e dummy g a u g e . T h i s v a l u e w a s c h e c k e d a f t e r e v e r y s c r a t c h t o a s s u r e t h a t no DC d r i f t h a d o c c u r r e d . T h e u n d e f l e c t e d s l i d e r a r m r e a d o u t w a s a l s o c h e c k e d a f t e r e v e r y r u n t o a s s u r e t h a t i t r e t u r n e d t o a z e r o f o r c e r e a d i n g . 3 .7 .4 T e s t i n g T h e c o m p l e t e r a n g e o f v e l o c i t i e s w a s r u n o n e a c h s p e c i m e n . T h r e e s p e c i m e n s w e r e t e s t e d i n e a c h e n v i r o n m e n t . T h i s e l i m i n a t e d t h e d e v e l o p m e n t o f t r e n d s c a u s e d b y i n d i v i d u a l s u r f a c e p r o p e r t i e s o f t h e s l i d e s . V e l o c i t i e s w e r e a l s o r u n i n a r a n d o m s e q u e n c e t o a v o i d t h e d e v e l o p m e n t o f t r e n d s d u e t o t h e i n f l u e n c e o f r e p e t i t i v e n e i g h b o u r i n g s c r a t c h e s . 3 .7 .5 T a l y s u r f A n a l y s i s U p o n c o m p l e t i o n o f e a c h t e s t t h e s p e c i m e n w a s r e m o v e d f r o m t h e s p e c i m e n d i s h a n d b l o w n d r y w i t h a i r t o r e m o v e t h e b u l k o f t h e f l u i d t h a t r e m a i n e d o n t h e s u r f a c e . No a t t e m p t w a s m a d e t o c l e a n t h e s p e c i m e n w i t h s o l v e n t a s t h i s w o u l d c e r t a i n l y h a v e i n f l u e n c e d t h e f r a c t u r e a n d f l o w o f t h e m a t e r i a l . A p r o f i l e w a s m a d e f o r e a c h s c r a t c h . T h e s p e c i m e n w a s t h e n e x a m i n e d u n d e r . • a n o p t i c a l m i c r o s c o p e f o r v i s u a l e v i d e n c e o f m a t e r i a l r e m o v a l . 40 C H A P T E R I V 4 . 1 . R e s u l t s a n d A n a l y s i s T h e e x p e r i m e n t a l m e a s u r e m e n t s a r e p r e s e n t e d i n F i g s . 1 1 - 2 2 . R e s u l t s a r e d i s p l a y e d f o r c o m p a r i s o n i n F i g s ' . 2 3 - 2 5 . 4 . 1 . 1 . F r i c t i o n F o r c e F r i c t i o n f o r c e r e g u l a r i t y v a r i e d w i t h e n v i r o n m e n t a n d i n t h e p r e s e n c e o f a i r a n d n i t r o g e n , w i t h v e l o c i t y . I r r e g u l a r i t y w h e n i t o c c u r r e d w a s c h a r a c t e r i z e d b y a j a g g e d f o r c e l i n e . G e n e r a l l y t h e g r e a t e s t i r r e g u l a r i t y o c c u r r e d i n t h e a l c o h o l e n v i r o n m e n t s . I n p r o p y l a l c o h o l t h e v a r i a t i o n o f f o r c e a b o u t i t s m e a n v a L u e w a s a b o u t 25 p e r c e n t . I n v a c u u m t h e v a r i a t i o n w a s l e s s t h a n 1 p e r c e n t . S e v e r a l t e s t s w e r e r e - r u n a t t h e c o m p l e t i o n o f t h e t e s t p r o g r a m a n d r e s u l t s o b t a i n e d w e r e c o n s i s t e n t w i t h t h o s e o b s e r v e d e a r 1 i e r . I n a l l c a s e s t h e f r i c t i o n f o r c e w a s e v a l u a t e d a s t h e m e a n v a l u e o f t h e f o r c e l i n e . D u r i n g t h e t e s t p r o g r a m i t w a s f o u n d t h a t d i s t u r b a n c e s e x t e r n a l t o t h e c h a m b e r w e r e t r a n s m i t t e d t o t h e s p e c i m e n i n f l u e n c i n g t h e r e s u l t s . U n s u c c e s s f u l a t t e m p t s w e r e m a d e t o b r a c e t h e c h a m b e r . S u b s e q u e n t l y c o n s i d e r a b l e c a r e w a s t a k e n d u r i n g t e s t i n g i n o r d e r t o a v o i d d i s t u r b a n c e s . A n F i g . 11 ( a ) R e c o r d e d F r i c t i o n F o r c e . . . H i g h V a c u u m V = 0 . 1 6 8 c m / s e c F = 1 2 . 0 gm 0 60 w 6 0 . u fe o fe 40 . o 1—1 H 2 0 . O I—I a fe 0 1 1 1 0 DATA — B E S T F I T C U R V E _ i I I 8 i l ! -o 0 . 1 0 . 2 0 . 3 O.i V E L O C I T Y c m / s e c F i g . 11 ( b ) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . H i g h V a c u u m V e r t . . . 1 0 , 0 0 0 X H o r i z . V = 0 . 1 2 5 c m / s e c A = 2 , 1 x 1 0 ^ mm 2 c 2 , 0 0 0 X F i g . 11 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . H i g h V a c u u m 0 0 <| W fe < P W u <: fe fe w fe r - ~ \ -co0\ o 8 o 8 o _ 8 _ I O DATA B E S T F I T C U R V E 8 - (b 0 . 1 0 . 4 F i g . 0 . 2 0 . 3 V E L O C I T Y c m / s e c 11 ( d ) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . H i g h V a c u u m 42 -KO-( i ) ( i i ) F i g . 12 (a) R e c o r d e d F r i c t i o n F o r c e . . . N i t r o g e n ( i ) V = 0.009 cm/sec F = 18.0 gm ( i i ) V = 0.4 cm/sec F = 15.0 gm 0 oO 3 60 Pi o 2 40.|_ o H H 20 Pi 0 T I O DATA BEST FIT CURVE feo___8_ _8__8 8 4 0.1 0.2 0.3 VELOCITY cm/sec F i g . 12 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . N i t r o g e n 0.4 V e r t . . . 1 0 , 0 0 0 X H o r i z . . . 2 , 0 0 0 X V = 0.094 cm/sec A = 2.4 x 10 ^ mm2 c F i g . 12 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . N i t r o g e n e e < w Pi < a w u < fe 0 1 1 1 O DATA — BEST FIT CURVE -0 o J 8 ° £ I - g c ! 8- - 4 1 1 1 0.1 0.2 0.3 VELOCITY cm/sec F i g . 12 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . N i t r o g e n 0.4 fe • r- 1 OO <*"N fe a H * cn 1—1 n It fe > H fD < < w ro r 1 • i o cn o C i—i cn H K ! < ro H o 0 3 o — fe cn r t ro o • • • > fe DISPLACED AREA mm o r-o -P- as H N3 o I 1 ' a M e f ' o CO AD / CD / O / O ' ( D O O O OO O O 1 1 O Bd o M > in H > r-1 H n < i I bob I I I fe 09 I—1 OJ 5* ro o o i i fe ro fe < > < o H rj II H' rt II O • o rt • OJ • fe • • o O 4> 3 O J> X H o o i-i o H 3 Co o O \ o 1 cn ?r X OS ro n e 9 o w tsj i-h o fe H fe- fe ll) N • • • • • > 1—1 H* o o o X fe 09 FRICTION FORCE gm ro o o as o fe 09 F i g . 14 (a) R e c o r d e d F r i c t i o n F o r c e . . . W a t e r V = 0.25 cm/sec F = 25.0 gm S DO W u P H o fe S5 o H H O 1—I PH fe 60 40 20. 0. > - 8 -O O o _Q O DATA BEST FIT CURVE -o-0.1 0.2 0.3 VELOCITY cm/sec F i g . 14 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . W a t e r 0.4 V = 0.168 cm/sec A = 2.5 x 10 ^ mm2 c V e r t 10,000 X H o r i z . . .1, 000 X F i g . 14 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . Water O DATA -- BEST FIT CURVE •_o 0 _ O U _ Q & 8 - 0 - - 6 -o -O-o 0 F i g . 14 (d) 0.1 0.2 0 VELOCITY cm/sec D i s p l a c e d A r e a v e r s u s V e l o c i t y Water 0.4 F i g . 15 (a) R e c o r d e d F r i c t i o n F o r c e . . . C a p r o i c A c i d V = 0.25 cm/sec F = 25.0 gm 0 00 w a rt o fe o H H u H rt 60. L_ 40 20 F i g c g - o - o - - o - -Q 8' O DATA - " BEST FIT CURVE —1 _o 1 1 0.1 0.4 0.2 0.3 VELOCITY cm/sec 15 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . C a p r o i c A c i d V e r t . . . 5 , 0 0 0 X H o r i z . . . 1 , 0 0 0 X V = 0.094 cm/sec 6 2 A = 2.3 x 10 mm c F i g . 15 (c) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . C a p r o i c A c i d 0 0 < W rt < O w u < fe CO H P 6. h-2 . F i g he o 8 - - ° -o o '8T I O DATA BEST FIT CURVE 4 - -1 0.1 0.4 0.2 0.3 VELOCITY cm/sec 15 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . C a p r o i c A c i d 46 F i g . 16 (a) R e c o r d e d F r i c t i o n F o r c e . . . O l e i c A c i d V = 0.25 cm/sec F = 42.0 gm 0 60 60. W u rt o rt 40. 53 O I—I H 20. U 1—1 rt rt 0. o u o h- o o O DATA BEST FIT CURVE O - 8 - O "<y~ o "8" l 0 . 1 0.4 F i g 0.2 0.3 VELOCITY cm/sec 16 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . O l e i c A c i d V = 0.009 cm/sec A -6 2 = 6.7 x 10 mm V e r t . . . 1 0 , 0 0 0 X H o r i z . . . 2 , 0 0 0 X F i g . 16 (c) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . O l e i c A c i d 0 0 < W rt < o w o < rt rt co 0 . o 1 8 O O O 8" - f j O DATA --BEST F I T CURVE. 0 . 1 0.4 0.2 0.3 VELOCITY cm/sec F i g . 16 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . O l e i c A c i d 1 jllii H 1 F i g . 17 (a) R e c o r d e d F r i c t i o n F o r c e . . . H e x a n e V = 0.25 cm/sec F = 30.0 gm 0 60 W CJ rt 60. o rt E5 O 40. 1—I H U I—I rt 20. fe 0. O DATA BEST FIT CURVE O he _ § _0 1 0.1 0.2 0.3 VELOCITY cm/sec F i g . 17 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . 0.4 V = 0.125 cm/sec A = 4.5 x 10 ^ mm2 V e r t . . . 1 0 , 0 0 0 X H o r i z . . F i g . 17 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e Hexane 1,500 X ..Hexane s e < w rt < P w o < rt rt I—I p 2 . 0 . o o 8 o o - "8' o 8 -O DATA BEST FIT CURVE O J 2 O 8 F i g . 17 (d) 0.1 0.2 0.3 VELOCITY cm/sec D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . H e x a n e 0.4 F i g . 18 (a) R e c o r d e d F r i c t i o n V = 0.009 cm/sec F o r c e . . . H e p t a n e F = 35.0 gm 0 oo w 60. u fe o fe 40. B5 o 1—1 H U 20. H fe fe • he o o o LQxv^o. D o o _ O DATA BEST FIT CURVE 8- $ l F i g , 0.1 0.2 0.3 VELOCITY cm/sec 18 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . Heptane 0.4 V e r t . . . 1 0 , 0 0 0 X H o r i z . . . 1 , 5 0 0 X V = 0.25 cm/sec A = 2.0 x 1 0 " 6 mm2 c F i g . 18 (c) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . Heptane CM 0 6 <! w fe < n w o «! fe fe OTJ H P F i g 1 1 1 O DATA § BEST FIT CURVE \ 8r3x 8- 8 9 J 8 ( — i i i -< 0.1 0.2 0.3 0. VELOCITY cm/sec 18 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y ... Heptane F i g . 19 (a) R e c o r d e d F r i c t i o n F o r c e . . . M e t h y l A l c o h o l V = 0.009 cm/sec F = 33.0 gm e oo w u rt o rt 53 o IH H C_> H rt rt 60 . I 4 0 . 20. I 0 O DATA — BEST FIT CURVE § T 8 - ^ - 8 _ - 8 - - Q -8 1 i 0.1 0.4 0.2 0.3 VELOCITY cm/sec ' i g . 19 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . M e t h y l A l c o h o l V e r t . . . 1 0 , 0 0 0 X H o r i z . . . 2 , 0 0 0 X V = 0.044 cm/sec < w rt < o w u < rt rt co i—i P A = 2.4 x 10 6 mm2 c F i g . 19 (c) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . M e t h y l A l c o h o l ! ! 4 . T O DATA -- BEST FIT CURVE o o -8—8—8- •8 J 0.1 0.4 F i g 0.2 0.3 VELOCITY cm/sec 19 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . M e t h y l A l c o h o l 50 DISTURBANCE e 60 60 w u fe o * 40 85 O H H 20 H OH fe 0, F i g . 20 (a) R e c o r d e d F r i c t i o n F o r c e . . . P r o p y l A l c o h o l V = 0.044 cm/sec F = 42.0 gm — 1 1 O 1 DATA BEST FIT CURVE O — -© o o J £ o 8 - 8 — 8 -1 _ Q. O 1 _ o _ o J 1 0.1 0.2 0.3 0 VELOCITY cm/ sec F i g . 20 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . P r o p y l A l c o h o l V e r t . . .10,000 X H o r i z . . .1, 000 X V = 0.009 cm/sec A = 6.4 x 10 ^ mm^  F i g . 20 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . P r o p y l A l c o h o l 6 B < to-rt < a w u <J fe fe CO F i O o 0. cP 8 ^ 8 c r o 8 o _e 8 ° : 8 O DATA BEST F I T CURVE.. 0.1 0.4 0.2 0.3 VELOCITY cm/sec g. 20 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . P r o p y l A l c o h o l F i g . 21 (a) R e c o r d e d F r i c t i o n F o r c e . . . H e p t y l A l c o h o l V = 0.044 cm/sec F = 38.0 gm e w 60 o rt o rt 40 53 O H H o 20 H rt rt F i g -° O — -rv- — -so _ "Q o o O Cr- 1$ O DATA BEST FIT CURVE 0.1 0.4 0.2 0.3 VELOCITY cm/sec 21 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . H e p t y l A l c o h o l V = 0.001 cm/sec A = 5.3 x 10 ^ mm2 V e r t . . . 10,000 X H o r i z . . .3 , 000 X F i g . 21 (c) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . H e p t y l A l c o h o l 2 . _ D 0 ° O ^ •8" o 0_ 8 8 o o -8- --§ O DATA BEST FIT CURVE 0.1 0.2 0.3 0.4 VELOCITY cm/sec F i g . 21 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . H e p t y l A l c o h o l F i g . 22 (a) R e c o r d e d F r i c t i o n F o r c e . . . D e c y l A l c o h o l V = 0.044 cm/sec F = 42.0 gm 0 60 w u o to 40 53 o H H 20 o H to l -O o ° O - o O DATA BEST FIT CURVE O O XT CP 0.1 0.4 0.2 0.3 VELOCITY cm/sec 22 (b) F r i c t i o n F o r c e v e r s u s V e l o c i t y . . . D e c y l A l c o h o l \ L V = 0.044 cm/sec A 5.1 x 10 ^ mm^  F i g . c V e r t . . . 10,000 X H o r i z . . . 2 , 000 X 22 ( c ) R e c o r d e d F r i c t i o n T r a c k P r o f i l e . . . D e c y l A l c o h o l 4. 2 . " o o 8 o o "8" o 1 o 8 O DATA - - BEST F I T CURVE o— o o o-o o 0.1 - J 0.4 0.2 0.3 VELOCITY cm/sec F i g . 22 (d) D i s p l a c e d A r e a v e r s u s V e l o c i t y . . . D e c y l A l c o h o l 60 . 1 A. . B . . C . . I 1 1 1 .HIGH VACUUM NITROGEN AIR 1 1 E. . F. . G. . 1 1 1 1 1 .CAPROIC ACID .OLEIC ACID .HEXANE 1 1 I 1 1 1 1 V = 0.4 cm/sec 1 50 . — D. . . WATER H . . HEPTANE e 60 40. N . c .n-ALCOHOLS ; o -FORCE ( 30 . O ; O O LCTION 20. <; ' O O O O 0 pel fe 10. 0. o 1 O 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 A B C D E F G H / 1 2 3 4 5 6 7 8 9 10 11 12 N c ENVIRONMENT F i g . 23 E f f e c t of E n v i r o n m e n t on F r i c t i o n F o r c e Co 10.0 9.0 8.0 o 7.0 6.0 5.0 < £ 4.0 <! n g 3.0 fe w 2.0 h. 0 0.0 I 1 I 1 ! y i 1 I 1 1 1 1 1 1 1 1 1 1 1 _ A. ..HIGH VACUUM . E. . .CAPROIC ACID • V = 0.4 cm/sec B . ..NITROGEN F. . •OLEIC ACID _ C. . .AIR G. . .HEXANE D. ..WATER H . . •HEPTANE — N . c .n-ALCOHOLS O — — Q 0 O \ O . _ — 0 O — O P 0 o- — O 1 t 1 1 1 1 1 i I 1 1 1 i 1 1 1 1 ! 1 1 A B C D E F G H 1 2 3 4 5 6 7 8 9 10 11 12 ENVIRONMENT F i g . 2 4 E f f e c t of E n v i r o n m e n t on D i s p l a c e d A r e a example of t h e e f f e c t of d i s t u r b a n c e i s compared to d i s t u r b a n c e f r e e f o r c e i n F i g . 20. P r e v i o u s to r u n n i n g t h e e x p e r i m e n t s i t was n o t i c e d t h a t t h e d e s i g n of t h e s l i d e r a s s e m b l y was c a u s i n g an u n d e s i r a b l e moment to r e s u l t f r o m t h e f r i c t i o n f o r c e a c t i n g t h r o u g h a p l a n e 6.0 cm. below t h e h o r i z o n t a l a x i s of t h e t u r r e t . : The e f f e c t of t h i s moment was to r e d u c e t h e e f f e c t i v e n o r m a l l o a d on t h e diamond. From p r e l i m i n a r y t e s t s i t was d e t e r m i n e d t h a t t h e a v e r a g e f r i c t i o n f o r c e v a l u e was 25 gm. A c t i n g w i t h a moment arm of 6.0 cm t h i s p r o d u c e d a moment of 150 gm-cm. To n u l l i f y t h i s e f f e c t , a 20 gm w e i g h t was added to t h e l o a d tray w h i c h a c t e d on a moment arm of 7.5 cm. T h i s c a u s e d a 150 gm-cm moment i n t h e o p p o s i t e d i r e c t i o n . Mean f o r c e v a l u e s t e n d e d to be s c a t t e r e d . T h i s i s c h a r a c t e r i s t i c of f r i c t i o n b e h a v i o u r and i s g e n e r a l l y a t t r i b u t e d to t h e m i c r o s c o p i c i n c o n s i s t e n c i e s i n t h e c o m p o s i t i o n of t h e s u r f a c e of t h e s o l i d . The e x t e n t of s c a t t e r v a r i e d c o n s i d e r a b l y f r o m one medium to t h e n e x t and g e n e r a l l y t e n d e d to d e c r e a s e w i t h an i n c r e a s e i n v e l o c i t y . T e s t s c o n d u c t e d i n h i g h vacuum, n i t r o g e n , d i s t i l l e d w a t e r , c a p r o i c a c i d and m e t h y l a l c o h o l had r e l a t i v e l y l i m i t e d s c a t t e r . T r e n d s a r e w e l l d e f i n e d . B e s t f i t c u r v e s were d e t e r m i n e d a r i t h m e t i c a l l y and drawn t h r o u g h t h e d a t a p o i n t s to r e p r e s e n t t h e s e t r e n d s . The e q u a t i o n s of t h e s e l i n e s a r e g i v e n i n T a b l e I. The s t a n d a r d d e v i a t i o n s of t h e b e s t f i t c u r v e s a r e 10 p e r c e n t or b e t t e r . S c a t t e r i s much g r e a t e r i n t h e o t h e r c a s e s and t h e s t a n d a r d d e v i a t i o n s of t h e b e s t f i t c u r v e s a r e as h i g h as 37 p e r c e n t f o r d e c y l a l c o h o l . The r e l a t i o n s h i p between f r i c t i o n f o r c e and v e l o c i t y changed w i t h e n v i r o n m e n t . Water, G a p r o i c a c i d , o l e i c a c i d , d e c a n o l and p r o p a n o l e x h i b i t e d c o n s t a n t f r i c t i o n f o r c e . F o r c e f e l l r a p i d l y to a c o n s t a n t v a l u e w i t h an i n c r e a s e i n v e l o c i t y i n vacuum, n i t r o g e n , a i r , hexane, h e p t a n e and m e t h y l a l c o h o l . O n l y s l i d i n g i n h e p t a n o l e x h i b i t e d a r a p i d r i s e i n f o r c e w i t h an i n c r e a s e i n v e l o c i t y . In a l l c a s e s f r i c t i o n f o r c e t e n d e d to be c o n -s t a n t a t v e l o c i t i e s g r e a t e r t h a n 0.125 cm/sec. 4.1.2 C o m p a r i s o n to T h e o r y T h e o r e t i c a l v a l u e s of f r i c t i o n f o r c e were c a l c u l a t e d f o r s l i d i n g i n a i r and vacuum o n l y . T hese v a l u e s a r e compared to t h e e x p e r i m e n t a l r e s u l t s of s l i d i n g i n t h e s e m e d i a . T h r e e p a r a m e t e r s i n t h e d e r i v e d f o r c e e q u a t i o n (16) a r e c o n s t a n t s . They a r e t h e r a d i u s of t h e s l i d e r R = 0.05 mm., t h e n o r m a l l o a d N = 200 gm. and t h e ENVIRONMENT FRICTION FORCE DISPLACED AREA (gm) (mm ; HIGH VACUUM 9.3 V " 0 - 1 5 1.2 X I O " 6 v " ° - 23 NITROGEN 14.6 V " 0 - 0 5 1.9 X i o " 6 v " ° - 05 AIR 33.0 V - ° ' 0 4 3.1 X i o " 6 v - ° - 11 WATER 25.0 2.5 X i o ' 6 v"°- 01 CAPROIC ACID '2 5 . 0 1. 7 X i o " 6 v " ° - 14 OLEIC ACID 37 . 0 4.1 X i o " 6 v-°- 05 HEXANE 26.0 V " 0 - 0 6 3.4 X i o " 6 v - ° - 09 HEPTANE 25.0 V " 0 - 0 7 2 . 0 X i o " 6 v"°- 13 METHYL ALCOHOL 23.0 V " 0 - 0 5 1.9 X i o " 6 v " ° - 07 PROPYL ALCOHOL 36.0 3.7 X i o " 6 v - ° - 08 HEPTYL ALCOHOL 45.0 V 0 ' 0 3 4.9 X i o " 6 + 1. 4 x 1 0 _ 6 V DECYL ALCOHOL 37 . 0 4.2 X i o " 6 T a b l e I R e s u l t s o f Curve F i t t i n g Analysis;,.. . E q u a t i o n s of B e s t F i t C u r v e s c o n t a c t c o n s t a n t K = 0.6. The mean f l o w p r e s s u r e p and t h e s h e a r s t r e n g t h m were d e t e r m i n e d f o r the i n d i v i d u a l e n v i r o n m e n t s . The mean f l o w p r e s s u r e of g l a s s i n a i r was d e t e r m i n e d from diamond p y r a m i d h a r d n e s s (DPH) t e s t s . The d e t a i l s of t h e h a r d n e s s t e s t s a r e p r e s e n t e d i n A p p e n d i x V I . The measured DPH number was 530 and when d i v i d e d by t h e c o n v e r s i o n f a c t o r o f 2.7 as s u g g e s t e d by H o l l a n d [22] 2 t h i s c o n v e r t s to t h e y i e l d s t r e n g t h a = 196 kg/mm . T h i s 2 compares f a v o r a b l y to t h e v a l u e of 202 kg/mm o b t a i n e d by A i n s w o r t h [ 3 4 ] . The p r o j e c t e d a r e a of t h e i n d e n t a t i o n s was d e t e r m i n e d and t h e s t a t i c mean f l o w p r e s s u r e was 2 e v a l u a t e d by u s i n g e x p r e s s i o n ( 3 ) . Hence p g = 571 kg/mm . The r a t i o o f s t a t i c mean f l o w p r e s s u r e to y i e l d s t r e n g t h i s Pg/tf- = 571/196 = 2.9 w h i c h compares f a v o r a b l y w i t h t h e v a l u e o f 3 o b s e r v e d by Bowden and T a b o r . T h i s s u g g e s t s a p l a s t i c i n d e n t a t i o n . No f r a c t u r e was o b s e r v e d a round t h e i n d e n t a t i o n . From e x p r e s s i o n (5) t h e dynamic mean f l o w p r e s s u r e 2 i s p^ = 1713 kg/mm . T h i s v a l u e i s f o r g l a s s i n a i r . I t i s p o s s i b l e to e s t i m a t e t h e mean f l o w p r e s s u r e i n vacuum from an o b s e r v a t i o n by W a l t o n [35] t h a t p m i n c r e a s e s by a f a c t o r of about 3 i n vacuum from t h a t o b s e r v e d i n a i r . 2 T h i s s u g g e s t s a mean f l o w p r e s s u r e of 5139 kg/mm f o r s l i d i n g i n vacuum. The v a l u e s of sh e a r s t r e n g t h i n a i r and vacuum were o b t a i n e d from t a b l e s c o m p i l e d by Bowden and Tabor [25] and S t a n w o r t h [ 3 6 ] r r e s p e c t i v e l y . The v a l u e s a r e s t a t i s t i c a l a v e r a g e s of sh e a r t e s t s c o n d u c t e d on g l a s s s p e c i m e n s . A c t u a l s h e a r s t r e n g t h s of s p e c i f i c g l a s s s l i d e s depend on age, c o m p o s i t i o n and s u r f a c e h i s t o r y and may 2 v a r y from t h e s e a v e r a g e s . X = 200 kg/mm f o r a i r and 2 A = 178 kg/mm i n vacuum. The d i f f e r e n c e , : " . i t has been r e a s o n e d , may be due to t h e p r e s s u r e v a r i a t i o n .ov' t h e p r e s e n c e of water v a p o u r i n t h e a i r . S u b s t i t u t i n g t h e s e v a l u e s i n t o t h e d e r i v e d e x p r e s s i o n s f o r c r o s s - s e c t i o n a l a r e a e q u a t i o n ( 1 2 ) , and f r i c t i o n f o r c e e q u a t i o n • (16) t h o s e v a l u e s were d e t e r m i n e d and a r e p r e s e n t e d i n T a b l e I I a l o n g w i t h t h e c o r r e s p o n d i n g e x p e r i m e n t a l r e s u l t s . 4.1.3 D i s p l a c e d A r e a T r a c k p r o f i l e s showed t h e p r e s e n c e of two o r t h r e e d i s t i n c t t r o u g h s . P r o f i l e s were not c o n s i s t e n t from t e s t to t e s t . An e x a m i n a t i o n of t h e c u t t i n g t i p of t h e m kg/mm2 • A • kg/mm2 A c (THEORETICAL) 2 i n 6 mm x 10 A. (EXPERIMENTAL) mm2 x 10^ DIFFERENCE P S F (THEORETICAL) gm gm gm F (EXPERIMENTAL) gm % DIFFERENCE HIGH VACUUM 5139 178 1.0 1.5 33.3 4.9 6.9 11.8 11.0 7.7 AIR 1713 200 4.9 3.4 44.2 8.5 23.4 31.9 34.0 6.1 ><d IN BOTH HIGH VACUUM AND AIR R = 0.05 mm , N = Or.2 kg ; , , K = 0.6 TABLE IT Comparison 6 f._The.qr.etical and E x p e r i m e n t a l R e s u l t s 61 diamond shown i n a f r o n t a l p r o j e c t i o n i n F i g . 16 r e v e a l s t h r e e major c u t t i n g a s p e r i t i e s . T hese may a c c o u n t f o r t h e t h r e e t r o u g h s . The s l i d e r was removed f o r c a l i b r a t i o n between t e s t s and a s l i g h t v a r i a t i o n i n o r i e n t a t i o n may have r e s u l t e d upon i n s t a l l a t i o n . T h e r e i s d i s t i n c t e v i d e n c e of b u i l t - u p edges on p r o f i l e s of s c r a t c h e s made i n v a c u u m , n i t r o g e n and t h e f o u r a l c o h o l s . The c r o s s - s e c t i o n a l a r e a s 'A 1 of t h e s e P b u i l t - u p edges were measured. The amount of d i s p l a c e d m a t e r i a l t h a t was pushed i n t o t h e f o r m c o f b u i l t - u p edges i s compared to t h e amount of m a t e r i a l d i s p l a c e d i n F i g . 25. The r a t i o of A /A i s p l o t t e d a g a i n s t e n v i r o n m e n t , p c r ° Hexane e x h i b i t e d t h e l e a s t amount of m a t e r i a l p l o u g h e d i n t o r a i s e d s h o u l d e r s . D i s p l a c e d a r e a i s p l o t t e d a g a i n s t v e l o c i t y i n F i g s . 1 1 - 2 2 and ; against e n v i r o n m e n t i n F i g . 24. The d a t a p l o t t e d a g a i n s t v e l o c i t y i s c o n s i d e r a b l y s c a t t e r e d i n a l l c a s e s a l t h o u g h t r e n d s can be o b s e r v e d . A g a i n b e s t f i t c u r v e s were o b t a i n e d a r i t h m e t i c a l l y and drawn t h r o u g h t h e d a t a p o i n t s to r e p r e s e n t t h e t r e n d s . D e t a i l s of t h e c u r v e f i t t i n g t e c h n i q u e a r e g i v e n i n A p p e n d i x V I I . L i n e a r c u r v e s a r e a p p a r e n t i n w a t e r , h e p t y l a l c o h o l and d e c y l a l c o h o l . A l l o t h e r s e x h i b i t an i n i t i a l d rop i s d i s p l a c e d a r e a b e f o r e f l a t t e n i n g o u t . 1.0 0.9 0.8 0.7 0.6 0.5 A P c 0.4 0.3 0.2 0.1 0.0 1 I I 1 I I I I 1— I— i 1—1—I 1—I—I 1—I r A. . .HIGH VACUUM B. ..NITROGEN C . . .AIR D. . .WATER E. ..OLEIC ACID F. ..CAPROIC ACID G. ..HEXANE H. . .HEPTANE N ..n-ALCOHOLS c J I 0 I I Ci £ _ _ D _ J I L 0.4 cm/sec O O J I I I 1 I A B C D E F G H 1 2 4 5 6 7 8 9 10 11 12 N ENVIRONMENT F i g . 25 E f f e c t o f E n v i r o n m e n t on the E x t e n t o f R a i s e d Edge M a t e r i a l An o p t i c a l e x a m i n a t i o n of t h e f r i c t i o n t r a c k s r e v e a l e d no c h i p d e b r i s . A l l t r a c k s were smooth s i d e d and of u n i f o r m w i d t h . CHAPTER V 5.1 D i s c u s s i o n The p u r p o s e of t h i s work was to o b s e r v e t h e f r i c t i o n b e h a v i o u r of p l o u g h i n g c o n d u c t e d i n a v a r i e t y of e n v i r o n m e n t s . An e x p e r i m e n t a l a p p a r a t u s was d e s i g n e d to p r o d u c e s h a l l o w p l a s t i c f r i c t i o n t r a c k s by s l i d i n g a r o u g h l y s p h e r i c a l diamond on a s o d a - l i m e g l a s s s u r f a c e . A s i m p l e t h e o r y a c c o m p a n i e s t h e r e s u l t s to p r o v i d e some u n d e r s t a n d i n g of t h e b a s i c mechanisms i n v o l v e d d u r i n g s l i d i n g . The t h e o r y does n o t a c c o u n t f o r b o u n d a r y l u b r i c a t i o n e f f e c t s and i t can o n l y be a p p l i e d to vacuum and open a i r c o n d i t i o n s . The c l o s e , a g r e e m e n t between the t h e o r y and t h e d a t a t e n d s to s u g g e s t t h a t t h e r e l a t i v e l y s i m p l e t h e o r e t i c a l a s s u m p t i o n s a r e v a l i d ( r e f e r to T a b l e I I ) . The d a t a shows w e l l d e f i n e d t r e n d s when p l o t t e d a g a i n s t v e l o c i t y ( r e f e r to F i g s . 1 1 - 2 2 ) . S c a t t e r i s l i m i t e d i n d i c a t i n g t h e r e l a t i v e r e p r o d u c e a b i l i t y of t h e d a t a . F r i c t i o n f o r c e t e n d s to e i t h e r d r o p r a p i d l y to a f l a t c u r v e a t v e l o c i t i e s below 0.1 cm/sec. or to r e m a i n f l a t o v e r t h e f u l l r a n g e of v e l o c i t i e s . O n l y i n t h e c a s e of h e p t y l a l c o h o l d i d f r i c t i o n f o r c e r i s e i n i t i a l l y w i t h v e l o c i t y . C l a y t o n [ 371. p r o p o s e d an e x p l a n a t i o n f o r t h e f i r s t k i n d of b e h a v i o u r . At r e l a t i v e l y h i g h s l i d i n g s p eeds ( 0.1 cm/sec) the t i m e of l o c a l i z e d c o n t a c t between t h e s u r f a c e s i s r educ ed ".and, as a r e s u l t , so i s t h e c o n t a c t a r e a . T h i s amounts to a d e c r e a s e i n f r i c t i o n f o r c e as a r e s u l t of a r e d u c t i o n i n t h e s h e a r i n g component ( i . e . a b o u n d a r y l u b r i c a t i o n e f f e c t ) . I t i s c l e a r f r o m t h e t h e o r y t h a t an i n c r e a s e i n mean f l o w p r e s s u r e due to a r e d u c t i o n : . i n t h e a v a i l a b l e t i m e of l o c a l e n e r g y d i s s i p a t i o n s u c h as o b s e r v e d by Kurnakov and Zhemchuzhny [28] can a l s o have the e f f e c t of r e d u c i n g t h e f r i c t i o n f o r c e . T h i s e f f e c t would a l s o a c c o u n t f o r t h e o b s e r v e d d e c r e a s e i n c r o s s - s e c t i o n a l a r e a . I t i s r e a s o n a b l e to assume t h a t b o t h e f f e c t s c o u l d o c c u r s i m u l t a n e o u s l y i n t h e p r e s e n c e of a l i q u i d medium. C l a y t o n a l s o o b s e r v e d s i m i l a r b e h a v i o u r to t h a t o b s e r v e d f o r s l i d i n g i n h e p t a n o l . He r e a s o n e d t h a t a s u r f a c e a c t i v e medium has g r e a t e r t i m e f o r p h y s i c a l a d s o r p t i o n onto t h e s u r f a c e when t h e s l i d e r i s moving a t slow v e l o c i t i e s hence the medium r e d u c e s t h e c o n t a c t a r e a and s u b s e q u e n t l y t h e f r i c t i o n f o r c e . I t i s p o s s i b l e t h a t a c o m b i n a t i o n of t h e Kurnakov e f f e c t and t h i s l a t t e r e f f e c t c o u l d p r o d u c e a f l a t f r i c t i o n f o r c e c u r v e s i m i l a r to t h a t o b s e r v e d i n t h e w a t e r e n v i r o n m e n t . S o u t h w i c k [38] o b s e r v e d t h e same b e h a v i o u r w h i l e s l i d i n g g l a s s on g l a s s i n w a t e r . A l l t h e e n v i r o n m e n t a l media i n c r e a s e d m a t e r i a l r e m o v a l beyond t h a t o b s e r v e d i n h i g h vacuum. These R e h b i n d e r e f f e c t s a r e shown i n F i g . 24. The r e s u l t s confirm R e h b i n d e r ' s o b s e r v a t i o n s t h a t m a t e r i a l d i s p l a c e m e n t i s enhanced by a medium t h a t i n c r e a s e s t h e p l a s t i c i t y of a s o l i d . S c a n n i n g e l e c t r o n m i c r o g r a p h s of t h e f r i c t i o n t r a c k s i n d i c a t e d an i n c r e a s e i n t h e e x t e n d of p l a s t i c f l o w i n s c r a t c h e s made i n h e p t a n o l , p r o p a n o l , d e c a n o l and o l e i c a c i d . T r a c k s p r o d u c e d i n t h o s e media r e v e a l e d a s e r i e s of a r c - s h a p e d h e r t z i a n - t y p e c r a c k s r u n n i n g a c r o s s t h e w i d t h of s c r a t c h e s made a t v e l o c i t i e s g r e a t e r t h a n 0.044 cm/sec. These m i c r o g r a p h s a r e shown i n F i g . 26.. From the c u r v a t u r e of t h e c r a c k s i t i s s u s p e c t e d t h a t t h e y were formed b e h i n d . t h e s l i d e r where t h e e l a s t i c t e n s i l e s t r e s s e s were the g r e a t e s t [ 3 5 ] . The f r e q u e n c y and e x t e n t of c r a c k i n g v a r y c o n s i d e r a b l y a l o n g t h e t r a c k . These v a r i a t i o n s a r e a c c u r a t e l y r e f l e c t e d i n t h e i r r e g u l a r i t y of t h e f r i c t i o n f o r c e w i t h d i s t a n c e as r e c o r d e d on t h e s t r i p c h a r t . The f a c t t h a t p l a s t i c t e a r i n g i s n o t o b s e r v e d a t t h e l o w e r v e l o c i t i e s c o u l d be t h e r e s u l t of a h a r d e r s o l i d or r e d u c e d s t r e s s e s due to t h e e f f e c t s of i n c r e a s e d t i m e of a d s o r p t i o n as s u g g e s t e d by C l a y t o n . T h e r e i s q u a l i t a t i v e s i m i l a r i t y w i t h t h e r e s u l t s of t h i s work and t h e r e s u l t s of d r i l l i n g e x p e r i m e n t s o b s e r v 67 ( i ) H i g h Vacuum M a g n i f i e d 2000 X V = 0.044 cm/sec ( i i ) H e p t y l A l c o h o l M a g n i f i e d 2000 X V = 0.025 cm/sec SLIDING DIRECTION FOR ALL CASES ^ ( i i i ) O l e i c A c i d M a g n i f i e d 2000 X V = 0.094 cm/sec ( i v ) O l e i c A c i d M a g n i f i e d 4000 X V = 0.094 cm/sec F i g . 26 S c a n n i n g E l e c t r o n M i c r o g r a p h s o f F r i c t i o n T r a c k s by Nadeau [21] and Westwood, M a c M i l l a n and H u n t i n g t o n [12] A c o m p a r i s o n i s shown i n F i g . 27. The e x p e r i m e n t a l e v i d e n c o n f i r m s t h a t , of t h o s e media t e s t e d , h e p t a n o l p r o d u c e d t h optimum m a t e r i a l r e m o v a l . I t i s i n t e r e s t i n g to n o t e t h a t h e p t a n o l enhanced b o t h b r i t t l e e l a s t i c f r a c t u r e as o b s e r v e d by Westwood and Nadeau, and p l a s t i c d i s p l a c e m e n t as o b s e r v e d i n t h i s work. The : shape cof.: the _ s i i d er a p p e a r s to have s i g n i f i c a n t l y c o n t r i b u t e d to t h e n a t u r e of t h e m a t e r i a l r e m o v a l . The diamond a s p e r i t i e s w i t h t h e i r s m a l l r a d i i p r o d u c e d a s l i d i n g f r i c t i o n f o r c e w i t h a l a r g e p l o u g h i n g term. The t h e o r y s u g g e s t s t h a t i t can be as h i g h as 42 p e r c e n t o f t h e t o t a l f r i c t i o n f o r c e ( r e f e r to T a b l e I I ) . Boundary l u b r i c a t i o n e f f e c t s were n o t as n o t i c e a b l e as i n Westwood's work. Westwood n o t e d t h a t f r i c t i o n f o r c e d r o p p e d l i n e a r l y w i t h an i n c r e a s e i n m o l e c u l a r c h a i n l e n g t h . T h i s i s a c o n f i r m a t i o n of the s l i d i n g f r i c t i o n r e s u l t s of Hardy and D o u b l e d a y [39] who a t t r i b u t e d t h i s b e h a v i o u r to a r e d u c t i o n i n t h e r e a l a r e a of c o n t a c t as c h a i n l e n g t h i n c r e a s e . T h i s b e h a v i o u r was n o t o b s e r v e d i n t h e p r e s e n t work. T h i s i s a t t r i b u t e d to t h e s m a l l e r r a d i u s of t h e s l i d e r u s e d . F r i c t i o n t r a c k s e x h i b i t e d b u i l t - u p edges and no s i g n s of e l a s t i c a l l y p r o d u c e d c h i p d e b r i s to i n d i c a t e b r i t t l e f r a c t u r e . I t was n o t e d t h a t t h e e x t e n t of b u i l t - u p edges was d ependent on t h e geometry 6 9 F i g . 27 Comparison of Present Results to Previous Work t h e s l i d e r . The d e e p e r p e n e t r a t i o n ' s 'were acc o m p a n i e d by more p r o m i n e n t p l o u g h - u p s h o u l d e r s . I t i s p o s s i b l e t h a t m a t e r i a l was compressed b e n e a t h t h e s l i d e r as w e l l a l t h o u g h t h e r e i s no e x p e r i m e n t a l v e r i f i c a t i o n of t h i s . An i n t e r e s t i n g c o m p a r i s o n i s made between the enhancement of m a t e r i a l r e m o v a l f r o m t h a t o b s e r v e d i n vacuum and t h e e x t e n t of s u r f a c e a c t i v i t y of t h e l i q u i d media as r e v e a l e d i n t h e l i t e r a t u r e . I t i s w e l l e s t a b l i s h e d t h a t e x p o s u r e to water or water v a p o u r f a c i l i t a t e s c r a c k growth i n g l a s s [ 3 5 ] . T h i s i s c o n f i r m e d by t h e r e s u l t s of t h i s work. I t i s t h e r e f o r e p o s s i b l e t h a t t h e i n c r e a s e i n b o t h f r i c t i o n f o r c e and m a t e r i a l d i s p l a c e m e n t o b s e r v e d i n t h e n i t r o g e n a t m o s p h e r e was due to t h e p r e s e n c e of water v a p o u r . An a n a l y s i s of t h e n i t r o g e n d i d r e v e a l a p p r e c i a b l e t r a c e s of water v a p o u r as h i g h as 3 p e r c e n t by volume. The e f f e c t of t h e p r e s s u r e d i f f e r e n c e c a n n o t t h e r e f o r e be d e t e r m i n e d i n l i g h t of t h i s f a c t . I t i s also s u s p e c t e d t h a t t h e l i q u i d media c o n t a i n e d t r a c e s of w ater a l t h o u g h no t e s t s were c o n d u c t e d to s u b s t a n t i a t e t h i s s u s p i c i o n . S i n c e water i n m i n u t e amounts can i n f l u e n c e t h e f l o w and f r a c t u r e p r o p e r t i e s of g l a s s [ 1 3 ] , to p r o p e r l y d e t e r m i n e the R e h b i n d e r e f f e c t s p r o d u c e d by a s p e c i f i c l i q u i d medium, i t s w ater c o n t e n t must be r e d u c e d . S t u d i e s on t h e e f f e c t s of a d s o r b e d a c t i v e s p e c i e s on g l a s s s u r f a c e s have shown t h a t o l e i c a c i d has a g r e a t e r a f f i n i t y f o r t h e s o l i d t h a n e i t h e r w a ter or. s h o r t c h a i n l e n g t h a l c o h o l s [40] f o r m i n g s t r o n g e r , more permanent bonds w i t h t h e s u r f a c e . I t has a n a e v e n ' g r e a t e r a f f i n i t y f o r t h e g l a s s t h a n does c a p r o i c a c i d . S h a f r i n [41] o b s e r v e d t h a t when t h e number of c a r b o n atoms i n t h e m o l e c u l a r c h a i n i s l e s s t h a n or e q u a l to 12 ( i . e . n S 12) the f l u i d bonds w e a k l y to t h e s u r f a c e and i s e a s i l y s q u e e z e d out of c r a c k s when t h e s o l i d i s s u b j e c t e d to c o m p r e s s i v e f o r c e s . C a p r o i c a c i d has 6 c a r b o n atoms i n i t s m o l e c u l a r c h a i n . However when n > 16 s u c h as i n t h e c a s e of o l e i c a c i d w h i c h has 18 c a r b o n atoms i n i t s c h a i n , t h e a d s o r b e d m o n o l a y e r forms a s o l i d c h e m i c a l bond. U s i n g R e h b i n d e r ' s e x p l a n a t i o n t h a t i n c r e a s i n g t h e a f f i n i t y of t h e medium f o r t h e s u r f a c e of t h e s o l i d e nhances t h e t e n d e n c y of t h e s o l i d to f l o w p l a s t i c a l l y , t h i s would a c c o u n t f o r o l e i c a c i d e x h i b i t i n g s u c h a s t r o n g i n f l u e n c e on t h e f r i c t i o n b e h a v i o u r . F u r t h e r i n v e s t i g a t i o n of t h e c h e m o m e c h a n i c a l i n t e r a c t i o n s between g l a s s and o t h e r l i q u i d media must be c o n d u c t e d i n c o n j u n c t i o n w i t h t h e s t u d y of R e h b i n d e r e f f e c t s . 5.2 C o n c l u s i o n s The r e s u l t s of t h e p r e s e n t r e s e a r c h a l l o w t h e f o l l o w i n g c o n c l u s i o n s to be drawn: A. S c r a t c h i n g g l a s s w i t h a r o u g h l y s p h e r i c a l diamond p r o d u c e d optimum m a t e r i a l d i s p l a c e m e n t when c o n d u c t e d i n an e n v i r o n m e n t of h e p t y l a l c o h o l . T h i s i s i n agreement w i t h p r e v i o u s s t u d i e s . B. An i n c r e a s e i n m a t e r i a l r e m o v a l c o i n c i d e d w i t h t h e enhancement of t h e p l a s t i c f l o w b e h a v i o r of t h e g l a s s . T h i s c o n f i r m s R e h b i n d e r ' s o b s e r v a t i o n s . C. No n e g a t i v e R e h b i n d e r e f f e c t s were o b s e r v e d . In a l l g a s e o u s and l i q u i d e n v i r o n m e n t s m a t e r i a l r e m o v a l was g r e a t e r t h a n t h a t o b s e r v e d i n t h e d r y f r i c t i o n s t a t e . D. An e x p e r i m e n t a l a p p a r a t u s was d e v e l o p e d c a p a b l e of p r o d u c i n g smooth f r a c t u r e - f r e e f r i c t i o n t r a c k s on g l a s s m i c r o s l i d e s a t s l i d e r s p eeds below 0.4 cm/sec and i n a v a r i e t y of e n v i r o n m e n t s . E x p e r i m e n t a l r e s u l t s d i s p l a y e d w e l l d e f i n e d t r e n d s i n d i c a t i n g a f a v o u r a b l e d e g r e e of r e p r o d u c e a b i l i t y . E. F r i c t i o n b e h a v i o u r i n n i t r o g e n d i f f e r s by l e s s t h a n 35 p e r c e n t f r om t h a t o b s e r v e d i n h i g h vacuum. T h i s d i f f e r e n c e may be a t t r i b u t e d more to t h e p r e s e n c e of w ater v a p o u r i n t h e n i t r o g e n t h a n to t h e p r e s s u r e a d j u s tment. F. G e n e r a l l y an i n c r e a s e i n m a t e r i a l r e m o v a l c o r r e s p o n d e d to an i n c r e a s e i n f r i c t i o n f o r c e . A s i m p l e t h e o r e t i c a l f o r m u l a was used s u c c e s s f u l l y to p r e d i c t t h i s b e h a v i o u r i n a i r and h i g h vacuum. O n l y t h e v a l u e s of f l o w p r e s s u r e and s h e a r s t r e n g t h of the m a t e r i a l were changed w i t h the e n v i r o n m e n t . The p r e d o m i n a n t e f f e c t of t h e w ater v a p o u r i n t h e a i r was to l o w e r t h e mean f l o w p r e s s u r e t h e r e b y i n c r e a s i n g b o t h the f r i c t i o n f o r c e and the m a t e r i a l r e m o v a l . 5.3 S u g g e s t i o n s F o r F u t u r e R e s e a r c h T h r e e a s p e c t s o f the e x p e r i m e n t a l s e t - u p can be i m p r oved f o r f u t u r e work. A diamond w i t h a more u n i f o r m p r o f i l e s h o u l d be used to c o n t r o l t h e geometry of the f r i c t i o n t r a c k s p r o d u c e d . T h i s improvement would e l i m i n a t e v a r i a t i o n s i n the m a t e r i a l f l o w p a t t e r n s c a u s e d by uneven s l i d e r p r o f i l e . Water c o n t e n t i n t h e l i q u i d media s h o u l d be r e d u c e d as much as p o s s i b l e . The use of w ater a b s o r b i n g compounds would p e r m i t the media to be j u d g e d on t h e i r own m e r i t s as m a t e r i a l s o f t e n i n g a g e n t s w i t h o u t the i n f l u e n c e of w a t e r . The s l i d e r a s s e m b l y s h o u l d be r e - d e s i g n e d as shown i n F i g . 28 to e l i m i n a t e the moment p r o d u c e d by t h e f r i c t i o n f o r c e . The diamond t i p must a c t on the same p l a n e as t h e h o r i z o n t a l a x i s of r o t a t i o n a c t i n g t h r o u g h the t u r r e t . I n t h i s manner the e f f e c t i v e l o a d on the diamond t i p w i l l a l w a y s be t h e w e i g h t s u p p o r t e d by t h e l o a d t r a y . 75 BIBLIOGRAPHY 1. E d i s o n , T.A., T e l e g r . J o u r n a l , 5, 1 8 9 , ( 1 8 7 7 ) . 2. R e h b i n d e r , P.A., P r o c . 6 t h P h y s i c s Conf. Moscow, ( 1 9 2 8 ) . 3. R e h b i n d e r , P.A., "New P h y s i c o - C h e m i c a l Phenomena i n the D e f o r m a t i o n and M e c h a n i c a l T r e a t m e n t of S o l i d s " , N a t u r e ( L o n d o n ) , 159 [ 4 0 5 2 ] , 866-67, ( 1 9 4 7 ) . 4. R e h b i n d e r , P.A., S c h r e i n e r , L.A.., and Z h i g a c h , K.F., "H a r d n e s s R e d u c e r s i n Rock D r i l l i n g " , C.S.L.R.O., M e l b o u r n e , A u s t r a l i a , ( 1 9 4 8 ) . 5. Westbrook, J.H. and J o r g e n s e n , P . J . , " I n d e n t a t i o n Creep o f S o l i d s " , T r a n s . AIME, 233 [2] 425-28, (1965) . 6. Westwood, A.R.C., G o l d h e i m , D.L. and L y e , R.C., " R e h b i n d e r E f f e c t s i n MgO", ( 1 9 6 7 ) , P h i l . Mag., 16, 505. 7. Westwood, A.R.C., G o l d h e i m , D.L. and L y e , R.C., " F u r t h e r O b s e r v a t i o n on R e h b i n d e r E f f e c t s i n MgO", ( 1 9 6 8 ) , P h i l . Mag., 17, 951-959. 8. Westwood, A.R.C., M a c M i l l a n , N.H., and K a l y o n c u , R.S., " E n v i r o n m e n t - S e n s i t i v e H a r d n e s s and M a c h i n a b i l i t y of A l 0 " , J . Amer. Ceram. S o c , 56 [ 5 ] , 258-262 , (1973 j . 5 9. Westwood, A.R.C., Swain, M.V. and L a t a n i s i o n , R.M., " F u r h t e r S t u d i e s on E n v i r o n m e n t - S e n s i t i v e H a r d n e s s and M a c h i n a b i l i t y o f A 1 » 0 ", J.Amer. Ceram. Soc., 58 [9-10] 372-376, ( 1 9 7 5 ) . 10. Westwood, A.R.C. and G o l d h e i m , D . L . , " O c c u r r e n c e and Mechanism o f R e h b i n d e r E f f e c t s i n CaF ", J . A p p l . P h y s . , 39 [ 7 ] , 3401-3405, ( 1 9 6 8 ) . 11. Westwood, A.R.C. and G o l d h e i m , D.L., "Mechanism f o r E n v i r o n m e n t a l C o n t r o l o f D r i l l i n g i n MgO and CaF^ M o n o c r y s t a l s " , J . Amer. Ceram. Soc., 53 [ 3 ] , 142-47, (1970) . 12. Westwood, A.R.C., M a c M i l l a n , N.H. and H u n t i n g t o n , R . D . , "Chemomechanical C o n t r o l o f S l i d i n g F r i c t i o n B e h a v i o r i n N o n - M e t a l s " , M.M.L. T e c h n i c a l R e p o r t , (Nov. 1974). 13. W i e d e r h o r n , S.M. and R o b e r t s , D.E., " I n f l u e n c e of Normal A l c o h o l s on the A b r a s i v e Wear of G l a s s " , Wear, 32, ( 1 9 7 5 ) , 51-72. 14. G n i r k , P.E. and Cheatham, J.B., " I n d e n t a t i o n E x p e r i m e n t s on Dry Rocks Under P r e s s u r e " , J . P e t . T e c h . , ( S e p t . 1963), 1031-1039. 76 15. G n i r k , P.E. and Cheatham, J.B., "An E x p e r i m e n t a l Study of S i n g l e B i t - T o o t h P e n e t r a t i o n i n t o Dry Rock a t C o n f i n i n g P r e s s u r e s 0 to 5, 000 psiV,S.oc. P e t . Eng. J . , (June 1965), 117-130. 16. G n i r k , P.E. and Cheatham, J.B., "A T h e o r e t i c a l D e s c r i p t i o n of R o t a r y D r i l l i n g f o r I d e a l i z e d Down-Hole B i t / R o c k C o n d i t i o n s " , Soc. P e t . Eng. J . , (Dec. 1969), 443-450. 17. G a r n e r , N.E., " C u t t i n g A c t i o n of a S i n g l e Diamond Under S i m u l a t e d B o r e h o l e C o n d i t i o n s " , J . P e t . T e c h . , (June 1967), 937-942. 18. Rowley, D.S. and A p p l , F.C., " A n a l y s i s of t h e C u t t i n g A c t i o n of a S i n g l e Diamond", Soc. P e t . Eng. J . , ( S e p t . 1968), 269-280. 19. Rowley, D.S. and A p p l , F.C., " A n a l y s i s of S u r f a c e Set Diamond B i t Pef ormance 1', Soc. P e t . Eng. J . , {Sept. 1969), 301-310. 20. E c k e l , J.R., " E f f e c t of P r e s s u r e on Rock D r i l l a b i l i t y " , P e t . T r a n s . AIME, ( 1 9 5 8 ) , V o l . 213. 21. Nadeau, J . S . , " E n v i r o n m e n t a l . E f f e c t s i n Comminution and Rock D r i l l i n g " , ( 1 9 7 5 ) , R e p o r t to E n e r g y , M i n e s and R e s o u r c e s . 22. H o l l a n d , L., "The P r o p e r t i e s of G l a s s S u r f a c e s " , Chapman and H a l l , London, ( 1 9 6 4 ) , pp. 59. 23. Bowden, F.P. and T a b o r , D., "The F r i c t i o n and L u b r i c a t i o n of S o l i d s " , V o l . I.,. O x f o r d P r e s s , London, (1 9 5 0 ) , pp. 90. 24. K r a g e l s k i i , I.V., " F r i c t i o n and Wear", B u t t e r w o r t h s , London, ( 1 9 6 5 ) , pp. 165. 25. Bowden, F.P. and T a b o r , D., "The F r i c t i o n and L u b r i c a t i o n of S o l i d s " , V o l . I I , O x f o r d P r e s s , London, (1964) pp. 348. 26. I b i d . , pp. 323. 27. I b i d . , pp. 335. 28. Kurnakov, N.C. and Zhemchuzhny, S.F., " F l u i d P r e s s u r e and Hardness..of P l a s t i c B o d i e s " , S. P e t e r s b . P o l i t e k h . I n s t . , 19, ( 1 9 1 3 ) . 29. Bowden, F.P., and T a b o r , D., "The F r i c t i o n and L u b r i c a t i o n of S o l i d s " , V o l . I I , O x f o r d P r e s s , London, ( 1 9 6 4 ) , pp. 125. 77 30. K r a g e l s k i i , I.V., " F r i c t i o n and Wear", B u t t e r w o r t h s , London, 1965, pp. 9. 31. G r e e n , M.A.C., " V i s c o e l a s t i c E f f e c t s i n Boundary Lubrication!;',, Ph.D. T h e s i s , Department of M e c h a n i c a l E n g i n e e r i n g , The U n i v e r s i t y of B r i t i s h C o l u m b i a , ( 1 9 7 4 ) . 32. McGregor, K., "The D r i l l i n g of Rock", M a c L a r e n , London ( 1 9 6 7 ) , pp. 185. 33. P f l e i d e r , E.P., "Diamond O r i e n t a t i o n i n D r i l l B i t s " , T r a n s . AIME, (Feb. 1952), 177-186. 34. A i n s w o r t h , L., J . Soc. G l a s s T e c h . , 38, 479-536, ( 1 9 5 4 ) . 35. W a l t o n , W.H., " M e c h a n i c a l P r o p e r t i e s of N o n - M e t a l l i c B r i t t l e M a t e r i a l s " , B u t t e r w o r t h s , London, ( 1 9 5 8 ) , pp. 69. 36. S t a n w o r t h , J . E . , " P h y s i c a l P r o p e r t i e s of G l a s s " , O x f o r d P r e s s , London, ( 1 9 5 0 ) , pp. 114. 37. C l a y t o n , D., "An I n t r o d u c t i o n to Boundary and Extreme P r e s s u r e L u b r i c a t i o n " , Br. J . A p p l . Phys., 2nd S u p p l . , 1, ( 1 9 5 1 ) , 25. 38. S o u t h w i c k , R.D., "The S t r e n g t h of A b r a d e d G l a s s " , P a r t V I I , P r e s t o n Lab. Rep. No. 57-077, ( 1 9 5 7 ) . 39. Hardy, W.B. and D o u b l e d a y , I . , "Boundary L u b r i c a t i o n — The P a r a f f i n S e r i e s " , P r o c . Roy. S o c , A100, (1922) 550. 40. H o l l a n d , L., "The P r o p e r t i e s of G l a s s S u r f a c e s " , Chapman and H a l l , London, ( 1 9 6 4 ) , pp. 379. 41. S h a f r i n , E.C., "The L u b r i c a t i n g P r o p e r t i e s of Monomo1ecular F i l m s A d s o r b e d on S o l i d S u r f a c e s " , Rep. U.S. Nav. Res. Lab. P r o g r e s s , ( J u l y 1958). APPENDIX I CALIBRATION OF SLIDER ARM C a l i b r a t i o n of s l i d e r arm d i s p l a c e m e n t was done i n a manner as shown i n F i g . A . I . I . The w e i g h t s were s u p p o r t e d on a t r a y hung by a s t r i n g w h i c h was f a s t e n e d d i r e c t l y below t h e diamond c u t t i n g t i p by means of an a u x i l i a r y c o l l a r . D i s p l a c e m e n t of t h e s l i d e r arm was measured w i t h a d e p t h m i c r o m e t e r r i g i d l y mounted to t h e s u p p o r t b a s e . R e - c a l i b r a t i o n between t e s t r u n s was a c h i e v e d by s e t t i n g up t h e c a l i b r a t i o n a p p a r a t u s i n t h e same manner and l o a d i n g 100 gm to t h e l o a d t r a y . A c o n v e n i e n t s c a l e was t h e n s e l e c t e d on t h e B r u s h c h a r t r e c o r d e r w h i c h r e c o r d e d beam d e f l e c t i o n . In most c a s e s a c h a r t s c a l e of 5.0 gm/div. was u s e d . The s l i d e r arm d e f l e c t i o n i s t a b u l a t e d a g a i n s t l o a d i n T a b l e A V.I.I. DEPTH MICROMETER MICROMETER MOUNT COLLAR DIAMOND STRING WEIGHT & TRAY F i g . A . I . I . Set-up f o r C a l i b r a t i o n of S l i d e r Arm APPLIED LOAD (kg) DEFLECTION (mm) 0.00 0.0000 0.31 0.0254 0.76 0.0635 1.2 2 0.1016 1.67 0.1397 2 .13 0.1778 2 .58 0.2159 T a b l e A . I . I . C a l i b r a t i o n o f S l i d e r Arm D e f l e c t i o n w i t h Load APPENDIX I I MICRO-SLIDE GLASS COMPOSITION Type: C o r n i n g Type 2947 s o d a - l i m e g l a s s m i c r o s c o p e s l i d < D i m e n s i o n s : 1 i n . x 3 i n . x 0.96 mm" C o m p o s i t i o n : SiO, A 1 2 0 3 MgO N a 2 0 F e 2 0 3 CaO O t h e r s 71.7% 2.0% 3.8% 14. 6% 0. 04% 7 . 3% B a l a n c e P h y s i c a l P r o p e r t i e s : C o e f f i c e n t of T h e r m a l E x p a n s i o n 91 x 10 to t h e -7/ C R e f r a c t i v e Index T r a n s m i s s i o n S o f t e n i n g P o i n t 1.52% 91. 2% 723°c 81 APPENDIX I I I VELOCITY MEASUREMENT A s t e e l c o n t a c t was s l i d a l o n g a 200 ohm c o i l of r e s i s t a n c e w i r e to measure v e l o c i t y . The c o n t a c t was r i g i d l y c o n n e c t e d to t h e main h y d r a u l i c s h a f t hence i t moved at t h e v e l o c i t y of t h e s l i d e r . The d i s c r e t e r e s i s t a n c e o u t p u t was r e c o r d e d on t h e B r u s h r e c o r d e r . N o t i n g t h a t t h e d i s t a n c e between winds on t h e r e s i s t a n c e c o i l was 0.5 mm and t a k i n g i n t o a c c o u n t t h e time s c a l e on t h e c h a r t r e c o r d e r , t h e v e l o c i t y was s i m p l y t h e s l o p e of t h e r e c o r d e d c u r v e . T h i s c u r v e was l i n e a r f o r a l l s e t t i n g s of t h e Nupro m i c r o v a l v e . A d i a g r a m o f t h e s l i d i n g r e s i s t a n c e c i r c u i t i s shown i n F i g . A. I I I . 1. The c a l i b r a t i o n c u r v e of v e l o c i t y v e r s u s v a l v e s e t t i n g i s shown i n F i g . A. I I I . 2 . The c u r v e was i d e n t i c a l f o r v e l o c i t y c a l i b r a t i o n s made w i t h t h e _ g vacuum chamber a t b o t h 4 x 10 t o r r and a t a t m o s p h e r i c p r e s s u r e . 82 MOTION SLIDING CONTACT • V W A V 2 00 ft. 1. 5 v BRUSH RECORDER F i g . A . I I I . l . C i r c u i t U s e d , f o r . V e l o c i t y Measurement 83 2 4 6 8 10 12 14; 16 18 20 22 VALVE SETTING NUMBER F i g . A . I I I . 2 . V e l o c i t y C a l i b r a t i o n C urve APPENDIX IV TEMPERATURE MEASUREMENT I t was assumed t h a t a t s t e a d y s t a t e t h e t e m p e r a t u r e of a l l s o l i d u n i t s w i t h i n t h e vacuum chamber and i n t h e r m a l c o n t a c t w i t h e a c h o t h e r would be t h e same. Hence a F e n w a l l 2 i n . g l a s s p r o b e t h e r m i s t o r was imbedded w i t h i n t h e t r o l l e y t r a c k p l a t e and packed w i t h s t r a n d s of t h i n c o p p e r w i r e to make a snug h e a t c o n d u c t i n g f i t . The t h e r m i s t o r was n o t i m p l a n t e d i n t h e t r o l l e y as the l e a d s may have become e n t a n g l e d i n t h e m a n i p u l a t o r arm. The l e a d s were f e d t h r o u g h a m u l t i - r o d s e c t i o n of t h e chamber. DC v o l t a g e was s u p p l i e d by a 6 v o l t d r y c e l l b a t t e r y and t e m p e r a t u r e was i n d i c a t e d by t h e v o l t a g e p o t e n t i a l measured a c r o s s t h e t h e r m i s t o r . The t h e r m i s t o r c i r c u i t i s shown i n F i g . A . I V . l . S p e c i f i c a t i o n s : 135 K @ 25°C D i s s i p a t i o n C o n s t a n t : 1 m i l l i w a t t p e r d e g r e e C Time c o n s t a n t : 23 s e c o n d s i n s t i l l a i r 0.3 s e c o n d s i n r a p i d l y s t i r r e d water C o e f f i c i e n t @ 25°C -- 4.6% R/C° N e g a t i v e c o e f f i c i e n t t e m p e r a t u r e s e n s i t i v e t h e r m a l r e s i s t o r — i t s a b s o l u t e r e s i s t a n c e i s a f u n c t i o n of i t s a b s o l u t e t e m p e r a t u r e . Has a r a n g e 0 to 115°F f u l l s c a l e C a l i b r a t i o n : A t e m p e r a t u r e c o n t r o l l e d l i q u i d b a t h was p r e p a r e d . B o t h t h e F e n w a l l t h e r m i s t o r and a s t a n d a r d m e r c u r y thermomet were immersed i n t h e b a t h . A s t i r r e r was u s e d i t o mix t h e b a t h . The t e m p e r a t u r e of t h e b a t h as i n d i c a t e d on t h e thermometer was v a r i e d f r o m 40°C to 1°C by a d d i n g i c e to t h e p r e v i o u s l y h e a t e d w a t e r . T e m p e r a t u r e and t h e r m i s t o r v o l t a g e were r e c o r d e d as t h e b a t h c o o l e d . The r e s u l t s were p l o t t e d on a g r a p h of t h e r m i s t o r v o l t a g e v e r s u s t e m p e r a t u r e . T h i s g r a p h i s shown i n F i g . A.IV.2. 86 v W W 150 k n 6 v ~= F i g . A . I V . l T h e r m i s t o r C i r c u i t • 4 .5 .6 . 7 . 8 .9 1.0 THERMISTOR VOLTAGE F i g . A.IV.2. T e m p e r a t u r e C a l i b r a t i o n C urve THERMISTOR' 87 APPENDIX V PROPERTIES OF LIQUID MEDIA 1) N - C a p r o i c A c i d ( h e x a n o i c a c i d ) F o r m u l a CH 3 ( C H ^ ^ C O ^ F.W. 116.16 M . l . -2°C (Eastman Kodak) 2) O l e i c A c i d ( 9 - o c t a d e c e n o i c a c i d ) F o r m u l a CH (CH ) CH : C H ( C H ^ ) 7 C 0 2 H F.W. 282.47 low l i n o l e i c a c i d c o n t e n t max. 5% p o l y u n s a t u r a t e s ( F i s h e r S c i e n t i f i c ) 3) Hexane F o r m u l a C .. H, , 6 14 F . W. 86.18 B o i l i n g r a n g e 65.3° - 67.6°C D e n s i t y (g/ml) .665 R e s i d u e a f t e r evap. .0003% A c i d i t y (as CH 3C00H) P.T. S u l f u r compounds (as S) T h e i p h e n e P.T. C o l o u r (APHA) 5 F l a s h p o i n t -7°F ( F i s h e r S c i e n t i f i c ) 001% 4) Heptane F o r m u l a C-H^, I 16 F.W. 100.21 (Eastman Kodak) 88 5) M e t h y l A l c o h o l F o r m u l a CH .OH F . W. 32 . 04 Reagent Grade 6) P r o p y l A l c o h o l F.W. 60.10 A n a l y t i c a l Reagent A c i d i t y as CH 3C00H .015% A l k a l i n i t y as NH^ .002% R e s i d u e a f t e r evap. .005% B o i l i n g Range 95° - 98°° Sp. g r a v . @ 25/25°C .802-.804 ( M a l l i n c k r o d t C h e m i c a l Works) 7) H e p t y l A l c o h o l F.W. 116.20 Spec. B.P. 174-176°C (Eastman Kodak) 8) D e c y l A l c o h o l F o r m u l a C H ^ C H ^ g O H F.W. 158.29 (Eastman Kodak) APPENDIX VI INDENTATION HARDNESS OF MICROSLIDES The i n d e n t a t i o n t e s t s were c a r r i e d out on a W i l s o n Tukon 136° diamond p y r a m i d h a r d n e s s t e s t e r . The n o r m a l l o a d was 100 gm and t h e t i m e of i n d e n t e r c o n t a c t w i t h t h e s u r f a c e was 30 s e c o n d s . T e s t s were c o n d u c t e d i n open a i r on r e c e n t l y exposed g l a s s s u r f a c e s . F o u r i n d e n t a t i o n s were made and t h e d i a g o n a l s were measured u s i n g a B a u sch and Lomb o p t i c a l l e n s . The a v e r a g e d i a g o n a l was e v a l u a t e d and s u b s t i t u t e d i n t o t h e f o r m u l a f o r diamond p y r a m i d h a r d n e s s (DPH) number. a DPH = 2L s i n 2 d 2 where a = 136° apex a n g l e "_L = l o a d d = l e n g t h of a v e r a g e d i a g o n a l i n mm. The a v e r a g e d i a g o n a l was d = .0187 mm. g i v i n g a DPH v a l u e of 530. The a v e r a g e d i a g o n a l v a l u e g i v e s an a v e r a g e p r o j e c t e d a r e a v a l u e of 1 .TT'O A, [d cos (^) ] = 1.75 x 10 4 mm2 The v a l u e of y i e l d s t r e n g t h 'a' i s d e t e r m i n e d by d i v i d i n g t h e DPH number by 2.7 as s u g g e s t e d by H o l l a n d [22] = 530/2 . 7 2 = 19 6 kg/mm 90 The v a l u e of s t a t i c mean p r e s s u r e 'p ' i s d e t e r m i n e d f r o m s e x p r e s s i o n (3) s e c t i o n 2.2. P g = L/Aj 0.1/1.75 x 1 0 ~ 4 2 = 571 kg/mm APPENDIX V I I CURVE FITTING ANALYSIS The c r o s s - s e c t i o n a l a r e a and f r i c t i o n f o r c e d a t a was f i t t e d to e i t h e r l o g a r i t h m i c or l i n e a r c u r v e s the g e n e r a l e q u a t i o n s of w h i c h were r e s p e c t i v e l y : y = r x (a) and y = f + gx (b) where x d e n o t e s the v e l o c i t y V of t h e s l i d e r and y d e n o t e s e i t h e r the c r o s s - s e c t i o n a l a r e a of the f r i c t i o n t r a c k A or c t h e f r i c t i o n f o r c e F. B o t h (a) and (b) c o u l d be h a n d l e d i n t h e same manner when (a) was t r a n s f o r m e d by t a k i n g the n a t u r a l l o g of b o t h s i d e s of the e q u a t i o n , l n ( y ) = l n ( r ) + s l n ( x ) (c) p u t t i n g b o t h e q u a t i o n s i n t o the form Y = A + BX (d) T h i s e q u a t i o n was s o l v e d by the f o r m u l a e A = Y - BX (e) B = (X Y - X Y) / (X" - X") ( f ) where the b a r above the symbol d e n o t e s an a v e r a g e v a l u e . S o l v i n g (e) and ( f ) a l l o w e d s u b s t i t u t i o n of A and B i n t o e x p r e s s i o n (d) and s u b s e q u e n t l y e q u a t i o n s (a) and (b) c o u l d be d e r i v e d . 

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