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Study of corrugated board cutting by high velocity liquid jet Szymani, Richard 1970

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A STUDY OF CORRUGATED BOARD CUTTING BY HIGH VELOCITY LIQUID JET by RICHARD SZYMANI M.Eng., College of Agr i c u l t u r e , Poznan, Poland, 1963 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Forestry We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1970 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the 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 reference and study. I f u r t h e r agree t h a t permiss ion fo r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of 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 understood that copying or 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 ga in s h a l l not be a l lowed without my w r i t t e n p e r m i s s i o n . Department o f Forestry The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Date September 29, 1970 ABSTRACT The a p p l i c a t i o n of high v e l o c i t y l i q u i d j e t s for corrugated board cutti n g was investigated as a possible new method of s l i t t i n g operations. Eleven types of corrugated board ranging from 91 pounds per 1,000 square feet board weight (125 p s i - nominal burst test) to 297 pounds per 1,000 square feet (350 p s i - burst test) were selected f o r the study. P l a i n water or water with polymer add i t i v e were used as the cut-t i n g f l u i d s . The conditions under which cutting of corrugated boards was c a r r i e d out were as follows: nozzle diameters 0.0082 and 0.0102 i n . , pressure l e v e l s 20,000, 30,000 and 40,000 p s i ; feed rates 300, 500 and 700 fpm. The obtained r e s u l t s i n d i c a t e that s l i t t i n g speeds with high v e l o c i t y l i q u i d j e t s are w e l l above those achievable by the e x i s t i n g conventional methods. I t has also been shown that the use of a low con-centration of polyethylene oxide (Polyox WSR - 301) resulted i n a marked increase i n cutting e f f i c i e n c y as compared with p l a i n water. Measurements of l i q u i d retention a f t e r cutting.-have shown that wetting of corrugated boards during the c u t t i n g operation i s i n s i g n i f i c a n t and as such can be neglected. I t has been demonstrated that the edgewise compression strength of corrugated board, cut with the l i q u i d j e t , i s almost twice that cut with the t y p i c a l conventional s l i t t e r . Based on the analysis of scanning electron micrographs i t has been observed that the p r i n c i p a l f a i l u r e mechanism during cutt i n g with high v e l o c i t y l i q u i d j e t involves breaking of the i n t e r f i b r e bond with r e s u l t i n g separation of f i b r e s . i i i i i Corrugated board cut t ing with high ve loc i ty l i q u i d je ts has been found to eliminate crushing and tearing of the board as w e l l as dust generation. The concept provides a means to reduce t r im waste and par-t i c l e contamination. Jet cut t ing i s i d e a l l y suited for numerically con-t r o l l e d systems and appears to lend i t s e l f for adaptation to commercial app l i ca t ion . TABLE OF CONTENTS Page ABSTRACT , • i i TABLE OF CONTENTS . . . . . . . . . . . . . . . . . . i v LIST OF TABLES v i LIST OF FIGURES . . . . . . . . . . . . . v i i ACKNOWLEDGEMENT . . . . . . . . . . . . x Chapter I. INTRODUCTION . . . . . . . . . . . . 1 I I . LITERATURE REVIEW 3 A. L i q u i d Jet Cutting Concept — H i s t o r i c a l Development . 3 B. F l u i d Dynamics of Jets 7 1. Jet.Energy . . . . . 7 2. Jet Impingement . , 8 3. Jet D i s i n t e g r a t i o n . . . . . . . . . . 8 4. Penetration of Li q u i d J e t s ' . . . . . . . . . . . . 11 5. Nozzle Design 14 ITI. MATERIALS AND METHODS , 16 A. Equipment . . . . . . • 16 1. High. Pressure Pump System 16 2. Nozzle Assembly 17 3. - Control System . . . . . . . . . . . . . . . . . 18 4. Feed Mechanism . . . . . . . . . . . . . . . . . 18 5. L i q u i d Requirements . . . . . . . . . . . . . . . 18 B. Specimen Preparation . . . . . . . . . . 20 C. Test Conditions . 21 D. Testing Procedure 21 i v V Chapter Page IV. RESULTS AND DISCUSSION 25 A. Energy Requirements 25 1. F l u i d Properties 25 2. Nozzle Diameter . . 28 3. Pressure Level . . 29 4. Board Properties 29 B. Wetting During Cutting •. . 29 1. F l u i d Properties 30 2. Nozzle Diameter 30 3. Pressure Level . . . . . . . . . 31 4. Feed Rate '. . . . 31 5. Interaction of L i q u i d Pressure and Feed Rate . 32 6. Board C h a r a c t e r i s t i c s . . 32 C. Evaluation of Cut Quality . . . . . . . . . . . . 33 1. F l u i d Properties 34 2. Nozzle Diameter . 34 3. Pressure Level 35 4. Feed Rate 35 5. Board Properties 36 D. S t a t i s t i c a l Analysis . . . . . 36 E. F a i l u r e Mechanism 38 V. CONCLUSION 41 VI. RECOMMENDATIONS . . . . . . . . . . 42 LITERATURE CITED 43 TABLES 47 FIGURES 59 LIST OF SYMBOLS . 82 LIST OF TABLES Table Page 1. Experimental Corrugated Board Properties . 47 2. Actual Feed Rates at Which Complete Cut has been Obtained at a Given Nozzle Diameter and Pressure Level . 48 3. L i q u i d Retention A f t e r Cutting of Corrugated Board with High V e l o c i t y Polymer and Water Jet . . 49 4. S t a t i s t i c a l Data of a Polymer Retention A f t e r Cutting. 52 5. S t a t i s t i c a l Data of Water Retention A f t e r Cutting . . 53 6. Edgewise Compression Strength of Corrugated Board Aft e r Cutting with Commercial S l i t t e r Polymer Jet and Water Jet 54 7. S t a t i s t i c a l Data of Edgewise Compression Strength Af t e r Polymer Jet Cut 57 8. S t a t i s t i c a l Data of Edgewise Compression Strength A f t e r Water Jet Cut 58 v i LIST OF FIGURES Figure Page 1. View of high pressure pump system . . . . . . . . . . . . . 59 2. View of high pressure pump system and feed mechanism . . . 59 3. View of nozzle assembly and high ve loc i t y l i q u i d j e t . . . 60 4. View of feed mechanism and nozzle assembly . . . . . . . . 60 5. Cross-sect ional diagram showing de ta i l s of nozzle design . 61 6. The effect of polymer vs . water j e t penetration during cut t ing of Douglas-f i r wood, where j e t was perpendicu^ l a r to annual rings and feed rate tangential 62 7. Relationship between pressure l e v e l and j e t force for the two nozzle s izes used i n the experiment . . . . . . . . 63 8. Relationship between f l u i d pressure and je t energy for nozzle s izes used i n the experiment 64 9. Photographs of polymer j e t (a),.and water j e t (b). Pressure l e v e l 40,000 p s i , nozzle diameter 0.0102 i n 65 10. L iqu id retent ion i n boards after cut t ing wi th polymer and water j e t as a function of board type 66 11. Polymer retent ion i n board after cut t ing as a function of pressure l e v e l and board type . . . . . . . . 67 12. Water retent ion i n board after cut t ing as a function of pressure l e v e l and board type . . . . . . . 68 v i i v i i i Figure Page 13. Polymer retention i n board a f t e r cutting as a function of feed rate and board type 69 14. Water retention i n board a f t e r c u t t i n g as a function of feed rate and board type , 70 15. L i q u i d retention i n boards (125/A and 125/B) a f t e r c u t t i n g with water and polymer j e t 71 16. Edgewise compression strength a f t e r c u t t i n g with commercial s l i t t e r , polymer and water j e t . . . . 72 17. Edgewise compression strength of boards a f t e r c u t t i n g with -, polymer j e t as a function of pressure l e v e l and board type 73 18. Edgewise compression strength of boards a f t e r cutting with water j e t as a function of pressure l e v e l and board type 74 19. Edgewise compression strength of boards a f t e r c u t t i n g with polymer j e t as a function of feed rate and board type . 75 20. Edgewise compression strength of boards a f t e r c u t t i n g with water j e t as a function of feed rate and board type . . 76 21. Scanning electron micrographs of corrugated board (125/B) cut with water j e t at pressure l e v e l of 40,000 p s i N and 300 fpm feed rate . . . . . . 77 22. Scanning electron micrographs of debris removed from the cut by l i q u i d j e t during cutting of corrugated board . . 78 23. Scanning electron micrographs of corrugated board (125/B) cut with commercial s l i t t e r at approximately 300 fpm . . 79 i x Figure Page 24. Scanning electron micrographs of corrugated board (125/B) cut with laboratory knife 80 25. Scanning electron micrographs of sugar maple wood cut with high ve loc i ty water je t at 40,000 p s i pressure l e v e l and by using 0.0082 i n nozzle diameter 81 ACKNOWLEDGEMENT The author would l i k e to express h is gratitude and appreciation to Dr. N . C. Franz, Professor, Faculty of Forestry, for h i s professional assistance i n a l l phases of the experiment and preparation of the thes i s , as w e l l as for h is understanding guidance over the past two years of my residence at th is un ive r s i ty . Acknowledgement i s made to Dr. I . S. Gartshore, Assis tant Professor, Faculty of Applied Science; to Dr. L . Paszner, Research Associate, Faculty of Forestry, for many he lpfu l suggestions and constructive c r i t i c i s m ; to Dr. A. Kozak, Assis tant Professor, Faculty of Forestry, for help wi th the s t a t i s t i c a l analysis and computer programming; to Mr. E. Thykeson, Senior Research Engineer, MacMillan Bloedel Research L t d . , Packaging Research, Vancouver, for permission to use equipment and. for h i s kind assistance and co-operation. The author extends h i s appreciation to Mr. D. Freson, Engineer, MacMillan Bloedel Packaging L t d . , Corrugated Container D i v i s i o n , New Westminster, for valuable information and for supplying the experimen-t a l mater ia l . The National Research. Council of Canada and the Univers i ty of B r i t i s h Columbia provided v i t a l f i n a n c i a l assistance, which i s acknow-ledged w i t h grat i tude. x CHAPTER I INTRODUCTION In the corrugated paper container industry, which i s s t r i v i n g to improve q u a l i t y and reduce production costs, automation has by necessity become v i t a l to production. Only l i m i t e d achievements are found i n the area of conventional s l i t t i n g and scoring operation. While automated machines cut, glue and p r i n t boxes, cartons and other items at prodigious speeds, the frequent requirements f o r set-up changes of s l i t t i n g and scoring discs remains l a r g e l y a manual task. Setting of d i s c - l i k e cut-ters requires s k i l l e d manpower, i s time consuming, and leads to consider-able loss i n production capacity 5when frequent change i n l o c a t i o n of the s l i t t i n g cut i s required. In addition, present conventional s l i t t i n g and scoring operations are characterized by sub s t a n t i a l trim waste, crushing and tearing at the cut surfaces and generation of dust. The dust can increase f i r e hazard and cause problems i n subsequent p r i n t i n g . A d d i t i o n a l d i f f i c u l t i e s are experienced i n that p a r t i c l e s may contaminate c e r t a i n packaged products. It has been found that the high v e l o c i t y l i q u i d j e t concept could / be applied to s l i t t i n g operations, to overcome many of the l i m i t a t i o n s associated with systems currently i n use C8). Crushing, tearing and dust generation can be avoided with the use of high v e l o c i t y l i q u i d j e t . There i s no t o o l wear and t o o l reaction imposed on the machine and the work i s very small. However, the most important production advantages 1 2 are r e a l i z e d by the adaptation to high speed numerically c o n t r o l l e d oper-ations.and the reduction of waste. Experiments have shown that i n terms of energy required to produce a given cut, the high v e l o c i t y l i q u i d j e t i s f ar superior to the l a s e r beam C6) which has received much attention and p u b l i c i t y as a new cutting device. In considering the use of high v e l o c i t y l i q u i d j e t for c o n t r o l l e d s l i t t i n g operation of paper products, p a r t i c u l a r l y corrugated boards, a series of experiments was undertaken. The primary objectives of these experiments were to: 1. Measure the r e l a t i o n s h i p between energy l e v e l and corrugated board properties during cutting, and explore the e f f e c t of various operating variables on the e f f i c i e n c y of the c u t t i n g process. These variables included: f l u i d proper-t i e s , nozzle diameter, f l u i d pressure, specimen feed rate, and board properties. 2. Determine l i q u i d retention following cutting with the l i q u i d j e t . 3. Evaluate the cut q u a l i t y . 4. Study the f a i l u r e mechanism. CHAPTER I I LITERATURE REVIEW A. L iqu id Jet Cutting Concept ;— H i s t o r i c a l Development The deformation of so l ids by water impact has long been observed i n the form of erosion of rocks by streams and r i v e r s . The erosion of steam turbine blades by c o l l i s o n with water droplets which are suspended i n the steam i s also due to the high speed impact of l i q u i d on s o l i d . Impact of water droplets on a s o l i d has also been observed as "erosion" of a i r c r a f t f l y i n g at high speed through r a i n . The h i s tory of high ve loc i t y l i q u i d je ts as a cut t ing too l i s c lose ly t i ed to advances i n metallurgy, power sources, and pumping equip-^-ment. The f i r s t extensive use of high ve loc i ty water je ts for cut t ing materials was advanced i n the mining industry. Actual appl ica t ion of water je ts i n underground mining has been confined mainly to the coal industry. The waste water i n some cases was used to transport the broken coal to the surface. Such experiments were f i r s t conducted as early as 1936 i n the Soviet Union. Boyd (5) published an extensive l i t e r a t u r e survey i n which i s presented information gained from experiments with coal mining and trans-port by hydraul ic methods i n the Soviet Union and New Zealand. Further, he discusses the conditions required for extract ion of bituminous coal deposits i n the United States. The system was recommended favourably for economic coal extract ion by means of high ve loc i ty water j e t s . 3 4 Investigations of rock breaking wi th water je t s have been re -ported by Zelenin , Vesselov and Koniashin (37). Experiments are des^ cribed which were carr ied out i n 1956 and 1957 i n the U.S .S .R. The equipment consisted of two hydrocompressors with working pressures up to 2,000 atm; Nozzle diameters i n these experiments ranged from 0.8 to 1.5 mm. The authors also derived an equation for the t o t a l energy required i n order to obtain a given cut. Further use of high pressure water je t s i n rock tunnel excavation has been investigated by McClain and Cr i s ty (18). In a series of explor-atory experiments they intended to evaluate a promising new method for rock breakage. Based on a preliminary study, they found that a mechanical mole using water je ts as a cut t ing device would be feas ib le . A considerable amount of research has been conducted on high pres^- . sure erosion je ts to d r i l l and excavate rocks. Maurer (17) describes i n -vest igat ions i n which "high pressure erosion je t s were used to d r i l l var^ ious types of rocks. Pressures up to 5,000 atm. were used to produce je t v e l o c i t i e s of 200 ^ 1000 m/sec through 1^ -5 mm diameter nozzles. In view of the tests described by Maurer i t appears tha t , la rger je ts are possibly more e f f i c i e n t . I t was observed that wi th large diameter holes less power Is los t i n the in te rac t ion between impinging and returning f l u i d . Cutting of s t e e l , n i c k e l and t i tanium by supersonic and hypersonic o i l je ts has been described by.Schwacha (29) i n a patent assigned to North American A v i a t i o n , Inc. The patent relates to l i q u i d j e t cut t ing of hard, hlghvstrength and res is tant mater ia ls , - Schwacha also describes the use of abrasive materials i n conjunction wi th high ve loc i ty je t s for improved cut t ing e f f i c i ency . Pressures i n the order of 100,000 to 200,000 p s i , and 5 nozzle diameters from 0.0025 to 0.021 i n were used i n h i s experiments. The Mining I n s t i t u t e and the I n s t i t u t e of High Pressure Physics of the Academy of Science of U.S.S.R. (36, 37) conducted numerous inves-ti g a t i o n s with high v e l o c i t y l i q u i d j e t s . The study was rel a t e d to the theory of j e t flow with subsonic and hypersonic v e l o c i t i e s of the order up to 600-650 m/sec. A number of inv e s t i g a t i o n s i n destructing rocks and metals are also included. Yugov and Osipov (36) published r e s u l t s of laboratory investigations on the destruction of various materials by water j e t s of supersonic speeds. Their report included a study on the influence of material properties on the speed of destruction, factors r e l a t i n g to speed of outflow, distance between material and nozzle, angle of j e t incidence, pressure pulsation and nozzle diameter. Descriptions of the test r e s u l t s for c o a l , marble, granite and duraluminium cutt i n g are presented. Therein suggestions as to the p o s s i b i l i t y of cutti n g and processing wood by water j e t s were also made. F i r s t studies on wood cuttin g by high v e l o c i t y l i q u i d j e t s are described by Bryan (6). He investigated the use of small high v e l o c i t y l i q u i d j e t s as a possible new method of cuttin g wood with minimal material loss and t o o l maintenance. Bryan studied numerous variables r e l a t e d to the c u t t i n g process as w e l l as mechanisms of energy t r a n s f e r . A theory has been developed by him on j e t penetration into wood. Under the conditions of h i s study, the cuttin g e f f i c i e n c y i n terms of surface,..generated per unit of energy input was approximately 2 per cent of that normally obtained with conventional power saws. Information on the use of high speed water j e t s f o r cutting news-6 pr in t has been presented recently by Harris (14). Newsprint s l i t t i n g by water je ts has passed beyond the experimental stage and i s being applied to a r o l l rewinder involved i n the recovery of defective r o l l s of news-p r in t . This appl ica t ion has been successfully developed by the National Research Counci l , D i v i s i o n of Mechanical Engineering i n co-operation with the Canadian Internat ional Paper Company at Gatineau, Quebec. Cutt-ing speed used i n the process i s 5,000 fpm, nozzle diameter i s 0.010 i n and a water pressure of 50,000 p s i i s reported. The resul ts of a series of j e t cut t ing tests conducted on commer-c i a l corrugated board products has been published by Franz (8). The c r i -te r ion for evaluation of the resul ts i n the i n i t i a l test series was simp-l y the appearance of the cut, i . e . , whether or not a clean cut was ob-tained. From the descr ip t ion , i t i s evident that board density appears to have a marked influence on the pressure l e v e l and nozzle diameter re-quired to obtain a cut at a given feed rate . Also i t was noted that one can expect large increases i n the cut t ing capab i l i ty with small increases i n pressure l e v e l . Further, i t i s demonstrated that je ts not only pro-duce a clean and accurate cut butv also<>eliminate crushing breaking or tearing commonly associated with conventional s l i t t i n g . Further study of j e t s l i t t i n g has been recommended i n order to define more accurately interact ions of pressure, j e t diameter, feed ra te , and board propert ies . A review of the current status of high ve loc i ty l i q u i d j e t pro-cessing indicates that the concept of cut t ing by high ve loc i t y water j e t i s very promising for cut t ing of paper products. Addi t iona l re la ted l i t e r a t u r e i s c i ted i n the text where i t applies to a spec i f i c top ic . 7 B. F l u i d Dynamics of Jets Theoret ical and experimental inves t iga t ion of je t s i s a highly complex and broad f i e l d i n i t s e l f . However, before the h igh-ve loc i ty l i q u i d j e t cut t ing phenomena can be understood i t i s necessary to con-sider b r i e f l y some of the aspects re lated to: the energy of l i q u i d j e t ; j e t impingement; j e t d i s in tegra t ion ; penetration of a j e t ; and nozzle design. Good treatments of the f l u i d j e t theory have been presented by Birkhof (2) and Pa i (26). 1. Jet Energy. '-'.v. ' A l i q u i d j e t which flows out of a nozzle with a constant 2 v e l o c i t y , v , has a k i n e t i c energy per uni t mass equal to v / 2 . For a l i q u i d passing a sect ion where the ve loc i t y i s not uniform (two- or three-dimensional f low), the true k i n e t i c energy per uni t time i s always greater than that based on the average v e l o c i t y . The true k i n e t i c energy f lux i s found by integrat ing over the ent i re flow area. The r a t i o of the true k i n e t i c energy per uni t time to that based on the average ve loc i t y i s ca l l ed the k i n e t i c correct ion factor where: / . (u 2/2)(updA) / . u 3dA a = A = A > 1 [1] (v /2)(vpA) v A Considering water, and based on the average v e l o c i t y , the k i n e t i c energy per uni t time i s given by equation: E = 0.0053 d 2 v 3 [2] where d i s the je t ' diameter i n inches and v j e t ve loc i t y i n f t / s ec . 8 This equation i s modified l a t e r by loss c o e f f i c i e n t s . ' 2. Jet Impingement When a l i q u i d j e t impinges on an object, a force w i l l develop between the j e t and the object. The t o t a l force at an impingement sur^ face can be re l a t e d to gross flow q u a n t i t i e s , but pressure and v e l o c i t y are not e a s i l y deducible t h e o r e t i c a l l y . An i n v e s t i g a t i o n of the v e l o c i t y f i e l d as w e l l as momentum d i s t r i b u t i o n i s of great i n t e r e s t . Great d i f f i -c u l t i e s , however, are met i n carrying out t h e o r e t i c a l investigations be-cause of the small diameter and high v e l o c i t i e s of the j e t s under con-s i d e r a t i o n . Elementary textbooks commonly discuss the two-dimensional l i q u i d j e t to show how mass and momentum conservation conditions s u f f i c e to determine the force and the l i m i t i n g thickness of j e t splash zones. The three-dimensional flows are l e f t rather untouched. An attempt to analyze three-dimensional oblique impingement of a l i q u i d j e t was made recently by Michelson (22). Considering a c i r c u l a r l i q u i d j e t of area A which s t r i k e s a f l a t surface, and ignoring gravity, f r i c t i o n and surface tension Bernoulli's theorem i s applicable. In the case of normal impingement the force normal to the surface i s : 2 F = pv A [3j where P i s the l i q u i d density and v i t s v e l o c i t y . 3. Jet D i s i n t e g r a t i o n The form of the j e t i s one of the basic factors which a f f e c t s the successful a p p l i c a t i o n of l i q u i d j e t s at high pressures f o r cutting 9 operations. The j e t must remain coherent at the point of impact. Since the average pressure beneath the j e t depends on i t s average density, a dispersed je t i s considerably less effect ive as a penetration device. The character of the j e t break-up depends on many factors inc luding i t s v e l o c i t y , the a i r res is tance, the phys ica l properties of the l i q u i d , and the nozzle geometry. A number of theore t ica l and experimental studies have been devoted to the problem of the d is in tegra t ion of a l i q u i d j e t flowing into a gas medium. The f i r s t analysis of the d is in tegra t ion of je ts for an idea l l i q u i d was made by Rayleigh C28). Weber (35) has extended Rayleigh 's theory to viscous l iqu ids . ' However, the d is in tegra t ion process has been studied only at low exis t v e l o c i t i e s . The inves t iga t ion of a wider range of v e l o c i t i e s i s p a r t i c u l a r l y of p r a c t i c a l in te res t . New experimental resul ts have recently been obtained by Vereshchagin et al. (33). They demonstrated by taking photographs of the water j e t at various pressures that at small pressures the j e t has a form of an expanding core and of a jacket made of droplets which accompany the core. As the pressure and consequently the j e t ve loc i ty increases, the cone expands, but the core remains. When the j e t approaches the speed of sptmd In the a i r , the outflowing je t loses i t s conica l shape and becomes more compact, and f i n a l l y at a cer ta in distance from the nozzle the con-tinuous rod of l i q u i d disappears., and the ent i re j e t i s transformed in to a mixture of l i q u i d droplets and a i r . The question arose'as to what l i m i t i n g ve loc i ty the j e t may reach. Vereshchagin (33, 34) holds that Joule-rThcrmpson's effect creates a l i m i t . 10 In l i qu ids the concentration of molecules i s by far greater than for gases, and for most l i qu ids a negative effect i s to be expected, i . e . , a heating of l i q u i d i f i t expands. The magnitude of Joule-Thompson effect i s expressed by the formula: ~ )P AT - -A 12 dp [4] 1 P where: 3 C : i s thermal capacity at constant pressure, Kcal/mm r centigrade; T: i s absolute temperature i n °K; 3 VJ • i s spec i f i c volume m / k g ; 2 p: i s pressure, kG/cm ; 2 p^, p^1 f i n a l and i n i t i a l pressure, respect ive ly , kG/cm ; (—) i s coeff ic ient of thermal expansion at constant pressure, m-V kg grade; A: i s the thermal equivalent of working un i t , kcal/kGm. Development of a theore t ica l model of the d is in tegra t ion effect i n the region of wavelike deformation was prevented for a long time be-cause of lack of understanding. Recently, Ivanov (16) carr ied out an experiment i n which he obtained photographs of the deformation processes of je t s wi th high ex i t v e l o c i t i e s . The photographs included axisyme-t r i c d i s in tegra t ion , wavelike deformations, and the beginning of atomiza-t i o n . In addi t ion , the length of the continuous part of the j e t was measured by the electrocontact method. To es tab l i sh the three-dimensional 11 shape of the j e t , i t was filmed i n two project ions. This experiment c l a r i f i e d the nature of the length v a r i a t i o n of the continuous part of th j e t at v e l o c i t i e s corresponding to a pressure range from zero to one thousand atmospheres. In the range of v e l o c i t i e s used i n the ex-periment the surface deformations of the j e t were mainly axisymetric. Axisymetric perturbations were also observed which, beyond a cer ta in t r ans i t i on v e l o c i t y , give r i s e to wavelike deformations. When the r e l a -t i ve v e l o c i t y i s reduced by an accompanying flow, the deformations must be suppressed by the surface tension. However, Ivanov demonstrated that such deformations are not suppressed. The cosinusoidal shape of the surface becomes unstable, and i s replaced with an axisymetric shape with a central c y l i n d r i c a l sec t ion. The deformation of the l a t t e r i s i n t e r -rupted by the appearance of perturbations on the c y l i n d r i c a l part before d i s in tegra t ion . 4. Penetration of Liquid Jets At very high v e l o c i t i e s the charac te r i s t ics of l i q u i d j e t impact apparently become s imi l a r i n many ways to those of a metal projec-t i l e c o l l i d i n g wi th a s o l i d target . The fracture process i s conditioned by the l i q u i d mass, i t s terminal v e l o c i t y , and the diameter of the j e t . The experimental evidence which has been given by Bowden and Brun-ton C4) suggests that for impact v e l o c i t i e s above 500 m/sec. a l i q u i d mass c o l l i d i n g with a s o l i d surface behaves i n a compressible manner. As a re-s u l t , a short intense compression pulse moves into the s o l i d from the re -gion of impact and part of the deformation produced i n the target can be related to th is compression wave. In th i s respect the l i q u i d deforms the target i n much the same way as a s o l i d p r o j e c t i l e . The main difference i s that the duration of the pressure pulse i s shorter i n the case of l i q -uid impact, and more nearly resembles the pulse produced by an exploding charge. The remainder of the deformation consits of a shearing and tear-ing of the surface brought about by l i q u i d flowing at high speed across the surface. An extensive treatment of the theory of j e t penetration has been presented by Pack and Evans (24). Making c e r t a i n s i m p l i f y i n g assumptions, they developed a formula for the penetration into a d u c t i l e target by a high v e l o c i t y 'Munroe' j e t . A general summary of work on the formation of 'Munroe' j e t s has been given i n a paper by B i r k h o f f , MacDougall, Pugh and Taylor (3). At the high pressures set up by a 'Munroe' j e t the strength of the target plays only a subsidiary part i n the phenomena. The action of the j e t i s divided into two stages, each making i t s con-t r i b u t i o n to the t o t a l penetration. In the f i r s t stage a hole i s formed by the l a t e r a l compression of the target as the j e t penetrates i t , the second stage begins when the l a s t p a r t i c l e of the j e t has caused to act, the hole continues to deepen u n t i l the r e s i d u a l energy i n the target has been spent. Based on the test r e s u l t s of the studies on wood cutting by high v e l o c i t y l i q u i d j e t s and by t h e o r e t i c a l consideration Bryan (6) also suggests that penetration during cutt i n g r e s u l t s from two separate actions. F i r s t , d i r e c t penetration occurs as a r e s u l t of the extreme stress gen-erated at the point of impact. As suggested by the experimental data the f i r s t penetrating action w i l l be c o n t r o l l e d by the density of the work 13 piece, the energy density at the point of impact, and the t o t a l volume of the j e t . These quanti t ies w i l l be functions of j e t ve loc i t y v , j e t Y Y diameter d, j e t density j /g , and wood density w/g. The second ac t ion , ca l l ed secondary penetration i s a deepening of the kerf after i n i t i a l penetration, and i s d i r e c t l y re la ted to the t o t a l energy per uni t length of the j e t . Dimensional analysis suggested that the rec ip roca l of the surface tension i s an important va r i ab le . Bryan found that the depth of penetration D can be represented by the equation: D = d + C 2 N w d, 15] showing the effectiveness of a j e t for cut t ing to be a function of i t s diameter d, and dimensionless quanti t ies which are defined as: Y /Y N = j / w = dimensionless number Y • 2 Np = v /dg = Froude number and 2 N = p dy /a s Weber number. w • and are dimensionless coeff ic ients which can be evaluated by using two experimentally determined values for D from two different sets of condit ions. Equation I.5.] shows how the types of penetrating actions which are affected by the dif ferent va r i ab les , but i t does not take in to con-s idera t ion the specimen feed rate . From the test resu l t s wi th wood Bryan (6) found that depth of penetration w i l l be an inverse function of the square root of feed ra te . 14 The magnitude of the effect also w i l l be a function of j e t v e l o c i t y , since these two factors influence the amount of f l u i d that s t r ikes a given point . Considering th is information a general expression including the effect of feed rate can be wr i t ten as: D = ( C l N y N F d + C2 Nw a ) 1 6 1 where v i s the ve loc i t y of the j e t and R specimen feed rate . The penetration mechanism during cut t ing by water j e t at super-sonic ve loc i t y also has been described by Yugov and. Osipov (36). In cut-t ing of Inkerman stone they reported almost l i nea r re la t ionships between the depth of cut t ing and the magnitude of pressure. A maximum penetration was achieved at a 90° angle of incidence of the j e t on the sample. Accord-ing to the data obtained from these experiments, the depth of penetration i s inverse ly proport ional to the feeding speed'. The area of the cut i n -creases with increased feeding,, then reaches a maximum, followed by a decrease at a cer ta in point . The above presented findings can provide valuable ins ight in to the effects of var iables involved and predict ions that can be made for j e t penetration. However, they are not en t i r e ly applicable to th is par-t i c u l a r s i tua t ion since only complete severance of the board was of con-cern. 5, Nozzle Design The design of the nozzle i s an important factor i n project ing a cohesive j e t . The main source of the j e t break-up i s the turbulance of the flow i n the nozzle . Projections or roughness i n the wal ls of a f l u i d 15 passage w i l l considerably increase the turbulance. The most reasonable theore t ica l approach to the design problem was suggested by Farmer and At tewel l (7). The concept i s based on the Helmholtz-Kirchoff free streamline theory, which i s applicable to two-dimensional, laminar flow. They found i n the i r invest igat ions that the most ef fect ive nozzle type i s the one having a streamline p r o f i l e , as derived from Helmholtz-Kirchoff theory. For maximum coherence i t i s desirable to have a s l i g h t l y contrac-t ing throat at the nozzle ex i t 'since the je t w i l l expand on leaving the nozzle . In addi t ion i t i s essent ia l to avoid sharp angles and projections i n the nozzle and to po l i sh the ins ide to as fine a f i n i s h as poss ib le . CHAPTER I I I MATERIALS AND METHODS A. Equipment 1. High Pressure Pump System The apparatus used i n th is experiment (Figs. 1 and 2) was a high pressure pumping system produced by the McCartney Manufacturing Company, Inc . , Baxter Springs, Kansas, U .S .A. Presently i t i s avai lable commer-c i a l l y and i s s imi l a r to units used by the chemical processing indus t r ies . The uni t consists of an e l e c t r i c a l l y powered, var iable flow hydrau-l i c pump coupled to a double-acting pis ton and cy l inder . A x i a l l y attached to th i s low pressure pis ton are two much smaller high pressure plungers which i n turn generate the f i n a l working pressure. The pressure i n t e n s i -f i c t i o n i s based on the d i f f e r e n t i a l area p r i n c i p l e . The r e su l t ing r a t io of i n t e n s i f i e r pressure output to that of the hydraulic drive unit i s 40 to 1 or 80 to 1 depending on the high pressure pis ton diameter selected. Continuous flow i s obtained by use of a volume accumulator which eliminates pressure f luctuat ions during stroke reversa ls . The hydraul ic d r iy ing uni t i s mounted as an in t eg ra l part of the main frame of the i n t e n s i f i e r pump. The system i s also equipped with an oil-vtQrnwater cooler wi th thermostatic con t ro l . Character is t ics of the high pressure pump: Number of cylinders 2 Pis ton diameter high pressure 7/8 i n or 5/8 i n Stroke length 6.0 i n Suction pressure 30 - 50 psig 16 17 Discharge pressure 40,000 p s i or 70,000 p s i (maxium) Cycling rate (variable) 0 - 3 0 cycles/min Displacement volume 50 or 25 gph (approx. at 30 cycles) Control a i r 60 - 80 psig Instrument a i r 3 - 1 5 p s ig , ins t rument : ai r s igna l to flow control E l e c t r i c motor 30 HP 220/440 3 phase 60 cycles Class 1 Div . 1 Group C Liqu id pumped f i l t e r e d tap water at approx. 20°C or water with polymer addit ive 2. Nozzle Assembly In addi t ion to the above described high pressure pump system, the equipment includes a nozzle assembly (Figs. 3, 4 ) . The nozzle assemb-l y has been mounted on a frame which allows v e r t i c a l and hor izonta l adjust-ments. Signif icance of nozzle design has been recognized. However, the nozzles used i n th i s experiment were made from commercial saphire o r i f i c e jewels mounted i n brass holders, Figure 5 gives the design de ta i l s and speci f ica t ions of the nozzles used. The actual nozzle having a diameter of 0.0102 i n d i f fe r s s l i g h t l y from the drawing because i t has been a l -tered i n the laboratory by enlargement of a commercial nozzle 0.0055 i n diameter. As a receiver for the outflowing l i q u i d j e t a pipe par t ly f i l l e d w i t h gravel.was chosen whose top and bottom were made of a brass screen. The pipe was placed v e r t i c a l l y i n a p l a s t i c container covered with ure-thane foam which preyented splashing and allowed for complete absorption of the j e t energy. After leaving the pipe the l i q u i d accumulated i n the container, which was equipped to overflow to drainage. 18 3. Control System The system i s equipped with a pressure gauge rated to 100,000 p s i and a safety valve, which i s placed between the nozzle assembly and high pressure i n t e n s i f i e r . The f l u i d pressure can be adjusted to any desired l e v e l within the working range of the system by use of a pneumatic control of the hydraulic pump discharge volume. In addition, the desired maximum discharge pressure of the f l u i d can be adjusted by a pressure r e -l i e f valve located i n the low pressure hydraulic system. 4. Feed Mechanism The specimen feed mechanism shown i n F i g . 4 consists of a var-i a b l e speed drive e l e c t r i c a l motor and aapinch r o l l f o r carrying the corru-gated board specimen past the nozzle o r i f i c e . The pinch r o l l consists of a r o t a t i n g cylinder 4 i n i n diameter and i s covered with e a s i l y compres-s i b l e foam rubber. Slippage between the drive r o l l and the test specimen was found to be n e g l i g i b l e . The above mentioned feed mechanism provides feed rates from zero to 1,000 fpm. The desired feed rates were set with the aid of a strobo-scope and by converting rate of r o t a t i o n to p e r i p h e r i a l v e l o c i t y . 5. L i q u i d Requirements a. Water. A large part of the experiment was c a r r i e d out using f i l -tered tap water. The following water consumption equation has been derived by Bryan (.6): Volume 2 19 where d i s the diameter of the nozzle opening i n inches and P i s the f l u i d pressure i n pounds per square inch. b. Polymer additive In order to study the e f f e c t of polymer additive and to v e r i f y an e a r l i e r patent (9)>an aqueous s o l u t i o n of polyethylene oxide (Polyox WSR - 301) manufactured by Union Carbide Chemicals Company has been used i n part of the experiment. The concentration of polymer used i n the experiment was 0.3 weight per cent which i s within the recommended range (9). From the four methods of d i s s o l v i n g the r e s i n described by the manufacturer, e.g., b o i l i n g water, v e n t u r i , non-solvent and high shear, i t has been found that the adaptation of v e n t u r i approach would be most appropriate and p r a c t i c a l . The v i s c o s i t y of the polymer was determined a week a f t e r mixing with a Brookfield RVF Viscometer. Determinations of polymer v i s c o s i t y were made both before f i l l i n g the high pressure i n t e n s i f i e r pump and a f t e r leaving through the pipe which normally i s connected to the nozzle. By using no. 1 spindle and 10 rpm at 25°C, v i s c o s i t y numbers i n the order of 20 and 12 cps were obtained,respectively. From the readings obtained i t can be seen that a l t h o u g h high pres-sure was not applied,the v i s c o s i t y of the polymer was s u b s t a n t i a l l y reduced. The data suggest that the pressure i n t e n s i f i c a t i o n process of the polymer w i l l lower the v i s c o s i t y (molecular weight) by shear and s c i s s i o n of the l i n e a r chains. This i s i n agreement with observations made by Gadd (10, 11) who observed that Polyox solutions degraded or aged e i t h e r by gentle pumping for a few hours or by storage f o r about a week. 20 Polyethylene oxide "Polyox WSR ^ 3 0 1 " i s an unbranched chain mole-cule of approximately 4 x 10 molecular weight. According to the manu-facturers , the unique properties of Polyox resins include: - complete water s o l u b i l i t y ; - the water s o l u b i l i t y i s unaffected by aging; - l o w atmospheric moisture pick-up i n dry form; - products are of apparently low o r a l t o x i c i t y ; - no stream po l l u t i on from plant wastes. B. Specimen Preparation Eleven different types of commerical corrugated board were selected for experiments to provide a wide range of properties which could be en-countered i n industry. The board types differed according to burst strength, board weight and construction. Samples ranged from 125 p s i burst strength and 91 lbs per 1,000 sq f t board weight to 350 p s i and 297 lbs per 1,000 sq f t and included both A and B f lu te as w e l l as s ingle and double w a l l construction. Detai led charac ter i s t ics of the test mater ia l are presented i n Table 1. The test mater ia l was conditioned i n a control led temperature and humidity room maintained at 72°F and 50 per cent r e l a t i ve humidity with equi l ibr ium moisture content conditions for corrugated boards at approxi-mately 7.8 per cent. The 6 x 12 i n specimens were cut from previously conditioned samples haying the corrugations p a r a l l e l wi th the smaller dimensions. The prepared mater ia l was held i n the control led environment as above, 21 using a rack arrangement which ensured uniform moisture d i s t r i b u t i o n . • ' Specimens were stored i n polyethylene bags to minimize moisture change during tes t ing procedures. C. Test Conditions Specimens were cut perpendicular to the corrugations using combi-nations of cut t ing f l u i d , nozzle diameter, feed rate and pressure l e v e l as l i s t e d below: Cutting f l u i d f i l t e r e d tap water or water with 0.3% polymer add i t ive ' Nozzle diameter 0.0082 i n and 0.0102 i n Feed rate 300, 500 and 700 fpm Pressure l e v e l 20,000; 30,000; and 40,000 p s i The distance between the nozzle o r i f i c e and the table was kept constant at 5/8 i n . The above parameters were selected on the basis of previous invest igat ions (8); information obtained from MacMillan Bloedel Packaging L t d . , Corrugated Container D i v i s i o n i n New Westminster, and consideration of the capab i l i t i e s of the high pressure pump system. D. Testing Procedure 1, The energy l e v e l required for cut t ing a spec i f i c type of board was determined by the a b i l i t y to obtain a cut wi th a given combination of l i q u i d type, nozzle diameter, feed rate and pressure l e v e l . The cut-t ing procedure was defined as fol lows: 22 a. Manual se t t ing of j e t and specimen pos i t ioning -adjustments; b. Select ion of desired speed on the var iable speed feed mechanism by using stroboscope; c. Start the pump and es tabl i sh stable l i q u i d flow at the desired pressure l e v e l ; d. ; Place the specimen on the table and approach the revolving cyl inder which carr ied i t past the nozzle o r i f i c e ; e. Make cut , , recover and weigh specimen. 2. L iqu id retent ion i n the board was determined by the weight loss of the specimens due to evaporation of the l i q u i d absorbed during cu t t ing . Immediately after cu t t ing , the specimens were weighed, and allowed to recondit ion to o r i g i n a l moisture content i n a temperature and humidity control led room maintained at 72°F and 50 per cent R.H. The specimens were weighed p e r i o d i c a l l y u n t i l the equi l ibr ium moisture content was reached. The amount of l i q u i d retent ion was expressed i n grams per cm length of both sides of the kerf and was calculated at an average over a distance of 12 inches (30.48 cm). 3. Information concerning the effect of l i q u i d j e t cut t ing on the cut qua l i ty of the board was-gained by using the TAPPI standard edge-' wise compression strength tes t . - Thus, a comparison was made of cuts pro-duced by: Ca) h igh energy l i q u i d j e t using tap water; (b) high energy l i q u i d j e t using water wi th polymer addi t ive ; and (c) a t y p i c a l commer-c i a l s l i t t e r , cut. I t i s evident from the ex i s t ing l i t e r a t u r e (19, 20) that the cut-t ing operation of corrugated board may affect or weaken the fibrous network 23 for some small distance i n t o the specimen. For these reasons, the edge f a i l s at a stress l e v e l less than that at which i t w i l l rupture the com-bined board. Therefore, i f cutting weakens the fibrous network at the specimen edge, i t may be anticipated that various methods of cutting may cause varying degrees of damage and consequently cause a v a r i a t i o n i n the strength of the test specimens. Thus, the tes t i s w e l l suited f o r a comparative evaluation of the l i q u i d j e t cut q u a l i t y . The above mentioned compression t e s t , known also as a column com-pression (crush) t e s t , was conducted on a Hinde and Dauch Crush Tester which i s used f o r several t e s t procedures covered by TAPPI and ASTM stan-dards. This approach o f f e r s a prospect f o r the evaluation of cut q u a l i t y of paper board materials and provides some basis f o r p r e d i c t i n g the prob-able crushing resistance of the f i n i s h e d containers as they are subjected to crushing forces under warehouse stacking conditions. The influence of the cut q u a l i t y on the top load compression strength i s evident p a r t i c u l a r -l y i n telescope type boxes such as the f u l l telescope box, and the t e l e -scope cover box. Specimens were c a r e f u l l y cut from commercially-slit, conditioned samples and from reconditioned samples following j e t cutting. The cut samples were 1 x 4 inches and having corrugations p a r a l l e l with the smaller dimension. M u l t i p l e regression analyses were c a r r i e d out i n order to provide information on how each of the variables or t h e i r i n t e r a c t i o n a f f e c t the degree of wetting and edgewise compression strength. Because of the r e l a -t i v e l y large number of variables involved i n the study, the s t a t i s t i c a l analyses were performed f o r each board separately. 4. Evidence pertaining to the f a i l u r e mechanism was gained by 24 appl ica t ion of scanning electron microscopy. The scanning technique was i d e a l l y suited for th is purpose as i t permits study of surfaces of r e l a -t i v e l y coarse topography. Information obtained from the scanning e lec-tron micrographs of board edges exposed by high ve loc i t y l i q u i d j e t i s of great value i n attempting to explain the f a i l u re mechanism i n -volved. Further, the technique provided a means for comparative study of cut edges made by high v e l o c i t y l i q u i d j e t , laboratory knife and the commercial s l i t t e r . . In addi t ion , scanning electron micrographs of wood surfaces as exposed by high ve loc i t y l i q u i d j e t were prepared i n order to explore fur-ther the f a i l u r e mechanism by comparison of wood and paper products. CHAPTER IV RESULT'S AND DISCUSSION A. Energy Requirements When corrugated board i s cut, energy i s u t i l i z e d l a r g e l y i n the creation of new surface area. Furthermore, a c e r t a i n minimum force or energy i s required to overcome the strength or cohesion of the board's f i b r e network before the d i s i n t e g r a t i o n process begins. Once these threshold force or energy l e v e l s have been exceeded, the amount of energy required to remove a unit volume of given material would be ex-pected to remain nearly constant, This allows for a large increase i n feed with small increase i n energy. C a l c u l a t i o n of the energy requirement to remove a unit volume i s one approach that has been used i n the case of water j e t processing (17, 37). This method of quantifying i n terms of s p e c i f i c energy i s very useful i n cases such as rock cutting or d r i l l i n g , where the amount of material removed can be r e a d i l y determined. Because severance i s of p r i -mary importance, rather than the n e g l i g i b l e amount of material removed dur-ing c u t t i n g of corrugated board, a treatment of the energy r e l a t i o n s h i p s has been l i m i t e d to consideration of those parameters which are of prac-t i c a l s i g n i f i c a n c e : i . e . , (1) f l u i d properties; (2) pressure l e v e l s ; (3) nozzle diameters; (4) feed rates; and (5) p h y s i c a l properties of specimen. For the purpose of t h i s report, the c u t t i n g e f f i c i e n c y i s expressed i n terms of energy per unit length of the cut. 1. F l u i d Properties I t i s to be expected that a change i n f l u i d properties would i n -fluence the c h a r a c t e r i s t i c s and effectiveness of high v e l o c i t y l i q u i d j e t s . 25 26 An approach reported to y i e l d large increases i n cut t ing ef f ic iency by use of long chain polymeric additives was selected for study C9). The experimental data presents resul ts of tests i n which p l a i n tap water as w e l l as an aqueous so lu t ion of polyethylene oxide as the cut t ing f l u i d were used. I t i s evident i n Table 2 that the polymer addi t ive has a marked and favorable influence on the cut t ing e f f i c i ency . The cut t ing capacity at 20,000 p s i wi th the polymer j e t i s comparable to that of the water j e t at 40,000 p s i when using the same nozzle diameter. The data suggests that by using a polymer j e t i n the l i gh t e r board type, e .g . , 125/A and 175/A at 20,000 p s i pressure l e v e l the feed rates could be over twice that used i n the case of a water j e t . I t can also be seen from the data i n Table 2 that the polymer j e t , when using an 0.0082 i n nozzle i s more e f f i c i e n t than the water j e t when using an 0.0102 i n nozzle . By com-^  parison of cross-sec t ional areas of both je ts i t can be seen that the smaller diameter polymer j e t i s more e f f i c i e n t , having only 64.6 per cent of the area used by water j e t . In order to explore more'deeply the effect of polymer as compared to water, a supplemental cut t ing test has been conducted. In th is test the depth of j e t penetration during cut t ing of wood was measured. The test resul ts and the cut t ing conditions are given i n F i g . 6. From the presented data' i t i s evident that depth of penetration i s up to 50 per cent higher i n the case of the polymer j e t as compared to that obtainable w i t h the water j e t , With an increase i n nozzle diameter or pressure l e v e l the difference i n penetration increases. From this graphical presentation i t can be seen that the re la t ionship between pressure l e v e l and depth of 27 penetration i s almost l i n e a r . This observation as w e l l as general f l u i d mechanics suggests that the cut t ing act ion i s related to the j e t force (F ig . 7) rather than to the j e t energy (F ig . 8) . Based on the v i s u a l observations and c l ea r ly evident i n F i g . 9, the polymer j e t i s less dispersed than the water j e t when using the same nozzle diameter and pressure l e v e l . This can be explained based on the observation made by Vereshchagen (32) that decrease of j e t con ic i ty (d i s -persion) can be achieved by v i s c o s i t y increase of the f l u i d . I t i s also evident from the ex i s t ing l i t e r a t u r e (1, 10, 11, 12, 13) that very d i lu t e solutions of cer ta in macromolecules can have a dramatic effect i n reduc-ing drag i n turbulent flow condit ions. One of the materials reported to reduce drag i n water i s polyethylene oxide. Polyox has been shown to be ef fec t ive at very low concentrations — less than 100 weight parts per m i l l i o n . The optimum concentration i n reducing drag i s reported to be 20 w.p'.p.m. (1). According to Gadd (10) the contaminant molecules i n -crease the f l u i d v i s c o e l a s t i c i t y and the essent ia l requirements for re -duction of turbulent drag i s obtained by molecular elongation. I t i s possible that the presence of elongated molecules might lead to increased d i s s ipa t ion of turbulence by reduced tranverse motion of the j e t . Gadd (10) observed that the-Reynolds number must exceed cer ta in threshold v a l -ues i f reduction i n turbulent drag i s to be expected. I t i s also evident that , the phys ica l properties of f l u id s which reduce drag do not follow a common pattern, and may even vary markedly for one given addi t ive as the concentration i s increased. No completely sat-i s fac tory explanation of th is anomaly has yet been found, although in ten-28 sive e f f o r t s have been made by many inv e s t i g a t o r s . Also, these obser-vations might not ne c e s s a r i l y apply to this p a r t i c u l a r s i t u a t i o n where the flow conditions are e n t i r e l y d i f f e r e n t . As an example, the optimum concentration of the polyethylene oxide "Polyox WSR - 301" s o l u t i o n as a cutting f l u i d w i l l be much higher i n th i s a p p l i c a t i o n than that i n the case of reduction of drag mentioned above. Based on the preliminary t e s t s , t h i s optimum concentration would be close to that used i n the experiment, e.g., 0.3 per cent. The degradation of molecular length of "Polyox WSR - 301" solu-t i o n , when subjected to continued mechanical shearing action, may be con-siderable f o r some applications. This phenomena was observed during pump-ing without pressure i n t e n s i f i c a t i o n and has been mentioned i n the descrip-t i o n of l i q u i d requirements. The polyethylene oxide i s also affected by aging. Their d i r e c t e f f e c t on cutting of corrugated boards has not been studied herewith. 2. Nozzle Diameter The influence of nozzle diameter on the cutting e f f i c i e n c y has been studied only for the water j e t . The data suggest that an i n -crease i n energy l e v e l by using large nozzle diameter w i l l r e s u l t i n large gains i n feed rates. This was observed i n the case of 125/A board which at 20,000 p s i can be cut at 300 fpm feed rate by using an 0.0082 i n nozzle diameter. The same board can be cut at 700 fpm, at the same pressure l e v e l , by using an 0.0102 i n nozzle diameter. I t appears that an increase i n force l e v e l of 55 per cent (Fig. 7) amd energy l e v e l of 55 per cent (Fig. 8) permits doubling of permissible feed rates. 29 3. Pressure l e v e l Increases i n pressure l e v e l cause substant ia l allowable i n -creases i n feed rates . This was observed i n pa r t i cu la r i n the case of 125/A board during cut t ing wi th the water j e t by using an 0.0082 i n nozzle diameter. By increase of pressure l e v e l from 20,000 p s i to 30,000 ps i the feed rate at which a cut was obtained increased from 300 to 700 fpm. This suggests that increase i n pressure l e v e l allows large increase i n feed rate without affect ing the cut qua l i t y . 4. Board properties By considering the board propert ies , the board weight per sur-face area seems to have marked influence on the feed rate used during cut-t i n g . With an increase of board weight,the feed rate at which cut was ob-tained decreases. The board density, which depends on the board s t ruc-ture, seems to affect the cut t ing ef f ic iency to a lesser extent. This was observed i n the cases of boards 125/A and 125/B during cut t ing with the water j e t at 20,000 p s i , with the 0.0082 i n diameter nozzle . In the case of the board type 125/B^despite much higher density but s l i g h t l y lower weight (Table 1) severance was obtained at 700 fpm where i n the case p i 125/A board such effect was observed only at 300 fpm feed rate . The data presented i n Table 2 suggest that an increase i n weight basis of the board requires a subs tant ia l increase i n energy l e v e l of the j e t j which i n th i s case was control led by varying specimen feed ra tes . B. Wetting During Cutting , The degree of wetting i s of great importance during cut t ing of 30 paper products with high ve loc i ty l i q u i d j e t . Amount of l i q u i d reten-t ion depends not only on the parameters re lated to the l i q u i d j e t , such as (1) f l u i d propert ies; (2) nozzle diameter; (3) pressure l e v e l ; (4) feed rate; and (5) in te rac t ion of l i q u i d pressure and feed ra te , but i s also influenced by (6) the charac te r i s t i c of the paper board inc luding the surface area generated during cu t t ing . The data r e l a t i ng to the degree of wetting are given i n Table 3. The resul ts associated with s t a t i s t i c a l analysis for l i q u i d retent ion have been presented i n Tables 4 and 5. 1. F l u i d Properties I t has been demonstrated that f l u i d properties have marked i n -fluence not only on the cut t ing ef f ic iency, but also on.the l i q u i d reten-t ion when cut t ing with polymer and water j e t . The amount of polymer re -tention i n the board (F ig . 10) on the average was approximately 50 per cent less as compared to that obtained during cut t ing with water. The degree of wetting during cut t ing appears to be inversely related to the cut t ing eff~? • ic iency of the l i q u i d j e t . With the use of polymer j e t the cut t ing e f f i -ciency i s nearly 50 per cent higher than that had with the water j e t (F ig . 6) , With the decrease of cut t ing ef f ic iency the l i q u i d j e t begins to stag-nate and therefore the amount of l i q u i d retained i n board i s increased. 2. Nozzle diameter Since the nozzle i s one of the factors which influences amount of l i q u i d del ivered during cu t t ing , an increase of l i q u i d retent ion can be expected wi th an increase of nozzle diameter. From F i g . 10 i t i s apparent 31 that when an 0.0082 i n diameter nozzle i s used the amount of l i q u i d reten-t ion was approximately 60 per cent of that obtained with a nozzle diame-ter of 0.0102 i n . The increase of l i q u i d retent ion i n th is case i s pro-por t iona l to the increase of the cross-sect ional area of the nozzle . 3. Pressure l e v e l The effect of pressure l e v e l on the amount of l i q u i d retent ion has been presented graphical ly i n F igs . 11 and 12. From these figures i t i s evident that with an increase of pressure l e v e l the r e l a t i v e amount of l i q u i d retent ion decreases, despite the larger volumetric l i q u i d de-l i v e r y . Increase i n pressure l e v e l causes a substant ia l increase i n force and energy of the l i q u i d j e t (Figs. 7 and 8) . Therefore i t can be assumed that, at higher pressure l e v e l s , the j e t stagnation i s reduced which should be i n d i rec t r e l a t i on with cut t ing ef f ic iency as pointed out e a r l i e r . 4. Feed rate From the s t a t i s t i c a l data given i n Tables 4 and 5, i t i s evident that the feed rate s i g n i f i c a n t l y influences the degree of wett ing. A s i g -n i f i c a n t effect of the feed rate on the polymer re tent ion was observed for the fol lowing boards: 200/A, 200/B, 275/A, 275/B and 350/A. I t was found that about.70 to 80 per cent pf the t o t a l va r i a t i on of polymer re -tention could be explained by va r i a t i on i n feed ra tes . S imi lar trends are observed during cut t ing w i t h the water j e t . Polymer and water reten-t i on as a function of feed rate are presented i n Figs. ' 13 and 14, respec-t i v e l y . Polymer retention (F ig . 13) decreases i n a l l the boards tested wi th the increase of feed rate from 300 to 500 fpm. However, further in^-32 crease of feed rate up to 700 fpm has no e f f e c t on polymer retention. In contrast to polymer retention, the feed rate has a greater e f f e c t on the retention of water as shown i n F i g . 14. The increase of feed rate from 300 to 700 fpm r e s u l t s in' a further 40 to 50 per cent decrease of water retention i n the board types with lower basis weight. In the 200/A, 200/B and 275/B boards the decrease of water retention i s about 30 per cent. A decrease of l i q u i d retention, with the increase of feed rate, can be ex-plained by lower volumetric delivery per unit contact time of the board and l i q u i d . 5. Interaction of L i q u i d Pressure and Feed Rate From the s t a t i s t i c a l data given i n Tables 4 and 5, i t i s evident that a high influence i n the degree of wetting i s also exerted by i n t e r -a ction of feed rate and pressure l e v e l . E f f e c t of th i s i n t e r a c t i o n f o r the boards 125/A and 125/B i s presented g r a p h i c a l l y i n F i g . 15. In both cases an increase i n pressure l e v e l and feed rate r e s u l t s i n a decrease of l i q u i d retention. This i s v a l i d when feed rate increases from 300 to 500 fpm are considered. By even further increase of feed rate from 500 to 700 fpm and at higher.pressure l e v e l s the amount of l i q u i d retention increased due to j e t stagnation and lower cutt i n g e f f i c i e n c y . This i s true only f o r these two board types, but not i n general. I t i s expected, how-ever, that by re s t o r i n g the required cutting e f f i c i e n c y ^ b y increasing the pressure l e v e l and nozzle diameter r e l a t i o n s h i p , lower l i q u i d retentions may be obtained even at these higher feed rates and low basis weight boards. 6. Board C h a r a c t e r i s t i c s From graphical presentation of l i q u i d retention versus board 33 weight (F ig . 11) i t i s evident that there i s d i rec t re la t ionship between board weight and degree of wett ing. With regard to board density (F ig . 12) an inverse re la t ionship between density and degree of wetting has been established. Because of various board structures having A and B f lu t e s , s ing le and double w a l l s , and different strengths, board density does not necessar i ly re la te to the board resistance and accessible sur-face area to wetting during cu t t ing . The amount of l i q u i d retent ion was generally low. In the l i gh t e r board types, e . g . , from 125 p s i to 175 p s i nominal burst strength (F ig . 10), the amount of water retent ion on both sides of the cut did not ex-ceed 0.3 g/cm. Retention of polymer wi th in the same range of board types as above was below 0.2 g/cm. According to the random measurements conducted during water j e t cut t ing about 70 per cent of the absorbed water evaporated wi th in the f i r s t hour during condit ioning to equi l ibr ium moisture content at con-stant temperature (72°F) and RH (50 per cent) . C. Evaluation of Cut Quali ty i Comparative cut qua l i ty obtainable by using water and polymer je ts has been evaluated by the suggested TAPPI Standard Edgewise Compression Test, These values were compared w i t h the values obtained from what was considered a t y p i c a l s l i t t e r cut. From the test resul ts presented i n Table 5 and F i g . 16, i t i s evident that a cut by l i q u i d j e t y ie lds board edgewise compression strength up to 90 per cent higher as compared wi th an i n d u s t r i a l s l i t t e r cut. The 3 4 high value for the edgewise compression strength i s apparently due to the absence of crushing and tearing of the cut board. The l i q u i d j e t , which i s a point source of energy, apparently pu l l s the f ibres apart during cut t ing but does not weaken the fibrous network or construction of the board to the extent that a commercial s l i t t e r does. A preliminary study indicated that the edgewise compression strengths of the board after laboratory knife cut i s comparable to that obtained after a l i q u i d j e t cut. 1. F l u i d properties When using a polymer so lu t ion as a cut t ing f l u i d , the edgewise compression strength values of the boards are s l i g h t l y higher than those of boards cut wi th water. This was observed p a r t i c u l a r l y i n the case of l i g h t board types, e .g . , 125/A, 125/B and 175/A. (F ig . 16). The higher comr-pression strength after cut t ing wi th a polymer j e t can be related to the higher cut t ing e f f i c iency ; polymer j e t s being more coherent and there-fore more e f f i c i e n t . This apparently weakens the fibrous structure to a lesser extent than the water j e t does. I t i s possible that a small amount of polymer which i s retained i n boards after drying might f o r t i f y the f i b -rous web. 2, Nozzle diameter The' influence of the.nozzle diameter on the edgewise compression strength of the board becomes apparent after cut t ing with water j e t when tvro nozzles wi th dif ferent diameters were compared. However, based on the s t a t i s t i c a l analysis (Table 7) the s ign i f i can t effect of nozzle s ize on edgewise compression i s only apparent i n the case of 125/A board. 35 A s l i g h t increase i n compression strength can be observed with larger nozzle diameter only during cutting of the following boards: 175/A, 175/B and 200/A (Table 5), and when using a water j e t at 40,000 p s i pres-sure l e v e l . Otherwise, the diameter of the nozzle does not seem to have an important e f f e c t on the edgewise compression strength of corrugated boards. 3. Pressure Level The e f f e c t of the pressure l e v e l on edgewise compression strength, a f t e r cutting with polymer and water j e t , i s i l l u s t r a t e d i n Figs. 17 and 18, r e s p e c t i v e l y . From these graphical presentations, i t can be seen that with an increase of pressure l e v e l , the edgewise compression strength i n -creases. An increase of f l u i d pressure appears to be of greater consequence i n the case of the polymer j e t than that of water j e t . This again can be rel a t e d to the increase i n cutti n g e f f i c i e n c y — i . e . , improved depth of penetration of the polymer j e t , as compared with the r e s u l t s observed with the water j e t (Fig. 9). 4. Feed Rate From the s t a t i s t i c a l data (Tables 1 and 8), i t i s evident that feed rate has s i g n i f i c a n t influence on the edgewise compression strength. This was observed a f t e r c u t t i n g with the polymer j e t (Table 7) i n the case of the following boards: 125/A, 125/B, 175/A, 200/A, and 275/A. A s i m i l a r pattern was observed a f t e r cutting with the water j e t (Table 8). Edgewise compression strength as a function of feed rate and board type has been presented i n Figs. 19 and 20. These data suggest that 36 increases i n feed rate cause s l i g h t decrease i n edgewise compression strength. By considering the high v a r i a t i o n experienced during t e s t i n g the e f f e c t of feed rate on edgewise compression strength i s n e g l i g i b l e . 5. Board properties The r e l a t i o n s h i p between weight, density and edgewise compres-sion strength of the boards i s given i n Figs. 17 and 19. In most cases at the higher board weight (lower density) i t appears that the pressure l e v e l and feed rate have a larger e f f e c t on the edgewise compression strength of the board as compared with low weight and high density. The influence of the board weight on the edgewise compression strength be-comes p a r t i c u l a r l y apparent a f t e r c u t t i n g with a commercial s l i t t e r (Fig. 16). With the increase of board weight and board thickness, higher crush-ing e f f e c t takes place during the c u t t i n g process. D. S t a t i s t i c a l Analysis Since the basic c r i t e r i o n i n t h i s study was presence or absence of complete severence of the work piece, numerous l e v e l s of the v a r iables were missing. This precluded the use of s t a t i s t i c a l methods based on analysis of variance. In view of this, multiple regression analyses were ca r r i e d out for each of the board types to study the influence of indivi^-dual v a r i a b l e s as w e l l as t h e i r i n t e r a c t i o n } a n d to e s t a b l i s h the most s i g -n i f i c a n t v a r i a b l e s contributing to the degree of wetting and edgewise com-pression strength of the board tested. Results of these analyses are pre-sented i n Tables 4, 5, 7 and 8. Board wetting during c u t t i n g with the 37 polymer j e t was influenced most s i g n i f i c a n t l y by feed rate (x^). About 70 to 80 per cent of v a r i a t i o n i n 200/A/B, 275/A and 275/B boards (Table 4) was due to the rate of feeding. The i n t e r a c t i o n of feed rate and pressure l e v e l also was found to be an important v a r i a b l e that c o n t r i -buted s i g n i f i c a n t l y to the v a r i a t i o n i n degree of wetting as observed i n the case of 125/A and 200/B type boards. For these boards 69 and 62 per cent of t o t a l v a r i a t i o n , r e s p e c t i v e l y , was explained by t h i s i n t e r a c t i o n . The i n t e r a c t i o n of feed rate and pressure l e v e l was also found to be s i g -n i f i c a n t during c u t t i n g with the water j e t (Table 5). This was to be ex-pected since feed rate and pressure l e v e l c o n t r o l the amount of l i q u i d a v a i l a b l e for wetting per unit length of the board during cutting. Once again, feed rate was the s i g n i f i c a n t var iable that influenced edgewise compression strength (Tables 7, 8). For board types 125/B, 200/A and 125/A the v a r i a t i o n i n edgewise compression strength explained by this v a r i a b l e ranged from 27 to 55 per cent (Table 7). Other s i g n i f i c a n t var^-iables were pressure l e v e l , nozzle•diameter ,and t h e i r i n t e r a c t i o n . The si g n i f i c a n c e of nozzle diameter i s apparent only i n the case of the board 125/A (Table 8). The v a r i a t i o n of edgewise compression strength a f t e r cutting at various pressure l e v e l s and feed rates was r e l a t i v e l y h igh. To allow def in i te conclusions on th is va r i ab l e , more r e p l i c a t i o n s would have to be included, R e l i a b i l i t y - and r e p r o d u c a b i l i t y of the test would also have to be more c l e a r l y es tabl ished. From the foregoing sections i t can be seen that factors such as f l u i d properties (water vs. polymer additive) have a marked influence on the cut t i n g e f f i c i e n c y as expressed i n terms of the maximum feed rate at 38 which a given work piece can be severed. Further, i t was found that fac-tors affect ing cut t ing ef f ic iency also have a marked influence on both wetting during cut t ing and edgewise compression strength of the samples included i n th i s study. The cut t ing var iables are usual ly in te r re la ted and optimum conditions could be obtained for each corrugated board type. E. Fa i lu re Mechanism The mechanism associated with the f a i l u r e of wood f ib re products such as corrugated board during cut t ing can l o g i c a l l y be related to the forces which i n i t i a l l y hold the f ib re web together. The cohesivesand adhesive forces,which are involved i n holding a sheet of paper together, o have been discussed by Nissan (23, 24), Ranby (27)j Higgins (15), McKen-z ie et al. (21) and Van Der Akker (31), among others. They concluded that hydrogen bonds are most important i n providing paper strength. These bonds are due to sharing a proton by two electronegative atoms, l i k e oxy-gen. They usual ly involve two hydroxyl groups and g lycos id ic oxygen atoms on the basic uni ts of ce l lu lose and hemicellulose chains. Hydrogen bonds are usual ly quite weak and can be eas i ly broken by exposure to a polar medium or by mechanical s t r a in ing . The strength of th is bond var ies from -1 -1 -1 -1 less than 1"Kcal. g mole up to some 10 K c a l , g mole (31) depend-ing on the nature of the atoms wi th which the hydrogen bond i s br idging and the presence of other atoms or groups nearby. The equi l ibr ium d i s -tances between the atoms which are bonded by the hydrogen vary from about 2,4 to 3.5 % (31). In paper making processes f ibres are brought i n close proximity to each other through the evaporation of the water medium and 39 by introduct ion-of surface tension forces associated with the removal of water. Each contact area between f ibres i s a po ten t ia l s i t e for i n t e r -f ibre bonding. When a paper sheet i s subjected to applied forces, f a i l u r e may occur e i ther between f ibres ( in te r f ib re bond breakage) and/or wi th in i n d i v i d u a l f ibres ( ih t ra f ib re breakage or adjustments). The type of f a i l u r e depends upon the r e l a t i v e strength of i n t e r f ib re bonds and f ib re strength, as w e l l as the i r in t e rac t ion . In the case of high v e l o c i t y l i q u i d j e t cu t t ing , the cut t ing force can be considered as a complex i n -terac t ion of t e n s i l e , shear, bending and f l e x u r a l forces exerted on both the f ibres and i n t e r f i b r e bonds. Scanning electron micrographs presented i n F ig s . 21 and 22, respect ively, show surfaces generated and debris carr ied from the cut by l i q u i d j e t . Based on v i s u a l analysis of these micrographs i t can be seen that the f ibres appear to be pul led out from the f ib re webs rather than severed. This indicates that i n t e r f i b r e bond breakage i s the main cause of f a i l u r e . There i s some ind ica t ion that at least a port ion of f ibres are broken. However, part of these broken f ibres were present i n the board since the corrugated medium was made from reclaimed pulp. This has been confirmed by examination of the board f ibres under l i g h t microscope. The reason for the i n t e r f i b r e bond f a i l u r e l i e s i n the weak nature of the hydrogen bond and the high energy density during l i q u i d j e t impact. Due to the extremely short time avai lable for the f ib re web to contact wi th the cut t ing l i q u i d , there i s a very small l i k e l i h o o d of a possible 40 bond weakening during cut t ing by a polar medium, i . e . , water. In contrast to the l i q u i d j e t exposed surfaces, scanning electron micrographs of the surfaces exposed by cut t ing with commercial s l i t t e r and laboratory knife are also presented i n F igs . 23 and 24, respect ive ly . These micrographs demonstrate that the f ibres are mainly severed — cut or broken — as expected. The scanning electron micrographs of wood surfaces as exposed by high v e l o c i t y water j e t were also included herewith i n F i g . 25, i n order to explore further the f a i l u r e mechanism by comparison of wood and paper products. Mechanism of f a i l u r e i n the wood i s different than i n paper board. Fa i lu re i n wood can be described as a d i s in tegra t ion process to the l e v e l of f i b r i l s and fracture of f ibres (6). The d i s i n -tegrat ion process can be related to d i rec t penetration by the j e t . This i s due to high stress at the point of impact. Fracture i n wood i s asso-ciated with secondary penetration and w i l l be control led by shear stresses developed as a resu l t of f r i c t i o n between woody tissues and the high ve lo -c i t y l i q u i d j e t . I t i s possible that f l u i d pressure levels could be found at which a change i n f a i l u r e pattern during cut t ing of r e l a t i v e l y weakly bonded papers could be obtained, No such effect was observed wi th in the range of pressures used herein. Nevertheless, the scanning electron micrographs served exce l l en t ly the purpose of v i s u a l demonstration of differences i n cut qua l i ty between the methods used. CHAPTER V CONCLUSION. Based on the experimental evidence presented, the fol lowing con-clusions can be reached. 1. Acceptable cut t ing of corrugated boards can be obtained with high ve loc i ty l i q u i d je ts at speeds i n excess of current production requirements. Acceptable speeds, according to the information obtained from l o c a l corrugated container industry, range from about 180 to 500 fpm for the products included i n th is experiment. 2. Substantial increase i n cut t ing ef f ic iency can be achieved by using low concentrations solutions of polyethylene oxide (Polyox WSR - 301). 3. From the experimental data i t i s evident that wetting of corrugated board during the cut t ing operation i s minor and can be neglected. 4. Corrugated board cut by l i q u i d j e t displays edgewise compression strength nearly twice of that obtained with the t y p i c a l con-ventional s l i t t e r . 5. Based on the scanning electron micrographs observations, i t appears that the p r i n c i p a l f a i l u r e mechanism during cut t ing wi th high v e l o c i t y l i q u i d j e t involves breaking of the i n t e r f i b r e bond. 6. The experimental'data col lec ted so far suggest that cut t ing by high v e l o c i t y l i q u i d j e t technique can offer substant ia l poten-t i a l for i n d u s t r i a l appl ica t ion of corrugated board s l i t t i n g operation. 41 CHAPTER VI RECOMMENDATIONS In order to make a proper assessment of the high v e l o c i t y l i q u i d j e t use for corrugated board s l i t t i n g operations, more complete informal t ion i s required. Addi t iona l invest igat ions should include: 1. Optimizing the concentration of the polyethylene oxide (Polyox WSR - 301). 2. Invest igat ion of possible applicat ions of other polymers than polyethylene oxide which could reduce drag under turbulent condit ions. 3. Optimization of nozzle design for high v e l o c i t y l i q u i d j e t processing. 4. Use of high ve loc i ty l i q u i d j e t for cut t ing of other wood f ibre products such as newsprint, hard board and high pressure lam^-inates . I t i s self-evident that the l i q u i d j e t concept lends i t s e l f for cut t ing of other materials such as leather , c l o t h , e tc . 5. Consideration be given to possible applicat ions of l i q u i d j e t cut t ing to pe r iphe r i a l operations such as manufacture of die board stock. 6. An appraisal of the value of l i q u i d j e t cut t ing i n terms of inherent advantages of the process, e . g , , reduction of waste, numerically control led operation, f l e x i b i l i t y , safety, freedom from tear--Ing and dust, high edgewise compression' strength, advantages i n products design and p r in t i ng should be widely pub l i c i zed . 42 LITERATURE CITED 1. Barnard, B . I . S . and S e l l i n , R . H . I . 1969. Grid Turbulance i n Di lu te Polymer Solut ions. Nature, 222: 1160-1162. 2. Bi rkhof f , G. 1957. Je t s , Wakes and Cav i t i e s . Academic Press, I nc . , New York, 353. 3. , MacDougall, D . P . , Pugh, E . M . , and Taylor , G . I . 1948. Explosives with Lined Cav i t i e s . J . Appl . Phys. 19: 563-582. 4. Bowden, F . P . , and Brunton, I . H . 1961. The Deformation of Solids by L iqu id Impact at Supersonic Speeds. Proceedings of the Royal Society, A, 263: 433-450. 5. Boyd, W. T. 1959. Mining and Transporting Coal Underground by Hydraulic Methods: A Li te ra ture Survey. Information C i r c u l a r , No. 7887. U.S . Bureau of Mines. 6. Bryan, E . L . 1963. High Energy Jets as a New Concept i n Wood Machining. Ph.D. thes i s , Ann Arbor, Michigan, 120. 7. Farmer, I.W. , and Attewel, f , p .B . 1964. Rock Penetration by High % Ve loc i ty Water Je t . Int . I . Rock Mech. Min . S c i . 2(2): 135-153, 8. Franz, N.C. 1970. High^-energy Liqu id Jet S l i t t i n g of Corrugated Board, Tappi. 53 (6): 1111-1114, 9. _ _ _ _ _ _ « 1970. High Ve loc i ty L iqu id Je t . U .S .A . Patent No. 3,524,367, August 18, 1970. 10. Gadd, G,E. 1966. Reduction of Turbulant F r i c t i o n i n Liquids by Dissolyed Addi t ives . Nature, 212: 874T-877. 11. _ _ _ _ _ • 1968. Effects of Drag-Reduction Addit ives on 76rtex Stretching. Nature, 217: 1040-1042. 43 44 Created, C.A. 1969. Effects of polymer Addi t ive on Grid Turbu-lance. Nature, 224: 1196-1197. G i l e s , W.B. 1969. Or i f i ce Flows of Polyethylene Oxide Solut ions. Nature, 224: 584-585. H a r r i s , H.D. 1970. Cutting wi th High Speed Water Je ts . Manu-facturing Developments. V o l . 2, No. 1. Nat ional Research Council of Canada. A p r i l 1970, 2. Higgins, H . G . , and McKenzie, A.W. 1963. The Structure and Properties of Paper. XIV. Effects of Drying on Cel lu lose Fibres and the Problem of Maintaining Pulp Strength. Appita 16: 145-164. Ivanov, V . A . 1966. Dis in tegra t ion of L iqu id Je t . Zhurnal P r i k l a -dnoi Mekhaniki i Tekhnicheskoi F i z i k i , 7(4): 30-37. Maurer, W.C. 1968. Novel D r i l l i n g Techniques. Pergamon Press, London, 114. McClain, W . C , and C r i s t y , G.A. 1970. Examination of High Pressure Water Jets for Use i n Rock Tunnel Excavation. Spon-sored by Department of Housing and Urban Development and the AEC. I den t i f i c a t i on : ORNL-HUD-l, UC-38-Engineering and Equip-ment. Contract No. W-7405-engr-26. McKee, R . C . , and Gander, J.W. 1957. Top-load Compression. Tappi 40(1): 57-64. ____________________ , and Wachuta, J .R . 1961. Edgewise Compression Strength of Corrugated Board, paperboard Pack-aging, November, 70^-76. McKenzie, A.W., and Higgins, H.G. 1955. The Structure and Pro-pert ies of Paper. I I I . Signif icance of Swelling and Hydro-gen Bonding i n In ter f ibre Adhesion. Aust. J . Appl . S c i . 6: 208^217. Michelson, I . 1969. F l u i d Jet Impingement — A n a l y t i c a l Solut ion and Novel Phys ica l Charac te r i s t i c . Nature, 223: 610-611. 45 Nissan, A . H . 1958. Fundamentals of Adhesion from Molecular For-ces i n Ce l lu lose . Tappi 42: 928-933. , and S te rs te in , S.S. 1964. Cel lu lose Fibre Bonding. Tappi 47: 1-6. Pack, D . C , and Evans, W.M. 1951. Penetration by High Ve loc i ty 'Munroe' Je ts . Proc. Soc. B. , 64, 298-310. P a i , S . I . 1954. F l u i d Dynamics of Je ts . Van Nostrand Company, I n c . , New York, 227. o Ranby, B.G. 1962. Summing Up of the Symposium. In Formation and Structure of Paper. Ed. F. Balam, Tech. Sec. B .P . & B . M . S . , London, 901-910. Rayleigh, J.W.S. 1944. Theory of Sound. Dover Publ ica t ions , New York, r V o l , 1, 504. Schwacha, B.G. 1961. L iqu id Cutt ing of Hard Mate r i a l s . U.S . Patent No. 2,985,050. Issued March 23, 1961. U.S . Patent Off ice . Assigned to North American Av ia t i on , Inc. Semerchan, A . A . , Vereshchagin, L . F . , F i l l e r , F .M. , and Kuzin , N.N. 1958. D i s t r i b u t i o n of Momentum i n a Continuous L i q u i d Jet of Supersonic V e l o c i t y . Soviet Phys: Techni-c a l Phys . , 3 (2) : 408-412. Van Den Akker, I . A . 1959. St ructura l Aspects of Bonding. Tappi 42C12): 940-947. Vereshchagin, L . F . , Semerchan, A . A . , and F i l l e r , F .M. 1957. Some Investigations on a Water Jet Flowing out of Nozzle under Pressure up to 2,000 atm. Tzv. Akad. Nauk. SSSR. Otd, Tekhn, Nauk. 1: 57-61. (D.S. I .R. Trans la t ion) . , F i r sov , A . I . , Galaktinov, y . A . , and F i l l e r , F .M. 1956. Some Investigations on Dy-namics of F l u i d Jets Flowing out of Nozzle under the Pressure up to 1,500 atm. Zhurnal Teknicheskoi F i z i k i . V o l . 26(11): 2570-2577. 46 34. Vereshchagin, L . F . , Semerchan, A . A . , and Sekoyan, S.S. 1959. Decay of a High-Speed Water Jet . Zhurnal Tekhnicheskoi F i z i k i , V o l . 29(1): 45-50. 35. Weber, C. 1931. Zum Z e r f a l l eines F luss igke i t s s t rah les .Zs . fur angewandte Math, und Mech., 2: 136-154. 36. Yugov, V .G. and Osipov, A . I . 1962. The Use of High-Speed Water Jets i n Wood Cutting and Processing. Translat ion No. 149, Bureau of Trans. Department of the Secretary of State, Canada. (Translated from: The Transactions of the Central S c i e n t i f i c Research Ins t i tu te of Mechanization and Energy Requirements of the Forest Industry of U . S . S . R . , 15(6), 1960.) A 37. Zelenin , A . N . , Vesselov, G .M. , and Koniashin, Y . G . 1958, Rock breaking with Water Jet Under Pressure up to 2,000 atm. A r t i c l e published i n "Problems of Min ing ." Academy of Science U.S .S .R. Ugletehizdat , Moskow, 1958: 112-122. TABLE 1 EXPERIMENTAL CORRUGATED BOARD PROPERTIES NO. BURST STRENGTH p s i CONSTRUCTION TYPE BOARD WEIGHT AT TEST BOARD THICKNESS' . cm BOARD DENSITY . 3 gram/ cm NOMINAL ACTUAL FLUTE TYPE 3 LINER/FLUTE „ lbs/1,000 ft lbs/1,000 f t 2 kg/m 2 1 125 159 A 26/26/26 100 0.49 0.51 0.096 2 125 166 B 26/26/26 91 0.44 0.29 0.152 3 175 189 A 37^/26/37% 119 0.58 0.51 0.114 4 175 196 B 3Ihl26/3Ih 114 . 0.55 0.31 0.177 5 200 281 A (heavy duty) 158 0.77 0.51 0.151 6 200 230 B 42/26/42 124 0.60 0.31 0.193 7 200 338 A/B 42/26/26/26/26 (double wal l ) 213 1.04 0.78 0.133 8 275 341 A 69/26/69 186 0.91 0.54 0.168 9 275 335 B 69/26/69 181 0.88 0.34 0.259 10 350 475 A 69+42/26/69 244 1.19 0.60 0.199 11 350 541 A/B 42/26/42/26/42 (double wal l ) 297 1.45 0.83 0.174 aFLUTE A - 32 to 37 f lutes to the l inear foot . FLUTE B - 45 to 52 f lutes to the l inear foot . TABLE 2 ACTUAL FEED RATES AT WHICH COMPLETE CUT HAS BEEN OBTAINED AT A GIVEN NOZZLE DIAMETER AND PRESSURE LEVEL 3 -BOARD CHARACTERISTICS FEET RATE , fpm • - - -.- - • POLYMER JET WATER JET NO. BURST STRENGTH, (Nominal) p s i FLUTE TYPE BOARD WEIGHT „ , 2 gram/cm BOARD DENSITY^ gram/cm NOZZLE DIAMETER, i n 0.0082 0.0082 0.0102 PRESSURE LEVEL, p s i 20,000 30,000 40,000 20,000 30,000 40,000 20 ,000 30,000 40,00C 1 125 A 0,049 0.096 700 700 700 300 700 700 700 700 70C 2 125 B. 0.044 0.152 700 700 700 700 700 700 700 700 70C 3 175 . A 0.058 0.114 700 700 700 300 500 700 500 700 70C 4 175 B 0.055 0.177 700 700 700 - 500 700 700 700 70C 5 200 A 0.077 0.151 700 700 700 - - 700 - 7C0 70( 6 200 B 0.060 0.193 700 700 700 - - 700 300 700 70( 7 200 A/B 0.104 0.133 300 700 700 - - 300 - 300 70( 8 275 A 0.091 0.168 300 700 700 - - 300 - - 70( 9 275 B 0.088 0.259 300 700 700 - - 300 - - 70( 10 350 A 0.119 0.199 300 700 700 - - 300 - - 50( 11 350 A/B 0.145 0.174 — — 700 — — — — L i m i t i n g feed rates would be above these values, b FLUTE A - 32 to 37 f lu tes to the l i nea r foot . FLUTE B - 45 to 52 f lutes to the l i nea r foot . co TABLE 3 LIQUID RETENTION AFTER CUTTING OF CORRUGATED BOARD WITH HIGH VELOCITY POLYMER AND WATER JET BOARD TYPE FEED RATE fpm . LIQUID RETENTION, g/cm POLYMER JET 3 WATER JET b BOARD NO. BURST STRENGTH, (Nominal) p s i FLUTE TYPE NOZZLE DIAMETER , i n 0.0082 0.0082 0.102 PRESSURE LEVEL, p s i 20,000 30,000 40,000 20,000 30,000 40,000 20,000 30,000 40,000 300 0.28 0.12 0.08 0.30 0.20 0.12 0.44 0.36 0.24 1 125 A 500 0.12 0.08 0.04 - 0.12 0.12 0.36 0.20 . 0.16 700 0.16 0.00 0.00 — 0.20 0.08 0.28 0.16 0.12 300 0.12 0.08 0.04 0.16 0.12 0.12 0.32 0.28 0.20 2 125 B 500 0.08 0.04 0.00 0.16 0.16 0,08 0.24 0.16 0.12 700 0.04 0.04 0.08 0.20 0.12 0.08 0.16 0.16 0.12 300 0.28 0.16 0.08 1.36 0.28 0.20 0.68 0.28 0.28 3 175 A 500 0.16 0.04 0.04 - 0.20 0.12 0.48 0.24 0.24 700 0.12 0.08 0.04 — — 0.16 — 0.24 0.20 300 0.20 0.08 0.08 - 0.20 0.12 0.48 0.28 0.24 4 175 B 500 0.12 0.08 0,04 — 0.16 0.08 0.36 0.24 0.24 700 0.08 0.04 0.04 0.08 0.32 0.20 0.12 Average value i n g/cm calculated over 30 cm kerf length ( 1 measurement ) . 'Average value i n g/cm calculated over 30 cm kerf length (Q measurement s) . TABLE 3 (Continued) BOARD TYPE FEED RATE fpm LIQUID RETENTION, g/cm POLYMER JET 3 WATER JET b BOARD NO. BURST STRENGTH, (Nominal) ps i FLUTE TYPE NOZZLE DIAMETER, i n 0.0082 0.0082 0.102 PRESSURE LEVEL, p s i 20,000 30,000 40,000 20,000 30,000 40,000 20,000 30,000 40,000 300 0.40 0.20 0.20 0.36 0.64 0.44 5 200 A 500 0.32 0.12 0.04 - — 0.32 - 0.52 0.36 700 0.36 0.12 0.04 — 0.36 — 0.36 0.24 300 0.20 0.08 0.08 _ 0.24 0.56 0.36 0.32 6 200 B 500 0.32 0.08 0.04 - — 0.32 - 0.28 0.24 700 0.08 0.04 0.04 — — 0.08 — 0.24 0.16 300 0.76 0.48 0.24 1.36 0.68 7 200 •A/B 500 - 0.28 0.20 - — — — - 0.68 (double 700 - 0.20 0.16 — — — — - 0.56 wall) 300 0.56 0.32 0.20 _ _ 0.60 8 275 A 500 .- 0.16 0.08 - — — — — 0.52 700 0.28 0.12 0.40 3Ave rage va] ue i n g/ cm calcu la ted ov er 30 cm kerf length (1 measurement). ^Average value i n g/ cm calculated over 30 cm ker f . l eng th (2 measurements) . TABLE 3 (Continued) BOARD TYPE FEED RATE fpm LIQUID RETENTION , g / C m , • POLYMER JET 3 WATER JET b BOARI NO. BUREST STRENGTH, (Nominal) p s i FLUTE TYPE NOZZLE DIAMETER, i n 0.0082 0.0082 0 .102 PRESSURE LEVEL, p s i 20,000 30,000 40,000 20,000 30,000 40,000 20,000 30 ,000 40,000 300 0.48 0.20 0.04 0.40 9 275 B 500 - ' ' 0.12 0.04 — — — _ _ 0.36 700 0.1-2 0.08 — — — 0.24 300 1.52 0.84 0.32 1.24 10 350 A 500 - 0.84 0.28 - - - — 1.12 700 — 0.44 0.20 T- — — 300 0.48 _ 11 350 A/B 500 - - 0.40 - - V - - - -(double 700 - 0.36 - . - - - - -wall) Average value i n g/cm calculated over 30 cm kerf length (1 measurement). Average value i n g/cm calculated over 30 cm kerf length (2 measurements). TABLE 4 STATISTICAL DATA OF A POLYMER RETENTION AFTER CUTTING BOARD TYPE BURST FLUTE SIGNIFICANT NO. STRENGTH TYPE VARIABLE p s i R 2 N S E E DF 1 125 A X 7 0.6987 9 0.1283 8 2 125 B c X 7 0.2383 9 ^0.0933 8 3 175 A X 7 X 7 X 14 0.6136 0.8510 9 0.1320 0.0885 8 4 175 B — - — -5 200 A X13 0.7594 9 0.1759 8 6 200 B X 7 0.6262 9 0.0911 8 7 200 A/B X 3 0.7036 7 0.3225 6 8 275 A ; X 3 0.7825 7 0.2074 6 9 275 B X 3 X 3 X 9 0.8106 0.9625 7 0.1835 0.0913 6 10 350 A X 3 0.7207 7 0.6401 6 11 350 A/B x 14 0.8421 3 0.0973 2 Symbols: - nozzle diameter x r x„ x^ - pressure l e v e l x„ - x . x . - feed rate - l i q u i d re tent ion/ edgev;ise compression strength x^ . x^ x , - X x„ 1 • 3 - x 2 . x 3 x 10 11 x 12 X 13 1 4 - x . - X , - x r _ x . x r x„ x^ X , These symbols will also apply in Tables 5, 7 and 8. TABLE 5 STATISTICAL DATA OF WATER RETENTION AFTER CUTTING BOARD TYPE BURST STRENGTH p s i FLUTE TYPE SIGNIFICANT VARIABLE N SE, DF 125 125 175 175 x 13 X l X13 x. X l X 7 x. X 3 X 9 x 2 X 3 X 9 x 3 X l l X 3 X 5 X l l 0.5719 0.7073 0.4133 0.6099 0.5393 0.6663 0.7392 0.5575 0.7234 0.8475 32 36 0.1843 0.1550 0.1333 0.1103 0.2686 26 0.2335 0.2111 0.1947 28 0.1570 0.1190 31 35 25 27 200 x 13 0.4558 18 0.2505 17 200 X 13 X 3 X13 X 3 X 7 X13 0.7500 0.8060 0.8873 0.1712 20 0.1552 0.1219 19 TABLE 6 EDGEWISE COMPRESSION STRENGTH OF CORRUGATED BOARD , AFTER CUTTING WITH COMMERCIAL SLITTER3 POLYMER JET AND WATER JET BOARD TYPE FEED RATES fpm POLYMER JET WATER JET COMMERCIAL SLITTER CUT NOZZLE DIAMETER, i n 0.0082 0.0102 0.0082 BOARD NO. BURST STRENGTH (Nominal) p s i FLUTE TYPE PRESSURE LEVEL, ps". 20,000 30,000 40,000 20,000 30,000 40,000 20,000 30,000 40,000 300 113 119 125 107 110 111 111 117 108 1 125 A 500 107 123 123 • - 114 113 105 108 116 73 700 115 112 125 — 111 123 108 105 103 300 102 109 120 102 102 107 101 100 100 2 125 B 500 108 110 109 92 105 . 103 104 100 103 79 700 102 105 105 102 . 102 106 107 103 106 300 105 109 116 _ 105 109 104 103 111 3 175 A 500 100 110 109 - • 99 101 106 102 110 67 700 103 115 116 - — 107 — 106 110 300 101 105 106 114 107 100 110 108 4 175 B 500 108 117 112 — 110 105 110 102 110 84 700 112 108 114 - - 106 108 109 109 Average value from 6 measurements expressed i n . l b s . / 4 l i nea r inch . A\TPracre^ T r a i l ipacnrompnfc PYtirpccorl nn 1 V i c /A 1-i-noov TABLE 6 (Continued) BOARD TYPE FEED RATES POLYMER JET WATER JET COMMERCIAI SLITTER CUT NOZZLE DIAMETER, i n 0.0082 0.0102 0.0082 BOARD NO. BURST STRENGTH. (Nominal) p s i FLUTE TYPE fpm PRESSURE LEVEL, p s i 20,000 30,000 40,000 20,000 t 30,000 40,000 20,000 30,000 40,000 300 125 134 137 _ 130 _ 137 138 5 200 A 500 127 134 137 - - 128 133 131 93 700 122 170 140 • — 126 — 118 123 300 114 126 128 _ _ 124 I l l 111 118 6 200 B 500 123 132 122 - - 122 - 111 118 78 700 121 128 133 — —* 125 — 119 118 300 213 229 249 _ 211 236 7 200 A/B 500 - 241 229 - - - - - - 232 155 (double 700 - 207 248 - - - - - • 236 wall) 300 160 165 177 _ 156 164 8 275 A 500 - 161 161 - - - - 169 114 700 160 . 173 162 TABLE 6 (Continued) BOARD TYPE FEED RATES fpm POLYMER' tJ_;r WATER JET COMMERCIAL SLITTER CUT NOZZLE DIAMETER, i n 0.0082 0.0102 0.0082 tfOARD NO. BURST STRENGTH (Nominal) p s i FLUTE TYPE PRESSURE LEVEL, p s i 20,000 30,000 40,000 20,000 30,000 40,000 20,000 30,000 40,000 300 168 165 168 ' 1 170 177 9 275 B 500 _ 166 178 - • . - - - - 171 120 700 173 173 172 300 189 240 254 219 10 350 A . 500 - 202 240 - - - - - 229 135 700 218 242 300 284 11 350 A/B 500 - 291 - — — _ _ _ 197 700 297 — TABLE 7 STATISTICAL DATA OF EDGEWISE COMPRESSION STRENGTH AFTER POLYMER JET CUT BOARD TYPE NO. BURST STRENGTH p s i FLUTE TYPE SIGNIFICANT VARIABLE N SE. E DF 1 2 3 4 5 6 7 8 9 10 11 125 125 175 175 200 200 200 275 275 350 350 A B A : B A B A/B A B A A/B 3^ 3 13 x 2 X 8 x. 1 3 13 13 0.5514 0.2747 0.6363 0.4743 0.1657 0.4388 0.4175 0.2455 0.4423 27 27 27 30 24 30 21 4.9327 26 5.1321 26 4.9132 6.6964 5.5928 6.6597 5.8578 12.3342 26 29 23 29 20 0.1852 21 7.3887 20 0.4795 21 21.2180 20 0.3305 9 8.3457 8 TABLE 8 STATISTICAL DATA OF EDGEWISE COMPRESSION STRENGTH AFTER WATER JET CUT BOARD TYPE BURST FLUTE SIGNIFICANT NO. STRENGTH TYPE VARIABLE p s i R N SE„ DF 1 2 3 4 5 6 7 8 9 125 125 175 175 200 200 200 275 275 A B A B A B A/B A B X 13 x. x„ X , 0.0906 48 0.1189 59 0.1792 39 0.3339 27 0.2637 . 30 6.2595 47 4.4878 53 4.9988 53 7.7690 .26 6.8988 29 0.5643 12 10.0033 11 0.0926 12 12.5388 11 0.0584 12 6.7692 11 59 FIG. 2. View of high pressure pump system and feed mechanism. 60 FIG. 5. Cross-sect ional diagram showing de t a i l s of nozzle design. 62 0 . 6 0 . 5 -o Polymer, 0.0102 i n nozzle diameter _e Water, 0.0102 in nozzle diameter Polymer, 0.0082 i n nozzle diameter __ Water, 0.0082 i n nozzle diameter o C 25 O t-t „ H W I S W 10,000 20,000 FLUID PRESSURE, p s i 30,000 40,000 FIG. 6, The e f f e c t of polymer vs. water j e t penetration during cut t i n g of Douglas-fir wood, where j e t was perpendicular to annual rings and feed rate tan-g e n t i a l . 63 7 . 0 10,000 20,000 30,000 40,000 FLUID PRESSURE, p s i FIG. 7. Relationship between pressure l e v e l and je t force for the two nozzle s izes used i n the experiment. 64 FIG. 8. Relationship between f l u i d pressure energy for nozzle s izes used i n the and j e t experiment.' 65 F I G . 9. Photographs of polymer j e t (a), and water j e t (b). Pressure l e v e l 40,000 p s i , nozzle diameter 0.0102 i n . Water, 0.0082 i n n o z z l e d i a m e t e r P o l y m e r , 0.0082 i n n o z z l e d i a m e t e r ^ Water, 0.0102 i n n o z z l e d i a m e t e r P r e s s u r e l e v e l = AO,000 p s i Feed r a t e = 300 fpm. _jy__I__ 175/A 175/B 200/A 200/B 200/A/B 275/A BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e t y p e i FIG. 10. L i q u i d r e t e n t i o n i n b o a r d s a f t e r c u t t i n g w i t h p o l y m e r and w a t e r j e t as a f u n c t i o n o f b o a r d t y p e . 275/B 350/A 350/A/B 0 125/A 125/B 175/A 175/B 200/A 200/B 200/A/B 275/A 275/B 350/A 350/A/B BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type FIG. 11. Polymer retention i n board after cutt ing, as a function of pressure l e v e l and board type. • I I I I I I ' 1 ' 1 In 0 125/A 125/B 175/A 175/B 200/A 200/B 200/A/B 275/A 275/B 350/A 350/A/B BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type ON FIG. 12. Water retention i n board after cut t ing as a function of pressure l e v e l and board type. 1.2 . 1.0 -e a 60 z o M H Z W H 0.8 0.6 o 0.4 -0.2 --o • 300 fpir feed rate _a 500 fpm feed rate _^ 700 fpm feed rate Nozzle diameter = 0.0082 i n Pressure l e v e l = 40,000 p s i 125/A -125/B 175/A 175/B 200/A 200/B 200/A/B 27.5/A 275/B 350/A 350/A/B BOARD TYPE, NOMINAL.BURST STRENGTH, p s i / f l u t e type FIG. 13. Polymer retention i n board after cut t ing as a function of feed rate and board type. <J3 } ' ' 1 • • ' I - I I I - I 0 125/A 125/B 175/A 175/B 200/A 200/B 200/A/B 275/A 275/B 350/A 350/A/B BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type o FIG. 14. Water retention i n board after cut t ing as a function of feed rate and board type. 71 20,000 30,000 40,000 FLUID PRESSURE, p s i FIG. 15. L iqu id retent ion i n board (125/A and 125/B) after cut t ing with water and polymer j e t . 60 50 " i g 40 2 H oo S3 o M CO S 30 pi o u w o o M U o B 20 10 Commercial s l i t t e r cut Polymer j e t cut Water j e t cut Nozzle diameter = 0.0082 i n Pressure l e v e l = 40,000 p s i Feed rate = 300 fpm. 125/A 125/B FIG. 16, 175/A 175/B _ _ ; _ L 200/A 200/B 200/A/B 275/A 275/B BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type Edgewise compression strength a f t e r c u t t i n g with commercial s l i t t e r , polymer and water j e t . 350/A 350/A/B r 33 H O Z W C<S H CO Z o M CO CO w O o w CO M 12 w o Q W 60 50 20 30 20 10 9 — —0 • — — • Board weight o 20,000 p s i pressure l e v e l 30,000 ps i pressure l e v e l 40,000 p s i pressure l e v e l Nozzle diameter = 0.0082 i n Feed rate = 300 fpm. " 150 250 200 50 0 125/A 125/B FIG. 17. 175/A 175/B 200/A 200/B 200/A/B 275/A 275/B BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type 350/A 350/A/B Edgewise compression strength of boards after cut t ing wi th polymer j e t as a function of pressure l e v e l and board type. o o o CO H 100 P> o CQ 0 0 H o w Pi LO 2: o M CO CO w a o u w co M 12 W O Q W 60 50 40 30 20 10 J . 20,000 p s i p-r-essure l e v e l 30,000 p s i pressure l e v e l 40,000 p s i pressure l e v e l Nozzle diameter = 0.0102 i n . Feed rate = 300 fpm. X JL 125/A 125/B FIG. 18. 175/A 175/B 200/A 200/B 200/A/B 275/A 275/B BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type 350/A 350/A/B Edgewise compression strength of boards after cut t ing with water jet-as a function of pressure l e v e l and board type. 5 3 O M CO CO W Pi o cj w CO r-l St w o Q W 60 -c ^ 50 re H o w pi H co 40 30 20 10 _o Board density _o 300 fpm feed rate __ 500 fpm feed rate __ 700 fpm feed rate Nozzle diameter = 0.0082 i n Pressure l e v e l = 40,000 p s i 0.25 0.20 .0.15 0.10 - 0.05: 125/A 125/B 175/A 175/B 200/A 200/B 200/A/B 275/A 275/B 350/A BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type 350/A/B FIG. 19. Edgewise compression strength of boards a f t e r c u t t i n g with polymer j e t as a function of feed rate and board type. S a H M CO i s w Q s <! o pq L n ' • • • 1 1 ' 1 1 1 1 125/A 125/B 175/A 175/B 200/A 200/B 200/A/B 275/A 275/B 350/A 350/A/B BOARD TYPE, NOMINAL BURST STRENGTH, p s i / f l u t e type FIG. 20. Edgewise compression strength of boards after cu t t ing with water j e t as a function of feed rate and board type. 22 X 23% X FIG. 21. Scanning electron micrographs of corrugated board (125/B) cut with water j e t at pressure l e v e l of 40,000 p s i and 300 fpm feed ra te . 78 FIG. 22. Scanning electron micrographs of debris removed from the cut by l i q u i d je t during cut t ing of corrugated board. 79 FIG. 23. Scanning electron micrographs of corrugated board (125/B) cut with commercial s l i t t e r at approxi-mately 300 fpm. 80 24 X 120 X FIG. 24. Scanning electron micrographs of corrugated board (125/B) cut wi th laboratory kn i fe . FIG. 25. Scanning electron micrographs of sugar maple wood cut with high v e l o c i t y water j e t at 40,000 p s i pressure l e v e l . LIST OF SYMBOLS Quantity Accelerat ion Density Symbol Engineering Dimensions f t / sec 2 4 lb /sec / f t Depth of penetration Energy per uni t time xn f t - l b / s ec Force lb Jet diameter i n Jet ve loc i t y Mass Pressure Speci f ic weight Specimen feed rate Surface tension V m R-' a-' f t / sec lb : s e c 2 / f t l b / i n 2 l b / f t 3 in/min dynes/cm Time sec 

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