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Fracture toughness design in equine hoof wall Bertram, John E.


This study applied an engineering -fracture mechanics approach to the investigation of the fracture resistance of Equine hoof wall. The fracture mechanics parameters of stress intensity factor (K), strain energy release rate (G) and the J-integral (J) were used to determine the effect of notch orientation and specimen hydration on fracture, using the compact tension test geometry. The J-integral was found to provide the best indication of fracture behaviour because it is not based on strict linear elastic behaviour, as are K and G. Hoof wall has greatest fracture resistance for cracks running vertically, parallel to the tubular structures found in hoof wall keratin. For fully hydrated material tested in this direction, the mean critical J value at failure was 1.19 x 10[sup 5] J/m[sup 2] . This was nearly three times larger than the value determined for the weakest orientation, in which the crack ran parallel to the material between the tubules. Hydration level was also found to profoundly affect the fracture toughness. An intermediate hydration level (75X RH) gave the highest mean critical J values (2.28 x 10 J/m[sup 2]), which represented a two-fold increase over fully-hydrated and dehydrated material. These results have been related to the morphology and function of the hoof in the living animal.

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