The strain rate dependent mechanical properties and modelling of bovine cortical bone in compression
Doctoral Thesis
2008
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University of Cape Town
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Abstract
Conventional Hopkinson bar experiments resulted in a specimen strain rate that decreases beyond reaching a maximum value at the rise time. The variation in dynamic strain rate was rectified by shaping the Hopkinson bar input pulse with a reusable, conical striker bar. The hypothesis investigated was that a varying strain rate history could result in the measurement of a smeared response for materials with significant strain rate sensitivity. Results indicate that nonuniform, dynamic strain rates result in irregular stress-strain curves; however the stress-strain responses comprise the same corridor as the constant strain rate responses. Bovine cortical bone exhibits significant strain rate sensitivity, with distinct corridors of quasi-static and dynamic stress-strain response. Fracture occurs at a higher stress for both increasing strain rate and bone density. A microstructural investigation indicated that longitudinal compression of bovine bone leads to the formation of shear bands and that fracture depends on the orientation of the vascular porosity.
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Includes abstract.
Includes bibliographical references (p. 245-253).
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Van der Westhuizen, A. 2008. The strain rate dependent mechanical properties and modelling of bovine cortical bone in compression. University of Cape Town.