Strain rate and density dependent behaviour of bovine cancellous bone in compression

Master Thesis


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University of Cape Town

The mechanical properties of bone are determined by means of low strain rate testing performed quasi-statically on the Zwick Universal Testing Machine and high strain rate testing performed on the Split Hopkinson Pressure Bar. Cancellous bone is sourced from the vertebrae of five bovine of slaughtering age. Two sizes of specimens are machined. For quasi-static testing an aspect ratio of 2:1 is used (10 mm high and 5 mm in diameter). A ratio of 1:1 is utilised for the dynamic testing (5 mm in both length and diameter). Tests are conducted at four different strain rates of 10-4, 10-3, 10-2 and 10-1 /s for quasi-static tests and a range of approximately 800 to 1300 /s for the high impact tests. A total of 68 specimens are tested quasi-statically, with 17 specimens assigned to each strain rate. The dynamic data is gathered from tests on 18 specimens. Therefore, a total of 86 specimens are used for the combined data. The trends in yield stress, yield strain and Young’s modulus as a function of both strain rate and density were investigated. Results show that, as expected, density has a far greater effect on the mechanical properties of cancellous bone than strain rate. Due to the high scatter in results, the exact relationships are difficult to determine, although results of this work generally fall within the findings of the literature reviewed.

Includes abstract.

Includes bibliographical references (leaves 133-138).