Affiliations: [a] Department of Mechanical, Aerospace and Biomedical Engineering, The University of Tennessee, Knoxville, TN, USA | [b] Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran | [c] Department of Mechanical Engineering, Ecole Polytechnique, Montreal, Quebec | [d] Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan | [e] Department of Rehabilitation Medicine, University of Toronto and Mount Sinai Hospital, Toronto, Ontario, Canada
Correspondence:
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Address for correspondence: Professor A. Shirazi-Adl, Department of Mechanical Engineering, Ecole Polytechnique, P.O. Box 6079, Station centre-ville, Montreal, Quebec, Canada H3C 3A7. Fax.: +1 514 340 4176; E-mail: [email protected].
Abstract: We investigated the effect of loading rate on tensile properties of sheep bone-anulus-bone specimens in axial direction. Disc anulus Samples with adjacent bone attachments were prepared from lateral, posterior and anterior regions of sheep lumbar spinal segments. The specimens were then tested at different strain rates under non-destructive cyclic tensile loading followed by destructive tensile loading. Each specimen was prepared by embedding the bony parts in the polymethylmetacrylate (PMMA) exposing the anulus portion to support tension. The results of non-destructive cyclic tests indicated a decrease in the hysteresis energy loss as strain rate increased. In the destructive tests, no significant differences in ultimate stress, ultimate strain and strain energy density were observed at different strain rates or annulus locations. However, there was a significant increase in the modulus at linear region as strain rate increased. Two major modes of failure were observed; rupture in the anulus mid-substance and at the anulus-endplate junction. The former failure was more frequent with no clear pattern across strain rates and locations, while the latter failure at anulus-endplate junction occurred primarily at slow strain rates.
