Journal
JOURNAL OF BIOMECHANICS
Volume 40, Issue 12, Pages 2731-2737Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jbiomech.2007.01.005
Keywords
cortical bone; tension; damage; modulus; viscoelasticity
Categories
Funding
- NATIONAL INSTITUTE OF ARTHRITIS AND MUSCULOSKELETAL AND SKIN DISEASES [R29AR044927, R01AR044927, R01AR043785, R56AR044927] Funding Source: NIH RePORTER
- NIAMS NIH HHS [AR44927, R01 AR043785-08S1, R01 AR044927, R01 AR043785, R29 AR044927, AR43785, R56 AR044927] Funding Source: Medline
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Stiffness degradation and strength degradation are often measured to monitor and characterize the effects of damage accumulation in bone. Based on evidence that these properties could be affected by not only damage magnitude but also test conditions, the present study investigated the effect of hold condition and recovery time on measures of tensile damage. Machined human femoral cortical bone specimens were subjected to tensile tests consisting of a pre-damage diagnostic loading cycle, a damage loading cycle and post-damage cycle. Controlled variables were recovery time (1, 10, and 100 min) and hold condition (zero load or zero strain) after the damage cycle. Damage measures were calculated as the ratio of each post-damage cycle to the pre-damage value for loading modulus, secant modulus, unloading modulus, stress relaxation and strain (stress) recovery at I min post-diagnostic time. The damage cycle caused reductions in all measures, and some measures varied with recovery time and hold condition. Apparent modulus degradation for both hold conditions decreased with recovery time. Stress relaxation was unaffected by recovery time for both hold conditions. Zero-strain hold conditions resulted in lower values for degradation of modulus and change of relaxation. Stress or strain recovery after the damage cycle was evident through 100min, but 90% of the recovery occurred within 10min. The results demonstrate that choice of test conditions can influence the apparent magnitude of damage effects. They also indicate that 10min recovery time was sufficient to stabilize most measures of the damage state. (c) 2007 Elsevier Ltd. All rights reserved.
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