An investigation of the high cycle fatigue behavior of bovine trabecular bone
Author(s)Hastings, Abel Z., 1973-
Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.
Lorna J. Gibson.
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Fractures can be caused by fatigue loading due to prolonged exercise and age-related fragility. Fatigue loading causes microdamage in bone that leads to both a loss of stiffness and strength. Some engineering materials, such as steels, have a fatigue limit, which is represented by a stress plateau in the stress-life (S-N) curve. When loaded to levels below the stress plateau, these materials have an infinite fatigue life. Other materials, such as aluminum, do not exhibit a fatigue limit. For these materials, the endurance limit is defined as the stress amplitude corresponding to a somewhat arbitrary large number of cycles of fatigue (e.g. various texts suggest 10⁶ to 10⁸ cycles ). In previous work on compressive fatigue of bovine trabecular bone, it was hypothesized that there was a fatigue limit at a normalized stress, [Delta] [rho]/E₀, of approximately 0.0035. This study tested this hypothesis by fatigue testing bovine trabecular bone loaded to one of four normalized stresses ranging from 0.0015 to 0.0035. Failure was defined as a 10% loss in the secant modulus of the specimen. The data show that the rate of decrease of modulus reduction per cycle increased with increasing normalized stress. A fatigue limit in bovine trabecular bone was not found. While a threshold below which the fatigue life is infinite was not found, an endurance limit corresponding to 10⁶ cycles to failure was found at a normalized stress of about 0.00137. The study also showed that normalized secant modulus decreased with normalized number of cycles in the same manner for all normalized stresses.
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, February 2004.Includes bibliographical references (p. 64-70).
DepartmentMassachusetts Institute of Technology. Dept. of Materials Science and Engineering.
Massachusetts Institute of Technology
Materials Science and Engineering.