MODEL OF FLEXURAL FATIGUE DAMAGE ACCUMULATION FOR CORTICAL BONE

Analytical models that predict modulus degradation in cortical bone su bjected to uniaxial fatigue loading in tension and compression are pre sented. On the basis of experimental observations, damage was modeled as self-limiting for tension but not for compression. These mechanisti c uniaxial damage models were then developed into a model for flexural fatigue of cortical bone based on laminated beam theory. The unknown coefficients in the uniaxial damage models were obtained by successful ly fitting the resulting equations to uniaxial fatigue data from the l iterature on human cortical bone in tension and compression. Then, the predictions of the flexural model for the behavior of human cortical bone were compared with experimental results from a small but independ ent set of specimens tested at three different ranges of load in our l aboratory. The behavior of the modulus degradation curves and the flex ural fatigue lives of the specimens were in excellent agreement with t he predictions of the model.