Effects of Stress Frequency and Bone Density on Fatigue Lives and Crack Growth Behavior in Bovine Bone

To investigate the effects of stress frequencies and bone density on the fatigue lives and crack growth behaviors, rotating bending fatigue tests on bovine compact bone were performed under various stress frequencies ranging from 0.3 Hz to 30 Hz. Cycle-dependent features were observed in the fatigue behavior of bovine bone within the above range of stress frequencies. This result differs from the previous findings that fatigue lives increase with stress frequency in the range above 30 Hz ; therefore in bone fatigue tests, it is wrong to estimate fatigue behaviors at lower stress frequencies from those obtained at higher stress frecluencies. The fatigue lives and the crack initiation time for the bone specimens were expressed as functions of both the applied stresses and the bone density. l These expressions may be useful for predicting the time when cracks may be induced in bone by daily activities