Wear rate effects on strength of bone

The wear rate sensitivity of hardness and strength is a key parameter for evaluating the surface integrity of a machined bone. The wear rate is presented as a parameter that accounts for the increase in strength, hardness, and decrease in toughness. The wear rate parameter is both a function of the cutting tool speed and bone geometry. The Rockwell hardness test is used to assess the surface hardness and identify the wear rate effect. An additional load deconvolution analysis is presented to account for the deformation and fracture mechanisms evident from a direct surface measurement using scanning electron microscopy (SEM). Archimedes’ method is used to measure the apparent density, and a porosity correction is applied to the hardness and strength data to compute a yield stress, which is in good agreement with uniaxial compressive strength and microindentation hardness measurements reported in the literature. The combined hardness model (CHM) is also presented as an indentation model that simultaneously accounts for bone plasticity, fracture, and densification from an excessively high projected area hardness calculation. The simulated crack lengths are shown to be within an order of magnitude accuracy with SEM direct crack measurements. Each method used was able to capture the wear rate sensitivity and insensitivity for the bovine distal and proximal femur, respectively.