Abstract
The fatigue damage behavior of bone has attracted significant attention in both the mechanical and orthopedic fields. However, due to the complex and hierarchical structure of bone, describing the damage process quantitively or qualitatively is still a significant challenge for researchers in this area. In this study, a nonlinear bi-modulus gradient model was proposed to quantify the neutral axis skewing under fatigue load in a four-point bending test. The digital image correlation technique was used to analyze the tensile and compressive strains during the fatigue process. The results showed that the compressive strain demonstrated an obvious two-stage ascending behavior, whereas the tensile strain revealed a slow upward progression during the fatigue process. Subsequently, a theoretical model was proposed to describe the degradation process of the elastic modulus and the movement of the neutral axis. The changes in the bone properties were determined using the FEM method based on the newly developed model. The results obtained from two different methods exhibited a good degree of consistency. The results obtained in this study are of help in terms of effectively exploring the damage evolution of the bone materials.
Highlights
Bone, as a supporting organ of our body, is vulnerable to fatigue loadings due to its brittle nature
The difference in the elastic modulus of these materials and bone tissue can result in a serious “stress shield”, which is one of the main causes leading to interface loosening or even implantation failure [1,3]
The strain values of the four specimens were extracted under different fatigue values to determine the position of the neutral axis of the specimens
Summary
As a supporting organ of our body, is vulnerable to fatigue loadings due to its brittle nature. The damage resistance of bone can be improved by modifying its hierarchical structure. It is challenging for researchers in the orthopedic and mechanical fields to model the bone damage and fracture process. The bone graft materials are widely used to repair segmental defects and restore mechanical function [1,2,3]. It is vital to study the bone modulus, especially the evolution of the bi-modulus during fatigue damage. Osteons are the main structural unit in the cortical bone, which are assembled from the collagen fiber arrays [4,5]. The fibers are composed of type-I collagen fibers and hydroxyapatites [6]
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