Local strain and microdamage assessment during micromechanical testing of single bovine trabeculae and cortical bone tissue

This work examined the mechanical properties of single bovine trabeculae andcortical bone tissue experimentally. In particular, microdamage and local strainswere assessed for bovine bone tissue. A three-point bending experimental setupwas designed capable of measuring local strains at the surface of such smallspecimens, using the digital image correlation technique. Microdamage formationand propagation were detected using the bone whitening effect, an opticalnon-invasive technique. This technique enabled to follow the progression oflocal strains and microdamage in real-time from which local strains at microdamageinitiation and failure could be derived.This technique was used to investigate three fundamental aspects of bonemechanics. The first study examined the strain rate sensitivity of single bovinetrabeculae. No linear relationship was observed between the strain rate and theYoung’s modulus, the amount of microdamage, the maximum tensile strain atfailure and at microdamage initiation. The second study compared the mechanicalbehaviour of single bovine trabeculae and similarly sized cortical bone samples.Cortical bone tissue exhibited significantly lower maximum strains andless accumulated damage at failure. However, no significant difference was detectedfor the maximum strain at microdamage initiation. Finally, the anisotropyof bovine cortical bone tissue was investigated. No significant difference wasfound between the Young’s modulus, the amount of microdamage and failurestrains of longitudinal and tangential bone samples. However, these parameterswere significantly lower for the radial samples. For strains at whiteningonset, no significant difference was seen for the longitudinal and radial groups,whereas the tangential values were significantly greater.The insights gained from this work enhanced our understanding of the damageproperties of bovine bone at the microstructural level. Future work is requiredto investigate the relevance of the above findings to human bone tissue