Nano-Indentation of Anisotropic Material: Numerical Approaches to Extract Elasticities from Nano-Indentation

Abstract

Division of Biomechanics participates in a project together with Department of Cancer Research and Molecular Medicine, NTNU, on effects of proton pump inhibitor medication on bone quality. This common anti-stomach acid medication seems to result in an increased bone fragility in humans. As a step towards comparing mechanical properties at micro level, between sick and healthy bone tissue, mice femur have been tested at micro level using the increasingly popular tool, nanoindentation. Futher, an analytical finite element model has been created in an effort to increase the understanding of nanoindentation of bone. It is concluded that the experimental protocol is not accurate enough(SD ~ 5GPa for reduced Young's modulus) as a result of multiple factors, mainly indentation locations. The experimental results were compared to the finite element model. It was possible to match the data curves of the experimental tests with the analytical tests by adjusting the model parameters. Unfortunatly, this resulted in divergent results(plastic yield stress of ~ 600MPa and reduced Young's modulus of nearly 60% of the experimental data(32,45 GPa and 20GPa). As an effort to reduce the divergence between the experimental and analytical testing, multiple suggestions were made.