PSI - Issue 66

Antonio R Quiñonero-Moya et al. / Procedia Structural Integrity 66 (2024) 175–180 A. R. Quiñonero-Moya et al. / Structural Integrity Procedia 00 (2025) 000–000

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1. Introduction Understanding bone microfracture could help in assessing bone fracture risk at the macroscale. The increasing aging of the world population results in a more significant number of bone pathologies. Although morphometric studies are usually carried out, research focusing on microconstituent mechanical properties is limited, especially in terms of toughness. At the microscale, cortical bone has three main structural components: secondary osteons, interstitial tissue and cement lines. Several numerical models have been developed in the literature to study cortical bone microcracking. Giner et al. (2017) used a Continuum Damage Mechanics model to study bone microcracking and estimated the cement lines critical energy release rate � . Li et al. (2013) used XFEM to model the failure of all the microconstituents. Maghami et al. (2021, 2024); Maghami and Najafi (2023) used the Phase Field (PF) model to assess the behavior of cortical bone microcracking. Ural and Mischinski (2013) used the Cohesive Zone Model (CZM) to model the failure of cortical bone. In this work, the microcracking of cortical bone has been simulated and validated with experimental tests. The CZM has been used to model the failure of the cement lines, while the failure of the interstitial tissue has been modeled using the PF model. A good agreement regarding the crack path and the maximum load has been achieved between the experimental tests and the numerical model. 2. Experimental tests Four samples of ovine cortical bone were obtained from the diaphysis of a tibia, being 1 mm thick Giner et al. (2017). All the tissues from the samples were removed except for the cortical bone. A notch of approximately 0.5 mm radius was created on the samples. Three-point bending tests were carried out using an electromechanical universal testing machine. The applied load speed was 1 mm/s so quasi-static conditions are considered. The experimental setup and the load-displacement curve for each test are shown in Fig. 1.

Fig. 1. Experimental setup (left). Load - displacement curves from three-point bending tests (right). Giner et al. (2017). Reproduced with permission of Elsevier. 3. Numerical model The microconstituents of cortical bone were modeled using a 2D plane stress Finite Elements model (see Fig. 2). Image segmentation was used to adequately capture the osteon and interstitial tissue distribution near the crack propagation zone. Homogenized material properties of interstitial tissue were used far from the region of interest. The