Experimental and Numerical Study on Fracture in Notched Functionally Graded Metallic Biomaterials

In the present study, mode-I fracture of U-notched specimens fabricated from Functionally Graded Metallic Biomaterials has been studied experimentally and numerically. For the experimental part of the study, the desired graded plates were first produced, and then, the required notched specimens were cut from them and tested under the three-point bending in two different configurations of notch arrester and notch divider. Moreover, the effect of notch depth on critical values of fracture load and J integral was studied experimentally. Finite element method was used for the numerical part of study where the isotropic constitutive law as well as Hollomon’s equation were employed to define the material behavior. Also, in this work, the quantity of J integral has been calculated using the Rice theory, and material properties of each point within the graded regions have been specified using the strain gradient plasticity theory and variation in Vickers micro hardness. In order to have a better understanding of behavior of the graded specimens, the value of J integral at a constant load has been calculated and compared for graded and corresponding homogeneous materials. Comparison of experimental results with the numerical ones proves the capability of the employed numerical scheme in predicting the value of J integral. Also, it was observed that in contrast to homogeneous materials, the critical quantities of J integral and fracture load show an ascending-descending trend as the notch depth increases.