Study on comparison between three point bending and four point bending test condition for functionally graded material beam with crack

Abstract

Given their distinct composition and gradient structure, cracks in functionally graded materials (FGMs) can provide serious difficulties. Predicting failure and improving material design require an understanding of fracture dynamics in FGMs. The manner in which cracks initiates and propagates can be influenced by the constant changes in material properties. Because of variations in material toughness over the gradient, cracks propagate differently than in homogeneous materials. The FGM is loaded in three point bending and four point bending loading conditions, and the obtained crack propagation angles and crack propagation paths are showcased in the present paper. A functionally graded material beam (FGM) is modeled using dummy thermal load condition for obtaining varying material properties in desired direction for finite element analysis. An initial crack/defect is incorporated in the FGM beam at bottom mid location. The FGM beam is considered as simply supported beam and the same boundary conditions are applied to it. Detailed comparison of crack propagation paths is made between the three point bending and four point bending loading conditions. In case of three point bending loading only mode I condition of failure is occurring, where as in case of four point bending loading all the three modes condition i.e., mode I, II & III of failure is occurring also called as mixed mode failure condition.