Study The Stress Intensity Factor Of Cracked Semi-circular Bending Specimen By Numerical Simulation

Failure load of Structures often is very low because of the cracks. Effects of thedefects on the buildings constructed by brittle materials are serious. Because of the largestress gradient near the crack tip, Strength criterion, which based on the hypothesis thatthe material is uniform and continuous, is no longer effective. So, it is very useful tostudy the fracture toughness of materials. The stress intensity factor (K factor) is animportant parameter for studying the fracture of the linear elastic materials. Determiningthe fracture toughness (KIC) is very important for establishing the Fracture criterion thatbased on the stress intensity factor. Because of the heterogeneity of brittle materials isvery serious and it is difficult to prepare specimen or apply load, so the traditional smallspecimen test for measuring the fracture toughness of metallic materials, such ascompact tension specimen method, three point bending test, cannot be used to brittlematerials. Semi-circular bending (SCB) test is an advanced method for measuring thefracture toughness of brittle materials. In this test,such problems need to be solved:1)the formula of KIunder mode-I loading;2)the change regulation of KIand KIIundermixed mode loading;3)calculating the coordinates of crack tip of pure mode-II crackand the ratio between KIand KIIunder mixed mode loading. It is hard to get thetheoretical solution of SCB test because of the complex boundary conditions. In thispaper, finite element method is used to finish these studies:1)proving the interactionintegral method is reliable for measuring the K factor;2)the formula of the K factor ofpure mode-I fracture of SCB test and Brazilian disk(BD) test;3)formula of KIand KIIwhen a/R and β (the angle between crack and vertical direction)are in a certain range;4)the coordinate of the crack tip of pure mode-II crack;5)the precision of KI/KIIischecked as high.