Research On Dynamic Fracture Toughness Of Granite And Finite Element Analysis

With the development of science and technology, the stability problem of the crack under the dynamic loading are becoming increasing important. Theoretical and Experimental technology research on the dynamic fracture problem cause great attention in academic for many years. However, due to the complexity of the problem there has no formed recognition or standardized criterion on this issue so it still needs lots of time to study. Dynamic fracture toughness testing and characterization are mostly concentrated on the metal material and the exploitation of mineral resources involved in the rock material, the stability and destruction are the two major problems of rock mechanic studies. In order to avoid the possibility of disaster, we must understand the mechanism dynamic failure and study the dynamic mechanical properties.In this paper, the central cracked circular disk specimens were used to study the dynamic fracture toughness of brittle materials.The CCCD specimen has been widely used to test the fracture toughness subjected to pure mode I,pure mode II and mixed-mode loading. We promote the equation of quasi-static stress intensity factor for dynamic fracture toughness calculation.the maximum load under the balance dynamic force was substituted into the equation to get the value of dynamic fracture toughness. The results show that the fracture toughness is between5-17MPa-m1/2and the loading rate range from5×104-25x104MPa· m1/2·s-1, with increasing loading rate, Test verified the dynamic fracture toughness and loading rate has good correlation,In this paper, The load used in finite element computation is an average load of test. Dynamic finite element analysis is carried out to determine the SIF evolution,and then get the fracture toughness. In spite of an average error of6.2%between the finite element results and test processing,the dynamic fracture toughness of granite is7.42MPa·w1/2with an average loading rate of6.57×104MPa·m1/2s-1.It is feasible to promote the quasi-static formula to the dynamic situation.