The Study Of The Numerical Solving On 3D Crack J-integral

At present, along with the development of elasto-plastio fracture mechanics, the double criterion (cracked and plastic instability) _J-integral disabled assessed-picture technique have become the primary basis of the defective cracked assessment, which based upon the strict theory. However, the key that the technique to be succeeded applied is the calculation of the J-integral. Although the EPRI give a set of the approximate engineering solution method, actually the crack of parts in engineering project mostly presents inner 3D effect. If using 2D elastic-plastic or 3D elastic analysis, the result can't be precise. Because these methods have neglected the reassignation of the stress and strain which happened at nearly the top of cracks, carrying on 3D elastic-plastic analysis and J-integral calculation become the foundational work to study the expander and safety assessment of the pressure vessel cracks.On the basis of 2D J-integral expression by Rice, the text has deduced a 3D crack J-integral expression, verified it have nothing to do with the integral path, changed the "parallel slice" integral calculus which be widespread adopted in head of the cracks, adopted the "fan slice" integral calculus which reproduced the stress situation about the head of cracks. This kind of method takes full the stress-current change about the head of cracks into account, and reduces errors.The calculating model of semi-elliptical surface cracks is proposed by using the strong function of building model, analyzing and calculating in ANSYS. With the benefit of finite element method and Gaussian integral method, adopted the hexahedron 20 nodes element, 3D cracks J-integral formula will be converted into the numeric integral format_Gaussian integral format, which be prone to solve, and then the overall 3D J-integral calculating process is finished, program for calculating J-integral in the method of surrounding integral with APDL.