A Numerical Technique for Three-dimensional Fatigue Crack Growth Simulation

摘要

A numerical procedure based on ANSYS applicable to the simulation of the fatigue crack growth of 3D mixed-mode is described. This procedure expresses the geometry discontinuity caused by a crack with two groups of joined Coons surfaces, which separately represent the top surface and undersurface of the crack, and then gives a subdivision for the cracked structure to ensure the quality of the mesh near the crack tip. According to this subdivision, finite element analysis (FEA) is performed to calculate the three types of stress intensity factors (SIF),KⅠ, KⅡ and KⅢ. Based on the theory of linear-elastic mixed-mode crack growth and the Paris equation, the extended direction and distance at each point along the crack front curve are obtained, and then a new crack front and expanded partial crack surface can be formed. The characteristic of parameters chosen enables the procedure to be implemented automatically and efficiently, and fatigue crack growth can then be easily simulated in a step-by-step way. Following the described technical details, some simulations of typical 3D crack fatigue growths are performed. This method's geometric adaptability and high efficiency is also demonstrated. In addition, subjected to simple load or under simple stress field, the angle of deflection of crack growth is usually obviously larger than other steps, while this conclusion may be incorrect for the case of a complex structure subjected to complex load.