Numerical Simulation Of Metal Component’s Faigue Crack Initiation And Propagation

Modern large-scale machinery and equipment, rapid, precision, making theemerging phenomenon of fatigue damage come out one after the other. Study of fatigue isbased on experimental rearch, long test time and high test costs is an important factorrestricting fatigue study. Numerical Simulation of superiority has become increasinglyprominent with the continuous development of computer. In this paper, the fatigueprocess is divided into two stages, crack initiation process in crystallography scale andmacroscale crack propagation.Grains are usually simulated as a regular hexagon or quadrilateral, which can notreflect the heterogeneity of the micro-grain interior deformation. In this paper, Voronoidiagram is used to simulate the grain. For polycrystalline materials, the grains areoriented in a random way leading to macroscopically isotropic material properties.However, each grain is anisotropic on the microscopic scale. Then we extract the averageshear stress on each slip bands through the Python language. The number of cycles ofcrack initiation is calculated using the Tanaka-Mura model. The introduction of the shortcrack will lead to the new distribution of stess. The above step calculation again andagain until the short cracks throughtout the entire model. Which means that the wholeprocess of the initiation.After the nucleation of short cracks, comes into macroscopic crack propagationstage，and is simulated with Paris model. The key problem is that the calculation of stressintensity factor. In this paper, extended finite element method(XFEM) is used to simulatethe crack propagation. The use of the Partition of Unity Method allows the behavior ofinterest to be known throughout the element-not just at the nodes, and the mesh need notalign to boundaries.In this paper, a combination of micro and macro simulation of fatigue life test notonly the number fatigue life obtained but also clearly shows the process of crackinitiation and propagation. The results of numerical simulations show that the number ofcrack initiation is about1million, and the crack propagation is about120thousand which means89%of the fatigue life is crack initiation. The consistency of simulation resultswith experimental findings show the feasibility and accuracy of this numerical simulationmethods.