Numerical Simulation Of Stress Off The Compound Crack Propagation

From the view of material intensity science and fracture mechanics, crackles mean nothing but damages. They cause many project components suddenly ruptured and led to malignant accidents. But through exploring the usages of crack, using the crack propagation to realize stress blanking, a new concept of fracture technology is developed. Combining with traditional mechanical processing technique, it exploits a new technology field. Along with the development of practices and the diversity of the blanking, new requirements for fracture technology are presented. This study comes from the "incontrollable problem at last stage" in blanking workpiece with non-symmetrical geometry in the bearing industry, which means the crack propagates beyond the pre-cut V-notch field at the last stage. This paper focuses on the numerical simulation of the crack propagation process in stress blanking.Start with summarizing previous works done by previous researchers, combined with finite element methods, this paper uses FEA software to analyze the static and dynamical stress and displacement stats of the three-point bending sample (3PBS), and to compare the mechanical parameters on opposite sides of the axis of the upper and bottom V-notches. The results show that the static stress and displacement states are symmetrical on opposite sides of the axis whether the sample is symmetry in geometry or not. The dynamical responses of the opposite sides are symmetrical when the geometry of the sample is symmetry; the responses are not symmetry when the geometry is not symmetry. These results are consistent with experiments and numerical analyses done by researchers.This paper attentively studies numerical methods to simulate crack propagation. Firstly, the element birth and death module of ANSYS is used to realize the simulation of crack propagation. All elements of the model are set to be live at the beginning. The elements on the path of crack propagation are called death elements, which will be killed according the simulation results in ANSYS. In post process stage, the crack propagation path is shown by means of showing all live elements with no the death elements. Then the FRANC2D/L software is used to simulate the quasi-static crack propagation of 3PBS. To realize the simulation of crack propagation, the software uses singular elements to replace elements around the crack tip, and the mesh around the tip is refined to insure the precision in calculation. The singular elements move forward when the crack propagates, so the singular elements are always around the crack tip, and the mesh around the tip is refined. The automatic meshing technology is used to automatically delete old elements around old tip, move the tip, and generate new singular elements and auxiliary elements which connect singular elements and other elements during the process of crack propagation. Using FRANC2D/L software, the different affections on the crackpropagation path with the sample geometrical symmetry and support symmetry are studied under the quasi-static condition. The results show that in the precondition of support symmetry, symmetrical has little affections on crack propagation path, which is always moving along the axis of the V-notches. The path of non-symmetrical geometry is regular at initial stages and right-hand bend at anaphase. In the precondition of geometry symmetry, the symmetry of support stats has obvious affections on the path. Along with the non-symmetry degree of support stats increased, the offset of the crack propagation path to the axis is more increased; when the non-symmetry degree of support stats is decreased, the crack propagation path trends towards the axis of the V-notches. Under the situation of non-symmetrical geometry and support, when the right support is immovable, adjusting the left support can influence the crack propagation path. When the left support is adjusted to some location, the crack propagation path will be always along the axis of the V-notches, and at other locations, the path will be right-hand bend or l...