The Numerical Simulation And Analysis Of Laser Repair Welding At Crack Tip

Crack defects widely exist in materials and engineering structures, and they not only reduce the carrying capacity but also cause stress concentration at crack tip. What’s more, the crack defects are often the sources of various fracture, and even catastrophic failures. Therefore, it is of theoretical significance and practical value to study how to prevent crack propagation.The region of crack tip is the most dangerous in the whole crack, so it’s the key of crack arresting to research how to prevent the propagation of crack tip. Now, because of the complexity and economy of experiment, numerical simulation method becomes the effective means of carrying out the research of crack arrest. Therefore, the quasi-static static crack and dynamic crack are used to investigate the method of laser repair welding at crack tip based on the finite element method (FEM) and the extended finite element method (XFEM) in this paper, respectively.First of all, the temperature field of laser repair welding at crack tip is simulated. In the process of numerical simulation, the user’s subroutine of laser heat source is called to execute based on ABAQUS, and temperature dependent material properties are used. In order to improve the calculation accuracy and reduce computing time, the model is divided and the mesh at crack tip is refined. Through the post-processing, the time dependent temperature curve of each node is provided.Secondly, based on the result of the temperature field, the distribution of residual stress field is simulated by method of thermal coupling sequence. In the process of numerical simulation, it’s discussed that the continuous laser heat source and pulsed laser heat source influence the residual stress field, it’s also discussed that the crack length influences the residual stress field. It shows that the simulative results of residual stress fields by the continuous laser heat source and pulsed laser heat source are the same, when the pressure of pulsed laser’s shock-wave isn’t taken into consideration. It also shows that the values of residual compressive stresses along the crack propagation direction and the thickness direction increase with the decrease of the crack length.Once more, the crack tip opening angle (CTOA) and the J-integral of quasi-static static crack are provided by FEM. It shows that, before and after laser repair welding at crack tip, the middle tier is always the most dangerous region of crack tip. After crack arresting, the critical load of crack propagation increases, which indicates the improvement of load carrying capacity. In addition, the J-integral is analyzed, and it presents closed trend at crack tip after crack arresting.Finally, the crack tip opening displacement (CTOD) and the J-integral of dynamic crack are provided by XFEM. It shows that the critical load of crack propagation increases after crack arresting, which indicates the improvement of load carrying capacity. In addition, the J-integral is analyzed, and it presents closed trend at crack tip after crack arresting.In short, by using the three-point bend specimen with crack defect as example in this paper, the theoretical analysis and numerical simulation of laser repair welding at crack tip are carried out based on ABAQUS. The result shows that the crack tip is strengthened and the trend of crack tip extension is retarded after crack arresting. Consequently, this paper lays the foundation for the method of laser repair welding at crack tip.