Research on residual stress evolution of diesel engine piston manufacturing based on finite element method

摘要

Residual stresses generated during casting and heat treatment are one of the major challenges faced by piston manufacturing. Therefore, the change of piston residual stress from casting stage to heat treatment stage is studied by orthogonal experiment and single factor experiment. A finite element model is established to simulate the casting process and heat treatment process, the parameters such as pouring temperature, mold temperature and shake-out temperature are mainly considered in the casting simulation, while the parameters such as heating rate, holding temperature, holding time and cooling rate are mainly studied in the heat treatment simulation. At the same time, the residual stress of the piston after casting and heat treatment is measured by X-ray diffraction to verify the simulation results. The results show that the average residual stress at each measuring point of the piston is 223.6 MPa when there is no sand falling in the casting stage. The residual stress field of the piston is redistributed after sand falling, and the average residual stress value is 161 MPa, which is reduced by 29 before and after sand falling. Heat treatment can significantly reduce or even eliminate the residual stress. The average residual stress of piston is reduced to 15.2 MPa, accompanied by the great release of residual stress. This study provides a cross-software multi-process residual stress analysis method, which is of great significance for reducing and eliminating casting residual stress.