Study on modelling simulation and distribution characteristics of residual stress during robotic weld end grinding of high strength modulated steel

Abstract

Welding technology is widely used in the aerospace, construction, machinery, and rail transportation industries. After the welding process is completed, the weld seam is typically ground to improve the assembly accuracy and surface integrity of the structural part. However, residual stresses on the surface after grinding often affect the product performance and service life of structural components. Therefore, the formation mechanism and distribution of residual stresses after the robotic weld end grinding of high–strength modulated steel welds were investigated. First, a local contact geometric model of the grinding wheel and weld was established, and a grinding -force contact model was built based on this model. Next, a model of the heat-flow distribution in robotic end grinding was analysed, and the magnitudes of the heat flow in the contact and weld-width directions were calculated for the contact area. The results of these calculations were similar to the actual heat-flow distribution. Then, based on a theoretical analysis, the finite element method was used with a birth–death element to establish a force-thermal coupled residual stress prediction model, which could simulate the material removal process during actual grinding. Finally, the accuracies and reliabilities of the theoretical and simulation models were experimentally verified. The maximum error between the maximum simulated temperature and experimentally measured value was 10 %. The minimum error was 3 % when using the same process parameters, and the residual stress error was approximately 15 %. Based on the simulations, the variations in the temperature and residual stresses with time and position were explored. The highest weld-contact surface temperature of 417.75 °C was found when grinding using process parameters ap = 0.2 mm, vs = 23.55 m/s, vw = 20 mm/s. The residual tensile stresses could be up to +553 MPa in the longitudinal direction and −161 MPa in the transverse direction. The temperature in the zone of demarcation between the weld and base material was 212.8 °C, with maximum residual tensile stresses in both the longitudinal and transverse directions, of up to 352 MPa. The analysis revealed that the magnitude of the residual stresses was consistent with the temperature variation pattern, and that the grinding depth had the greatest influence on the residual stress distribution.