Development of numerical analysis model for resistance spot welding of automotive steel

Abstract

Resistance spot welding (RSW) is a process in which contacting metal surfaces are joined by the pressure and heat obtained from resistance to electric current flow. It is widely accepted in the industry due to its advantages in high speed and suitability for automation. The RSW process is extremely important to quality in automotive industry because approximately 6000 spot welds were used in automotive body. In addition, the RSW process is a complicated process that includes electrical, thermal and mechanical phenomena. For this reason, it is necessary that researchers should perform electric field, heat transfer and thermo-elastic-plastic analysis, and consider phase change, contact conditions and temperature dependence of material properties in order to simulate a realistic RSW process. There were lots of previous studies for RSW simulation by using Finite element method (FEM), but most of studies have performed qualitative analysis which predicts the shape of weld nugget fatigue life and residual stress. Therefore, this study defines the contents which mentioned above based on the theoretical background and reproduces a 3D DC RSW process through using ABAQUS, commercial FEM program. It also obtains the reliability in terms of simulation results through quantitative approach by comparing between the nugget shape and the actual experimental results. The error percentage of nugget width between simulation and experiment shows outstanding results that from 0.44 % to 3.80 %. Based on the simulation results through these theoretical backgrounds, it is possible to effectively trace the weld nugget shape of all steels, provided the temperature dependent material properties are available. An illustration of such a simulation to predict the nugget shape and size of resistance spot welded SPRC 340 steel is presented in the paper.