Contact analysis of fractal surfaces in earlier stage of resistance spot welding

A revised fractal contact model followed Zhu is utilized to analyze the contact behaviors of electrode/workpiece (E/W) and workpiece/workpiece (W/W) interfaces for aluminum alloy and low carbon steel, respectively. The influences of load, fractal parameters and temperature on the contact rate and the effect of strain hardening exponent on the plastic area fraction are explored, respectively. Analysis results show that the contact rate of W/W interface is bigger than that of E/W interface for Al and the opposite is true for Fe. For a same interface, the contact rate for Al is bigger than that for Fe. The reduction of elastic modulus will increase the contact rate. The deformation type of the contact spot under heavy load changes from elastic to plastic and again to elastic via the elastoplastic deformation. Comparison with the predicted and the experimental curve illustrates that the predicted curve is in better agreement with the measured and the analysis results are right.