Papers by Author: Nai Feng Fan

Abstract: Resistance spot welding (RSW) is an important welding process in modern industrial production, and the quality of welding nugget determines the strength of products to a large extent. Limited by the level of RSW quality monitor, however, RSW has rarely been applied to the fields with high welding quality requirements. Associated with the inversion theory, in this paper, an electromagnetic inverse model of RSW was established, and the analysis of influence factors, such as the layout of the probes, the discrete program and the regularization method, was implemented as well. The result shows that the layout of the probe and the regularization method has great influence on the model. When the probe is located at the y direction of x-axis or the x direction of y-axis and Conjugate Gradient method is selected, a much better outcome can be achieved.

Abstract: Since the nucleation of resistance spot welding is a close and invisible process, it is difficult to monitor its nucleation quality reliably. In order to estimate the quality of weld spot, this paper uses magnetic flux density around the nugget to reconstruct the current distribution in the faying surface between two workpiece. In the study, we found the inverse model of welding current and its magnetic flux density around the nugget. Since the model had ill-posedness, the regularization method was required to solve the problem. Conjugate Gradient Method was used to reconstruct the current distribution. The result shows that the image can reflect the main characteristic of current distribution, and it can be used for estimate the quality of weld spot.