An evaluating model of nugget size for resistance spot welding

In resistance spot welding of aluminum alloy, the current (I), electrode force (F) and electrode displacement (D) are studied by means of a special welder which was equipped with many sensors. The results showed that many factors effecting nugget size have their own characteristics on three dynamic parameters I, F and D. Based on the analysis of these characteristics with fuzzy mathematics, an evaluating model of nugget size is established. The model can be used for estimating the nugget size and detecting expulsion online. At the same time, the possible causes for the expulsion and unqualified nugget size will be prompted with the help of this model.