Sustainable Manufacturing Processes in the Automotive Industry: Acoustic Emission Proposal to Reduce the Mechanical Testing Residues

Expulsion is a common happening in the spot welding process due to misalignment of process parameters which splashes out molten metals during the fusion process. The process parameters (welding current, welding cycle, electrode compressing force, and electrode tip diameter) play a crucial role in establishing a sound weld and therefore a comparative study is developed to understand the phenomena for two different electrode compressing mechanisms. Mild steel sheets are conventionally used to characterize the weld expulsion in 75KVA pedestal AC spot welding machines; by examining very light expulsion. The welded samples are then subjected to mechanical tests such as the tensile test, hardness test, and metallurgical observation. The welding processes are also electrically recorded for acoustic behaviors as well as the dynamic resistances. The signal can be used to determine the weld quality without engaging the destructive test. In overall, the characterization results have shown that the expulsions reduce the weld strength significantly; though it happened for very light expulsion.