Fundamental analysis of the in situ simulation of resistance spot welding processes

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Resistance spot welding is a joining process for metallic materials which is simple to implement, highly productive and reliable. Due to its high economy and the achievable low cycle times, resistance spot welding is increasingly used for demanding welded joints, such as the joining of light metal sheets, thin-plate thick-plate connections, mixed compounds and coated sheets. With tighter tolerance zones in combination with a steady increase in quality requirements the necessity of a secure control of the process occurs. Even the requirement of a quality assessment of each individual welding point is possible. Destructive testing procedures cannot be used for this 100% inspection. Nondestructive testing methods (NDT) are currently being developed and used in the first practical applications. But, NDT always involves additional equipment and organizational effort. In addition to NDT, a large number of object-specific data and parameters are available due to the digitization of production over the entire process chain (e.g. from the sheet metal on the coil to the finished car-body). These data can be used in the future for the simulation-based analysis of each individual workpiece in each process step. This new approach can significantly reduce the effort for destructive or non-destructive testing. For this purpose, an in-situ simulation (a process-related, real-time-capable simulation, implemented in the welding inverter), of the resistance welding process is carried out with the process data and parameters valid for the current workpiece. Critical welds can be identified automatically and selected for further testing. Furthermore, the in-situ simulation with allows the machine operator an intuitive "insight" into the welded connection by visualizing the weld nugget that has just been created. In addition, pre-simulations can be carried out "in-situ", i.e. on the machine, for example for the determination of welding range diagrams or parameter adjustments.The aim of this research project is to develop, implement and test suitable model approaches for the in-situ simulation of resistance spot welding processes. Finally, the potential of in-situ simulation will be investigated and evaluated experimentally.