Simulation and Evaluation of New Thermographic Techniques for the Deployment in the Automotive Industry

Abstract

For the process control of resistance spot welds in automotive body structures, there are still many destructive testing methods in use. A general aim is to reduce the production costs by replacing these techniques with non-destructive procedures ensuring the joint quality as well. Since thermal pulse techniques with flash light excitation start to establish themselves for the laser weld inspection, this work focuses on the characterization of resistance spot welds. In a first approach the determination of the nugget diameter as the most important quality criterion. Three-dimensional finite element models of typical spot weld geometries are developed and validated using both model and experiment. They allow to describe the distribution of the idealized transient surface temperature corresponding to the inner heat transfer of the sample in the actual measurement. Revealing more details about their origin optimized evaluations of the experimental data can be adapted. An adequate way to test the robustness of analysis algorithms is presented and first results of recent studies measuring the diameter of typical spot welds under production line conditions are presented.