Multiphysics simulation of the resistance spot welding detection using electromagnetic ultrasonic transverse wave

Resistance spot welding (RSW) quality substantially influences the autobody's mechanical properties and safety performance. Nondestructive testing (NDT) method is widely used to evaluate the quality of RSW, but the traditional ultrasonic testing method has high requirements for coupling conditions and flat surface of the weld part. The electromagnetic acoustic transducer (EMAT) is a novel NDT technology, which has advantages of noncontact, no coupling media, and low requirements for surface flatness of the workpiece. Therefore, the electromagnetic ultrasonic transverse wave (EUTW) is developed to realize the evaluation of RSW quality in this paper. Under the COMSOL platform, the finite element method (FEM) modeling is proposed by multiphysics simulation. The multiphysical fields include electromagnetic field, acoustic field, and solid mechanics. The generation mechanism and propagation rules of EUTW in various spot welds are studied by simulation analysis. The correctness of FEM modeling is validated by EUTW experiments; results show that the experimental waveforms of EUTW are consistent with the simulation waveforms. Finally, an evaluation method of the nugget size of RSW is proposed based on the simulation and experiments analysis of EUTW detection of RSW with different nugget diameter and indentation depth. The approach presented in this paper can provide the theoretical foundation and new method for the noncontact, high efficient, and low-cost detection of RSW quality of the autobody.