Abstract: The Lamb wave testing for the automobile spot weld is proposed, which can be used for evaluating the diameter and the maximum tension load of the spot weld. The propagation mechanics of Lamb wave in the sample of spot weld is difficult to be investigated by analytical method because of the wave dispersion and type transformation in the wave conductor with complex shape, so the finite element method is adopted to simulate the Lamb wave propagation in the samples. The simulation results reveal that the A0 modal Lamb wave transmitted through the weld nugget has a close relationship with the characters of nugget shape such as the nugget diameter and the indentation depth. Thus, the shape and mechanical property of spot weld may be evaluated by Lamb wave method. A0 modal Lamb wave can be excited by adjusting the incident angle of probe. Experimental results indicate that the peak value of received A0 modal Lamb wave decreases with the increase of the nugget diameter and the maximum tension load of the spot weld, which are consistent with the finite element modulation, and can be used in the nondestructive evaluation on practical spot-welded structure.

Key words: Finite element analysis, Lamb wave, Spot weld