Nondestructive Spot Weld Quality Evaluation by Measurement of Structural Vibration Transfer Through Joined Panels

A nondestructive test method using structural vibrations was proposed for spot weld quality evaluations. The wave propagations in multi-spot-welded structures were analyzed using the spectral element method. The resonance frequency showed dependence on the spot stiffness due to the out-of-phase vibration modes locally generated at the testing spot. The experiments to measure the local vibrations were performed. A vehicle specimen made of multi-spot-welded ultra-high-strength steel panels was used for the evaluation. After exciting one side of the spot by an electric shaker, the resulting vibrations were measured on the other side. The transmitted responses by the input vibrations at the testing spot were obtained. The resonance frequencies depended on the wavelength for local vibrations in the specimen. The weld stiffness was predicted using the vibration transfer function. The estimated weld quality was compared to the actual spot diameter. The weld quality had influence on the dynamic properties and resonant modal vibration of the part under tests. To minimize the effect of the geometric and boundary conditions, the local vibrations affected only by the weld quality was used in this study. The proposed method enabled the efficient structural integrity evaluation using the vibration measurements of the welded structure.