Thermographic and Acoustic Imaging of Spot-Welded and Weld-Bonded Joints

The work presented here is part of a research effort focused on developing nondestructive evaluation (NDE) and testing techniques that are sufficiently fast, robust, accurate, and cost effective for on-line inspection of automotive structures. A series of laboratory experiments was conducted to assess the feasibility of thermographic and acoustic methods for evaluating the quality of individual spot welds and the structural integrity of spot-welded and weld-bonded joints. Emphasis was placed on identifying structurally weak “stick” welds, which are much more difficult to detect than broken welds. After nondestructive evaluation, the samples were subjected to mechanical tests to determine the strength of individual spot welds. Analytical and numerical models are also being developed to help interpret results of the laboratory experiments. The insight gained from the data and modeling results are essential in moving from qualitative techniques that identify flaws to quantitative methods that assess the severity of defects.