A comparison of resistance spot weld quality assessment techniques

Resistance Spot Welding (RSW) is used in many different manufacturing industries to join sheet metal components due to its quick cycle times, low cost, ease of implementation and adaptability to different joint configurations and materials. However, quality variation in spot welding can affect both the functionality and safety of products. Therefore, the quality assurance of spot welds is vital in many industries. Spot weld quality is assessed in several ways, ranging from physical weld nugget measurements, to ultrasonic inspection and mechanical strength testing. This paper investigates four commonly used weld quality testing protocols: tensile shear, a chisel test, ultrasonic inspection and peel strength testing. We present a range of spot welding data to demonstrate the variability of the results and assess the correlation between nugget diameter (the industry standard) and the strength of the joint. This study highlights the benefits and limitations of each quality assessment technique, and limitations associated with using one metric to infer the outcome of another. Comparisons are made between the industry standard, measurement of weld nugget diameter, and each additional testing protocol. This provides insights into the validity of each test for assessing joint quality in industry.