Improvements in Ultrasonic Inspection of Resistance Spot welds

Resistance welding is an electrothermic process commonly used in Industry for joining sheet metal, particularly steel, in applications such as automobile bodies and chassis assemblies. The method is suitable for partial or total automation, and is very reliable. However, as with any process, problems can occur and inspection is therefore necessary. Although ultrasonic inspection of spot welds has been used for many years, the technology still has problems with production rate and reliability, and is very operator dependent. This paper will look at the analysis of ultrasonic signals from weld inspection, and present some improvements in both probe technology and automatic analysis. Together these result in significant improvements in inspection reliability, and allow the inspection to be fully automated.