An algorithm for the estimation of the quality of the spot welds

Spot welds are widely used in industry, especially in automotive, so welds must be reliable. One of the approaches to estimate the quality of spot welds is to use ultrasonic testing. Spot welding is used in the automotive repair industry as well. However, a spot weld testing device, dedicated for the automotive repair industry, is not available. The objective of this work was to develop an algorithm for estimation of the quality of spot welds, to be used in a simple device in the automotive repair industry. The algorithm developed identifies the peaks in the acquired signal and separates the main peaks (ultrasonic signal reflected from the backwall of the weld) from intermediate peaks (which identify the defects in the weld or undersized weld). Then, according to the peak distribution and peak amplitude variations in the signal, the quality of the weld is determined and an automatic pass or fail indication given. The algorithm was verified using a finite element model of a good weld, an undersized weld and a weld with a pore.