Quantitative evaluation of spot welds by ultrasonic waves

This chapter introduces a new concept for nondestructive evaluation (NDE) of spot welds based on the ultrasonic measurement of the spot weld diameter (diameter of the nugget) which can then be used for failure load prediction. The Lamb wave transmission coefficient is measured for all welded specimens both by contact and immersion techniques. The Lamb wave, excited in the upper sheet, is incident onto the welded region, and the incident energy is passed into the lower sheet and is detected by the receiving transducer. The value of the transmission coefficient characterizes the dimensions the welded region. Topics considered include spot weld preparation, the estimation of the effective diameter of the welded region, contact measurements, and immersion measurement. It is determined that the Lamb wave transmission coefficient is proportional to D3, where D is the mean diameter of the welded region