Ultrasonic method for evaluation of resistance spot welding

A new ultrasonic method for evaluation or monitor of the resistance spot we lding process is introduced. The method is based on electrode built-in ultr asonic transducer technology by measuring acoustical signals transmitted th rough the weld region on line. The transmitted signal is affected by temper ature changes in the welded region during solidification and cooling of the melting pool. Parameters of the maximum thermal expansion, the slope of ti me delay and the range of the TOF are used to evaluate the weld quality.