Method for assessment of welded joints using ultrasound

摘要

Assessment of resistance welded joints with the use of an ultrasound sender and a receiver comprises: (a) the velocity variation c2(t) of ultrasound with time t in the welding region is determined during the welding process; (b) the temperature variation T(t) of the welding region is determined by comparing c2(t) with its known temperature relation; (c) the instant of melting ts of the weld material is determined by comparing T(t) with the melting temperature Ts of the weld material; and (d) the expected diameter of the weld blob at the end of the welding process is calculated from ts. The ultrasonic waves used are longitudinal waves. The instantaneous volume of the weld blob is calculated from the attenuation of the shear waves produced in the weld spot. The momentaneous electrode diameter is determined from the welding current intensity.