Process-integrated resistance spot welding testing using ultrasonic techniques

An ultrasonic test technique is presented which determines the temperature changes in the weld spot and weld nugget growth during resistance spotwelding. The ultrasonic signals are transmitted externally through the weld spot in a simple manner via the welding electrode on the one side and received by the electrode on the other. The size of the weld nugget can be computed on the basis of time-dependent changes in ultrasonic transmissivity during the welding process. The physical fundamentals on which this test method is based are explained and weld spot evaluation performed experimentally using iron and aluminium sheets. The completion of a prototype equipment was made possible thanks to the VALUE-I Programme of the European Community.