The feasibility of using a modifed ultrasonic test system was examined for nondestructive testing of spot welds on steel plate in the automobile industry, and results showed that stick welds as well as cold welds could be detected. This method of testing is suitable for quality assurance of spot welds in the series production line.

A modified ultrasonic testing method clearly detects stick welds and cold welds, this is not possible with normal ultrasonic methods. When testing under production conditions, 98% of the welds tested are correctly evaluated, i.e. values obtained from the ultrasonic test satisfactorily corresponded to the results from the teardown test.

This method of testing can be applied in sectors where the classical teardown test produces unsatisfactory results, e.g. with thicker plates, inaccessible positions, body shells etc. This is a nondestructive and manual method of testing which can firstly be applied, in addition to the teardown test, within selected areas of quality assurance and then gradually replace the destructive method.

In the case of aluminum, this new method does not give clear results due to the porous welds, however, with spot welds on thin steel plate this form of testing has proved to be an effective method in the field of quality assurance.