A laser-EMAT system for ultrasonic weld inspection

The non-destructive testing of welded metal components is an area where significant savings in test cost can be made if preparation costs can be minimised. The biggest cost associated with preparation is grinding off the weld cap in order to facilitate the detection of defects that may be present just under the cap. In addition there are also potential savings to be made if the actual testing time can be reduced or if the tests can be performed at temperatures above which conventional contacting ultrasonic techniques cannot be used. This paper describes a non-contact ultrasonic method that uses a pulsed laser as generator and an electromagnetic acoustic transducer (EMAT)as detector which has the potential to interrogate the entire cross section of a weld