ToFD test is one of the advanced ultrasonic methods that provides the ability to scan, store information, and visualize data to evaluate the test piece with the help of a computer.

Generally, this method is used to test the welding of pipes.

In carrying out this method, ultrasonic waves are used to diagnose and investigate defects, with the difference that in the usual method, sound return is used as a criterion, and in ToFD, sound diffraction is the basis.

TOFD equipment includes two separate probes for sending and receiving sound in such a way that the probes are completely opposite each other. The entire volume of the weld is covered by the transmitted ultrasonic waves and it is possible to check the accuracy of the weld.

If there is a defect, two signals due to sound diffraction are created at the beginning and end of the defect.

And the result of the scan is saved in an image as follows

The recorded images are a two-dimensional view of the thickness of the part and the height of the defects, the length of the scan and the position of the defects, which has a degree of accuracy and speed that can never be obtained with other ultrasonic techniques.