Time-of-flight diffraction
Time-of-flight diffraction technique is an ultrasonic method that diffracts sound waves at edges and flaws in welds. It measures crack height and length by timing the flight of sound.
Physical-Chemical Mechanism of Action
Time-of-flight diffraction uses the phenomenon of sound diffraction. When in contact with edges or flaws in the weld, the direction and speed of the sound change. The time it takes for sound to travel from a transmitter to a receiver varies depending on the location and size of the flaw.
Metallurgical Relevance & Risks in Welding
This technique detects microscopic cracks or deformations in welds that are not visible. Excessive crack height or length can lead to slag formation and consequently to component failure. Time-of-flight diffraction is particularly important for highly stressed applications such as mechanical engineering or aerospace.
Workshop Practice & Instructions
To apply time-of-flight diffraction, you need an ultrasonic device with appropriate software. The sound transmitter is placed on the weld, while the receiver is moved along the weld. Time measurement is done in microseconds. A crack height of over 0.5 mm or a crack length of over 1 cm is critical and indicates potential failure.