Time-of-Flight Diffraction Technique
The time-of-flight diffraction testing technique is an ultrasonic method that uses the time-of-flight diffraction of waves at crack tips to accurately measure flaws. It requires two probes and offers high detection sensitivity.
Physical-Chemical Mechanism of Action
Time-of-flight diffraction (TOFD) uses ultrasonic waves that are diffracted at crack tips. The time of flight of the waves is measured and analyzed to determine the vertical extent and depth of defects.
Metallurgical Relevance & Risks in Welding
TOFD is especially useful for inspecting weld defects like cracks or deformations. An inaccurate measurement can lead to wrong results and hide potential safety risks.
Workshop Practice & Action Instructions
Use two ultrasonic probes: one transmitter and one receiver. Position the probes parallel to the weld. The distance between the probes should be 50 to 100 mm. Measure the time of flight with an accuracy of ±2 µs and interpret the result using a TOFD diagram.