In ultrasonic testing, what is the "dead zone"?

In ultrasonic testing, the "dead zone" refers to the area close to the transducer where defects cannot be detected. This phenomenon occurs due to the transducer's construction and the time it takes for the sound waves to propagate through the material. After a pulse is emitted, there is a brief period during which the transducer cannot receive any returning echoes from flaws or defects in the material. This is primarily due to the initial pulse's energy being transmitted and the receiving elements being unable to detect reflections until a certain distance has been covered.

Understanding the dead zone is crucial for effective testing, as it indicates the limitation in the inspection near the transducer. Accurate awareness of this zone informs technicians to adjust their scanning techniques or equipment settings to ensure adequate coverage and to interpret data correctly, considering this inherent limitation.