Question

Ideally, when using TOFD on a discontinuity-free test object, the total number of signals of interest will be:

A) 2
B) 3
C) 4
D) 5

Answer 1

In an ideal scenario, two signals of interest should be detected by TOFD on a discontinuity-free test object: the lateral wave and the backwall echo, making the correct answer B) 2.

Step-by-step explanation:

The student is asking about Time of Flight Diffraction (TOFD), a nondestructive testing method used in ultrasonic testing (UT). In an ideal scenario where a test object is discontinuity-free, the total number of signals of interest that will be detected by TOFD should be two.

These signals are:

• The lateral wave - which travels along the surface of the material and is the first signal received after an ultrasonic pulse is emitted.
  
• The backwall echo - which is the reflection from the far side of the material, detected after the lateral wave.

There should not be any signals from discontinuities such as cracks or voids, as the object is assumed to be free of such defects. Therefore, the correct answer to the student's question is B) 2.