Question

Which of the following statement is correct based on the ultrasonic testing screen display as shown in the figure?

• A. Increase in defect size increases the backwall echo height
• B. Defect-free material shows both defect echo and backwall echo
• C. A large defect produces a large defect echo and a small backwall echo
• D. A small defect completely eliminates the backwall echo

Hint:

In UT, backwall echo reduces as defect size increases.

Answer 1

The Correct Option is C

Concept: In ultrasonic testing (UT), sound waves travel through material and reflect from discontinuities. The display shows:
• defect echo (from flaw)
• backwall echo (from far surface)

Step 1: Effect of defect size.
Large defect:
• reflects more energy → strong defect echo
• blocks wave propagation → weak backwall echo

Step 2: Interpretation of options.
• (A) incorrect: backwall echo decreases with defect size
• (B) incorrect: defect-free has only backwall echo
• (D) incorrect: small defect does not eliminate backwall echo

Step 3: Correct statement.
Large defect gives strong defect echo and weak backwall echo. Final Answer: \[ \boxed{\text{A large defect produces a large defect echo and a small backwall echo}} \]