CWI Nondestructive Examination Methods 3 — Questions and Answers
Question 1: What is the primary limitation of liquid penetrant testing (PT)?
- It cannot detect surface cracks
- It can only detect subsurface discontinuities
- It is limited to surface-breaking discontinuities only (Correct answer)
- It requires a magnetic field to work
Correct answer: It is limited to surface-breaking discontinuities only
PT relies on capillary action and can only detect discontinuities that are open to the surface.
Question 2: In ultrasonic shear wave testing, the refracted shear wave angle is produced using which principle?
- Doppler effect
- Snell's Law (Correct answer)
- Bragg's Law
- Faraday's Law
Correct answer: Snell's Law
Snell's Law describes the relationship between the incident angle and the refracted wave angle at a material interface.
Question 3: A CWI is reviewing a radiograph and sees a dark, elongated linear indication with fuzzy edges. This is most likely caused by:
- A crack
- Slag inclusion (Correct answer)
- Porosity
- Tungsten inclusion
Correct answer: Slag inclusion
Slag inclusions typically appear as dark, elongated indications with irregular or fuzzy edges on a radiograph.
Question 4: When using the wet continuous method of magnetic particle testing, the particles are applied:
- After the magnetizing current is stopped
- Before the magnetizing current is applied
- While the magnetizing current is flowing (Correct answer)
- After the developer is applied
Correct answer: While the magnetizing current is flowing
In the wet continuous method, particles are applied while the magnetizing current is flowing to maximize particle mobility and indication formation.
Question 5: What does the term 'impedance plane' refer to in eddy current testing?
- The physical surface of the test part
- A graphical display showing the relationship between resistance and inductive reactance (Correct answer)
- The depth at which eddy currents can be detected
- The calibration reference block surface
Correct answer: A graphical display showing the relationship between resistance and inductive reactance
The impedance plane is a 2D display (X vs. Y) that plots the resistive and reactive components of the probe's impedance to characterize material conditions.
Question 6: For radiographic testing, the geometric unsharpness (Ug) is increased by:
- Increasing source-to-film distance
- Decreasing source size
- Decreasing object-to-film distance (Correct answer)
- Increasing source-to-film distance and decreasing object-to-film distance
Correct answer: Decreasing object-to-film distance
Geometric unsharpness increases when the object-to-film distance increases or when source-to-film distance decreases.
Question 7: During visual inspection of a completed fillet weld, a CWI notices the weld face is concave. The primary concern is:
- Excessive heat input
- Reduced throat dimension and load-carrying capacity (Correct answer)
- Hydrogen-induced cracking risk
- Distortion of the base metal
Correct answer: Reduced throat dimension and load-carrying capacity
A concave fillet weld face reduces the effective throat, which reduces the weld's load-carrying capacity.
CWI Nondestructive Examination Methods 3
What is the primary limitation of liquid penetrant testing (PT)?