CWI NDE Methods and Symbols 3

Question 1

Which NDE method is MOST sensitive to surface cracks in ferromagnetic materials?

Accepted Answer

Magnetic particle testing (MT)

Answer

MT is most sensitive to surface and near-surface flaws in ferromagnetic materials because the magnetic field leaks strongly at discontinuities.

Question 2

In radiographic testing, what does IQI stand for and what is its purpose?

Accepted Answer

Image Quality Indicator; verifies the radiograph has sufficient sensitivity to detect defects

Answer

An IQI (also called a penetrameter) is placed on the part to verify that the radiographic technique has sufficient sensitivity to reveal defects of concern.

Question 3

What is 'geometric unsharpness' (Ug) in radiography, and how is it minimized?

Accepted Answer

Blurring caused by source size and geometry; minimized by increasing source-to-film distance or using a smaller source

Answer

Geometric unsharpness (Ug = Fd/D) increases with larger focal spot size (F) or shorter source-to-object distance; using a small source far from the object minimizes it.

Question 4

In ultrasonic testing, what type of wave travels along the surface of a material and is useful for detecting near-surface defects?

Accepted Answer

Rayleigh (surface) wave

Answer

Rayleigh waves travel along the surface with particle motion in an elliptical pattern, making them effective for detecting surface and very near-surface discontinuities.

Question 5

When the NDE symbol includes an 'R' in the tail of the weld symbol, what does it signify?

Accepted Answer

Radiographic testing is required

Answer

Per AWS A2.4, placing 'RT' or 'R' references in the symbol tail indicates that radiographic testing is required for that weld.

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CWI Practice Test

CWI NDE Methods and Symbols 3