Question 1

Which NDT method is most effective for detecting internal volumetric discontinuities such as porosity and slag inclusions?

Accepted Answer

Radiographic Testing (RT) uses X-rays or Gamma rays to penetrate the material, creating a shadow image that reveals volumetric internal defects like porosity and slag.

Question 2

Liquid Penetrant Testing (PT) can be used to detect:

Accepted Answer

PT relies on capillary action to draw liquid into surface-breaking flaws. It cannot detect anything that is not open to the surface.

Question 3

Magnetic Particle Testing (MT) is applicable to:

Accepted Answer

MT works by magnetizing the part. Therefore, it can only be used on ferromagnetic materials (like carbon steel). It will not work on aluminum or austenitic stainless steel.

Question 4

In Ultrasonic Testing (UT), sound waves are introduced into the part using a:

Accepted Answer

A piezoelectric transducer converts electrical energy into high-frequency sound waves (mechanical energy) that travel through the material.

Question 5

Which NDT method requires the part to be thoroughly cleaned of all paint, grease, and dirt before testing to function correctly?

Accepted Answer

For PT, any surface contaminant can block the penetrant from entering the discontinuity, making the test invalid. Cleanliness is critical.

Question 6

In Radiographic Testing, a 'darker' area on the film generally indicates:

Accepted Answer

Less dense areas (like gas pockets or slag) allow more radiation to pass through to the film, exposing it more and creating a darker image.

Question 7

Which MT technique is best for detecting longitudinal cracks in a pipe weld?

Accepted Answer

Magnetic lines of flux must run perpendicular to the discontinuity for detection. A yoke placed across the weld creates flux lines across the weld, which is perpendicular to a longitudinal crack.

Question 8

The time required for the penetrant to soak into potential discontinuities is called the:

Accepted Answer

Dwell time is the duration the penetrant is left on the surface to allow capillary action to draw it into flaws.

Question 9

Which UT wave mode is typically used for weld inspection (angle beam)?

Accepted Answer

Shear waves are used in angle beam testing to direct sound into the weld metal from the adjacent base metal at an angle (usually 45, 60, or 70 degrees).

Question 10

In RT, an Image Quality Indicator (IQI) or penetrameter is used to:

Accepted Answer

The IQI (wires or hole-type) proves that the radiographic setup is capable of detecting features of a specific size (sensitivity).

Question 11

Visual Testing (VT) should be performed:

Accepted Answer

Effective VT is a continuous process: checking fit-up (before), parameters/beads (during), and the final weld (after).

Question 12

Which NDT method uses an alternating current coil to induce currents in a conductive material?

Accepted Answer

Eddy Current Testing induces circulating electrical currents (eddy currents) in conductive materials. Defects disrupt these currents.

Question 13

In MT, which current type provides the best sensitivity for detecting sub-surface discontinuities?

Accepted Answer

HWDC provides a vibratory pulsing effect that gives mobility to the particles while maintaining the penetration of DC, making it best for sub-surface detection.

Question 14

Which of the following is an advantage of RT over UT?

Accepted Answer

A major advantage of RT is the permanent visual record of the internal quality. UT signals are transient (unless automated/recorded).

Question 15

A 'Couplant' is required for which NDT method?

Accepted Answer

Ultrasonic sound waves do not travel well through air. A liquid couplant (gel, oil, water) is needed to transmit the sound from the transducer into the test piece.

Question 16

Tungsten inclusions in a radiograph appear as:

Accepted Answer

Tungsten is denser than steel. It absorbs more radiation, preventing exposure of the film, resulting in distinct light (white) spots.

Question 17

In PT, the 'Developer' functions by:

Accepted Answer

The developer acts like a blotter, drawing the penetrant entrapped in the crack back to the surface and spreading it to make it visible.

Question 18

Which defect is planar and most difficult to detect with RT if not oriented parallel to the radiation beam?

Accepted Answer

Planar defects like laminations or tight cracks are very thin. If the X-ray beam hits them perpendicularly (broadside), they don't change the density enough to show up. They must be aligned with the beam.

Question 19

When performing UT, the 'Dead Zone' refers to:

Accepted Answer

The dead zone is the area just below the surface where the initial pulse obscures return signals, making near-surface flaw detection difficult.

Question 20

The 'Pie Gauge' is used in MT to verify:

Accepted Answer

The Pie Gauge (magnetic field indicator) is placed on the part to confirm the presence and approximate direction of the magnetic field.

Question 21

Leak Testing (LT) utilizing a 'Bubble Test' is most sensitive for detecting:

Accepted Answer

Bubble testing (soaping the surface and pressurizing) detects gas escaping through through-thickness leaks.

Question 22

In PT, 'Solvent Removable' refers to:

Accepted Answer

Solvent removable penetrants require wiping with a solvent-dampened cloth to remove excess surface penetrant before developing.

Question 23

Which radiation source is an isotope?

Accepted Answer

Iridium-192 (and Cobalt-60) are radioactive isotopes (Gamma sources). X-ray tubes are electrical devices.

Question 24

What is 'Demagnetization' and why is it important?

Accepted Answer

Residual magnetism can interfere with future welding (arc blow) or machining operations (chips sticking). Parts usually must be demagnetized after MT.

Question 25

The term 'Indication' in NDT refers to:

Accepted Answer

An indication is simply the signal (visual mark, blip on screen). It must be evaluated to determine if it is relevant, non-relevant, or false, and if it is a defect.

Question 26

For MT, the 'continuous method' is generally preferred over the 'residual method' because:

Accepted Answer

The continuous method (applying particles while magnetizing current flows) provides the strongest leakage field and best sensitivity.

Question 27

In UT, higher frequency transducers (e.g., 10 MHz) provide:

Accepted Answer

High frequencies have shorter wavelengths, allowing detection of smaller flaws (resolution), but they attenuate (weaken) faster in the material (less penetration).

Question 28

A 'Non-Relevant Indication' in NDT could be caused by:

Accepted Answer

Non-relevant indications are caused by known features (like threads or sharp corners) that are not flaws but produce NDT signals.

Question 29

Which NDT method is most suitable for detecting fatigue cracks in aluminum aircraft skins?

Accepted Answer

Aluminum is non-magnetic (no MT). Eddy Current is highly sensitive to surface cracks in conductive non-ferrous materials like aluminum aircraft structures.

Question 30

In RT, geometric unsharpness (penumbra) can be reduced by:

Accepted Answer

Geometric sharpness is improved by using a small radiation source and maximizing the distance between the source and the part (minimizing penumbra).

Question 31

The 'Prod' method in MT can cause:

Accepted Answer

Prods pass high current through the contact points. Poor contact can cause arcing (arc strikes), which are defects themselves in hardenable steels.

Question 32

Which developer type is generally considered the most sensitive for PT?

Accepted Answer

Nonaqueous wet developers (solvent suspended) typically provide the highest sensitivity and contrast for fine cracks.

Question 33

A 'Reference Block' (like IIW block) is used in UT for:

Accepted Answer

Calibration blocks with known dimensions and reflectors are essential to set up the UT scope for accurate distance and amplitude measurement.

Question 34

Visual inspection of a fillet weld reveals the leg size is undersized. This is a:

Accepted Answer

Undersized welds are dimensional discrepancies. They are detected by measurement (gauges) during VT.

Question 35

Fluorescent penetrant inspection (Type I) requires the use of:

Accepted Answer

Fluorescent penetrants contain dyes that glow under Ultraviolet (UV-A) black light, vastly increasing sensitivity compared to visible dyes.

Non-Destructive Testing (NDT) Practice Questions

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