Divergence Application Couplant

Free NDT Ultrasonic Testing Questions and Answers — Questions and Answers

Question 1: In a specific substance, the sound speed is:

Is constant (Correct answer)
Increases with distance from the transducer
Decreases with distance from the transducer
None of the above

Correct answer: Is constant

The speed of sound in a specific homogeneous material is a fundamental and constant property of that material under given conditions, such as temperature. It does not change with distance from the transducer or other factors during an ultrasonic test. This consistent speed is crucial for accurate distance measurements and flaw location in ultrasonic testing.

Question 2: The reflective surface of the discontinuity must have a diameter at least as long as ________ wavelength in order to provide a fair chance of being detected.

One
One-half (Correct answer)
One-quarter
Two

Correct answer: One-half

For reliable detection of a discontinuity using ultrasonic testing, the reflective surface of the discontinuity should ideally have a diameter at least as long as one-half of the wavelength of the ultrasonic wave. If the discontinuity is significantly smaller than half a wavelength, the sound wave tends to diffract around it, making detection difficult or impossible and reducing inspection sensitivity.

Question 3: The term for the combined impact of absorption and dispersion is:

Propagation
Shear factor
Impedance
Attenuation (Correct answer)

Correct answer: Attenuation

Attenuation is the term used to describe the decrease in the intensity of a wave as it propagates through a medium. This phenomenon is a combined result of absorption, where the material converts wave energy into other forms like heat, and dispersion (or scattering), where the wave energy is redirected in various directions. Therefore, attenuation directly represents the overall loss of wave energy due to these two effects.

Question 4: The capacity to identify a tiny discontinuity is known as:

Frequency
Wavelength
Sensitivity (Correct answer)
Resolution

Correct answer: Sensitivity

In Non-Destructive Testing, sensitivity refers to the system's ability to detect the smallest possible discontinuity or defect within a material. A highly sensitive test can identify very minute flaws, which is crucial for ensuring material integrity. This differs from resolution, which is the ability to distinguish between two closely spaced discontinuities.

Question 5: At a depth of roughly: Surface waves, also known as Rayleigh waves, travel along the surface of relatively thick solid materials.

Two wavelengths
Infinite wavelengths
One wavelength (Correct answer)
Three wavelengths

Correct answer: One wavelength

Rayleigh waves, also known as surface waves, propagate along the surface of a material. Their energy is largely confined to a shallow depth below the surface. Specifically, the significant energy of a Rayleigh wave is typically concentrated within approximately one wavelength of the surface, making them ideal for detecting surface and near-surface discontinuities.

Question 6: In the pulse echo mode, a single element transducer functions as follows:

Needs to have a high pulse rate
Can not start receiving reflected signals until the element has stopped ringing from its transmit function (Correct answer)
Can only be made with lithium sulfate
Should be used in the dual mode

Correct answer: Can not start receiving reflected signals until the element has stopped ringing from its transmit function

In the pulse-echo mode, a single element transducer acts as both transmitter and receiver. After transmitting an ultrasonic pulse, the transducer continues to vibrate or "ring" for a short period. It cannot effectively receive the faint reflected signals (echoes) from discontinuities until this ringing has subsided, ensuring clear detection of the returning waves.

Question 7: In general, resolution rises:

With an increase in transducer frequency (Correct answer)
With increased depth of a defect
With a decrease in the transducer frequency
When the transducer diameter is reduced

Correct answer: With an increase in transducer frequency

Resolution in ultrasonic testing refers to the ability to distinguish between two closely spaced discontinuities. Generally, resolution improves with an increase in transducer frequency because higher frequencies produce shorter wavelengths. These shorter wavelengths allow for more precise detection and separation of adjacent reflectors, leading to a clearer image of the material's internal structure.

Question 8: DAC represents:

Divergence Application Couplant
Distance Application Code
Distance Amplitude Correction (Correct answer)
Direct Amplitude Code

Correct answer: Distance Amplitude Correction

DAC stands for Distance Amplitude Correction, a crucial technique in ultrasonic testing. This method is used to compensate for the natural loss of signal amplitude (attenuation) as the ultrasonic wave travels deeper into the material. By creating a DAC curve, inspectors can compare the amplitude of indications at different depths to a reference level, ensuring consistent evaluation regardless of defect location.

Question 9: Which kind of calibration block is utilized similarly to the small angle-beam block and looks a lot like it?

A shear wave calibration block
An IIW block
A DSC block (Correct answer)
A rompus block

Correct answer: A DSC block

The DSC block, which stands for Distance/Sensitivity Calibration block, is specifically designed for calibrating ultrasonic equipment, particularly for shear wave applications. It is used to establish distance and sensitivity settings, much like the IIW block. Its design often includes specific reflectors and dimensions that allow for accurate setup and verification of the ultrasonic testing system.

Question 10: Other names for longitudinal waves are:

Compressional waves
Surface waves
Pressure waves
Both Pressure waves and Compressional waves are correct (Correct answer)

Correct answer: Both Pressure waves and Compressional waves are correct

Longitudinal waves are characterized by particle motion that is parallel to the direction of wave propagation. This motion creates alternating regions of compression (increased density and pressure) and rarefaction (decreased density and pressure) within the material. Due to these characteristics, they are commonly referred to as both compressional waves and pressure waves.

Question 11: The following is the measurement of a defect's signal in relation to other background reflections:

Signal to noise ratio (Correct answer)
Acoustic impedance
Reflection
Refraction

Correct answer: Signal to noise ratio

The signal-to-noise ratio (SNR) is a critical parameter in Non-Destructive Testing, representing the strength of a defect's reflected signal compared to the level of unwanted background reflections or electronic noise. A high signal-to-noise ratio indicates a clear and strong indication from a discontinuity, making it easier to detect and interpret, while a low ratio can obscure defects.

Free NDT Ultrasonic Testing Questions and Answers

In a specific substance, the sound speed is: