NDT Ultrasonic Testing Principles 2

Question 1

What is the acoustic impedance of a material defined as?

Accepted Answer

The product of material density and ultrasonic wave velocity

Answer

Acoustic impedance (Z) equals material density (ρ) multiplied by the ultrasonic wave velocity (v), expressed as Z = ρv.

Question 2

When an ultrasonic wave travels from steel into water, what primarily occurs at the interface?

Accepted Answer

Partial reflection and partial transmission due to impedance mismatch

Answer

At any interface between materials of different acoustic impedances, the wave is partly reflected and partly transmitted; the proportions depend on the impedance difference.

Question 3

Which type of ultrasonic wave motion involves particles oscillating perpendicular to the direction of wave propagation?

Accepted Answer

Shear (transverse) wave

Answer

Shear waves, also called transverse waves, have particle motion perpendicular to the direction of wave travel, unlike longitudinal waves where motion is parallel.

Question 4

What is the primary purpose of couplant in contact ultrasonic testing?

Accepted Answer

To eliminate the air gap and improve acoustic energy transfer between transducer and part

Answer

Couplant fills the microscopic air gap between the transducer and test surface, since air has very low acoustic impedance and would cause nearly total reflection of ultrasonic energy.

Question 5

The near field (Fresnel zone) of an ultrasonic transducer is characterized by:

Accepted Answer

Highly irregular intensity variations making flaw sizing unreliable

Answer

The near field has complex interference patterns causing irregular amplitude variations, making flaw sizing and detection unreliable in this zone.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT Ultrasonic Testing Principles 2