Ultrasonic Testing Principles Flashcards
7 cards from real NDT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ultrasonic Testing Principles flashcards as text
What is the acoustic impedance of a material defined as?
Answer: The product of material density and ultrasonic wave velocity
Acoustic impedance (Z) equals material density (ρ) multiplied by the ultrasonic wave velocity (v), expressed as Z = ρv.
When an ultrasonic wave travels from steel into water, what primarily occurs at the interface?
Answer: Partial reflection and partial transmission due to impedance mismatch
At any interface between materials of different acoustic impedances, the wave is partly reflected and partly transmitted; the proportions depend on the impedance difference.
Which type of ultrasonic wave motion involves particles oscillating perpendicular to the direction of wave propagation?
Answer: Shear (transverse) wave
Shear waves, also called transverse waves, have particle motion perpendicular to the direction of wave travel, unlike longitudinal waves where motion is parallel.
What is the primary purpose of couplant in contact ultrasonic testing?
Answer: To eliminate the air gap and improve acoustic energy transfer between transducer and part
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.
The near field (Fresnel zone) of an ultrasonic transducer is characterized by:
Answer: Highly irregular intensity variations making flaw sizing unreliable
The near field has complex interference patterns causing irregular amplitude variations, making flaw sizing and detection unreliable in this zone.
Snell's Law in ultrasonics describes:
Answer: The refraction of ultrasonic waves at the interface between two materials
Snell's Law defines how the angle of an ultrasonic beam changes (refracts) when it crosses from one medium to another, based on the ratio of wave velocities in each material.
What effect does increasing ultrasonic test frequency have on resolution and penetration?
Answer: Improves resolution but reduces penetration depth
Higher frequency produces shorter wavelengths, improving resolution and sensitivity to small defects, but attenuation increases with frequency, reducing maximum penetration depth.