ETC Materials Testing & Quality Assurance 4

Question 1

A soil sample has a liquid limit of 45 and a plastic limit of 20. What is the plasticity index (PI)?

Accepted Answer

25

Answer

Plasticity Index = Liquid Limit − Plastic Limit = 45 − 20 = 25, representing the range of moisture content over which soil behaves plastically.

Question 2

What property does a Shore durometer test measure?

Accepted Answer

Surface hardness of rubber and plastics

Answer

A Shore durometer measures the resistance of soft materials like rubber and plastics to permanent indentation, reported on the Shore A or Shore D scale.

Question 3

What does a positive material identification (PMI) test verify?

Accepted Answer

The alloy composition of a metal component

Answer

PMI uses XRF or OES spectroscopy to verify that a component's elemental composition matches the specified alloy grade.

Question 4

During a tensile test, a steel specimen necks and fractures. What does necking indicate about the material's behavior?

Accepted Answer

Onset of localized plastic deformation after ultimate tensile strength

Answer

Necking occurs after ultimate tensile strength is reached, when plastic deformation localizes in a reduced cross-section area until fracture.

Question 5

In ultrasonic testing, what is the primary advantage of phased array ultrasonic testing (PAUT) over conventional single-element UT?

Accepted Answer

PAUT electronically steers and focuses the beam without moving the probe

Answer

Phased array UT uses multiple elements fired in timed sequences to electronically steer, focus, and sweep the beam, providing faster and more comprehensive coverage than a single-element probe.

(ETC) Engineering Technician Certification Practice Test

(ETC) Engineering Technician Certification Practice Test

ETC Materials Testing & Quality Assurance 4