ME Material Properties and Testing 1 — Questions and Answers
Question 1: Which mechanical property describes a material's ability to absorb energy and plastically deform before fracturing?
- Toughness (Correct answer)
- Hardness
- Stiffness
- Ductility
Correct answer: Toughness
Toughness is the ability of a material to absorb energy and deform plastically before fracturing, represented by the area under the stress-strain curve.
Question 2: In a standard tensile test, the engineering stress is calculated by dividing the applied force by:
- The instantaneous cross-sectional area
- The original cross-sectional area (Correct answer)
- The gauge length
- The final cross-sectional area
Correct answer: The original cross-sectional area
Engineering stress uses the original (undeformed) cross-sectional area, while true stress uses the instantaneous cross-sectional area.
Question 3: The Charpy impact test measures which material property?
- Hardness
- Fatigue strength
- Impact toughness (Correct answer)
- Yield strength
Correct answer: Impact toughness
The Charpy impact test measures impact toughness by striking a notched specimen with a pendulum hammer and measuring the energy absorbed.
Question 4: Which hardness testing method uses a Vickers diamond pyramid indenter and is most suitable for thin materials?
- Rockwell
- Brinell
- Vickers (Correct answer)
- Shore
Correct answer: Vickers
The Vickers hardness test uses a square-based pyramid diamond indenter and is well-suited for thin materials because the indentation is very small.
Question 5: The proportional limit on a stress-strain curve is the point beyond which:
- Fracture occurs
- Necking begins
- Stress and strain are no longer proportional (Correct answer)
- Plastic deformation begins
Correct answer: Stress and strain are no longer proportional
Beyond the proportional limit, Hooke's Law no longer applies and the stress-strain relationship is no longer linear.
Question 6: Which of the following tests is used to measure the fatigue life of a material under cyclic loading?
- Creep test
- S-N (Wohler) test (Correct answer)
- Charpy test
- Izod test
Correct answer: S-N (Wohler) test
The S-N test (stress versus number of cycles) generates the Wohler curve, which characterizes a material's fatigue behavior under cyclic loading.
ME Material Properties and Testing 1
Which mechanical property describes a material's ability to absorb energy and plastically deform before fracturing?