ETC Materials Testing & Quality Assurance 2 — Questions and Answers
Question 1: What does a Charpy impact test measure in a material?
- Compressive strength
- Energy absorbed during fracture (Correct answer)
- Fatigue life under cyclic loading
- Creep resistance at elevated temperature
Correct answer: Energy absorbed during fracture
The Charpy impact test measures the energy a notched specimen absorbs when struck by a swinging pendulum, indicating toughness.
Question 2: In a Brinell hardness test, a 10 mm steel ball is pressed into a specimen. What is measured to calculate hardness?
- Depth of indentation only
- Diameter of the residual indentation (Correct answer)
- Rebound height of the indenter
- Time for indenter to reach full load
Correct answer: Diameter of the residual indentation
Brinell hardness is calculated by dividing the applied load by the curved surface area of the indentation, using the measured indentation diameter.
Question 3: Which destructive test method is used to determine a metal's yield strength, ultimate tensile strength, and elongation in one test?
- Hardness test
- Tensile test (Correct answer)
- Bend test
- Impact test
Correct answer: Tensile test
A tensile test (tension test) generates a stress-strain curve that reveals yield strength, ultimate tensile strength, and percent elongation simultaneously.
Question 4: A material exhibits a 0.2% offset yield strength. What does the 0.2% refer to?
- The percentage elongation at failure
- The plastic strain offset used to define yield (Correct answer)
- The reduction in cross-sectional area
- The elastic modulus as a percentage
Correct answer: The plastic strain offset used to define yield
The 0.2% offset method draws a line parallel to the elastic portion of the stress-strain curve starting at 0.2% strain to find yield strength for materials with no distinct yield point.
Question 5: What is the primary purpose of a hydrostatic pressure test on a pressure vessel?
- To measure wall thickness ultrasonically
- To verify structural integrity and check for leaks under pressure (Correct answer)
- To determine the material's corrosion resistance
- To calibrate the vessel's pressure gauge
Correct answer: To verify structural integrity and check for leaks under pressure
A hydrostatic test fills the vessel with water and pressurizes it above operating pressure to confirm it can hold pressure without leaking or failing.
Question 6: In quality control, what does AQL (Acceptable Quality Level) define?
- The maximum defect rate considered acceptable for a lot (Correct answer)
- The minimum sample size required for inspection
- The calibration interval for test equipment
- The tolerance band on a control chart
Correct answer: The maximum defect rate considered acceptable for a lot
AQL specifies the worst acceptable process average defect rate; lots meeting this level are accepted with a specified probability during sampling inspection.
Question 7: Which type of weld discontinuity does a guided bend test most effectively detect?
- Surface porosity
- Lack of fusion and cracks (Correct answer)
- Undercut at the weld toe
- Slag inclusion at the surface
Correct answer: Lack of fusion and cracks
The guided bend test flexes a weld cross-section around a die, opening up internal lack-of-fusion defects and cracks that would not be visible on the surface.
ETC Materials Testing & Quality Assurance 2
What does a Charpy impact test measure in a material?