Mechanical Behaviour Questions and Answers – Variables Affecting Tensile Properties

This set of Mechanical Behaviour Quiz focuses on “Variables Affecting Tensile Properties”.

1. With increasing gauge length, % elongation _____
a) Increases
b) Decreases
c) Remains constant
d) First increases then decrease

Explanation: Localised elongation is maximum in the fracture area. Necking occurs in localised deformations. It contributes most to the elongation.

2. What gauge length is commercially used?
a) 10 mm
b) 20 mm
c) 30 mm
d) 50mm

Explanation: Gauge length is specified while reporting the percentage elongation. 50mm is commonly used commercially.

3. As cast, small diameter bar specimens have ________ strength.
a) Higher
b) Lower
c) Same
d) Either higher or lower

Explanation: Small diameter bars cool faster. These have a different microstructure. These have good tensile strength.

4. What is not a variable which affects tensile properties?
a) Gauge length
b) Temperature
d) Strain rate

Explanation: When gauge length increases, elongation % decreases. With an increase in strain rate. Material tends to show brittle behaviour. Strength decreases as temperature increases.

5. For L/D ratio greater than ___________ the reduction in area is independent of ratio.
a) 0.2
b) 2
c) 5
d) 10

Explanation: For L/D ratio greater than 2, the reduction in area is independent of ratio. Gauge length to diameter ratio effects ductility of specimen. It generates a notch like effect.
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6. Specimen with L/D = 0 gives _________ strength.
a) Higher
b) Lower
c) Equal
d) Higher or lower

Explanation: specimen with gauge length zero will have L/D = 0. It will show high strength with little deformation. It generates a notch like effect.

7. With an increase in strain rate, ductility ______ and tensile strength _____
a) Increases, increases
b) Increases, decreases
c) Decreases, increases
d) Decreases, decreases

Explanation: With an increase in strain rate, ductility of materials decreases. It is because material shows brittle behaviour. Tensile strength of material increases.

8. Yield and flow strength at lower plastic strain is more dependent on _____ than ______
a) Strain rate, tensile strength
b) Tensile strength, strain rate
c) Strain rate, temperature
d) Temperature, tensile strength

Explanation: Yield and flow strength at lower plastic strain are more dependent on strain rate than tensile strength. In shaping processes strain rates are higher. It can lead to unexpected mechanical behaviour.

9. At strain rates _____ behaviour of the material is characterized by creep.
a) Low, 104 per second
b) Low, 10-4 per second
c) High, 104 per second
d) High, 10-4 per second

Explanation: At lower strain rates behaviour of the material is characterized by creep. These strain rates are less than about 10-4 per second. For higher strain rates materials behave in a different manner.

10. Elastic modulus and strength ____ and ductility ___ as the temperature of material increases.
a) Increases, increases
b) Increases, decreases
c) Decreases, increases
d) Decreases, decreases

Explanation: Elastic modulus and strength of material decrease as temperature increases. It is because bond length increases. Ductility on other hand increases with temperature.

11. Tensile curve gets lower down with an increase in temperature.
a) True
b) False

Explanation: With an increase in temperature, tensile strength decreases. Ductility increases with temperature. Hence tensile curve gets lower down.

12. In FCC metals, yield stress increases rapidly with decreasing temperature.
a) True
b) False

Explanation: In FCC metals, yield stress doesn’t depend on temperature much. For BCC materials, yield stress decreases with increasing temperature.

Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.

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