This set of Mechanical Metallurgy Multiple Choice Questions & Answers focuses on “Tension Test – True-Stress-True Strain Curve – 2”.
1. The young modulus of the material is decided by the __________
a) the shape of the specimen
b) size of the sample
c) binding force between the atoms in the sample
d) it does not depend on one factor
Explanation: The young’s modulus or the modulus of stiffness is the ability of an atomic bond to stretch and regain their original position. The material is deformed in the elastic region of the content.
2. The limit of elastic strain is 0.02 of the material having young’s modulus 200 MPa. Find the resilience of the material?
Explanation: Resilience is defined as the area under the stress-strain curve up to the elastic limit.
3. The Resilience is not equal to ____________
Where; σ-is yield stress, e-strain, E-young’s modulus
The area under the curve will be resilience. So:
So the 1/2*σ2/e is not possible.
4. The necessary property for the structural material is _________
a) high resilience
b) high toughness
c) low ductility
d) low stiffness
Explanation: The structural material should have high ductility and high tensile strength to sustain the load. So, the area under the stress-strain curve should be very high. Hence, the toughness will be high.
5. Which of the following has the highest toughness?
a) High-carbon spring steel
b) Medium carbon spring steel
c) Stainless steel
d) Cast iron
Explanation: The cast iron has high ductility, but the tensile strength is not up to the marks. Similarity Stainless steel has high yield strength. But the high carbon spring steel has the best combination of strength and flexibility. This gives the high carbon spring steel both strength and ductility.
6. The initial cross-sectional area of a rod is 500 m2 is reduced to 100 m2 at the breaking point. Calculate the true fracture strain of the material?
Explanation: The area at breaking point defines the true fracture area relation.
-> True fracture strain = ln (initial area/final area)
-> True fracture strain = ln (500/100) = ln 5
7. The total reduction in the area of the specimen is 0.5. Find the true fracture strain of the material?
Explanation: The true fracture strain in terms of reduction in area is written as follows.
-> True fracture strain= ln[1/(1-q)]; Where the q is the reduction in the area of the specimen.
-> ln 2
8. The true local necking strain is defined as __________
a) strain up to the failure point
b) strain required up to maximum tensile strength point
c) strain from tensile strength point to the failure point
d) strain up to yield point
Explanation: The true local necking strain is defined as the strain required to deform the specimen from maximum load to fracture.
9. The rate of strain hardening and strain hardening exponents in the flow curve is always the same.
Explanation: The flow curve is expressed as:
Where the n is strain hardening exponent. The rate is strain hardening is defined as the change in stress values as the strain is increased.
10. It is possible to have actual strain values more than one for some components and systems.
Explanation: The true strain is defined as:
-> ln (final length/original length)
So, assuming if the material is deformed more than five times the original length, then the true strain value will be more than one.
Sanfoundry Global Education & Learning Series – Mechanical Metallurgy.
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