Materials Science and Manufacturing Engineering Miscellaneous
- A bar is compressed to half of its original length. The magnitude of true strain produced in the deformed bar is (correct to two decimal places).
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∈T = ln lf ² li
Correct Option: A
∈T = ln lf ² li
- In a two-stage wire drawing operation, the fractional reduction (ratio of change in crosssectional area to initial cross-sectional area) in the first stage is 0.4. The fractional reduction in the second stage is 0.3. The overall fractional reduction is
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40% Reduction = 1 × 0.4 = 0.4
30% Reduction of 0.6 = 0.6 × 0.3 = 0.18
Total Reduction = 0.58Correct Option: B
40% Reduction = 1 × 0.4 = 0.4
30% Reduction of 0.6 = 0.6 × 0.3 = 0.18
Total Reduction = 0.58
- A metal rod of initial length L0 is subjected to a drawing process. The length of the rod at any instant is given by the expression, L(t) = L0 (1 + t²), where t is the time in minutes. The true strain rate (in min–1) at the end of one minute is _______.
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L(t) = L0 (1 + t²)
⇒ dL = L0 × 2t dtAs d ∈T = dL L d ∈T = L02t dt L0 (1 + t²) d ∈T = 2t dt 1 + t²
at t = 1 min∈T = 2 × 1 = 1 min- 1 T 1 + 1²
Correct Option: A
L(t) = L0 (1 + t²)
⇒ dL = L0 × 2t dtAs d ∈T = dL L d ∈T = L02t dt L0 (1 + t²) d ∈T = 2t dt 1 + t²
at t = 1 min∈T = 2 × 1 = 1 min- 1 T 1 + 1²
- In a wire drawing operation, diameter of a Steel wire is reduced from 10 mm to 8 mm. The mean flow stress of the material is 400 MPa. The ideal force required for drawing (ignoring friction and redundant work) is
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Di = 10 mm, Di = 8mm
σ0
= 400 MPaσd = σ0ln Di ² Df σd = 400ln 10 ² 8
σd = 178.51 MPaIdeal force = 178.51 × 106 × π (0.008)² 4
I deal force 8.97 KNCorrect Option: B
Di = 10 mm, Di = 8mm
σ0
= 400 MPaσd = σ0ln Di ² Df σd = 400ln 10 ² 8
σd = 178.51 MPaIdeal force = 178.51 × 106 × π (0.008)² 4
I deal force 8.97 KN
- Cold shut is a defect in casting due to
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NA
Correct Option: D
NA