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GATE 2022 MT – Question 33

Mechanical Behaviour of Materials · Dislocations and strengthening · 1 mark · Multiple select

Let $\dot\epsilon,\rho,v$ denote strain rate, dislocation density, and dislocation velocity. If Orowan’s equation for dislocation plastic flow holds, which relationships are correct?

  1. $\dot\epsilon\propto v^2$
  2. $\dot\epsilon\propto v$
  3. $\dot\epsilon\propto\rho^2$
  4. $\dot\epsilon\propto\rho$

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Show answer and explanation

Correct answer: (B) $\dot\epsilon\propto v$; (D) $\dot\epsilon\propto\rho$

Explanation

Orowan gives $\dot\epsilon=\rho bv$ up to a fixed geometry factor. With Burgers magnitude fixed, strain rate is linear in both mobile dislocation density and velocity. Correct choices: **B, D**.