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GATE 2021 MT – Question 17

Mechanical Behaviour of Materials · Plasticity and yield criteria · 1 mark · Multiple choice

For the uniaxial tensile stress–strain behaviour of polycrystalline aluminium, which statement is FALSE?

  1. True stress is always higher than engineering stress
  2. At the ultimate tensile stress point on the true stress–strain curve, $d\sigma/d\epsilon=0$
  3. Resilience is the area under the elastic region of the engineering stress–strain curve
  4. Maximum true stress does not correspond to maximum load

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Correct answer: (B) At the ultimate tensile stress point on the true stress–strain curve, $d\sigma/d\epsilon=0$

Explanation

Maximum tensile load satisfies the Considère criterion dσ/dε=σ, not zero.

Thus **B** is false. The zero slope condition applies to the engineering stress at maximum load, not to the true-stress curve.