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GATE 2021 MT – Question 42

Mechanical Behaviour of Materials · Plasticity and yield criteria · 2 marks · Multiple choice

Single-crystal aluminium is in uniaxial tension along [112]. At applied stress 100 MPa and critical resolved shear stress 25 MPa, which slip system activates?

  1. $[\bar101](111)$
  2. $[\bar110](111)$
  3. $[101](11\bar1)$
  4. $[011](11\bar1)$

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Correct answer: (A) $[\bar101](111)$

Explanation

For A, slip direction [−101] lies in plane (111). With tensile axis [112], |cosλ|=1/√12 and |cosφ|=4/√18, giving Schmid factor 0.2722 and resolved stress 27.22 MPa. This exceeds CRSS 25 MPa; the other listed systems do not.

Hence **A**.