GATE 2019 MT – Question 42
An aluminium single crystal is pulled along $[1\bar10]$. Which slip system is activated first?
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Correct answer: (A) $(1\bar1\bar1)[0\bar11]$
Explanation
Slip starts on the system with largest resolved shear $\tau=\sigma\cos\phi\cos\lambda$. For A, the tensile-axis dot product with the normalized plane normal has magnitude 2/√6 and with the slip direction 1/2, giving Schmid factor 1/√6≈0.408. For B,C,D, the plane normal (−1,−1,1) is perpendicular to (1,−1,0), giving zero Schmid factor. Therefore A.