GATE 2026 MT – Question 51
For plane-strain fracture-toughness testing of maraging steel, the minimum thickness to achieve valid $K_{Ic}$ is ________ mm. (Answer in integer.) Given $K_{Ic}=90\ \mathrm{MPa}\sqrt{\mathrm m}$ and yield stress $\sigma_y=900\ \mathrm{MPa}$.
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Correct answer: 25 to 25
Explanation
The plane-strain size criterion is $B\ge2.5(K_{Ic}/\sigma_y)^2$. Substitution gives $B_{min}=2.5(90/900)^2=0.025\ \mathrm m$.
Converting to millimetres gives **25 mm**.