GATE 2026 AE – Question 58

Structures · Flight vehicle structures: torsion, bending and shear of thin-walled sections, loads on aircraft · 2 marks · Numerical answer

A thin-walled circular tube is made of a material whose magnitude of the ultimate strength, both in tension and compression, is 200 MPa. The mean radius of the tube is 0.2 m and the wall thickness is 0.004 m. Based on the maximum stress criteria, the maximum torque that the tube can sustain is ________ kN-m (round off to the nearest integer).

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Correct answer: 201

Explanation

In pure torsion the stress state is pure shear $\tau = \frac{T}{2\pi r^2 t}$, whose principal stresses are $\pm\tau$. With the maximum stress criterion, failure occurs when $\tau = 200$ MPa. So $T = 2\pi r^2 t \tau = 2\pi (0.2)^2 (0.004)(200 \times 10^6) = 2.01 \times 10^5$ N-m = 201 kN-m.