GATE 2020 ME (ME2) – Question 31
A machine member experiences fluctuating stress $\sigma=\sigma_0\cos(8\pi t)$. Material endurance limit is 350 MPa and design factor of safety 3.5. Find maximum allowable σ₀ (MPa), to two decimals.
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Correct answer: 99.98 to 100.02
Explanation
The mean stress is zero and the amplitude isσ0. Infinite-life design requires amplitude≤endurance limit/safety factor=350/3.5=**100.00 MPa**. The angular frequency does not alter this fatigue-limit calculation.