GATE 2019 ME (ME1) – Question 32
A high-cycle fatigue specimen has mean cyclic stress +140 MPa and minimum stress −70 MPa. Find R-ratio (minimum/maximum stress), to one decimal place.
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Correct answer: -.2 to -.2
Explanation
From $\sigma_m=(\sigma_{\max}+\sigma_{\min})/2$, the maximum stress is $2(140)-(-70)=350$ MPa. Hence $R=-70/350=\mathbf{-0.2}$.