Question
During a high cycle fatigue test, a metallic specimen is subjected to cyclic loading with a mean stress of +140 MPa, and a minimum stress of –70 MPa. The R-ratio (minimum stress to maximum stress) for this cyclic loading is _______ (round off to one decimal place)
Answer :
-0.2
σmin = 70 MPa (Compressive),
σmean = 140 MPa
σmin / σmax = ?
We know that, σmean = (σmax +σmin )/2
140 = (σmax − 70) /2
280 + 70 = σmax
σmax = 350 MPa (Tensile)
σmin / σmax = -70/250 = -0.2
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