Effect of stress ratio on the elevated temperature fatigue-crack propagation of Type 304 stainless steel

The effect of cyclic stress ratio (σmin/σmax) was examined for Type 304 stainless steel fatigue cycled at 1000°F using the principles of linearelastic fracture mechanics. Stress ratios varied between -0.15 and 0.75. It was found that at a given value of stress intensity factor range, ΔK, the fatigue-crack growth rate increased with increasing values of stress ratio. However, ΔK did not provide the best basis for correlating crack growth rate results for various stress ratios, and it was found that the term Kmax(1 - R)0.5 provided a much better correlation.