Effect of Strain Wave Shape on Thermal-Mechanical Fatigue Crack Propagation in a Cast Low-Alloy Steel

Abstract

The effect of strain wave shape on low cycle thermal-mechanical fatigue crack propagation in a cast low-alloy steel was investigated under in-phase loading condition with a temperature range of 300–550°C. It was found that the rate of crack propagation increased with the asymmetry of strain wave shape, the effect being greatest in the high strain range. This behavior was discussed on the basis of observations in electron fractography and the change of inelastic tensile creep strain range with the repeated strain cycles. It was shown that the accumulation of inelastic tensile creep strain, which was not recovered during the compressive strain period contributed to this behavior. Further, the parameter called the range of total J-integral was introduced by applying the strain range partitioning approach and the rate of crack propagation was correlated with this.