Mean Stress Correction in Low Cycle Fatigue Life of High Strength Steels

Fatigue strength of welded joints varies depending on the shape, filler metal, welding procedure, and post-treatment method. In addition, mean stress affects the fatigue behavior in terms of stress ratio. Typically, it is well known that tensile mean stress tends to decrease fatigue life while compressive mean stress increase fatigue life. There are various methods to incorporate the mean stress effect in fatigue strength, but there are relatively few correction methods in compressive mean stress, especially in low cycle fatigue regime.In this study, a load-based fatigue test was conducted to evaluate the effect of mean stress on the welded joints of High Yield strength steel(HY Steel) with T-joint shape. The effect of the mean stress on the welded part of HY Steel with a T-joint shape was investigated using stress-based mean stress correction methods and strain-based mean stress correction methods. When the effective mean stress approach, which can correct compressive mean stress and tensile mean stress, is applied to HY Steel with a T-joint shape, it shows accurate correction result than stress-based mean stress correction method and strain-based mean stress correction method. Sensitivity parameters to consider mean stress for HY steel are presented.