Modified strain-life equation to consider the effect of different prestrain paths for dual phase sheet steel

Fatigue tests of dual phase sheet steel (DP600) were conducted with strain controlled mode of fully reverse loading conditions at room temperature. The specimens were fabricated with three different prestrain paths such as as-received, uniaxial prestrain and plane strain prestrain. Fatigue properties for the all prestrain paths were determined from the fatigue test results. The strain-life curve equations were depended on the prestrain levels and paths. In this study a universal strain-life equation was proposed based on the experimental data to predict the fatigue life of dual phase sheet steel with different prestrain paths. The proposed model utilized fatigue properties of the as-received condition coupled with prestrain levels in the length, width, and thickness of the test specimen. The effectiveness of the proposed universal strain-life equation was demonstrated with a simple metal formed part that experienced various prestrain paths.