Quantitative analysis of the impact of forging operations on fatigue properties of steel components

Forging of metal components induces grain flow orientation, which leads to anisotropic mechanical properties. Therefore, it is critical to describe and take into account this grain flow anisotropy into fatigue life calculation. A new state variable to represent the grain flow orientation is defined and implemented in the finite element code Forge 3® so that forging can be simulated to predict the grain flow in a forged part. When focusing on steels containing malleable inclusions above a critical size, the Murakami equation can be used for describing high cycle fatigue. This criterion is extended to multiaxial fatigue analysis for materials with a grain flow. Therefore, the output of forging simulations in terms of grain flow can be used in anisotropic fatigue analysis. Moreover, residual stresses resulting from forging should also be taken into account to obtain accurate fatigue calculations. Once this integrated simulation tool is developed, a global optimization loop including Forging and Fatigue calculation can be carried out.