Energy-based Low-cycle Fatigue Lifetime Prediction Models of Gray and Nodular Cast Irons for Engine Exhaust Manifold Applications

In the present research, a new energy-based low-cycle fatigue lifetime prediction model has been presented. The objective is to calculate the fatigue lifetime of gray and nodular cast irons, including GJS-500-7 and GJL-250. Such these cast irons have been widely used in the engine exhaust manifold. The proposed model was based on the dissipated plastic strain energy density per cycle, including two correction factors for considering the effect of the temperature and the mean stress. The thermal term takes creep and oxidation effects into consideration. To calibrate the model, experimental data of strain-controlled isothermal low-cycle fatigue tests have been utilized. Obtained results showed an improvement in predicting the fatigue lifetime in comparison to classical approaches and also the plastic strain energy model without correction factors. Therefore, this model can be easily used for predicting the thermo-mechanical behavior of engine exhaust manifolds. In addition, the scatter-band analysis depicted that predicted lifetimes by the corrected plastic strain energy model was within a narrow band, in comparison to other models.