Constitutive modeling of ferritic stainless steels for automotive engine application

摘要

Deformation analysis of thermal and mechanical stress of exhaust manifold in the automotive engine has been performed in this study. Tensile tests of two kinds of ferritic stainless steels were carried out in a wide range of temperature from room temperature to 900 °C to investigate the flow stress and dynamic strain aging (DSA) effects on the deformation behaviors. For most tested materials yield stress and flow stress were well correlated with the reciprocal of homologous temperature T_m/T over the testing temperature range by a bi-linear type relationship. This relationship could be partially supported by the dislocation energy barrier model. It was attempted to develop a new constitutive relation to describe an abnormal increase of flow stress in DSA region. The suggested model adopted the normal distribution form for the DSA-induced stress increment. The prediction results showed that the proposed model provides a good correlation on the flow stress in the temperature range up to DSA region.