Effect of Triaxial State of Stress on Tensile Behavior of Modified 9Cr-1Mo Steel

Abstract

In this investigation, effect of triaxial state of stress on tensile behavior of modified 9Cr-1Mo steel has been studied. In order to introduce different triaxial states of stresses, circumferential notches of different notch root radii were incorporated in the smooth specimens. The tensile tests were conducted at room temperature and at a strain rate of 3 × 10−4 s−1 in air environment. The tensile strength increased, and the ductility (% reduction in area) decreased with a decrease in notch root radius. The curve fitting of tensile data of smooth specimen was carried out using various constitutive equations. The Voce constitutive equation was found to represent the tensile data of the smooth specimen up to the point of necking. An approach consisting of Voce equation for pre-necking and an exponential equation for post-necking behavior of the material was used as input material model which could predict the complete tensile response of the material. The tensile data obtained from the analysis were used as input for the estimation of tensile response of the notched specimens. The load–displacement curves of the notched specimens could be predicted well using finite element analysis. The comparison of stress and strain obtained from finite element analysis was also carried out with the Bridgman equations for the notched specimens. Significant difference in stress distribution was observed as compared to the distribution obtained by finite element analysis for relatively sharper notches.