Different constitutive models are available for capturing ductile failure in metals, one of which is called conventional plasticity models like von Mises, Tresca etc. and the other is the damage mechanics based models. von Mises theory is independent of hydrostatic stress in the material. So it is not able to capture ductile fracture process accurately. In recent years different damage mechanics models have been proposed to model ductile fracture. One of the best known damage models is the micromechanical model proposed by Gurson. In this paper, the modified Gurson model known as the Gurson-Tvergaard-Needleman (GTN) model is employed for constitutive modeling of a high conductivity-high ductility copper alloy (Cu-Cr-Zr-Ti alloy) used in a rocket engine thrust chamber at three temperatures (300 K, 550 K, 700 K). The model parameters are evaluated from tensile tests conducted on smooth round subscale sized specimens in a high temperature UTM. Stress analysis of the tensile specimens has been performed using the Multilinear Isotropic Hardening plasticity model in association with Gurson model for damage modeling with the ANSYS® (Version 11) FEA code. Nine GTN model parameters of the alloy have been identified based on comparison of engineering stress strain graphs from tests and analysis. The parameters thus evaluated are subsequently used for collapse analysis of a heated pressure vessel made of copper alloy and the evolution of voids in the structure studied.

Keywords: Micromechanical modeling, Gurson model, FEA, Ductile failure, Elevated temperature.