Damage accumulation and fracture initiation in （损伤积累和断裂启动中）.pdf

International Journal of Solids and Structures 44 (2007) 5163–5181 /locate/ijsolstr Damage accumulation and fracture initiation in uncracked ductile solids subject to triaxial loading Liang Xue * Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 5-011, Cambridge, MA 02139, USA Received 26 July 2005; received in revised form 16 November 2006 Available online 29 December 2006 Abstract A damage plasticity model for ductile fracture is proposed. This model is established on the cylindrical coordinate sys- tem of principal stress space. Experimental results show that fracture initiation in uncracked ductile solids is sensitive to the hydrostatic pressure and dependent on the Lode angle. The joint effects of pressure and Lode angle define a fracture enve- lope in principal stress space. Plastic deformation induced damage is calculated by an integral of the damage rate measured at current loading and deformation status with respect to the fracture envelope. A power law damage rule is proposed to characterize the nonlinearity in damage accumulation. A damage-related weakening factor is adopted to describe the mate- rial deterioration. The material parameters are calibrated from standard laboratory tests. The proposed model is numer- ically implemented. Four simulations with emphasis on crack path prediction are presented. 2006 Elsevier Ltd. All rights reserved. Keywords: Ductile fracture; Hydrostatic pressure; Lode dependence; Damage plasticity model 1. Introduction The ductile failure of structures usually cons