Prediction of slant ductile fracture using damage plasticity theory

Slant ductile rupture is one of the common failure modes in the pressure vessel and piping industry. Such failure in tubing and casing can be the result of excessive internal pressure and/or axial loading. The underlying physics of ductile rupture is essential in predicting the fracture modes and the crack propagation path for ductile metals. The slant fracture phenomenon is studied numerically by adopting a recently developed damage plasticity theory. The damage plasticity theory incorporates all three stress invariants in a nonlinear damaging process of the material. The numerical integration algorithm for the new model is presented for small strain case. Three applications of different loading conditions are shown to illustrate its effectiveness in predicting ductile fracture. Emphasis is given to the influencing factors to slant fracture and the shear nature of the crack pattern in these applications. These numerical solutions are in good agreement with the experimental observations.