Experimental and numerical investigation of ductile damage effect on load bearing capacity of a dented API XB pipe subjected to internal pressure

• Effect of ductile damage on indentation of an API XB steel pipe subjected to internal pressure is studied.
• The damage plasticity model proposed by Xue and Wierzbicki is used.
• The model incorporates effects of hydrostatic stress and Lode angle to define fracture envelope.
• Numerical calculations for various ranges of internal pressure are carried out.

In this paper, the effect of ductile damage on the behavior of a dented steel pipe subjected to internal pressure is investigated by experimental and numerical methods. In the numerical investigation the plastic behavior of pipes under indentation is studied using continuum damage mechanics theory and the elastic–plastic finite element analysis. Finite element calculations are carried out using the damage plasticity model proposed by Xue and Wierzbicki (X-W). The proposed damage plasticity model incorporates effects of four parameters that play important role in predicting the fracture initiation, namely the damage rule, the softening effect, the hydrostatic pressure and the Lode angle. The target dent depth is considered as an indication of the load bearing capacity of the pipe under indentation process by a rigid spherical indenter. To validate numerical calculations, a series of experimental tests are conducted on the pipe with atmospheric pressure. After verification, numerical calculations for different ranges of internal pressures with and without damage effect are carried out and results are compared. It is shown that damage plays an important role on the load bearing capacity of an indented pipe. Results of the present study confirm the credibility of the proposed model in predicting the ductile fracture under multi-axial state of stress loadings.