Damage evolution during cyclic plastic deformation of pipeline steel

ABSTRACT: In the oil and gas industry, one way of laying pipes on the seafloor is by the reeling process. In this process the pipe is subjected to a cyclic plastic deformation. Due to this plastic deformation the mechanical properties of the material are changed. In this study the finite element method is used to predict the influence of the cyclic plastic deformations on the mechanical behaviour of the material. The fraction model is used to describe the cyclic stress-strain behaviour. In order to be able to predict fracture of the material the Gurson-Tvergaard-Needleman damage model is used in conjunction with the fraction model. By comparing unit cell calculations with the damage model, the parameters q1 and q2 were determined for both the monotonic and cyclic loading conditions