Prediction of ductile failure in materials for onshore and offshore pipeline applications

This paper shows the procedures needed to calibrate a numerical model intended for ductile damage estimation of bulk materials. For this purpose, an extensive experimental campaign has been carried out on three steels used for offshore/onshore pipe applications. Tests have been performed providing very different stress states: tensile and compressive uniaxial tests, multiaxial tensile tests on round notched bars, 3-point bend tests, again on notched geometries, and plane strain tensile tests on large grooved specimens. Based on the gathered results, a standard plasticity model has been tuned and then the damage model parameters have been identified for each investigated material. The chosen theoretical formulation can take into account all of the experimental evidence: hence, the numerical model represents a useful tool for finite element simulation of engineering problems where information concerning the materials ultimate resistance capability is needed. Moreover, the proposed calibration technique has general validity and can be used to tune other similar damage models.