Structural Integrity Assessments of Pipelines Using Crack Growth Resistance Curves

This study explores further extension of the computational cell methodology to model Mode I crack extension in high strength pipeline and structural steels. First, validation analyses of the cell methodology described in this study compare predictions of crack growth response with experimentally measured R-curves for a standard DIN StE 460 steel. Next, laboratory testing of an API 5L X70 steel at room temperature using standard, deep crack C(T) specimens provides the crack growth resistance curve to calibrate the micromechanics cell parameters for the material. The cell model incorporating the calibrated material-specific parameters is then applied to predict the burst pressure of a thin-walled gas pipeline containing longitudinal cracks with varying crack depth to thickness ratios (a/t). The plane-strain analyses reported here demonstrate the capability of the computational cell approach to simulate ductile crack growth and to predict the burst pressure of thin-walled tubular structures containing crack-like defects.