THE APPLICATION OF NEUTRON-DIFFRACTION TO STRESS MAPPING AROUND A BLIND-HOLE DEFECT IN STRESSED PIPELINE STEEL

Neutron diffraction was used to map the local stress variation surrounding a 13 mm diameter blind-hole defect in a section of pipeline subjected to an applied bending stress. Comparison was made between the experimentally measured results and local stress predictions based on a two-dimensional analytical model as well as on three-dimensional finite element calculations. The two-dimensional analytical model proved to be unsatisfactory, predicting very large local stress variations at the defect edge which were not observed experimentally. Conversely, the three-dimensional model reflected all of the significant trends observed experimentally, although predicted stress levels were lower than the measured values due to limitations with the finite element package.