Comparative study on the ductile fracture behavior of various high-tensile strength marine structural steels

Abstract

In extreme or accidental conditions, such as ship-to-ship collision, grounding or explosion, marine structures may experience large inelastic deformation and ductile fracture. Ductile fracture may initiate also in marine structures due to fatigue and then cracks may propagate under usual loading magnitude. In shipbuilding industry, various steel grades are classified depending on yield stress and impact toughness. Structural steels for ships or offshore structures are required to be ductile material; however, the ductility limits of the high tensile steel grades used in modern shipbuilding beyond moderate plasticity have not been reported in literature with respect to different stress states and loading paths.In our previous study (Park et al., 2018), ductile fracture tests were conducted for EH36 grade high tensile strength steel. In the present paper, additional tests and ductile fracture model calibration are provided for AH36 and DH36 gradesteels. The tests were carried out with standard flat smooth, flat notched, center-holed tension specimens and pure shear specimens under room temperature and quasi-static conditions. The test results for smoot flat and notched tension specimens with large notch radius were utilized to calibrate the strain hardening function at the large strain region beyond the onset of necking. The loading path at fracture initiation was investigated using the experimental results and fini