3D cohesive modelling of hydrogen embrittlement in the heat affected zone of an X70 pipeline steel |
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Authors: | Antonio Alvaro Vigdis Olden Odd Magne Akselsen |
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Affiliation: | 1. Department of Engineering Design and Materials, NTNU, 7456 Trondheim, Norway;2. SINTEF Materials and Chemistry, 7456 Trondheim, Norway |
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Abstract: | A three-dimensional finite cohesive element approach has been developed and applied in order to simulate the crack initiation of hydrogen-induced fracture. A single edge notched tension specimen of an X70 weld heat affected zone was simulated. The results were compared to similar two-dimensional plane strain model and the cohesive parameters were calibrated to fit the experimental results. The three dimensional simulations gave higher values in terms of opening stress at the stress peak, plastic strain levels at the crack tip and hydrogen lattice concentration when compared with two-dimensional simulations under the same global net section stress levels. Nevertheless a higher cohesive strength was needed for the 2D model for the onset of crack propagation. The best fit to the experimental data were obtained for a cohesive strength of 1840 MPa and 1620 MPa for the 2D and 3D simulation respectively. The critical opening was assigned to 0.3 mm for both models. The threshold stress intensities KIC,HE were 142 MPa√m and 146 MPa√m for the 2D and 3D models, respectively. |
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Keywords: | Cohesive zone modelling Hydrogen embrittlement Heat affected zone Pipeline steel Three-dimensional model |
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