Numerical Simulation and Experimental Investigation of the Fracture Behaviour of an Electron Beam Welded Steel Joint

Abstract1. Introduction........................................................................................................................................ 51.1 Motivation ............................................................................................................................... 51.2 Outline ..................................................................................................................................... 52. Scientific background .................................................................................................................... 92.1 Electron beam welding ...................................................................................................... 92.2 Fracture mechanics .......................................................................................................... 102.2.1 The fracture mechanics approach.................................................................... 102.2.2 The Brittle fracture ................................................................................................. 122.2.3 The J-integral ........................................................................................................... 132.3 Constitutive damage models ......................................................................................... 152.3.1 The Rice and Tracey model ................................................................................ 152.3.2 The Rousselier model ........................................................................................... 162.3.3 The Gurson-Tvergaard-Needleman (GTN) model........................................ 182.4 Cohesive zone model (CZM) .......................................................................................... 212.5 ARAMIS system .................................................................................................................. 242.6 Synchrotron Radiation-Computed Laminography (SRCL) .................................. 253. Characterization of steel S355 electron beam welded (EBW) joints ............................ 273.1 Chemical composition ..................................................................................................... 283.2 Microstructures of steel S355 EBW joints ................................................................ 283.3 Mechanical properties of S355 EBW ........................................................................... 303.3.1 Hardness measurement ....................................................................................... 303.3.2 Tensile behaviour of different tensile specimens ....................................... 313.3.3 Fracture surface of notched specimens ........................................................ 413.4 Fracture behaviour of S355 EBW joints ..................................................................... 423.4.1 Fracture toughness tests .................................................................................... 423.4.2 Fracture surface analysis of C(T)-specimens .............................................. 453.5 Summary and conclusions ............................................................................................. 524. The Rousselier model................................................................................................................... 534.1 Parameter study using the Rousselier model ......................................................... 534.1.1 Influence of f0 ........................................................................................................... 544.1.2 Influence of fc ........................................................................................................... 564.1.3 Influence of sk ......................................................................................................... 574.1.4 Influence of lc ........................................................................................................... 594.2 Crack propagation in the homogeneous base material ....................................... 624.3 Crack propagation in an inhomogeneous region ................................................... 704.4 Discussion and Conclusions ......................................................................................... 755. The Gurson-Tvergaard-Needleman (GTN) model ............................................................... 775.1 Parameter study using the GTN model ...................................................................... 775.1.1 Influence of f0 ........................................................................................................... 785.1.2 Influence of fc ........................................................................................................... 805.1.3 Influence of ff ............................................................................................................ 815.1.4 Influence of fn ........................................................................................................... 835.1.5 Influence of n .......................................................................................................... 855.2 Crack propagation in the homogeneous base material ....................................... 895.3 Crack propagation in an inhomogeneous material................................................ 935.4 Discussion and Conclusions ......................................................................................... 966. The Cohesive zone model ........................................................................................................... 996.1 Parameter study using the cohesive model ............................................................. 996.1.1 Influence of cohesive strength T0 and cohesive energy 0 ................... 1026.1.2 Influence of the cohesive element.................................................................. 1046.1.3 Influence of the shape of the TSL ................................................................... 1066.2 Crack propagation in S355 base material ............................................................... 1076.2.1 Identification of the cohesive parameters ................................................... 1076.2.2 Identification of the shape of the TSL ........................................................... 1136.3 Crack propagation in S355 fusion zone (FZ) .......................................................... 1146.4 Crack propagation at the interface between the FZ and the HAZ ................... 1156.5 Discussion and Conclusions ....................................................................................... 1187. Optical measurement of crack propagation with the ARAMIS system ..................... 1217.1 Specimen preparation .................................................................................................... 1217.2 Experimental results obtained with ARAMIS ......................................................... 1227.3 Comparison of experiment with simulation results obtained with the GTNmodel ................................................................................................................................... 1277.4 Discussion and Conclusions ....................................................................................... 1318. In situ laminography investigation of damage evolution in S355 base material ... 1358.1 Laminography ................................................................................................................... 1358.2 In situ observation of damage evolution by laminography reconstruction 1378.3 Discussion and Conclusions ....................................................................................... 1659. Summary and Outlook ............................................................................................................... 1699.1 Summary ............................................................................................................................. 1699.2 Outlook ................................................................................................................................ 173Appendix ................................................................................................................................................ 17510. List of Publications .................................................................................................................... 17911. Bibliography ................................................................................................................................. 181Acknowledgements ............................................................................................................................ 191... Mehr