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

Haoyun Tu is an Assistant Professor at the School of Aerospace Engineering and Applied Mechanics, Tongji University, PR China. He received his BE and ME from Northwestern Polytechnical University, China and Dr.-Ing. from University of Stuttgart, Germany. His research interests are on fracture mechanism of metals and welded joints from metals with experimental and finite element methods as well as on characterization techniques such as 3D optical deformation measurement and Synchrotron radiation-computed laminography (SRCL).

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 σk ......................................................................................................... 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 ɛn .......................................................................................................... 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 Γ0 ................... 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