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

 
 
Springer (Verlag)
  • erschienen am 1. September 2018
 
  • Buch
  • |
  • Softcover
  • |
  • 192 Seiten
978-3-319-88405-9 (ISBN)
 
In this thesis, the author investigates experimentally and numericallythe fracture behavior of an electron beam welded joint made fromtwo butt S355 plates. The 2D Rousselier model, the Gurson-Tvergaard-Needleman (GTN) model and the cohesive zone model (CZM) wereadopted to predict the crack propagation of thick compact tension (CT)specimens. Advantages and disadvantages of the three mentioned modelsare discussed. The cohesive zone model is suggested as it is easy to usefor scientists & engineers because the CZM has less model parametersand can be used to simulate arbitrary crack propagation. The resultsshown in this thesis help to evaluate the fracture behavior of a metallicmaterial. A 3D optical deformation measurement system (ARAMIS) andthe synchrotron radiation-computed laminography (SRCL) techniquereveal for the first time the damage evolution on the surface of the sampleand inside a thin sheet specimen obtained from steel S355. Damageevolution by void initiation, growth and coalescence are visualized in2D and 3D laminographic images. Two fracture types, i.e., a flat crackpropagation originated from void initiation, growth and coalescenceand a shear coalescence mechanism are visualized in 2D and 3D imagesof laminographic data, showing the complexity of real fracture. Inthe dissertation, the 3D Rousselier model is applied for the first timesuccessfully to predict different microcrack shapes before shear cracksarise by defining the finite elements in front of the initial notch withinhomogeneous f0-values. The influence of the distribution of inclusionson the fracture shape is also discussed. For the analyzed material, ahomogeneous distribution of particles in the material provides thehighest resistance to fracture.
Softcover reprint of the original 1st ed. 2018
  • Englisch
  • Cham
  • |
  • Schweiz
Springer International Publishing
  • Für Beruf und Forschung
  • 163 farbige Abbildungen, 27 s/w Abbildungen
  • |
  • 163 Illustrations, color; 27 Illustrations, black and white; XVII, 171 p. 190 illus., 163 illus. in color.
  • Höhe: 235 mm
  • |
  • Breite: 155 mm
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  • Dicke: 10 mm
  • 299 gr
978-3-319-88405-9 (9783319884059)
10.1007/978-3-319-67277-9
weitere Ausgaben werden ermittelt

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 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 G0 ................... 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
In this thesis, the author investigates experimentally and numericallythe fracture behavior of an electron beam welded joint made fromtwo butt S355 plates. The 2D Rousselier model, the Gurson-Tvergaard-Needleman (GTN) model and the cohesive zone model (CZM) wereadopted to predict the crack propagation of thick compact tension (CT)specimens. Advantages and disadvantages of the three mentioned modelsare discussed. The cohesive zone model is suggested as it is easy to usefor scientists & engineers because the CZM has less model parametersand can be used to simulate arbitrary crack propagation. The resultsshown in this thesis help to evaluate the fracture behavior of a metallicmaterial. A 3D optical deformation measurement system (ARAMIS) andthe synchrotron radiation-computed laminography (SRCL) techniquereveal for the first time the damage evolution on the surface of the sampleand inside a thin sheet specimen obtained from steel S355. Damageevolution by void initiation, growth and coalescence are visualized in2D and 3D laminographic images. Two fracture types, i.e., a flat crackpropagation originated from void initiation, growth and coalescenceand a shear coalescence mechanism are visualized in 2D and 3D imagesof laminographic data, showing the complexity of real fracture. Inthe dissertation, the 3D Rousselier model is applied for the first timesuccessfully to predict different microcrack shapes before shear cracksarise by defining the finite elements in front of the initial notch withinhomogeneous f0-values. The influence of the distribution of inclusionson the fracture shape is also discussed. For the analyzed material, ahomogeneous distribution of particles in the material provides thehighest resistance to fracture.

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