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.

Engineering Sciences New Trends, Concepts and Research

The aim of this major reference work is to provide a first point of entry to the literature for the researchers in any field relating to structural integrity in the form of a definitive research/reference tool which links the various sub-disciplines that comprise the whole of structural integrity. Special emphasis will be given to the interaction between mechanics and materials and structural integrity applications. Because of the interdisciplinary and applied nature of the work, it will be of interest to mechanical engineers and materials scientists from both academic and industrial backgrounds including bioengineering, interface engineering and nanotechnology. The scope of this work encompasses, but is not restricted to: fracture mechanics, fatigue, creep, materials, dynamics, environmental degradation, numerical methods, failure mechanisms and damage mechanics, interfacial fracture and nano-technology, structural analysis, surface behaviour and heart valves. The structures under consideration include: pressure vessels and piping, off-shore structures, gas installations and pipelines, chemical plants, aircraft, railways, bridges, plates and shells, electronic circuits, interfaces, nanotechnology, artificial organs, biomaterial prostheses, cast structures, mining... and more. Case studies will form an integral part of the work.