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Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures

Welding is the most widespread technology for the connection of different materials, elements and structures. Loading capacity and knowledge about stress–strain behaviour is most important for safety and the reliable use of structures for different purposes in energy supplies and the transport of good and people. Filler material used in welding should be the same class as the base material ; however, welding codex often uses a filler with a higher yield strength than the base material (such as by repair welding). Welded joints are also often the location of potential flaws, where flaw assessments assume homogeneous material properties, although welds are heterogeneous. There is a compendium of yield load solutions for mismatched strength fracture mechanics specimens developed to address the heterogeneity in the weld joint. However, solutions for the yield load at different combinations of the strength mismatch within the weld are missing, where mechanical testing and finite element simulations are necessary. In addition to more conventional approaches, a multi-scale approach recently introduced in the assessment of weld heterogeneity sounds very promising. It is also efficient to consider residual stresses, which can strongly affect the stress distribution around flaws in heterogeneous weldments. The multi-scale methodology is computationally efficient and provides a possible means to bridge multiple length scales (from 10 nm in MD simulation to 10 mm in FE models). This could be a useful tool by considering an acceptable level of accuracy with respect to yield load in heterogeneous welds. In this book, modern trends in testing and simulating heterogeneous welded joints, including multi-scale approaches, resulting in appropriate flaw assessment procedures, are highlighted and discussed. The eleven research papers presented in this book give some overview of recent analytical, numerical, and experimental investigations in the field of yield strength mismatched welded joint behaviour. The papers cover several important issues to more accurately characterise the fracture mechanics behaviour and structural integrity assessment, as follows: Preface to ”Numerical and Experimental Analysis of the Fracture Behaviour of Heterogeneous Welded Structures” Welding is the most widespread technology for the connection of different materials, elements and structures. Loading capacity and knowledge about stress–strain behaviour is most important for safety and the reliable use of structures for different purposes in energy supplies and the transport of good and people. Filler material used in welding should be the same class as the base material ; however, welding codex often uses a filler with a higher yield strength than the base material (such as by repair welding). Welded joints are also often the location of potential flaws, where flaw assessments assume homogeneous material properties, although welds are heterogeneous. There is a compendium of yield load solutions for mismatched strength fracture mechanics specimens developed to address the heterogeneity in the weld joint. However, solutions for the yield load at different combinations of the strength mismatch within the weld are missing, where mechanical testing and finite element simulations are necessary. In addition to more conventional approaches, a multi-scale approach recently introduced in the assessment of weld heterogeneity sounds very promising. It is also efficient to consider residual stresses, which can strongly affect the stress distribution around flaws in heterogeneous weldments. The multi-scale methodology is computationally efficient and provides a possible means to bridge multiple length scales (from 10 nm in MD simulation to 10 mm in FE models). This could be a useful tool by considering an acceptable level of accuracy with respect to yield load in heterogeneous welds. In this book, modern trends in testing and simulating heterogeneous welded joints, including multi-scale approaches, resulting in appropriate flaw assessment procedures, are highlighted and discussed. The eleven research papers presented in this book give some overview of recent analytical, numerical, and experimental investigations in the field of yield strength mismatched welded joint behaviour. The papers cover several important issues to more accurately characterise the fracture mechanics behaviour and structural integrity assessment, as follows: - New mathematical model for the determination of yield loads for the present yield strength mismatch in weld configuration at different crack positions ; - New methodology for determining the actual stress–strain diagram based on analytical equations, in combination with numerical and experimental data, using 3D digital image correlation (DIC) ; - Simulation of local variation in material properties of the fracture behaviour in a multi-pass mismatched X-weld joint ; - Experimental procedures include the characterization of average material properties by tensile testing and evaluations of base and weld metal resistance to stable tearing by the fracture testing of fracture mechanics specimens containing a weld notch ; - Behaviour of welded joints in the simultaneous presence of several different types of multiple defects, such as linear misalignments, undercuts, incomplete root penetration and excess weld metal ; - Modified equation for estimating the C* integral for a welded compact tension (CT) specimen under creep conditions, etc.

heterogeneous welded joints ; fatigue and fracture of heterogeneous welded joints ; mechanical testing ; microstructure ; multi scale modeling ; finite element analysis ; structural integrity assessment ; flaw assessment procedures for heterogeneous welds

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