Design Of Steel Structures

Review on fracture and crack propagation in weldments - A fracture mechanics perspective

http://www.relialab.org/Upload/files/EFM3737.pdf

A generalized energy-based fatigue–creep damage parameter for life prediction of turbine disk alloys

Mechanism-based thermomechanical fatigue life prediction of cast iron. Part I: Models

Cyclic deformation at elevated temperature has been modeled for a polycrystalline nickel-based superalloy using the crystal-plasticity constitutive formulations. Finite element analyses were carried out for a representative volume element (RVE), consisting of randomly oriented grains and subjected to periodic boundary constraints. Model parameters were determined by fitting the strain-controlled cyclic test data at 650 °C for three different loading rates. Simulated results are in good agreement with the experimental data for both stress–strain loops and cyclic hardening behavior. The model was utilized to predict the stress relaxation behavior during the hold periods at the maximum and minimum strain levels, and the prediction compares well with the experimental results. Localized stress and strain concentrations were observed due to the heterogeneous nature of grain microstructure and the mismatch of the mechanical properties of individual grains.

/pdf/crystal-plasticity-modeling-of-cyclic-deformation-for-a-3r393ceak1.pdf

Crystal plasticity modeling of cyclic deformation for a polycrystalline nickel-based superalloy at high temperature

Simulation of crack growth under low cycle fatigue at high temperature in a single crystal superalloy

Based on a large set of 2D finite element analyses, parametric equations for weld toe stress concentration factors and through-thickness stress profiles are provided for butt-welded plates. These cover Single-V and Double-V joints subject to tensile and bending loading. Compared to the most widespread solutions in the literature, which have also been tested against the finite element data in this work, the application range is extended particularly with respect to the weld toe radius (0.1 ≤ ρ ≤ 4 mm) and angle (10° ≤ α ≤ 60°). Furthermore, two values of excess weld metal are considered (h = 0.75 ; 2.5 mm). The analyses are performed for a plate thickness of 10 mm. Besides the extended validity range, the proposed equations show also an improved accuracy compared to the existing solutions.

Extended parametric equations for weld toe stress concentration factors and through-thickness stress distributions in butt-welded plates subject to tensile and bending loading

The fracture mechanics-based IBESS approach is applied to the determination of FAT classes of butt welds with crack initiation along the weld toe. The aim is an investigation of the effect of the geometrical parameters toe radius, flank angle, reinforcement and secondary notches such as roughness or undercuts. The influence of these parameters is discussed both individually and in combination; however, excluding statistical distributions of them and the material data. The results, when compared with conventional FAT classes for butt welds, are encouraging with respect to a potential contribution of IBESS to the discussion of more advanced quality criteria for welds. To that purpose, demands for further research are proposed.

/pdf/effect-of-the-parameters-of-weld-toe-geometry-on-the-fat-4m4nnybiei.pdf

Yusuf Kiyak

Papers

Simulation of crack growth under low cycle fatigue at high temperature in a single crystal superalloy

Extended parametric equations for weld toe stress concentration factors and through-thickness stress distributions in butt-welded plates subject to tensile and bending loading

Effect of the parameters of weld toe geometry on the FAT class as obtained by means of fracture mechanics-based simulations

Reference loads for plates with semi-elliptical surface cracks subjected to tension and bending for application within R6 type flaw assessment

Stiffness/constraint effects in analytical flaw assessment. A technical note