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Abstract: The introduction of the wheel loads into a crane runway with a hot rolled I-section and a block rail fastened by longitudinal fillet welds forms a multiaxial fatigue problem. At the point of wheel load application the top region of the runway girder is subjected to a stress field comprising local stress components induced by the concentrated load, i.e. local transverse pressure and local shear stress in addition to the direct and shear stress components due to global bending. The superposition of all aforementioned stress components (and stress ranges, resp.) during each single crane pass results in a so-called non-proportional cyclic stressing of the rail welds with alternating principal stress direction. Due to the variation of the principal stress direction the conventional fatigue evaluation procedures appear not to be reliable. To approach the complex issue two crane runway girders were tested under proportional multiaxial loading, i.e. under flexural bending and stationary wheel load, both simultaneously pulsating. The paper presents the fatigue evaluation of these tests using different local concepts. [Copyright &y& Elsevier]

Abstract: Several lately proposed modifications or variants of the structural stress or strain concepts, of the notch stress or strain concepts (also termed ‘local stress or strain concepts’) and of the fracture mechanics concepts of fatigue assessment of welded joints are reviewed, whereas the wider context is presented in a recently republished and actualised standard work. The structural stress concepts described first are based on a linearisation of the stress distribution across the plate thickness or along the anticipated crack path and, alternatively, on the structural stress 1mm in depth below the weld toe. The structural stress is defined and set against design S–N curves. A further structural stress concept is presented for welded joints in thin-sheet steels and aluminium alloys. Among the elastic notch stress concepts, the variant with the reference notch radius, ρ r =1mm, recently verified also for welded joints in aluminium alloys with plate thicknesses t ⩾5mm and the variant with a small-size reference notch radius, ρ r =0.05mm, applicable to welded joints in thin-sheet materials, are outlined. The elastic–plastic notch strain concept is applied to a spot-welded tensile-shear specimen starting from a small-size keyhole notch at the nugget edge. The novel notch stress intensity factor (NSIF) approach relating to crack initiation and extrapolated to final fracture of seam-welded joints in steels and in aluminium alloys is reviewed. A more recently developed crack propagation approach for spot welds is finally described. [Copyright &y& Elsevier]

Abstract: Case-hardened gear wheels, e.g., in vehicle transmissions are cyclically most stressed components. Their lifetime is determined by the interaction of loading, tooth flank load-capacity and tooth foot load-capacity. The latter is influenced by a multitude of parameters like mean loading or residual stress state appearing during operation. To evaluate the tooth-foot load-capacity, the knowledge of the mean stress and residual stress sensitivity of the fatigue strength of the material conditions at the sites critical for failure is necessary. The examinations on hand concerning means stress sensitivity and residual stress sensitivity usually deal with homogeneous materials. Systematic analyses for case-hardened conditions are missing. In this work case-hardened notched specimens with different residual stress states are investigated under cyclic bending. The results are analyzed using a local concept and an additional fracture mechanical approach. With the local concept it was possible to determine the crack initiation site which was partly at the surface and partly below the surface. The fracture mechanical approach was necessary to understand the crack stop behavior and to determine the site critical for failure. An uniform description of the lifetime behavior of unpeened and shot peened specimen could be achieved using a modified Haigh diagram which takes into account the local stress state at the site critical for failure. [Copyright &y& Elsevier]