Papers by Keyword: Notch Stress Intensity Factor

Abstract: This paper summarizes recent theoretical studies on the three-dimensional singular stress state at sharp notches in infinite (or large) plates of finite thickness subjected to in-plane loading. In general, such loading produces a number of singular states: in-plane singularities (normally described as KI and KII fracture modes and known as Williams’ solution), singular states associated with corners and the out-of-plane singularity (KO mode), which is generated due to the Poisson’s effect. The latter mode has an interesting behavior and its intensity increases as a power function with the increase of the plate thickness when the notch is stresses in shear mode. From finite fracture mechanics considerations it is clear that at some certain thickness the out-of-plane singular mode will dominate over the fracture zone and with the further increase of the plate thickness will affect the strength of the notched plate, virtually reducing it to zero.

Abstract: The paper presents a simplified version of the Notch Stress Intensity Factor (NSIF) approach useful for fatigue strength assessments of welded joints. The evaluation of the NSIF from a numerical analysis of the local stress field usually needs very refined meshes and then large computational effort. A relationship is proposed here to estimate the Notch Stress Intensity Factor from finite element analyses carried out by using a mesh pattern with a constant element size. The main advantage of the presented relationship is that only the elastic peak stress numerically evaluated at the V-notch tip is necessary to estimate the NSIF instead of the whole stress-distance set of data (that is why the method has been called Peak Stress Method, i.e. PSM). An application of the PSM to fatigue strength assessment of fillet welded joints made of structural steels and aluminium alloys under tensile or bending loads is presented. In those joints, only mode I stress distribution is singular at the weld toe due to the presence of a V-notch angle equal to 135 degrees.

Abstract: A recent approach based on the local strain energy density (SED) averaged over a given control volume is applied to well documented experimental data taken from the literature, all related to steel welded joints of complex geometry. This small size volume embraces the weld root or the weld toe, both regions modelled as sharp (zero notch radius) V-notches with different opening angles. The SED is evaluated from three-dimensional finite element models by using a circular sector with a radius equal to 0.28 mm. The data expressed in terms of the local energy fall in a scatter band recently reported in the literature, based on about 650 experimental data related to fillet welded joints made of structural steel with failures occurring at the weld toe or at the weld root.

Abstract: The paper presents a simplified version of the Notch Stress Intensity Factor (NSIF) approach useful for fatigue strength assessments of welded joints. The evaluation of the NSIF from a numerical analysis of the local stress field usually needs very refined meshes and then large computational effort. A relationship is proposed here to estimate the Notch Stress Intensity Factor from finite element analyses carried out by using a mesh pattern with a constant element size. The main advantage of the presented relationship is that only the elastic peak stress numerically evaluated at the V-notch tip is necessary to estimate the NSIF instead of the whole stress-distance set of data (that is why the method has been called Peak Stress Method, i.e. PSM). An application of the PSM to fatigue strength assessment of fillet welded joints made of structural steels and aluminium alloys under tensile or bending loads is presented. In those joints, only mode I stress distribution is singular at the weld toe due to the presence of a V-notch angle equal to 135 degrees.