40CrMoV13.9 notched specimens under multiaxial fatigue: an overview of recent results

The multiaxial fatigue strength of circumferentially V-notched and semicircular notched specimens made of 40CrMoV13.9 has been investigated in this paper. The multiaxial load were applied using combined tension and torsion loading, both in-phase and out-of-phase. The axissymmetric V-notched specimens were characterized by a blunt notch tip (radius: 1 mm) and notch opening angle of 90o and the semicircular specimens were characterized by a constant notch tip radius. The net sectional area of both cases was equal with a diameter of 12 mm. The notched specimens were tested under pure mode I (tension), mixed mode I/III and pure mode III (torsion). More than 120 fatigue test data are used in this paper to evaluate the fatigue behaviour of 40CrMoV13.9 alloy. All fatigue data are analysed using the Average Strain Energy Density (ASED) criterion which employs the mean value of the strain energy density evaluated over a finite size semicircular sector surrounding the tip of the notch to predict the fatigue life of the tested specimens

Fatigue assessment of steel rollers by means of the local energy

This paper aims to analyses the fatigue behavior of steel rollers using the average strain energy density (SED) criterion. Considering the variability of the V-notch opening angle, a simple scalar quantity, i.e. the value of the strain energy density averaged in a control volume surrounding the notch tip, has been introduced to overcome the complexities in failure assessment of this component. The strain energy is obtained using close form solutions based on the relevant Notch Stress Intensity Factors (NSIF) for modes I, II and III. Referring to the conventional arc welding processes, the radius of the control volume is carefully identified with reference to conventional arc welding processes being equal to 0.28 mm for welded joints made of steel. In this paper firstly the employed methodology for the fatigue assessment is described and then the first synthesis of fatigue data by means of local SED for a specific geometry is shown

Different approaches for fatigue assessment of butt-welded joints

The main aim of this work is the fatigue strength assessment of butt joints with weld reinforcement, typically used in steel works and especially in shipbuilding applications. A sensitivity analysis has been carried out by varying different geometrical parameters of the welded joints. Moreover, two different approaches for fatigue strength estimates were applied, namely the Effective Notch Stress Approach, which is nowadays widely used and it is supported by comprehensive literature and the Strain Energy Density approach. Analyses were carried out using two different finite element codes: Ansys\uae and Adina\uae. The application of different software allowed verifying the quality of obtained results, disclosing certain essential aspects related to the extrapolation of values from integration points of finite elements

On the fatigue properties of a third generation aluminium-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB)

The present investigation is concerned with the high-cycle axial fatigue behaviour of a third generation Al-steel butt weld made by Hybrid Metal Extrusion & Bonding (HYB). In this particular weld, metallurgical bonding is achieved by a combination of microscale mechanical interlocking and intermetallic compound (IMC) formation, where the IMC layer is in the sub-micrometre range (<1µm). During high-cycle axial fatigue testing this microstructure provides a high intrinsic resistance against interfacial cracking. In the as-welded condition, fatigue fracture typically initiates at the weld toe on the aluminium side of the joint due to the unfavourable effect of having a geometrical stress riser localised inside the soft heat-affected zone. Since the interfacial bond strength is not a limiting factor, the fatigue properties of the Al-steel HYB butt weld are seen to fully match those of corresponding Al-Al weldments produced by gas metal arc welding, laser beam welding and friction stir welding. © 2021 Elsevier Lt

Mechanical Properties of Biocompatible 316L Steel Rhombic Dodecahedron Lattice Structures

Additive manufactured lattice structures have the potential of enhancing many of today’s engineered products manufactured by traditionally methods. The former provides the capability of altering the mechanical, thermal and acoustic properties of structures through the use of lattices. However, more investigation is needed to better understand the manufacturability and the mechanical behavior of sandwich structures. This paper investigates the influence of strut size on the global stiffness and the compressive strength using compression testing of sandwich structures. Digital Image Correlation (DIC) analysis is applied to determine the local strain distribution during the compression test. It is found that the compressive strength increases linearly with increased lattice strut diameter. Moreover, based on DIC the maximum strains are observed in the strut connection regions.Mechanical Engineerin

Modelling and fatigue assessment of steel rollers with failure occurring at the weld root based on the local strain energy

AbstractWeldments geometry with failures occurring at the weld toe or at the weld root cannot, by its nature, be precisely defined. Parameters such as bead shape and toe or root radius vary from joint to joint even in well-controlled manufacturing operations. The worst case configuration can be achieved by modelling as a sharp, zero radius, notch both the toe and the weld root. The intensity of asymptotic stress distributions obeying Williams’ solution are quantified by means of the Notch Stress Intensity Factors (NSIFs). For steel welded joints with failures originated from the weld roots, where the lack of penetration zone is treated as a crack-like notch, units for NSIFs are the same as conventional SIF used in LEFM. The different dimensionality of NSIFs for different notch opening angles does not allow a direct comparison of failures occurring at the weld toe or at the weld root. In order to overcome the problem related to the variability of the V-notch opening angle, a simple scalar quantity, i.e. the value of the strain energy density averaged in the structural volume surrounding the notch tip, has been introduced. This energy is given in closed form on the basis of the relevant NSIFs for modes I, II and III. The radius RC of the averaging zone is carefully identified with reference to conventional arc welding processes being equal to 0.28 mm for welded joints made of steel.The local-energy based criterion is applied here to steel welded rollers produced by Rulmeca subjected to prevailing mode I (with failures at the weld root). The aim of the paper is firstly to describe the employed methodology for the fatigue assessment and secondly to show the first synthesis of fatigue data by means of local SED for a specific geometry

Fatigue assessment of steel rollers by means of the local energy

This paper aims to analyses the fatigue behavior of steel rollers using the average strain energy density (SED) criterion. Considering the variability of the V-notch opening angle, a simple scalar quantity, i.e. the value of the strain energy density averaged in a control volume surrounding the notch tip, has been introduced to overcome the complexities in failure assessment of this component. The strain energy is obtained using close form solutions based on the relevant Notch Stress Intensity Factors (NSIF) for modes I, II and III. Referring to the conventional arc welding processes, the radius of the control volume is carefully identified with reference to conventional arc welding processes being equal to 0.28 mm for welded joints made of steel. In this paper firstly the employed methodology for the fatigue assessment is described and then the first synthesis of fatigue data by means of local SED for a specific geometry is shown

Fatigue of additively manufactured 316L stainless steel : the influence of porosity and surface roughness

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