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C L Williams - One of the best experts on this subject based on the ideXlab platform.
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estimating the fatigue stress concentration factor of machined surfaces
International Journal of Fatigue, 2002Co-Authors: Dwayne Arola, C L WilliamsAbstract:Abstract In this study the effects of surface texture on the fatigue life of a high-strength low-alloy steel were evaluated in terms of the apparent fatigue stress concentration. An abrasive waterjet was used to machine uniaxial dogbone fatigue specimens with specific surface quality from a rolled sheet of AISI 4130 CR steel. The surface texture resulting from machining was characterized using contact profilometry and the surface roughness parameters were used in estimating effective stress concentration factors using the Neuber Rule and Arola–Ramulu model. The steel specimens were subjected to tension–tension axial fatigue to failure and changes in the fatigue strength resulting from the surface texture were assessed throughout the stress–life regime (103≤Nf≤106 cycles). It was found that the fatigue life of AISI 4130 is surface-texture-dependent and that the fatigue strength decreased with an increase in surface roughness. The fatigue stress concentration factor (Kf) of the machined surfaces determined from experiments was found to range from 1.01 to 1.08. Predictions for the effective fatigue stress concentration ( K f ) using the Arola–Ramulu model were within 2% of the apparent fatigue stress concentration factors estimated from experimental results.
Dieter Radaj - One of the best experts on this subject based on the ideXlab platform.
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state of the art review on extended stress intensity factor concepts
Fatigue & Fracture of Engineering Materials & Structures, 2014Co-Authors: Dieter RadajAbstract:The stress intensity factor concept for describing the stress field at pointed crack or slit tips is well known from fracture mechanics. It has been substantially extended since Williams' basic contribution (1952) on stress fields at angular corners. One extension refers to pointed V-notches with stress intensities depending on the notch opening angle. The loading-mode-related simple notch stress intensity factors K1, K2 and K3 are introduced. Another extension refers to rounded notches with crack shape or V-notch shape in two variants: parabolic, elliptic or hyperbolic notches (‘blunt notches’) on the one hand and root hole notches (‘keyholes’ when considering crack shapes) on the other hand. Here, the loading-mode-related generalised notch stress intensity factors K1ρ, K2ρ and K3ρ are defined. The concepts of elastic stress intensity factor, notch stress intensity factor and generalised notch stress intensity factor are extended into the range of elastic–plastic (work-hardening) or perfectly plastic notch tip or notch root behaviour. Here, the plastic notch stress intensity factors K1p, K2p and K3p are of relevance. The elastic notch stress intensity factors are used to describe the fatigue strength of fillet-welded attachment joints. The fracture toughness of brittle materials may also be evaluated on this basis. The plastic notch stress intensity factors characterise the stress and strain field at pointed V-notch tips. A new version of the Neuber Rule accounting for the influence of the notch opening angle is presented.
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State‐of‐the‐art review on extended stress intensity factor concepts
Fatigue & Fracture of Engineering Materials & Structures, 2013Co-Authors: Dieter RadajAbstract:The stress intensity factor concept for describing the stress field at pointed crack or slit tips is well known from fracture mechanics. It has been substantially extended since Williams' basic contribution (1952) on stress fields at angular corners. One extension refers to pointed V-notches with stress intensities depending on the notch opening angle. The loading-mode-related simple notch stress intensity factors K1, K2 and K3 are introduced. Another extension refers to rounded notches with crack shape or V-notch shape in two variants: parabolic, elliptic or hyperbolic notches (‘blunt notches’) on the one hand and root hole notches (‘keyholes’ when considering crack shapes) on the other hand. Here, the loading-mode-related generalised notch stress intensity factors K1ρ, K2ρ and K3ρ are defined. The concepts of elastic stress intensity factor, notch stress intensity factor and generalised notch stress intensity factor are extended into the range of elastic–plastic (work-hardening) or perfectly plastic notch tip or notch root behaviour. Here, the plastic notch stress intensity factors K1p, K2p and K3p are of relevance. The elastic notch stress intensity factors are used to describe the fatigue strength of fillet-welded attachment joints. The fracture toughness of brittle materials may also be evaluated on this basis. The plastic notch stress intensity factors characterise the stress and strain field at pointed V-notch tips. A new version of the Neuber Rule accounting for the influence of the notch opening angle is presented.
Dwayne Arola - One of the best experts on this subject based on the ideXlab platform.
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estimating the fatigue stress concentration factor of machined surfaces
International Journal of Fatigue, 2002Co-Authors: Dwayne Arola, C L WilliamsAbstract:Abstract In this study the effects of surface texture on the fatigue life of a high-strength low-alloy steel were evaluated in terms of the apparent fatigue stress concentration. An abrasive waterjet was used to machine uniaxial dogbone fatigue specimens with specific surface quality from a rolled sheet of AISI 4130 CR steel. The surface texture resulting from machining was characterized using contact profilometry and the surface roughness parameters were used in estimating effective stress concentration factors using the Neuber Rule and Arola–Ramulu model. The steel specimens were subjected to tension–tension axial fatigue to failure and changes in the fatigue strength resulting from the surface texture were assessed throughout the stress–life regime (103≤Nf≤106 cycles). It was found that the fatigue life of AISI 4130 is surface-texture-dependent and that the fatigue strength decreased with an increase in surface roughness. The fatigue stress concentration factor (Kf) of the machined surfaces determined from experiments was found to range from 1.01 to 1.08. Predictions for the effective fatigue stress concentration ( K f ) using the Arola–Ramulu model were within 2% of the apparent fatigue stress concentration factors estimated from experimental results.
Dongjun Bang - One of the best experts on this subject based on the ideXlab platform.
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Deviatoric Neuber method for stress and strain analysis at notches under multiaxial loadings
International Journal of Fatigue, 2017Co-Authors: Ayhan Ince, Dongjun BangAbstract:Abstract Fatigue life prediction of notched components requires accurate local stresses and strains at notch areas. Researchers have developed a number of approximation methods to estimate local elasto-plastic stress and strain responses on the basis of elastic stress/strain results. The most two common methods are known as the Neuber Rule and the equivalent strain energy density (ESED) method. It has been presented that the Neuber Rule has a tendency to overestimate notch elasto-plastic strains and stresses while the ESED method tends to underestimate notch elasto-plastic strains and stresses. These drawbacks are attributed to the fact that the original Neuber Rule was developed for notched bodies under pure shear loading, but the Neuber Rule is applied to other multiaxial loadings where the present stress state can significantly vary from the pure shear stress state. Therefore, analytical approximation model based on the deviatoric form of the Neuber Rule has been proposed to estimate elasto-plastic stresses and strains at notches. Predicted notch root stresses and strains from the proposed model are compared with non-linear Finite Element Analysis (FEA) results for SAE 1045 and SAE 1070 steel notched-bars. The SAE 1045 and SAE 1070 steel notch-bars are subjected to monotonic and cyclic non-proportional loadings respectively. The model shows very good agreements with the FEA data for both steel materials.
Otto-ernst Bernhardi - One of the best experts on this subject based on the ideXlab platform.
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A constitutive model for anisotropic materials based on Neuber's Rule
Computer Methods in Applied Mechanics and Engineering, 2003Co-Authors: Roland Mücke, Otto-ernst BernhardiAbstract:Phenomenological approaches to fatigue damage prediction often rely on the assessment of local stress–strain concentrations in structural components. To avoid complex plastic analysis in fatigue assessment, approximate constitutive models have been developed to evaluate the local inelastic response of the material and which allow for an adequate lifetime prediction in a competitive time. One of these approximate methods is the Neuber Rule, which has originally been elaborated for the uniaxial loading state of isotropic materials. This paper addresses an approximate method for multiaxial loading of anisotropic materials. The proposed approach is based on a tensorial formulation of the Ramberg–Osgood equation and a generalization of the uniaxial Neuber hypothesis by assuming the equivalence of the deviatoric strain energy density for the elastic and inelastic solution in the notch region. After a decomposition of the stress tensor into a normalized direction tensor and a stress invariant, a nonlinear expression is obtained which can be iterated for the unknown inelastic stress state. It is shown that the proposed anisotropic Neuber Rule includes the multiaxial isotropic and the classical uniaxial formulation as special cases. Furthermore, aspects of parameter identification are discussed for directionally solidified Nickel-based superalloys with transverse isotropic properties and single crystal materials with cubic anisotropy. Two numerical examples demonstrate the applicability of the proposed approach.