On the interaction of normal and shear stresses in multiaxial fatigue damage

2019 ◽  
Vol 42 (9) ◽  
pp. 2000-2016 ◽  
Author(s):  
Shahriar Sharifimehr ◽  
Ali Fatemi
Keyword(s):  
Fatigue Damage ◽  
Multiaxial Fatigue ◽  
Shear Stresses ◽  
Normal And Shear Stresses

scholarly journals Interaction Between Normal and Shear Stresses and Its Effect on Multiaxial Fatigue Behavior

2019 ◽  
Vol 300 ◽  
pp. 16007 ◽  
Author(s):  
Shahriar Sharifimehr ◽  
Ali Fatemi
Keyword(s):  
Normal Stress ◽  
Fatigue Damage ◽  
Shear Failure ◽  
Fatigue Behavior ◽  
Damage Model ◽  
Multiaxial Fatigue ◽  
Experimental Program ◽  
Shear Stresses ◽  
Critical Plane ◽  
Normal And Shear Stresses

Interaction between normal and shear stresses plays an important role in multiaxial fatigue damage. The aim of this study was to investigate this interaction effect on fatigue behavior of shear failure mode materials under multiaxial loading conditions. In order to model the influence of normal stress on fatigue damage, the present study introduces a method based on the idea that the normal stress acting on the critical plane orientation causes two types of influence, first by affecting roughness induced closure, and second, by a fluctuating normal stress affecting the growth of small cracks in mode II. The summation of these terms could then be used in shear-based critical plane damage models, for example FS damage model, which use normal stress as a secondary input. In order to investigate the effect of the method, constant amplitude load paths with different levels of interaction between the normal and shear stresses were designed for an experimental program. The proposed method was observed to result in improved fatigue life estimations where significant interactions between normal and shear stresses exist.

Influence of Phase Shift and Amplitude Ratio on the Principal Stresses and Directions in Multiaxial Fatigue Testing

2015 ◽  
Vol 1111 ◽  
pp. 103-109 ◽  
Author(s):  
Lorand Kun ◽  
Ion Dumitru ◽  
Daniel Achiriloaiei ◽  
Karla Noemy Kun
Keyword(s):  
Shear Stress ◽  
Phase Shift ◽  
Fatigue Testing ◽  
Amplitude Ratio ◽  
Maximum Shear Stress ◽  
Multiaxial Fatigue ◽  
Experimental Program ◽  
Shear Stresses ◽  
Principal Stresses ◽  
Normal And Shear Stresses

The maximum values of normal and shear stresses are the basic parameters which influence directly the initiation and propagation of multiaxial fatigue cracks.Based on the above, the first part of the paper presents an analysis of principal stresses (normal and shear) in case of symmetrical tension-compression loadings with superimposed phase-shifted symmetrical torsion cycles. The influence of stress amplitude ratio and phase shift on the maximum (normal and shear) stresses and on the directions of the planes along which these act is analyzed and graphically represented using stress hodographs.The second part of the paper highlights the possibility of using the maximum value of the normal or shear stress as base parameter for durability studies under multiaxial fatigue, based on existing experimental data. The mentioned data is correlated with the results of an original experimental program carried out by the authors on 41Cr4 steel and conclusions are formulated with regard to the role of maximum shear stress in life-time calculation.

Modeling Multiaxial Fatigue Damage Using Polar Equations

2017 ◽  
Author(s):  
Jafar Albinmousa ◽  
Syed Haris Iftikhar ◽  
Mustafa Al-Samkhan
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Closed Form Solution ◽  
Damage Parameter ◽  
Multiaxial Fatigue ◽  
Loading Path ◽  
Shear Stresses ◽  
Critical Plane ◽  
Stress Strain ◽  
Loading Paths

It is estimated that more than 70% of failures in engineering components are associated with fatigue loading. Therefore, fatigue is a major design tool for mechanical components. These components are usually subjected to multiaxial cyclic loading. In fact, multiaxial state is very common as tension specimen is under triaxial strain state even though its stress state is uniaxial. There are three approaches to modeling fatigue damage: stress, strain and energy. Critical plane concept is established based on the fact that fatigue cracks initiate at specific plane(s), therefore, multiaxial fatigue damage parameter is evaluated at these plane(s). Critical plane fatigue models such as Fatemi-Socie is among the popular strain-based models. Because it was shown to provide estimation mostly within two factors of life for different materials and different multiaxial loading conditions. This paper presents a new method for analyzing critical plane damage parameters. Using plane stress-strain transformation, maximum values of normal and shear stresses and strains from hysteresis loops are obtained at 360 planes. Plotting these values on polar diagrams shows that multiaxial cyclic responses represent polar curves that can successfully be fitted with definitive known polar equations. In principle, this means that both critical plane and fatigue damage can be determined analytically for a given loading path. However, fitting constants must first be determined. A systematic analysis is performed on different experimental data that were obtained by testing two extruded magnesium alloys at proportional and 90° out of phase loading paths. A closed-form solution for Fatemi-Socie damage parameter is presented for these two loading paths.

An Experimental Investigation of the Yield Loci of 1100-0 Aluminum, 70:30 Brass, and an Overaged 2024 Aluminum Alloy After Various Prestrains

1986 ◽  
Vol 108 (4) ◽  
pp. 313-320 ◽  
Author(s):  
D. E. Helling ◽  
A. K. Miller ◽  
M. G. Stout
Keyword(s):  
Aluminum Alloy ◽  
Small Strain ◽  
Yield Locus ◽  
Material Behavior ◽  
Shear Stresses ◽  
2024 Aluminum Alloy ◽  
Yield Loci ◽  
Aluminum Alloy 2024 ◽  
Von Mises ◽  
Normal And Shear Stresses

The multiaxial yield behaviors of 1100-0 aluminum, 70:30 brass, and an overaged 2024 aluminum alloy (2024-T7) have been investigated for a variety of prestress histories involving combinations of normal and shear stresses. Von Mises effective prestrains were in the range of 1.2–32%. Prestress paths were chosen in order to investigate the roles of prestress and prestrain direction on the nature of small-strain offset (ε = 5 × 10−6) yield loci. Particular attention was paid to the directionality, i.e., translation and distortion, of the yield locus. A key result, which was observed in all three materials, was that the final direction of the prestrain path strongly influences the distortions of the yield loci. Differences in the yield locus behavior of the three materials were also observed: brass and the 2024-T7 alloy showed more severe distortions of the yield locus and a longer memory of their entire prestrain history than the 1100-0 aluminum. In addition, more “kinematic” translation of the subsequent yield loci was observed in brass and 2024-T7 than in 1100-0 aluminum. The 2024-T7 differed from the other materials, showing a yield locus which decreased in size subsequent to plastic straining. Finally, the implications of these observations for the constitutive modeling of multiaxial material behavior are discussed.

Computer analysis of thin-walled concrete box beams

1989 ◽  
Vol 16 (6) ◽  
pp. 902-909 ◽  
Author(s):  
Shahbaz Mavaddat ◽  
M. Saeed Mirza
Keyword(s):  
Key Words ◽  
Computer Analysis ◽  
Shear Stresses ◽  
Shear Lag ◽  
Applied Loading ◽  
Box Beam ◽  
Box Beams ◽  
Three Stages ◽  
Thin Walled ◽  
Normal And Shear Stresses

Three computer programs, written in FORTRAN WATFIV, are developed to analyze straight, monolithically cast, symmetric concrete box beams with one, two, or three cells and side cantilevers over a simple span or over two spans with symmetric mid-span loadings. The analysis, based on Maisel's formulation, is performed in three stages. First, the structure is idealized as a beam and the normal and shear stresses are calculated using the simple bending theory and St-Venant's theory of torsion. The secondary stresses arising from torsional and distortional warping and shear lag are calculated in the second and third stages, respectively. The execution times on an AMDAHL 580 system are 0.02, 0.93, and 0.25 s for the three programs, respectively. The stresses arising in each stage of analysis are then superposed to determine the overall response of the box section to the applied loading. The results are compared with Maisel's hand calculations. Key words: bending, bimoment, box beam, computer analysis, FORTRAN, shear, shear lag, thin-walled section, torsion, torsional and distortional warping.

Measurements in a Turbulent Boundary Layer Over a d-Type Surface Roughness

1975 ◽  
Vol 42 (3) ◽  
pp. 591-597 ◽  
Author(s):  
D. H. Wood ◽  
R. A. Antonia
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Turbulent Boundary Layer ◽  
Turbulent Energy ◽  
Shear Stresses ◽  
Normal Velocity ◽  
Mean Velocity ◽  
Outer Flow ◽  
Intensity Measurements ◽  
Normal And Shear Stresses

Mean velocity and turbulence intensity measurements have been made in a fully developed turbulent boundary layer over a d-type surface roughness. This roughness is characterised by regular two-dimensional elements of square cross section placed one element width apart, with the cavity flow between elements being essentially isolated from the outer flow. The measurements show that this boundary layer closely satisfies the requirement of exact self-preservation. Distribution across the layer of Reynolds normal and shear stresses are closely similar to those found over a smooth surface except for the region immediately above the grooves. This similarity extends to distributions of third and fourth-order moments of longitudinal and normal velocity fluctuations and also to the distribution of turbulent energy dissipation. The present results are compared with those obtained for a k-type or sand grained roughness.

scholarly journals Influence of Material Ductility on Fatigue Life under Multiaxial Proportional and Non-Proportional Normal and Shear Stresses

2019 ◽  
Vol 300 ◽  
pp. 17001 ◽  
Author(s):  
Cetin Morris Sonsino
Keyword(s):  
Fatigue Life ◽  
Tensile Elongation ◽  
Shear Stresses ◽  
Normal Strain ◽  
Proportional Loading ◽  
Ductile Materials ◽  
Critical Components ◽  
Material Ductility ◽  
Fatigue Life Reduction ◽  
Normal And Shear Stresses

Current experiences show that a non-proportional loading of ductile materials such as wrought steels, wrought aluminium or magnesium alloys, not welded or welded, causes a significant fatigue life reduction under an out-of-phase shear strain or shear stress superimposed on a normal strain or normal stress compared with proportional in-phase loading. However, when ductility, here characterised by tensile elongation, is reduced by a heat treatment or by another manufacturing technology such as casting or sintering, the afore-mentioned life reduction is compensated or even inversed, i. e. longer fatigue life results compared with proportional loading. Some actual results, determined with additive manufactured titanium, suggest that microstructural features such as manufacturing-dependent internal defects like microporosities should be considered in addition to the ductility level. This complex life behaviour under non-proportional loading cannot always be estimated. Therefore, in experimental proofs of multiaxial loaded parts, especially safety-critical components or structures, with real or service-like signals, emphasis must be placed on retaining non-proportionalities between loads and stresses/strains, respectively.

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