Nonproportional Low Cycle Fatigue of 6061 Aluminum Alloy Under 14 Strain Paths

Itoh, Takamoto; Nakata, Takumi; Sakane, Masao; Ohnami, Masateru

doi:10.1016/s1566-1369(99)80006-5

Cited by 83 publications

(84 citation statements)

References 9 publications

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Section: δεmentioning

confidence: 99%

“…The possibility of existence of a correlation of this sort was analyzed in [1]. As a result of the analysis of the mechanical characteristics of 11 different metallic materials (Kh16N9M2 [12], 08Kh18N10T [13], 45 [14], SS304 [8], SS310 [15], SS316 [2], SS16L [16], and SNCM630 [17] steels and 800H [18], VT9 [13], and Al6061 [8] alloys), a linear dependence was established between dimensionless parameters β and α characterizing, respectively, the degree of strain hardening under static deformation and the degree of additional strain hardening under nonproportional cyclic deformation (Fig. 1).…”

Section: δεmentioning

confidence: 99%

“…To perform the experimental investigation of the effects connected with the influence of the shape (disproportionality) of deformation cycles on the degree of strain hardening and durability, it is customary to subject thin-walled tubular specimens to simultaneous tension-compression and alternating torsion according to certain programs [2,3]. The phenomenological models taking into account the phenomenon of strain hardening for the prediction of the kinetics of elastoplastic deformation are proposed on the basis of the experimental data within the framework of the development of models of cyclic plasticity [4][5][6][7] or durability [8,9].The comparative analysis of the application of different approaches to the prediction of additional strain hardening under conditions nonproportional deformation along regular (closed) cyclic paths performed in [10] shows that, for the correct prediction of the levels of hardening, it is necessary to take into account both the shape of the path in a cycle and the stressed state of the material in which this cycle is realized. The approach proposed by the author in [11] is quite efficient for the materials insensitive to the form of stressed state.…”

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Prediction of Strain Hardening and Fatigue Life of Cyclically Unstable Materials

Borodii

2005

Strength Mater

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The data on cyclic deformation of materials with different cyclic properties are analyzed. The relationship between the level of additional strain hardening and the mechanical characteristics of a material is established. The proposed models take into account the influence of the form of stressed state on strain hardening and durability under conditions of nonproportional cyclic deformation. The models are constructed on the basis of the analysis of the experimental data on cyclic deformation of 304 stainless steel. The prediction of strain hardening and durability is performed with separate analysis of the influence of shape of the cycle and the form of stressed state. To take into account the influence of shape of the cycle, we use the coefficient of disproportionality of the cycle and the parameter of sensitivity to disproportionality. To take into account the form of stressed state, we use the coefficient of the form of stressed state and the corresponding parameter of sensitivity to the form of stressed state. The results of prediction of both strain hardening and durability of materials on the basis of the proposed phenomenological models reveal their fairly high efficiency.Keywords: fatigue, nonproportional deformation, strain hardening, the coefficient of disproportionality of a cycle, durability. Notation Δε-strain range in a cycle Δε nr -reduced strain range in a cycle Δε 1 -range of the principal stain in the direction of maximum strain range in a cycle Δε 1max -maximum possible range of the principal strain σ npr -maximum level of the strain hardening under nonproportional loading σ pr -maximum level of the strain hardening under proportional loading σ Y -yield strength of the material σ u -ultimate strength of the material ϕ -minimum angle between the maximum strain range in a cycle and the direction of maximum possible principal strain Φ -coefficient of disproportionality of a cycle L cyc -length of the path in a cycle p -coefficient of influence of the form of stressed state 0039-2316/05/3705-0525 α α , 1 -parameters of sensitivity to disproportionality determined according to the data on strain hardening and durability, respectively k k , 1 -parameters of sensitivity of the material to the form of stressed state determined according to the data on strain hardening and durability, respectively n B , -parameters of linear approximation of the experimental data on low-cycle fatigue in uniaxial tension-compression N -number of cycles to failureIntroduction. The phenomena of strain hardening and softening are typical of cyclically unstable materials under low-cycle strain-controlled loading. As shown in [1], this group of materials includes materials for which the ratio of the yield strength to the ultimate strength is smaller than 0.75. Note that this is true for the major part of structural steels and alloys. In the case where the cycles of deformation are nonproportional, the degree of strain hardening of materials of this sort can be several times (or even by an order of magnitude) higher than unde...

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Section: δεmentioning

confidence: 99%

Section: δεmentioning

confidence: 99%

mentioning

confidence: 99%

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Prediction of Strain Hardening and Fatigue Life of Cyclically Unstable Materials

Borodii

2005

Strength Mater

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“…Therefore, in order to avoid these disadvantages, Itoh et al proposed a strain parameter related to material property and loading path, which are available in both of short-life and long-life fatigue regimes. The parameter takes response to material deformation and is expressed by simple calculation based on strain model [9][10][11][12][13][14][15]. Based on the IS-method proposed by Itoh et al, analyses for pipes subjected to cyclic multiaxial/non-proportional loading are performed.…”

Section: Introductionmentioning

confidence: 99%

Evaluation and visualization of multiaxial fatigue behavior under random non-proportional loading condition

Morishita¹,

Ogawa²,

Itoh³

2017

Frattura Ed Integrità Strutturale

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ABSTRACT. In cyclic multiaxial stress/strain condition under nonproportional loading in which principal direction of stress/strain are changed in a cycle, it becomes difficult to analyze stress/strain ranges because of complexity of multiaxial stress/strain states depending on time in cycles. In order to evaluate stress/strain simply and suitably under non-proportional loading, Itoh and Sakane have proposed a method called as IS-method and a strain parameter for life evaluation under non-proportional loading  NP . In the method, 6-components of stress/strain are converted to an equivalent stress/strain indicating the amplitude and the direction of principal stress/strain as a function of time as well as an intensity of loading nonproportionality f NP . Based on IS-method, the authors also have developed a tool which enables to analyze multiaxial stress/strain condition with the nonproportionality of loading history and evaluate failure life under nonproportional multiaxial loading. The tool indicates the analyzed results on monitor and users can understand visually not only variation of the stress/strain conditions but also non-proportionality during the cycle, which helps the design of material strength.

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“…In recent literatures of multiaxial fatigue, it is reported that fatigue life evaluated by the Mises stress is overestimated [1][2][3][4][5][6][7][8] and the M magnitude depends on loading path [9][10][11][12][13][14][15][16]. In the multiaxial fatigue under non-proportional loading in which directions of principal stress and strain are changed in a cycle, it has been reported that fatigue lives are reduced accompanying with additional hardening which depends on both loading path and material [4][5][6][7][8][9][10][11][12][13][14][15][16]. In addition, Itoh et al presented a strain parameter for life evaluation under non-proportional loading considering the intensity of non-proportionality and the material dependency [12,14].…”

Section: Introductionmentioning

confidence: 99%

Multiaxial fatigue property of type 316 stainless steel using hollow cylinder specimen under combined pull loading and inner pressure

Morishita¹,

Takada²,

Itoh³

2017

Frattura Ed Integrità Strutturale

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ABSTRACT. Stress controlled multiaxial fatigue test was carried out using a hollow cylinder specimen of type 316 stainless steel. A newly developed fatigue testing machine which can apply push-pull loading and reversed torsion loading and inner pressure to the hollow cylinder specimen was employed. 5 types of cyclic loading paths were employed by combining zero to pull axial and hoop stresses: a Pull (only axial stress), an Inner-pressure (only hoop stress), an Equi-biaxial (equi-biaxial stress by axial and hoop stresses), a Square-shape (trapezoidal waveforms of axial and hoop stresses with 90-degree phase difference) and a L-shape (alternately axial stress and hoop stress) loading paths. Since directions of principal stresses are fixed in all the tests, all of the loading paths are classified into 'proportional loading'. In the Pull, the Inner-pressure and the Equi-biaxial tests, fatigue lives can be correlated on a unique line by a maximum equivalent stress based on von Mises. On the other hand, fatigue lives in the Square-shape and the L-shape tests were reduced comparing with that in the other tests, which was caused by yielding of larger plastic deformation.

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Nonproportional Low Cycle Fatigue of 6061 Aluminum Alloy Under 14 Strain Paths

Cited by 83 publications

References 9 publications

Prediction of Strain Hardening and Fatigue Life of Cyclically Unstable Materials

Prediction of Strain Hardening and Fatigue Life of Cyclically Unstable Materials

Evaluation and visualization of multiaxial fatigue behavior under random non-proportional loading condition

Multiaxial fatigue property of type 316 stainless steel using hollow cylinder specimen under combined pull loading and inner pressure

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