Three dimensional analysis of low cycle fatigue failure in engine part subjected to multi-axial variable amplitude thermo-mechanical load

The behaviour of composite cellular floor beams is becoming important as such members are increasingly used in multistory buildings. But, in the design of some special cellular beam with sharp corner web holes such as eye-shaped openings, the issue of low cycle fatigue failure becomes increasingly critical. In this paper, three-dimensional nonlinear finite element models of composite cellular floor beams with eye-shaped openings have been developed, taking into consideration the influence of the changes in degree of shear connections. The assessment based on stress amplitude for risk of fatigue failure under low cycle service load is presented as design guides in this paper. It is concluded that the risk grows along with the increase of composite actions in beams.

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Low-Cycle Fatigue Performance of Buckling Restrained Braces and Assessment of Cumulative Damage under Severe Earthquakes

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.763.867 ◽

2018 ◽

Vol 763 ◽

pp. 867-874

Author(s):

Yu Shu Liu ◽

Ke Peng Chen ◽

Guo Qiang Li ◽

Fei Fei Sun

Keyword(s):

Fatigue Life ◽

Energy Dissipation ◽

Structural Reliability ◽

Low Cycle Fatigue ◽

Engineering Application ◽

Fatigue Performance ◽

Cycle Fatigue ◽

Variable Amplitude ◽

Buckling Restrained Braces ◽

Energy Dissipation Devices

Buckling Restrained Braces (BRBs) are effective energy dissipation devices. The key advantages of BRB are its comparable tensile and compressive behavior and stable energy dissipation capacity. In this paper, low-cycle fatigue performance of domestic BRBs is obtained based on collected experimental data under constant and variable amplitude loadings. The results show that the relationship between fatigue life and strain amplitude satisfies the Mason-Coffin equation. By adopting theory of structural reliability, this paper presents several allowable fatigue life curves with different confidential levels. Besides, Palmgren-Miner method was used for calculating BRB cumulative damages. An allowable damage factor with 95% confidential level is put forward for assessing damage under variable amplitude fatigue. In addition, this paper presents an empirical criterion with rain flow algorithm, which may be used to predict the fracture of BRBs under severe earthquakes and provide theory and method for their engineering application. Finally, the conclusions of the paper were vilified through precise yet conservative prediction of the fatigue failure of BRB.

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A weight function method for multiaxial low-cycle fatigue life prediction under variable amplitude loading

The Journal of Strain Analysis for Engineering Design ◽

10.1177/0309324718763671 ◽

2018 ◽

Vol 53 (4) ◽

pp. 197-209 ◽

Cited By ~ 2

Author(s):

Xiao-Wei Wang ◽

De-Guang Shang ◽

Yu-Juan Sun

Keyword(s):

Fatigue Life ◽

Weight Function ◽

Life Prediction ◽

Function Method ◽

Low Cycle Fatigue ◽

Fatigue Life Prediction ◽

Cycle Fatigue ◽

Critical Plane ◽

Variable Amplitude ◽

Weight Function Method

A weight function method based on strain parameters is proposed to determine the critical plane in low-cycle fatigue region under both constant and variable amplitude tension–torsion loadings. The critical plane is defined by the weighted mean maximum absolute shear strain plane. Combined with the critical plane determined by the proposed method, strain-based fatigue life prediction models and Wang-Brown’s multiaxial cycle counting method are employed to predict the fatigue life. The experimental critical plane orientation and fatigue life data under constant and variable amplitude tension–torsion loadings are used to verify the proposed method. The results show that the proposed method is appropriate to determine the critical plane under both constant and variable amplitude loadings.

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Application of Differential Entropy in Characterizing the Deformation Inhomogeneity and Life Prediction of Low-Cycle Fatigue of Metals

Materials ◽

10.3390/ma11101917 ◽

2018 ◽

Vol 11 (10) ◽

pp. 1917 ◽

Cited By ~ 6

Author(s):

Mu-Hang Zhang ◽

Xiao-Hong Shen ◽

Lei He ◽

Ke-Shi Zhang

Keyword(s):

Fatigue Failure ◽

Low Cycle Fatigue ◽

Pure Copper ◽

Cyclic Strain ◽

Material Model ◽

Cycle Fatigue ◽

Nickel Based Superalloy ◽

Deformation Inhomogeneity ◽

Tension Peak ◽

Number Of Cycles

The relation between deformation inhomogeneity and low-cycle-fatigue failure of T2 pure copper and the nickel-based superalloy GH4169 under symmetric tension-compression cyclic strain loading is investigated by using a polycrystal representative volume element (RVE) as the material model. The anisotropic behavior of grains and the strain fields are calculated by crystal plasticity, taking the Bauschinger effect into account to track the process of strain cycles of metals, and the Shannon’s differential entropies of both distributions of the strain in the loading direction and the first principal strain are employed at the tension peak of the cycles as measuring parameters of strain inhomogeneity. Both parameters are found to increase in value with increments in the number of cycles and they have critical values for predicting the material’s fatigue failure. Compared to the fatigue test data, it is verified that both parameters measured by Shannon’s differential entropies can be used as fatigue indicating parameters (FIPs) to predict the low cycle fatigue life of metal.

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