Free energy formulation of fatigue crack initiation along persistent slip bands: calculation of SN curves and crack depths

Venkataraman, G.; Chung, Yip‐Wah; Nakasone, Yuji; Mura, T.

doi:10.1016/0956-7151(90)90132-z

Cited by 77 publications

(34 citation statements)

References 13 publications

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“…Suresh [13] outlines the dislocation gating mechanisms that are responsible for the formation of PSBs and creation of microvoids which eventually coalesce to nucleate fatigue cracks. Recent micromechanical models by Venkataraman and colleagues [14][15] have further quantified the crack nucleation process under idealized conditions. Favorably oriented coarse grains tend to preferentially nucleate cracks at PSBs.…”

Section: Distinguishing Features Of Small Crack Propagationmentioning

confidence: 99%

“…Another aspect of surface proximity is its effect on dislocation accumulation near the surface. Harvey et al [28] used atomic force microscope images of slip band emergence at the free surface in both HSLA steel and Ti to confirm a model for crack nucleation based on cumulative slip offset which incorporates grain size and other factors; the model is similar in nature to the very different approach of Venkataraman et al [14][15] based on PSB development. The role of dislocation density gradients in the propagation of small cracks in HCF has not been studied.…”

Section: Fracture Mechanics Parameters For Small Crack Propagationmentioning

confidence: 99%

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Basic issues in the mechanics of high cycle metal fatigue

McDowell

1996

Int J Fract

159

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Mechanics issues related to the formation and growth of cracks ranging from subgrain dimension to up to the order of one mm are considered under high cycle fatigue (HCF) conditions for metallic materials. Further efforts to improve the accuracy of life estimation in the HCF regime must consider various factors that are not presently addressed by traditional linear elastic fracture mechanics (LEFM) approaches, nor by conventional HCF design tools such as the S-N curve, modified Goodman diagram and fatigue limit. A fundamental consideration is that a threshold level for AK for small/short cracks may be considerably lower than that for long cracks, leading to non-conservative life predictions using the traditional LEFM approach.Extension of damage tolerance concepts to lower length scales and small cracks relies critically on deeper understanding of (a) small crack behavior including interactions with microstructure, (b) heterogeneity and anisotropy of cyclic slip processes associated with the orientation distribution of grains, and (c) development of reliable small crack monitoring techniques. The basic technology is not yet sufficiently advanced in any of these areas to implement damage tolerant design for HCE The lack of consistency of existing crack initiation and fracture mechanics approaches for HCF leads to significant reservations concerning application of existing technology to damage tolerant design of aircraft gas turbine engines, for example. The intent of this paper is to focus on various aspects of the propagation of small cracks which merit further research to enhance the accuracy of HCF life prediction. Predominant concern will rest with polycrystalline metals, and most of the issues pertain to wide classes of alloys.

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Section: Distinguishing Features Of Small Crack Propagationmentioning

confidence: 99%

Section: Fracture Mechanics Parameters For Small Crack Propagationmentioning

confidence: 99%

Basic issues in the mechanics of high cycle metal fatigue

McDowell

1996

Int J Fract

159

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“…Later, Mura and coworkers [13,14] developed their model based on free energy considerations. The total free energy of the system increases with fatigue cycle number due to the increase in stored elastic strain energy of accumulated dislocations.…”

Section: Energy-equilibrium Modelmentioning

confidence: 99%

“…Fatigue crack would initiate at these sites. Based on dislocation accumulation with cyclic loading, Mura and coworkers proposed a model [12][13][14] for fatigue crack initiation. Chan [15] extended Tanaka and Mura's model to include crack size and relevant micro structural parameters in the equations.…”

Section: Introductionmentioning

confidence: 99%

An energy-equilibrium model for complex stress effect on fatigue crack initiation

Zhao

Xie

Zhao

et al. 2014

Sci. China Phys. Mech. Astron.

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Based on Tanaka and Mura's fatigue model and Griffith theory for fracture, an energy-equilibrium model was proposed to explain the complex stress effect on fatigue behavior. When the summation of the elastic strain energy release and the stored strain energy of accumulated dislocations reach the surface energy of a crack, the fatigue crack will initiate in materials. According to this model, for multiaxial stress condition, the orientation of the crack initiation and the initiation life can be deduced from the energy equilibrium equation. For the uniaxial fatigue loading with mean stress, the relation between the maximum stress or the minimum stress and the stress amplitude is in agreement with an ellipse equation on the constant life diagram. If the ratio of the mean stress to stress amplitude is less than a critical value 0.17, and the stress amplitude keeps constant, the fatigue crack initiation life will decrease with the increase of the compress mean stress. In this model, the mean stress does not cause damage accumulation with the fatigue cycles in crack initiation. For this reason, the loading sequence of different load levels would induce the cumulative damage to deviate from the Palmgren-Miner cumulative damage rule. The procedure of estimating the damage under random loading is also discussed.

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“…For the case tested in air, k w is taken as 3 in the calculation [48]. For the case tested in 3.5 % NaCl solution, k w is taken as 25 times of that in air, i.e.…”

Section: Model For S-n Curve Prediction In Different Environmental Mediamentioning

confidence: 99%

A model to predict S–N curves for surface and subsurface crack initiations in different environmental media

Qian

Zhou

Hong

2015

International Journal of Fatigue

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a b s t r a c tThe influence of environmental media on crack propagation of a structural steel at high-cycle and veryhigh-cycle fatigue (VHCF) regimes was investigated with the fatigue tests in air, water and 3.5% NaCl aqueous solution. The fatigue strength in water and 3.5% NaCl solution is significantly decreased and the cracking morphology due to different driving forces is presented. A model is proposed to explain the influence of environmental media on fatigue life, which reflects the variation of fatigue life with applied stress, grain size, inclusion size and material yield stress. The model prediction is in good agreement with experimental observations.

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Free energy formulation of fatigue crack initiation along persistent slip bands: calculation of SN curves and crack depths

Cited by 77 publications

References 13 publications

Basic issues in the mechanics of high cycle metal fatigue

Basic issues in the mechanics of high cycle metal fatigue

An energy-equilibrium model for complex stress effect on fatigue crack initiation

A model to predict S–N curves for surface and subsurface crack initiations in different environmental media

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