Estimation of the fatigue strength distribution in high-cycle multiaxial fatigue taking into account the stress–strain gradient effect

Delahay, Thomas; Palin‐Luc, Thierry

doi:10.1016/j.ijfatigue.2005.06.048

Cited by 51 publications

(31 citation statements)

References 11 publications

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“…On the other hand, it is still possible that fatigue is initiated in a region of low stress because a large defect may be found there. The integration is performed either over the specimen volume, as in [3][4][5][13][14][15][16], or the specimen surface area, as in [4,5,17,18].…”

Section: Introductionmentioning

confidence: 99%

An investigation of a fatigue model with two competing failure mechanisms

Karlén¹,

Olsson²

2014

International Journal of Fatigue

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A new combined fatigue model that considers a defect based and a stress based mechanism is presented. The defect part is based on the weakest link theory, where the integration is performed either over the surface area or the volume of the component. The stress based mechanism is described by the normal distribution, where the stress is either the largest occurring stress value, the point stress, or the point stress adjusted with the stress gradient, denoted the gradient adjusted point stress. Experiments on notched specimens have been performed. The combined model behaves almost like only a stress based model at high failure probabilities. At low failure probabilities, results are less clear. There, the stress based model is not accurate and the defect based model (both for area and volume) dominates. Using the gradient adjusted point stress in the stress based model and the volumetric weakest link integral in the defect based model being described by gives the best overall fit to the probability of failure. It is noted that for design with respect to high failure probabilities (> 20 %), it is enough use only the gradient adjusted stress based model.

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Section: Introductionmentioning

confidence: 99%

An investigation of a fatigue model with two competing failure mechanisms

Karlén¹,

Olsson²

2014

International Journal of Fatigue

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“…Another way to model the fatigue limit scatter is to use the WL-integral, [7,8]. The integration can be performed over the specimen surface area [1,4,9,11,12] or as a volumetric entity [1,3,4,9,13,14].…”

Section: Introductionmentioning

confidence: 99%

An investigation of the location of fatigue initiation – Deterministic and probabilistic aspects

Karlén

Olsson

2014

International Journal of Fatigue

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Fatigue limit tests where there are two competing fatigue failure locations, two notches of different size, are performed in this paper. The normal distribution is used for describing the experimental outcome, where the largest occurring stress value or the gradient adjusted stress is used as a stress measure. Another model for describing the experimental outcome is the Weakest Link (WL)-integral where the integration is performed over the specimen surface area or the specimen volume. The longitudinal positions of the estimated fatigue failure sites are measured and investigated as well. Neither the normal distribution (point stress and gradient adjusted point stress), nor the WL-integral can explain the experimental outcome from the competing notch tests. They all predict the same trend, but not the same trend as in the experiments. When looking at the estimated longitudinal location of fatigue failure it can be seen that it differs considerably from experiment to experiment. If the stress is evaluated at the estimated fatigue failure location, it is seen that the local stress is much lower than the maximal stress. The load cases where there should be an equal amount of failures in both notches according to the different models do not agree with the experimental findings. It is concluded that stress based continuum models can not describe the experimental outcome when there are competing fatigue failure sites (notches) present.

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“…Motivated by microscopic observations that fatigue failure occurs by damage accumulation in a finite notch root damage process zone, which can encompass several grains, numerous research studies have explored estimation of the fatigue notch factor as well as fatigue strength as a function of an average stress over the fatigue damage process zone (Neuber 1961;Beremin 1983;Weixing 1992;Qylafku et al 1998Qylafku et al , 1999Ren and Nicholas 2003;Ranganathan et al 2004;Delahay and Palin-Luc 2006;Doudard et al 2007;Adib-Ramezani and Jeong 2007).These methods consider the average stress value over a significant length scale at the notch root when analyzing fatigue potency of a notched component. One of these methods, called the the point method, uses a specific distance known as the critical distance from the notch-root which may correspond to a grain size (Neuber 1958) or plastic zone size (Peterson 1959) and its corresponding average stress level to predict K f and fatigue life of notched components.…”

Section: Introductionmentioning

confidence: 99%

Microstructure-dependent fatigue damage process zone and notch sensitivity index

et al. 2011

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The development of simulation methods for calculating notch root parameters for purposes of estimating the fatigue life of notched components is a critical aspect of designing against fatigue failures. At present, however, treatment of the notch root stress and plastic strain field gradients, coupled with intrinsic length scales of grains or other material attributes, has yet to be developed. Ultimately, this approach will be necessary to form a predictive basis for notch size effects in forming and propagating microstructurally small cracks in real structural materials and components. In this study, computational micromechanics is used to clarify and distinguish process zone for crack formation and microstructurally small crack growth, relative to scale of notch root radius and spatial extent of stress concentration at the notch. A new nonlocal criterion for the fatigue damage process zone based on the distribution of a shear-based fatigue indicator parameter is proposed and used along with a statistical method to obtain a new microstructure-sensitive fatigue notch factor and associated notch sensitivity index, thereby extending notch sensitivity to explicitly incorporate microstructure sensitivity and attendant size effects via probabilistic arguments. The notch sensitivity values obtained for a range of notch root radii using the new statistical approach presented in this

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Estimation of the fatigue strength distribution in high-cycle multiaxial fatigue taking into account the stress–strain gradient effect

Cited by 51 publications

References 11 publications

An investigation of a fatigue model with two competing failure mechanisms

An investigation of a fatigue model with two competing failure mechanisms

An investigation of the location of fatigue initiation – Deterministic and probabilistic aspects

Microstructure-dependent fatigue damage process zone and notch sensitivity index

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