Calculation of the fatigue limit of pulsed laser hardened specimen based on an engineering interpretation of the weakest-link concept

Schnack, S.; Kienzler, Reinhold

doi:10.1016/s0013-7944(03)00043-2

Cited by 6 publications

(2 citation statements)

References 4 publications

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“…The competition between the two failure modes (area and volume) has been modeled in HCF using a Poisson process in [7][8][9]. In [11,12], the two different failure mechanisms are modeled as two different WL-integrals, one for area and one for volume.…”

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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“…The weakest‐link theory in conjuction with Weibull's distribution function 4,5 has been widely used for the assessment of ceramic components with respect to brittle fracture 6 and has recently been implemented in the special purpose computer code STAU 7 . In addition, Weibull's weakest‐link theory has been used for fatigue assessment of metal components in 8–29 . Although used for the fatigue design of roller bearings for years, weakest‐link theory is insufficiently known among designers and has therefore not been used extensively as a fatigue assessment tool for metal components in the industry.…”

Section: Introductionmentioning

confidence: 99%

Non‐local stress approach for fatigue assessment based on weakest‐link theory and statistics of extremes

Wormsen

Sjödin

Härkegård

et al. 2007

Fatigue Fract Eng Mat Struct

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A B S T R A C T In the present paper a non-local stress approach for fatigue assessment based on weakestlink theory and statistics of extremes is presented. It is a non-local stress approach in the sense that it takes the complete stress field into account rather than just the highest local stress. The statistical distribution of fatigue strength data from smooth standard specimens serves as a starting point for the computation of the probability of fatigue failure of a mechanical component under cyclic loading. The probability of fatigue failure can be obtained by post-processing results from a standard finite element stress analysis. It is shown that the non-local stress approach can be linked to the probability of finding the fatigue critical defect in the most highly stressed volume of the component. A numerical procedure is presented that is fully compatible with the results from a standard finite element stress analysis. It is further shown how the fatigue strength distribution can be transformed into a fatigue life distribution by using Basquin's equation. Finally, the nonlocal stress approach is used for predicting the fatigue limit of several specimens and predictions are compared with test results.Keywords block maximum method; effective stress amplitude; defects; finite element analysis; finite-element post-processor; statistics of extremes; surface effect; stress field; volume effect; weakest-link model. N O M E N C L A T U R E A = surface areaA 0 = reference surface area a = 'intrinsic' crack length a 0 = scale parameter in the generalized extreme value distribution a * 0 = characteristic largest defect size a crit = critical defect size B = Basquin coefficient b σ , b n = Weibull exponent G(a) = generalised extreme value distribution FEA = finite element analysis |J| = Jacobian determinant l = gauge length m = Basquin exponent n = number of cycles n = element face normal N = fatigue life (random variable) N * 0 = characteristic fatigue life N = element shape functions Correspondence: A. Wormsen.

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