Assessment of the period to fatigue macrocrack initiation near stress concentrators by means of strain parameters

Ostash, О. P.; Panasyuk,; Kostyk,

doi:10.1046/j.1460-2695.1999.00191.x

Cited by 3 publications

(8 citation statements)

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“…In developing the experimental procedure of NTOD measuring at cyclic loading, it was proposed [3, 4] to measure elastic component, Δ δ e , and total, Δ δ t (including elastic and plastic components) opening displacement ranges along the line of the centre of curvature of the notch of length h (Figure 2). Then the legs of the gauge are located outside the plastic zone and the opening displacement is the integral characteristic of elastoplastic strains not only on the lateral surfaces but also across the specimen thickness.…”

Section: Assessment Of the Local Strain Range δɛ*mentioning

confidence: 99%

“…It is assumed that these strains are largely caused by the integral deformation of the prefracture zone d * along the notch contour with the effective radius of curvature ρ eff = ρ + d * (see Figure 2). This enables us to suggest the following formulae for the evaluation of local elastic, , and elastoplastic, Δ ɛ *, strain ranges near the notch tip in terms of its opening displacement ranges [3, 4]: and …”

Section: Assessment Of the Local Strain Range δɛ*mentioning

confidence: 99%

“…If the level of strains is higher than 2%, the computed results are overestimated for all materials and radii ρ . In this case, the proposed experimental procedure proves to be more adequate because its applicability to the evaluation of invariant characteristics of material resistance to fatigue macrocrack initiation was checked in a broad strain range (0.2–5.0%) [4]. Due to its relative simplicity, this procedure can be efficiently applied in engineering practice.…”

Section: Assessment Of the Local Strain Range δɛ*mentioning

confidence: 99%

“…Therefore, the necessity arises for searching for more convenient and simple to use fracture mechanics parameters regarding fatigue failure near stress concentrators. To a certain degree, this could be attained by using strain parameters, as the strain magnitude can be assessed by applying either computational methods or direct measurements taken in situ [3, 4].…”

Section: Introductionmentioning

confidence: 99%

“…It is suggested [3, 4] that the principal parameters to define the process of macrocrack initiation are: (i) the local elastic–plastic strain range Δ ɛ * in the vicinity of a notch; and (ii) the characteristic distance d * (a certain constant of a material [1, 2]), which determines the initial size, a i of a macrocrack ( a i = d *) for the given material. As a result the relationship may be established, where N i is the period for fatigue macrocrack (of length a i = d *) initiation, and m being material constants.…”

Section: Introductionmentioning

confidence: 99%

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Local Strain Measurement for Prediction of Fatigue Macrocrack Initiation in Notched Specimens

Ostash

Chepil

2003

Strain

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On the basis of direct measurement of the opening displacement of the notch contour the procedure of the evaluation of local elastoplastic strains range, De Ã , is developed. The experimental values of De Ã are compared with the calculational data using known equations by Neuber, Glinka, etc. It is shown that for De Ã < 2% the experimental and calculational values are in good agreement but only in the case when the gradient of strains near the notch tip is taken into account. The proposed experimental method is used for the prediction of period N i to fatigue macrocrack initiation in specimens of a complicated shape.

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Section: Assessment Of the Local Strain Range δɛ*mentioning

confidence: 99%

Section: Assessment Of the Local Strain Range δɛ*mentioning

confidence: 99%

Section: Assessment Of the Local Strain Range δɛ*mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Local Strain Measurement for Prediction of Fatigue Macrocrack Initiation in Notched Specimens

Ostash

Chepil

2003

Strain

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Influence of different load models on gear crack path shapes and fatigue lives

Podrug

Jelaska

Glodež

2008

Fatigue Fract Eng Mat Struct

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A B S T R A C T A computational model for determination of the service life of gears with regard to bending fatigue at gear tooth root is presented. In conventional fatigue models of the gear tooth root, it is usual to approximate actual gear load with a pulsating force acting at the highest point of the single tooth contact. However, in actual gear operation, the magnitude as well as the position of the force changes as the gear rotates. A study to determine the effect of moving gear tooth load on the gear service life is performed. The fatigue process leading to tooth breakage is divided into crack-initiation and crack-propagation period.The critical plane damage model has been used to determine the number of stress cycles required for the fatigue crack initiation. The finite-element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth. a = crack size a 2 = crack-initiation size b 0i = shear fatigue strength exponent b i = axial fatigue strength exponent C = material parameter of Paris equation c 0i = shear fatigue ductility exponent c i = axial fatigue ductility exponent C sur = surface finish correction factor d s = shear damage parameter d t = tensile damage parameter E = elastic modulus FP = final contact point F j = force acting on the gear for jth load case G = shear modulus g = transition function HPSTC = highest point of the single tooth contact i = gear ratio IP = initial contact point K = cyclic strength coefficient k = empirical material constant K c = stress intensity factor critical value K cl = stress intensity factor when closure occurs K I = mode I stress intensity factor

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Comparison of Numerical Models for Gear Tooth Root Fatigue Assessments

Jelaska

Podrug

Glodež

2005

Recent Advances in Solids and Structures

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A several kinds of numerical models, including moving force model, for determination the service life of gears in regard to bending fatigue in a gear tooth root, is presented. The critical plane damage model, Socie and Bannantine [1], 1988, has been used to determine the number of stress cycles required for the fatigue crack initiation. This method determines also the initiated crack direction, what is good base for a further analyses of the crack propagation and the assessment of the total fatigue life. Finite element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth under a moving load. Moving load produces a non-proportional load history in a gear’s tooth root. An approach that accounts for fatigue crack closure effects is developed to propagate crack under non-proportional load. Although some influences (non-homogeneous material, traveling of dislocations, etc.) were not taken into account in the computational simulations, the presented model seems to be very suitable for determination of service life of gears because numerical procedures used here are much faster and cheaper if compared with the experimental testing. The computational results are compared with other researchers’ numerical results and with service lives of real gears. The fatigue lives and crack paths determined in this paper exhibits a substantial agreement with experimental results and significant improvement compared with the existing numerical models.

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Assessment of the period to fatigue macrocrack initiation near stress concentrators by means of strain parameters

Cited by 3 publications

References 0 publications

Local Strain Measurement for Prediction of Fatigue Macrocrack Initiation in Notched Specimens

Local Strain Measurement for Prediction of Fatigue Macrocrack Initiation in Notched Specimens

Influence of different load models on gear crack path shapes and fatigue lives

Comparison of Numerical Models for Gear Tooth Root Fatigue Assessments

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