The Threshold Stress Intensity Range in Fatigue

Davenport, R. T.; Brook, R.

doi:10.1111/j.1460-2695.1979.tb00374.x

Cited by 34 publications

(10 citation statements)

References 9 publications

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“…dotted line in Fig. 5 for the neat epoxy and Table 1) are in a good linear agreement with the static stress intensity factor K Ic , generally following the relationship DK Ic 5K Ic Ãð1-RÞ [50].…”

Section: Fatigue Crack Propagationsupporting

confidence: 73%

Fatigue crack propagation in triblock copolymer toughened epoxy nanocomposites

Klingler

Wetzel

2017

Polymer Engineering & Sci

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This study systematically investigates the influence of a Polymethylmethacrylate‐block‐Polybutylacrylate‐block‐Polymethylmethacrylate (PMMA‐b‐PBuA‐b‐PMMA) triblock copolymer (BCP) on the flexural properties, the static fracture toughness and especially the resistance to fatigue crack propagation (FCP) of a cycloaliphatic amine cured bisphenol A based epoxy resin (EP). The results show that already small concentrations of BCP can significantly improve fracture toughness and the resistance to fatigue crack propagation. Crack growth rate as well as the Paris' law exponent m were considerably reduced from m = 15.5 of the neat epoxy to m = 8.1 for the BCP toughened materials. Simultaneously, the resistance to fatigue crack propagation was found to increase drastically from a critical stress intensity factor range normalΔKIc of 0.39 MPam to 0.81 MPam. Fractography and structural analysis reveal that the improved resistance to fatigue crack propagation correlates to crack shielding and zone shielding mechanisms caused by the synergistic interaction of BCP‐rich domains and dispersed nanometer sized, presumably BCP‐rich particles in epoxy‐rich regions. POLYM. ENG. SCI., 57:579–587, 2017. © 2017 Society of Plastics Engineers

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Section: Fatigue Crack Propagationsupporting

confidence: 73%

Fatigue crack propagation in triblock copolymer toughened epoxy nanocomposites

Klingler

Wetzel

2017

Polymer Engineering & Sci

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“…5 ) closer to a linear relation, with AKth decreasing with increasing R. The wedging action of the wake zone accounts for the linear relation for Rc0.6 observed with Al-alloys and plain carbon steels.…”

mentioning

confidence: 65%

“…With "method b" [3], the mean K , of the cyclic loading condition is kept constant. The K,,, constant method [4,5,6] shown in Fig. 1 (c) has been used extensively in our laboratory.…”

Section: Introductionmentioning

confidence: 99%

NON‐PROPAGATION CONDITIONS (ΔK_th) AND FATIGUE CRACK PROPAGATION THRESHOLD (δK_T)

Marci

1994

Fatigue Fract Eng Mat Struct

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Fatigue crack propagation threshold values have been determined with two experimental methods, it., the constant R method and the constant K, , method. Three materials, namely A17075-T735 1 and Ti6Al4V STA in the LT-and TL-orientations, and a Ti-turbine disk material (IMI 685) in the CR-orientation, were investigated.The paper is divided into 3 parts. In the first part the test conditions, the experimental results and the conclusions drawn from the experimental results are presented, namely that the three different functional dependencies of AK* on R cannot be reconciled with present continuum mechanics concepts. In the second part, some facts used in conjunction with the da/dN -AK,, methodology are applied to the nonpropagation condition AKth. Parameters such as KO,, the threshold AKT, and a parameter "K,; are investigated by numerical modelling of their individual in3uence on the AKth versus R curves. This modelling work shows that the individual AKth versus R curves are primarily dependent on the KO, behavior of the respective material. Further, it is shown that the threshold AKT is a constant value, independent of any particular cyclic loading condition. In the third part of the paper, the AK,, concept is applied to the experimental results obtained in the first part. Using either experimentally or semiempirically determined KO, functions and the measured AKr values, the A K~ versus R curves of the three materials investigated were accurately reconstructed. It follows that the AKth versus R curves of the individual materials are the natural consequence of the driving force for fatigue crack propagation, namely AKem NOMENCLATURE FCP = fatigue crack propagation F-, F, , , = minimum and maximum load applied during a cycle K,,, K,,, = minimum and maximum stress intensity factor of a cycle AK = Kmx -Kmin = stress intensity range AKth = stress intensity range when FCP just ceases AKr = materal property describing the maximum AK which causes no continuous FCP KO, = the opening instant of the stress intensity factor under arbitrary cyclic loading K,,(max. value) = upper bound value of KO, at a given K,,, AKe, = effective part of AK front during a cycle F,,, K,, = minimum load and minimum stress intensity factor experienced by the crack KZaX = lowest K, , at which FCP occurs under zero-tension cycling R = Kmin/Kmax = stress intensity factor ratio R, = R-ratio at which Kmin = K,, and AK = AKT 4, ni = coefficients of polynomial equations 'Y(R), @ (Kmax) = polynomial functions

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“…Ansätze von Klesnil und Lukáš [12] und Davenport [13] sind meist für Stähle ermittelt worden und können nicht ohne weiteres auf Aluminium angewendet werden. Liaw [11] gibt einen guten Ü berblick über die verschiedensten Werkstoffe und lässt für Aluminiumwerkstoffe einen linearen Zusammenhang zwischen Schwellenwert und dem Spannungsverhältnis R erwarten.…”

Section: Schwellenwertverhaltenunclassified

Vorhersage des Ermüdungsrissausbreitungsverhaltens von Aluminiumlegierungen für Beanspruchungen mit variablen Mittelspannungen

Rödling¹,

Bär

Gudladt

2004

Materialwissenschaft Werkst

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For realistic lifetime predictions of cracked components the crack propagation behaviour under variable amplitude spectrum loads and for variable mean stress has to be known. Therefore a method on the basis of only two crack propagation experiments for the prediction of the crack propagation behaviour for variable mean stress was developed. Beside a crack propagation curve for a constant mean stress solely one further experiment, where the threshold was reached by an increase of the minimum stress level, was required. On the basis of this two investigations the threshold behaviour in dependence of the mean stress and the constants of the corresponding crack propagation calculation can be predicted. The procedure results in a self-contained function for the description of crack propagation curves for variable mean stress. The theoretical calculation was verified with experimental data of aluminium 6013 T62 and 2024 T351. It shows a very good correspondence to the experimental data. This results are an important basis for operational stability calculations of cracked components, especially for a load spectrum with variable mean stress. Further this method is an efficient possibility to investigate the complete crack propagation behaviour with variable mean stress.

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The Threshold Stress Intensity Range in Fatigue

Abstract: Abstract-The parameters are considered that control the threshold stress intensity in fatigue and relationships existing between these parameters are examined. A new relation is derived which is shown to be consistent with experimental data for a O.l5%C, 1,5%Mn steel.

Cited by 34 publications

References 9 publications

Fatigue crack propagation in triblock copolymer toughened epoxy nanocomposites

Fatigue crack propagation in triblock copolymer toughened epoxy nanocomposites

NON‐PROPAGATION CONDITIONS (ΔK_th) AND FATIGUE CRACK PROPAGATION THRESHOLD (δK_T)

Vorhersage des Ermüdungsrissausbreitungsverhaltens von Aluminiumlegierungen für Beanspruchungen mit variablen Mittelspannungen

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The Threshold Stress Intensity Range in Fatigue

Abstract: Abstract-The parameters are considered that control the threshold stress intensity in fatigue and relationships existing between these parameters are examined. A new relation is derived which is shown to be consistent with experimental data for a O.l5%C, 1,5%Mn steel.

Cited by 34 publications

References 9 publications

Fatigue crack propagation in triblock copolymer toughened epoxy nanocomposites

Fatigue crack propagation in triblock copolymer toughened epoxy nanocomposites

NON‐PROPAGATION CONDITIONS (ΔKth) AND FATIGUE CRACK PROPAGATION THRESHOLD (δKT)

Vorhersage des Ermüdungsrissausbreitungsverhaltens von Aluminiumlegierungen für Beanspruchungen mit variablen Mittelspannungen

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Product

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NON‐PROPAGATION CONDITIONS (ΔK_th) AND FATIGUE CRACK PROPAGATION THRESHOLD (δK_T)