Calculation of the Wöhler (S-N) curve using a two-scale model

Mlikota, Marijo; Schmauder, Siegfried; Božić, Željko

doi:10.1016/j.ijfatigue.2018.03.018

Cited by 58 publications

(35 citation statements)

References 27 publications

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“…In design against fatigue, linear elastic fracture mechanics (LEFM) approach is considered inherently conservative since a crack of a considerable size is assumed to preexist, and so the initiation life can be neglected. However, initial flaws in fatigue critical components may be of a size comparable with local microstructural features rendering the LEFM characterization of crack growth invalid. As an alternative, fatigue crack growth (FCG) models based on elastic‐plastic fracture mechanics parameters have been developed…”

Section: Introductionmentioning

confidence: 99%

Cracking simulation‐based fatigue life assessment

Farag

El‐Kady

Hammouda

2020

Fatigue Fract Eng Mat Struct

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A fracture mechanics numerical model is developed to simulate the collective behavior of growing short fatigue cracks originating from the surface of unnotched round specimens made of a two-phase alloy. The specimen surface roughness is considered resembling microcracks of different sizes and locations along the minimum specimen circumference. Material grains of different phases, sizes, and strengths are randomly distributed over that circumference.Variations in mechanical and microstructural features of grains are randomly distributed. Possible activities of surface cracks are predicted against loading cycles till either fracture occurs or all existing cracks become nonpropagating.The material's S-N curve and fatigue limit can, thus, be assessed. Published experimental data on ferritic-pearlitic steel specimens in push-pull constant amplitude loading (CAL) were utilized. Different specimens were randomly configured and virtually tested. Comparison of experimental results and corresponding predictions validates the model, which, further, recognizes the effect of surface roughness, specimen size, and mean stress on lives. K E Y W O R D Sendurance curve, ferritic-pearlitic steel, fracture mechanics, push-pull loading, short fatigue cracks, surface roughness

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Section: Introductionmentioning

confidence: 99%

Cracking simulation‐based fatigue life assessment

Farag

El‐Kady

Hammouda

2020

Fatigue Fract Eng Mat Struct

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“…Comparison between simulated and experimental Se values for AISI 1141 steel [9]. For details on the numerical determination of Se values, see [5,10,11]. FCC metals [4] BCC metals [4] HCP metals [4] Steels [6] Light metals [6] AA 1050 (FCC) -sim.…”

Section: Figurementioning

confidence: 99%

“…According to the TM model, micro-cracks form along slip bands (see Figure 3b), depending on grain size (i.e. slip band length) d, the average shear stress range Δτ on the slip band, the shear modulus G, the crack initiation energy Wc, Poisson's ratio ν, and the CRSS [10][11][12][13][14]. A more extended and detailed description of the implementation of the TM equation into FEM-based modelling and simulation of the crack initiation process has been reported in publications of the authors of this study in [5,[10][11][12][15][16][17][18] and by other researchers, too, in [13,14,19,20].…”

Section: Figurementioning

confidence: 99%

“…The multiscale approach for fatigue simulation, consisting of the CRSS determination either from micro-pillar tests (MPT) or from molecular dynamics (MD) simulations (both in Figure 3a), crack initiation simulations based on the TM equation ( Figure 3b) and long crack growth simulations based on fracture mechanics principles ( Figure 3c), has been previously reported in References [10,15,17,18,21,22]. The methodology forms the basis of the past [5] and present research work, which has been conducted with the aim to further elucidate the relevance of the parameter CRSS for the fatigue strength in general.…”

Section: Figurementioning

confidence: 99%

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Simulation-based Understanding of the Critical Resolved Shear Stress Relevance for the Fatigue Performance of Metallic Materials

Mlikota¹,

Schmauder²

2020

Preprint

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The paper introduces a valuable new description of fatigue strength in relation to material properties and thus a new perspective on the overall understanding of the fatigue process. Namely, a relation between the endurance limits and the accompanying values of the critical resolved shear stress (CRSS) for various metallic materials has been discovered by means of a multiscale approach for fatigue simulation. Based on the uniqueness of the relation, there is a strong indication that it is feasible to relate the endurance limit to the CRSS, and not to the ultimate strength as often done in the past.

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“…These initiation cycles are further transferred to the macroscale fatigue crack growth model based on power law equations (e.g., Paris law), which are finally used to estimate the total fatigue life, up to final fracture. By using the presented modelling workflow, the fatigue of metals can be simulated more or less independently of the experimental input [45,46,[49][50][51][52]. starting with the nanoscale, going up to micro-/mesoscales and ending up with the macroscale.…”

Section: Numerical Estimation Of Fatigue Behavior With the Help Of Crssmentioning

confidence: 99%

On the Critical Resolved Shear Stress and Its Importance in the Fatigue Performance of Steels and Other Metals with Different Crystallographic Structures

Mlikota

Schmauder

2018

Metals

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This study deals with the numerical estimation of the fatigue life represented in the form of strength-life (S-N, or Wöhler) curves of metals with different crystallographic structures, namely body-centered cubic (BCC) and face-centered cubic (FCC). Their life curves are determined by analyzing the initiation of a short crack under the influence of microstructure and subsequent growth of the long crack, respectively. Micro-models containing microstructures of the materials are set up by using the finite element method (FEM) and are applied in combination with the Tanaka-Mura (TM) equation in order to estimate the number of cycles required for the crack initiation. The long crack growth analysis is conducted using the Paris law. The study shows that the crystallographic structure is not the predominant factor that determines the shape and position of the fatigue life curve in the S-N diagram, but it is rather the material parameter known as the critical resolved shear stress (CRSS). Even though it is an FCC material, the investigated austenitic stainless steel AISI 304 shows an untypically high fatigue limit (208 MPa), which is higher than the fatigue limit of the BCC vanadium-based micro-alloyed forging steel AISI 1141 (152 MPa).

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Calculation of the Wöhler (S-N) curve using a two-scale model

Cited by 58 publications

References 27 publications

Cracking simulation‐based fatigue life assessment

Cracking simulation‐based fatigue life assessment

Simulation-based Understanding of the Critical Resolved Shear Stress Relevance for the Fatigue Performance of Metallic Materials

On the Critical Resolved Shear Stress and Its Importance in the Fatigue Performance of Steels and Other Metals with Different Crystallographic Structures

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