Crack initiation mechanisms in copper polycrystals cycled under constant strain amplitudes and in step tests

Figueroa, Juan Carlos Sánchez; Laird, C.

doi:10.1016/0025-5416(83)90076-9

Cited by 91 publications

(21 citation statements)

References 18 publications

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“…The EGM model can explain the occurrence of such PSB-GB cracks. The latter have been observed frequently [26,96,97] and are dominant at low and intermediate amplitudes. [98] B.…”

Section: Extrusions (And Intrusions) In Fatigued Fcc Metalsmentioning

confidence: 99%

Cyclic Slip Irreversibilities and the Evolution of Fatigue Damage

Mughrabi

2009

Metall Mater Trans B

182

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In this article, the physical origin of fatigue crack initiation in ductile metals is discussed from a historical perspective. The main focus is to assess those cyclic slip irreversibilities in a microstructural sense that occur not only at the surface but also in the bulk at the dislocation scale and to show how they contribute to surface fatigue damage. The evolution of early fatigue damage, as evidenced experimentally in the last decades, is reviewed. The phenomenon of cyclic strain localization in persistent slip bands (PSBs) and models of the formation of extrusions, intrusions, and microcracks are discussed in detail. The predictions of these models are compared with experimental evidence obtained on mono-and polycrystalline face-centered-cubic (fcc) metals. In addition, examples of the evolution of fatigue damage in selected fcc solid solution alloys and precipitation-hardened alloys and in body-centered-cubic (bcc) metals are analyzed. Where possible, the cyclic slip irreversibilities p, defined as the fraction of plastic shear strain that is microstructurally irreversible, have been estimated quantitatively. Broadly speaking, p has been found to vary over orders of magnitude (0 < p < 1), being almost negligible at low loading amplitudes (high fatigue lives) and substantial at larger loading amplitudes (low fatigue lives). and Dean of the School of Engineering. Since 2002, Hael Mughrabi has been formally retired but is still active in various forms in research and in committee work.Hael Mughrabi has published almost 300 papers and book chapters and has been editor or co-editor of several books and conference proceedings, mainly in the fields of crystal plasticity, materials characterization, metal fatigue, high-temperature mechanical properties of nickel-base superalloys, and modeling of mechanical behavior. He has been active in the organization and chairing of many international conferences and has frequently been invited as a plenary or keynote speaker. Hael Mughrabi has been a member of TMS for 25 years and of a number of other professional societies, including the German Materials Society (Deutsche Gesellschaft fu¨r Materialkunde (DGM)). He has been a member of the Board of Directors of DGM and Chairman of the DGM Awards Committee PKII and has been elected an Honorary Member of DGM. Hael Mughrabi is the holder of an Honorary Doctoral degree from the Ruhr University Bochum and the recipient of several national and international awards, including the highest award of DGM, the Heyn-Denkmu¨nze.

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“…The EGM model can explain the occurrence of such PSB-GB cracks. The latter have been observed frequently [26,96,97] and are dominant at low and intermediate amplitudes. [98] B.…”

Section: Extrusions (And Intrusions) In Fatigued Fcc Metalsmentioning

confidence: 99%

Cyclic Slip Irreversibilities and the Evolution of Fatigue Damage

Mughrabi

2009

Metall Mater Trans B

182

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“…Initially, this was surprising, since intercrystalline cracking was known to occur at higher amplitudes [52] but had not been noted at lower amplitudes. The PSB-GB cracks occur at low to intermediate loading amplitudes in the regime of PSB [53] and the author's research group [26]. Figure 7 shows an example, as observed on a fatigued copper polycrystal by SEM (figure 7a).…”

Section: Microstructural Mechanisms Of Fatigue Crack Initiation In Lomentioning

confidence: 99%

Microstructural mechanisms of cyclic deformation, fatigue crack initiation and early crack growth

Mughrabi

2015

Phil. Trans. R. Soc. A.

124

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In this survey, the origin of fatigue crack initiation and damage evolution in different metallic materials is discussed with emphasis on the responsible microstructural mechanisms. After a historical introduction, the stages of cyclic deformation which precede the onset of fatigue damage are reviewed. Different types of cyclic slip irreversibilities in the bulk that eventually lead to the initiation of fatigue cracks are discussed. Examples of trans- and intercrystalline fatigue damage evolution in the low cycle, high cycle and ultrahigh cycle fatigue regimes in mono- and polycrystalline face-centred cubic and body-centred cubic metals and alloys and in different engineering materials are presented, and some microstructural models of fatigue crack initiation and early crack growth are discussed. The basic difficulties in defining the transition from the initiation to the growth of fatigue cracks are emphasized. In ultrahigh cycle fatigue at very low loading amplitudes, the initiation of fatigue cracks generally occupies a major fraction of fatigue life and is hence life controlling.

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“…Therefore, it is possible that the grain boundary is damaged (microvoid, microcrack) by slips produced by hydrogen. For example, an intergranular crack initiates by cyclic slip at elevated temperature (10) or at low cycle fatigue (11), (12) .…”

Section: Introductionmentioning

confidence: 99%

Investigation of Mechanism for Intergranular Fatigue Crack Propagation of Low Carbon Steel JIS S10C in Hydrogen Gas Environment

Nishikawa

Oda

Nishikawa

2011

JMMP

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In order to investigate the mechanism for the intergranular fatigue crack propagation of a low carbon steel in a low pressure hydrogen gas environment, two kinds of examinations were carried out. One examined the effect of the cyclic pre-strain on the crack growth behavior. The other was the in-situ observation of intergranular fatigue crack propagation in a hydrogen gas environment. The main results are as follows. (1) SEM observation of the specimen surface morphology of a plain specimen fatigued in hydrogen gas showed that a gap at the grain boundary was induced by slip behavior, but not in nitrogen gas. (2) A specimen cyclic-prestrained in hydrogen gas showed slight influences on the increase in the crack propagation rate. (3) Mating intergranular facets on the fatigue fracture surfaces showed the matching of a striation-like pattern in the manner anticipated from the damage mechanism of (1). (4) The environment-change test from hydrogen to nitrogen during the fatigue test showed that intergranular facets appeared even in nitrogen. Results (3) and (4) suggests that the damaging process of (1) is valid in an actual fatigue crack. (5) In-situ observation of the crack propagation behavior in hydrogen gas showed that a crack propagated faster along the grain boundary. However, no visible discontinuous crack advances appeared as a large number of load repetitions was required. Phenomena considered to be a damage process (1) appeared ahead of a crack tip. Based on these results, a convincing mechanism for the intergranular fatigue crack propagation process is as follows. Grain boundaries just ahead of a crack tip are damaged due to the large number of hydrogen-enhanced slip repetitions, therefore, the fatigue crack becomes easier to propagate along the grain boundary in hydrogen.

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Crack initiation mechanisms in copper polycrystals cycled under constant strain amplitudes and in step tests

Cited by 91 publications

References 18 publications

Cyclic Slip Irreversibilities and the Evolution of Fatigue Damage

Cyclic Slip Irreversibilities and the Evolution of Fatigue Damage

Microstructural mechanisms of cyclic deformation, fatigue crack initiation and early crack growth

Investigation of Mechanism for Intergranular Fatigue Crack Propagation of Low Carbon Steel JIS S10C in Hydrogen Gas Environment

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