On crack closure in the near-threshold region

Minakawa, K.; McEvily, A.J.

doi:10.1016/0036-9748(81)90041-7

Cited by 296 publications

(73 citation statements)

References 7 publications

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“…[23,[53][54][55] From the viewpoint of plasticity-induced crack closure, [53] it follows from this discussion that the amount of plastic deformation (plastic zone size) at the maximum load, P max , is smaller in the presence of hydrogen than in its absence. Figures 10(a) and (b) illustrate the effect of hydrogen on the crack closure mechanism during one load cycle.…”

Section: Hydrogen-induced Striation Formation Mechanismmentioning

confidence: 99%

Hydrogen Embrittlement Mechanism in Fatigue of Austenitic Stainless Steels

Murakami

Kanezaki

Mine

et al. 2008

Metall Mater Trans A

201

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YUKITAKA MURAKAMI, TOSHIHIKO KANEZAKI, YOJI MINE, and SABURO MATSUOKAThe basic mechanism of the hydrogen embrittlement (HE) of stainless steels under fatigue loading is revealed as microscopic ductile fracture, resulting from hydrogen concentration at crack tips leading to hydrogen-enhanced slip. Fatigue crack growth rates in the presence of hydrogen are strongly frequency dependent. Nondiffusible hydrogen, at a level of 2 to approximately 3 wppm, is contained in ordinarily heat-treated austenitic stainless steels, but, over the last 40 years, it has been ignored as the cause of HE. However, it has been made clear in this study that, with decreasing loading frequency down to the level of 0.0015 Hz, the nondiffusible hydrogen definitely increases fatigue crack growth rates. If the nondiffusible hydrogen at O-sites of the lattice is reduced to the level of 0.4 wppm by a special heat treatment, then the damaging influence of the loading frequency disappears and fatigue crack growth rates are significantly decreased.

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Section: Hydrogen-induced Striation Formation Mechanismmentioning

confidence: 99%

Hydrogen Embrittlement Mechanism in Fatigue of Austenitic Stainless Steels

Murakami

Kanezaki

Mine

et al. 2008

Metall Mater Trans A

201

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“…Next, we evaluated the differences in the state of the fractured surface for each type of samples between both the humidity levels. Based on the characteristics of fractured surfaces, the crack closure can be classified into those due to oxides that have formed due to contact with the fractured surface (oxide-induced crack closure) 15) and those due to roughness of fractured surfaces (roughness-induced crack closure). 16) Figure 9 shows the back scattered electron images and the EPMA analysis results for the individual sample types.…”

Section: Moisture Air Effects On Fatigue Crack Propagation Propertiesmentioning

confidence: 99%

Effects of Moisture in the Air on Characteristics of Strength in High Strength Spheroidal Graphite Cast Iron

Shiraki

Morita

2015

Mater. Trans.

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The purpose of this study is to investigate the effects of humidity on the strength characteristics in high strength spheroidal graphite cast iron with two phases, which is ferrite and pearlite. Three spheroidal graphite cast irons (FCD400(FDI), FCD500(FPDI.82) and FCD600(FPDI.55)) were used as specimens. In addition, heat treatment (Normalizing) was conducted in FCD500 (PDI). Tensile test conforming to JIS was carried out using these resultant four materials in air and water. The specimen used was of the 14A type. The relationship between tensile strength and area ratio of brittle fracture was investigated. Fatigue crack propagation test conforming to ASTM was also carried out using these materials. Stress ratio R was 0.1, and the specimen used was of the 1CT type with a thickness of 12.5 mm. The test was carried out at room temperature and three kinds of humidity: 0, 40 and 80%. The relationship between the characteristics of fatigue crack propagation and crack closure generated on the fracture surface was investigated.Though tensile strength in FDI and FPDI.82 was not influenced by water brittlement, strength in PDI and FPDI.55, which included pearlite, was decreased by water brittlement. This phenomenon may mainly be caused by the amount of parlite in the matrix. The threshold stress intensity factor range ¦K th of all materials increased with increasing humidity. Crack closure was investigated in all materials. It seemed to become marked with increasing humidity. In the low ¦K eff region of all materials (except FPDI.55, 80%), the fatigue crack propagation rate was almost the same because of oxide-induced crack closure of the ferrite included in the matrix. In the high ¦K eff region of FPDI and PDI, the rate was not the same. The acceleration was investigated because of effect of a phenomenon similar to the water embrittlement of pearlite included in the matrix.

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“…As schematica lly ill ustrated in Fig. 11, these mechani sms involve the wedging action of crack flank corrosion deposits (Ritchie and others, 1980;Stewart, 1980;Suresh and others, 1981) and fracture surface asperities (Walker and Beevers, 1979;Minakawa and McEvily, 1981;, coupled with significant crack tip shear displacements (Davidson, 1981), fluid-induced pressure between the crack wa 11 s (Endo and others, 1972;others, 1985a, 1985b), and compression between the crack surfaces resulting from certain metallurgical phase transformations. Since a detailed description of these alternative closure mechanisms has been the subject of a recent review (Suresh and Ritchie, 1984b), only a brief summary is presented here.…”

Section: Mechanisms Of Fatigue Crack Growthmentioning

confidence: 99%