Studies on Substructures around a Fatigue Crack in &lt;I&gt;fcc&lt;/I&gt; Metals and Alloys

Karashima, Seiichi; Ogura, Tsugio

doi:10.2320/matertrans1960.9.205

Cited by 36 publications

(5 citation statements)

References 11 publications

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“…Therefore, the activation energy determined in the present study can be regarded as being similar to that for self-diffusion in the Fe-Si alloy. This result is also in good agreement with the creep test results for α -iron and its solid solution alloys of Karashima et al 34) This also implies that the hot deformation behavior of Fe-2 mass% Si alloy is controlled by diffusion-controlled climb of dislocations. In general, ferritic stainless steels alloyed with Cr have a higher activation energy, 397 kJ/mol, than Fe-Si ferritic steels.…”

Section: Parameters For Constitutive Equationsupporting

confidence: 81%

Hot Deformation Behavior of Fe-2%Si

2013

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The hot deformation behavior of a high purity binary ferritic Fe-2 mass% Si alloy, undergoing no phase transformation or precipitation reactions, was investigated by hot torsion tests. The parameters for the constitutive equation of Fe-2 mass% Si steel were experimentally determined from the stress-strain curves. The activation energy for hot deformation was close to that for lattice self-diffusion in α -Fe, indicating that hot deformation of Fe-2 mass% Si steel occurs by a thermally-activated, diffusion-controlled dislocation climb mechanism. The electron backscattering diffraction technique and transmission electron microscopy were used to analyze the microstructural changes occurring during hot deformation. It was found that the hot deformed microstructure consisted of equiaxed crystallites surrounded by a high proportion of high angle boundaries. These boundaries were homogeneously distributed in the microstructure. A gradual increase in the fraction of boundaries with a misorientation in the range of 10° to 18° was observed in samples obtained from interrupted torsion tests. The formation of high angle boundaries at temperatures above 0.5Tm is attributed to a gradual increase of the misorientation of low angle boundaries by the absorption of dislocations.

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Section: Parameters For Constitutive Equationsupporting

confidence: 81%

Hot Deformation Behavior of Fe-2%Si

2013

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“…The maximum of local stresses [19] and strains [20] is attained at a certain distance from the tip of the notch or crack. This fact forms the basis for the model of fatigue fracture of materials suggested by the authors [1, 3].…”

Section: Assessment Of the Local Strain Range δɛ*mentioning

confidence: 99%

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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“…(2) The plastic zone detected by X-ray microbeam technique is identical with the one proposed from macroscopic points of view. (3) Intimate relations exist between the propagation rate of fatigue crack and some structural parameters of the plastic zone.…”

mentioning

confidence: 99%

Studies on the Structure Developed around Fatigue Cracks of Aluminium Using a High Voltage Electron Microscope

Ogura

Karashima

1974

Trans. JIM

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The structures formed around fatigue cracks of aluminium were examined using a 500 kV electron microscope in order to confirm the previous results obtained by a 100 kV electron microscope and to find a clue to the elucidation of the mechanism of fatigue fracture involved.There was a well-defined substructure around a fatigue crack. A large number of dislocation loops and dislocation dipoles were found near sub-boundaries. A strain-concentrating region where many voids existed was observed in the vicinity of the fatigue crack. These results are in good agreement with those obtained in previous work by use of the 100 kV electron microscope and are also consistent with the previous X-ray observations. There was direct evidence that propagation of fatigue cracks occurs through growing-up and joining-up processes of the voids formed in the strain-concentrating regions.The mechanism of void formation due to the coalescence of vacancies is proposed on the basis of the present observations. The short-circuit diffusion along the sub-boundaries with the driving force caused by the stress gradient near the crack is suggested to explain the vacancy migration through the strain-concentrating regions.

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Studies on Substructures around a Fatigue Crack in <I>fcc</I> Metals and Alloys

Cited by 36 publications

References 11 publications

Hot Deformation Behavior of Fe-2%Si

Hot Deformation Behavior of Fe-2%Si

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

Studies on the Structure Developed around Fatigue Cracks of Aluminium Using a High Voltage Electron Microscope

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