Dislocation-depth distribution in fatigued metals

Kramer, I. R.; Feng, C.R.; Wu, Bulong

doi:10.1016/0025-5416(86)90300-9

Cited by 20 publications

(8 citation statements)

References 14 publications

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“…This value is in excellent agreement with that determined previously for Naval brass tested in CuSO4 [16]. Several previous SCC [16][17][18][19] and fatigue cracking [20,21] studies have shown that a high critical dislocation density develops in the near-surface region prior to cracking. According to the aforementioned fracture criterion, it can be postulated that fracture occurs when the total strain (from accumulated dislocations) in the material reaches a critical limit probably relating to the lattice cohesion.…”

Section: Environment-induced Deformation Localizationsupporting

confidence: 81%

Deformation evolution during initiation of transgranular stress corrosion cracking

Meletis

Lian

1996

Int J Fract

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Face centered cubic metals and alloys have multiple slip systems and are characterized by high dislocation velocities. Nevertheless, these materials suffer from transgranular stress corrosion cracking (T-SCC), that occurs by environmentally-induced cleavage. Since plasticity precedes fracture in all T-SCC phenomena, the evolution of deformation patterning during T-SCC is an important element of the local microfracture mode. Experimental observations show that the presence of the SCC-causing environment during straining is promoting localized plastic deformation at the near-surface region and producing an entirely different deformation pattern compared with that developing in laboratory air. The deformation evolving in the presence of the SCC electrolyte is highly localized, exhibiting closely spaced, coarse slip bands. The amount of localized strain developing at the nearsurface region prior to nucleation of stress corrosion cracks is equivalent to the strain required for ductile fracture of the material in air, suggesting the existence of a fundamental fracture criterion. The above phenomenology of the deformation evolution is considered in relation to T-SCC initiation and propagation. The T-SCC is suggested to be a macroscopically brittle but microscopically ductile fracture occurring by localized plastic flow. An environmentinduced deformation localization mechanism is described where the role of the environment involves generation of vacancies and subsequent dislocation nucleation from the near-surface region at loads well below those required for normal yielding. The evolution of the localized deformation pattern during T-SCC is suggested to be an outcome of nonuniformity and periodicity in the dissolution process.

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Section: Environment-induced Deformation Localizationsupporting

confidence: 81%

Deformation evolution during initiation of transgranular stress corrosion cracking

Meletis

Lian

1996

Int J Fract

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“…[17][18][19][20] Similar effects have been observed in materials undergoing fatigue cracking. [21][22][23][24] Thus, in relation to the fracture criterion, it can be postulated that, in general, fracture occurs when the total strain energy from the combined stress field of dislocations in the material reaches a critical limit relating to the lattice cohesion. In SCC, the critical dislocation density is localized and, in the ductile overload fracture, distributed within the entire volume of the material.…”

Section: Corrosion-may 1996mentioning

confidence: 99%

Environment-Induced Deformation Localization During Transgranular Stress Corrosion Cracking

Lian

Meletis

1996

CORROSION

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The nucleation and evolution of deformation patterns occurring during transgranular stress corrosion cracking (TGSCC) were studied in an attempt to produce new alternatives for addressing the nature of the embrittlement process. Flat, tensile α-brass (72% Cu-28% Zn) specimens were tested in 5 M aqueous ammonia (NH 4 OH) solution at a strain rate of 1 x 10 -5 /s. Slip-band spacing (SBS) and slip-band height (SBH) were measured as a function of strain by conducting interrupted experiments in the SCC environment and were compared with those developed during laboratory air experiments. The presence of the TGSCCcausing environment during straining promoted localized plastic deformation at the near-surface region and, more importantly, produced an entirely different deformation pattern from that developed in laboratory air. The deformation evolved in the presence of the TGSCC electrolyte was highly localized, exhibiting small SBS but large SBH. Also, a periodicity was exhibited by the crack initiation process. The amount of localized strain developed at the specimen near-surface region before nucleation of stress corrosion cracks was found to be equivalent to the strain required for ductile fracture of the material in air, suggesting the existence of a fundamental fracture criterion. Grounds for an environment-induced deformation localization mechanism were introduced to explain the phenomenology of TGSCC initiation and propagation.

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“…Thus, the application of deep penetrating molybdenum radiation in contrast to copper was applied, finding that the molybdenum resulted in a fairly linear increase of excess dislocation density throughout the fatigue life, subsequently demonstrating that XRD has the capability to estimate remaining fatigue life with good accuracy for a specimen previously subjected to four block loads of increasing amplitude. Kramer et al continued this work on determining the dislocation density in depth of steels, aluminium and brass in [71]. In contrast to the findings for aluminium, the steel only exhibited a minimum in the dislocation-depth profile for the early stages of fatigue damage.…”

Section: X-ray Diffraction Methodsmentioning

confidence: 99%

A review of fatigue damage detection and measurement techniques

Bjørheim

Siriwardane

Pavlou

2022

International Journal of Fatigue

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A vast amount of research has been carried out towards the goal of quantifying changes related to the fatigue damaging process in materials throughout the fatigue life. However, no recommended practice has been developed for the experimental measurement of fatigue damage before a macroscopic crack has been initiated. Therefore, this paper reviews the existing fatigue damage detection and measurement techniques on the basis of both momentum within the research field and their being considered non-destructive. The techniques are separated into two categories, namely, fatigue crack monitoring and fatigue damage monitoring. The parameters of these techniques, which quantify the physical and mechanical changes of the materials during the fatigue life, were critically reviewed in regard to the mechanism behind the change, limitations, shortcomings, etc. The acoustic emission, hardness, ultrasonic, magnetic and potential drop methods are applicable for in-situ measurements while positron annihilation and X-ray diffraction are more suitable for laboratory assessments. Even though all the revived methods are applicable for metals, acoustic emissions, X-ray diffraction, ultrasonic, strainbased and thermometric methods are also suitable for composites. The reliability, advantages, weaknesses, case/ material dependency and applicability of each method are compared and tabulated for making a framework for choosing suitable technique for fatigue crack or damage detection of material or components.

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Dislocation-depth distribution in fatigued metals

Cited by 20 publications

References 14 publications

Deformation evolution during initiation of transgranular stress corrosion cracking

Deformation evolution during initiation of transgranular stress corrosion cracking

Environment-Induced Deformation Localization During Transgranular Stress Corrosion Cracking

A review of fatigue damage detection and measurement techniques

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