The theory of thermally activated processes in brittle stress corrosion cracking

Krausz, A. S.

doi:10.1016/0013-7944(79)90027-4

Cited by 18 publications

(7 citation statements)

References 12 publications

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“…Instead, a more general condition is established by not stating in detail the relation between the applied stress (stress intensity factor, or crack driving force) and the mechanical work, and by allowing a general treatment through the introduction of the Markov chain system. An application to simple models of SCC was presented before [23][24][25]. These models were in agreement with the typical conditon of thermally activated fracture in static SCC as described in the excellent reviews by Pollet and Burns [4] and by Wiederhorn [5].…”

Section: Closing Commentssupporting

confidence: 61%

Reliability Theory of Stochastic Fracture Processes in Sustained Loading: Part I

Krausz

Necsulescu

1983

Zeitschrift Für Naturforschung A

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It is shown that the physical mechanism of thermally activated subcritical crack growth is always a stochastic process and leads, therefore, to probabilistic crack propagation. This process is the result of the random breaking of atomic bonds and has to be clearly distinguished from the well known Weibull distribution. A Markov chain analysis leads to the normal distribution of crack sizes. The results demonstrate that conventional deterministic finite life-time designs are unsatisfactory and can lead to early failure of machine or structure elements as the consequence of the probabilistic process of crack propagation. The conclusions lead to the reliability analysis of Part II.

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Section: Closing Commentssupporting

confidence: 61%

Reliability Theory of Stochastic Fracture Processes in Sustained Loading: Part I

Krausz

Necsulescu

1983

Zeitschrift Für Naturforschung A

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confidence: 99%

“…Numerous authors agree that SCC is controlled by thermal activation, e.g., [1][2][3][4][5][6], and it is recognized that the process is very complex indeed. The experimental results are often presentedinthe log velocity stress intensity factor KI, or log velocity-crack driving force G_ coordinate system: Fig.…”

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confidence: 99%

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confidence: 99%

“…Region III is a parallel process [3,[5][6][7], and consequently the fastest mechanism controls the overall velocity; here the stresses are very high, near the critical stress, and the bonds break before any corrosion reaction can take place. Following Charles and Hilling [8,9] it was shown by Wiederhorn [2] that, at least in glass-water environment, the crack propagation velocity associated with the corrosion process can be described by an equation of the type v~ exp(_ AG~=-°AV + YVm/~ ) kT where v is the crack velocity, AG ~ is the bond strength in the corroded zone, a is the applied stress, AV is the activation volume, V is'the molar volume of the glass, and 0 is the radius of curvature o~ the crack tip.…”

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A unified fracture kinetics representation of the three regions of stress corrosion cracking

Krausz

1983

Int J Fract

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Environmentally assisted crack propagation (or stress corrosion cracking, SCC) is a recurring problem in many aspects of engineering practice -witness the large number of publications appearing in both scientific and engineering journals.Numerous authors agree that SCC is controlled by thermal activation, e.g., [1][2][3][4][5][6], and it is recognized that the process is very complex indeed. The experimental results are often presentedinthe log velocity stress intensity factor KI, or log velocity-crack driving force G_ coordinate system: Fig. i is the sche-I matic representation of the three regions and the threshold zone that is always obtained in SCC experiments for all materials, in any environment and at any temperature.Attempts to describe the processthat is, to derive a mathematical description of the processes -have been made for some time; as a result, a great deal of information has become available.In Regions I and II corrosion reaction takes place in the crack tip zone, followed by the bond breaking steps. The rate of the crack propagation depends on the stress-enhanced chemical reaction, but the two regions are controlled by different mechanisms.In its simplest form, the corrosion reaction occurs in two consecutive steps: step one is the flow of the corrosive material to the crack tip, and step two is the chemical reaction between the reactant and the crack tip zone matrix.Since the process is consecutive, the overall rate is determined by the slower of the two steps.In Region I the rate of the chemical reaction determines the crack velocity; in Region II it is the rate of the reactant transport to the crack tip, because at intermediate stresses the rate of the corrosion reaction increases [2]. Region III is a parallel process [3,[5][6][7], and consequently the fastest mechanism controls the overall velocity; here the stresses are very high, near the critical stress, and the bonds break before any corrosion reaction can take place.Following Charles and Hilling [8,9] it was shown by Wiederhorn [2] that, at least in glass-water environment, the crack propagation velocity associated with the corrosion process can be described by an equation of the type v~ exp(_ AG~=-°AV + YVm/~ ) kT where v is the crack velocity, AG ~ is the bond strength in the corroded zone, a is the applied stress, AV is the activation volume, V is'the molar volume of the glass, and 0 is the radius of curvature o~ the crack tip. Further refinements of this equation were discussed by Wiederhorn [2], and detailed analysis of the kinetics of these regions were developed by Brown [3]. The kinetics analysis has led to the following general equation for the crack velocity Int Journ of Fracture 23 (1983)

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Creep Crack Growth in austenitic steels — applicability of fracture mechanics parameters

Grüeter¹,

Zeibig²

1980

Materialwissenschaft Werkst

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The comparison of fracture mechanics parameters, which have been applied to creep crack growth in case of the austenitic stainless steels AISI 304 and AISI 316, is possible only to a limited extent thus showing evidence that a reliable judgement cannot be given at this moment. With respect to the mechanical characterization of a cracked component by using small specimen data the J-integral resp. modified versions like C* have to be favoured for future work. The net-section stress seems to show promise under certain conditions as well. The application of the stress intensity factor will not characterize properly creep cracking by giving a conservative interpretation of the mechanical behaviour. With regard to fracture mechanics parameters the effects of temperature, geometry and environment on creep crack growth have also been discussed.

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The theory of thermally activated processes in brittle stress corrosion cracking

Cited by 18 publications

References 12 publications

Reliability Theory of Stochastic Fracture Processes in Sustained Loading: Part I

Reliability Theory of Stochastic Fracture Processes in Sustained Loading: Part I

A unified fracture kinetics representation of the three regions of stress corrosion cracking

Creep Crack Growth in austenitic steels — applicability of fracture mechanics parameters

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