A new criterion for brittle-to-ductile fracture transition

Chan, Kwai S.

doi:10.1016/0001-6160(89)90116-8

Cited by 27 publications

(6 citation statements)

References 29 publications

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“…The developed technique might provide ways of assessing a growing crack and confirming the theory of growing cracks for the first time. For example, Chan proposed a criterion for stable crack growth on the basis of the mechanics of a growing crack [27], concluding that stable crack extension is realized as a result of sufficient plastic deformation when the following  exceeds 34.5, while a crack is propagated without experiencing any propagation resistance when  is less than 34.5;…”

Section: Comparison With Displacement Field Based Crack Driving Forcementioning

confidence: 99%

Direct measurement procedure for three-dimensional local crack driving force using synchrotron X-ray microtomography

et al. 2008

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X-ray microtomography has been utilized for the observation of ductile fractures in an aluminum alloy with an Al/Al-Si dual phase structure. A procedure for analyzing a series of tomographic images is proposed for extracting the variation in the local crack-tip opening displacement (CTOD), and its feasibility is confirmed. Complicated crack growth behavior and the formation of uncracked ligaments ahead of a crack tip are observed in the alloy owing to the marked difference in local fracture toughness between the two phases. The proposed technique has provided a quantitative interpretation for such phenomena. It is clarified that a conventional measurement significantly overestimates the CTOD level. The transition behavior in CTOD has been revealed over a certain distance across an interface between the two phases, suggesting the existence of scaling effects that influence the microstructure/fracture relationship. Overall the current method could offer a highly effective way of assessing 3-D local fracture behavior.

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Section: Comparison With Displacement Field Based Crack Driving Forcementioning

confidence: 99%

Direct measurement procedure for three-dimensional local crack driving force using synchrotron X-ray microtomography

et al. 2008

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“…However, the ratio of J/aysBn for all experiments was sufficiently small to suggest dominant plane strain [ 51,531 and fracture surfaces were always macroscopically flat and normal to the applied load. Stable crack growth under plane-strain deformation was modelled by Rice et al [57] and Chan [58]. Chan argues that T R is finite when a threshold value of ETE/oo is exceeded (where 4 is constrained ductility and oo is flow strength), and increases monotonically as this material property variable increases.…”

Section: Initiation and Growth Fracture Toughnesses: Discussionmentioning

confidence: 99%

Elevated Temperature Fracture of Particulate‐reinforced Aluminum Part I: Fracture Toughness

Somerday

Leng

Gangloff

1995

Fatigue Fract Eng Mat Struct

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The plane-strain initiation and growth fracture toughnesses of powder-metallurgy-processed, Sic particulate-reinforced 2009 plate were measured at temperatures from 25°C to 316°C. Initiation toughness from electrical potential monitoring (KII0) is 18 M P a 6 at 25°C. and is nearly constant to 220°C before decreasing sharply to 6 M P a f i at 316°C. Growth toughness, given by the tearing modulus (TR), is less than 3 from 75°C to 125°C. and increases dramatically above 200°C. The magnitude and temperature dependence of initiation toughness depend on detection of the critical fracture event.Standard measures of toughness K,, and K,,, exceed K,,,, and increase to a plateau with increasing temperature. The fracture mode for the composite is microvoid nucleation, growth and coalescence at all temperatures. Void nucleation is associated with Sic; such particles both crack and create stress and plastic strain concentrations that rupture the interface or adjacent matrix, particularly at corners. Matrix plasticity and cavitation increase with increasing temperature. Void growth is regular at all temperatures, but limited by adjacent SIC particles. Both K,,,, and TR are governed by the temperature-dependent crack-tip plastic stress and strain fields, and the intrinsic damage resistance of the composite microstructure. NOMENCLATURE a = crack length E = elastic modulus J = J-integral B, = net specimen thickness J,, = elastic component of J-integral Jlc = engineering value of critical J-integral for fracture initiation Jlc, = lower-bound value of critical /-integral for fracture initiation JpI = plastic component of J-integral K = stress intensity factor K,, = engineering value of critical stress intensity for fracture initiation K,,, = engineering value of critical stress intensity calculated from J,, K,lci = lower-bound value of critical stress intensity calculated from Jlci K,,, = maximum stress intensity in fatigue cycle n = work-hardening exponent P = applied load TR = tearing modulus W = specimen width 6 = load-line displacement E = total true strain v = Poisson's ratio CT = true stress EF =constrained ductility u0 = flow strength cuts = tensile strength cys = yield strength 565 566 B. P. SOMERDAY et al.

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“…where E is Young's modulus, TR is the material tearing modulus, e is Napier's constant, and Rp is the plastic zone diameter. TR was calculated as follows [64] :…”

Section: Local Deformation At the Intergranular And Quasi-cleavage Crack Tipmentioning

confidence: 99%

“…where ,  and  are constants and were assumed to be 0.65, 5.08, and 0.2 respectively [64] . The calculated TR values were 12.5 and 8.7 for intergranular cracks and quasi-cleavage cracks, respectively.…”

Section: Local Deformation At the Intergranular And Quasi-cleavage Crack Tipmentioning

confidence: 99%

Local Deformation and Fracture Behavior of High-Strength Aluminum Alloys Under Hydrogen Influence

Shimizu

Toda

Uesugi

et al. 2019

Metall Mater Trans A

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The local deformation and fracture behavior of high-Zn Al-Zn-Mg(-Cu) alloys under hydrogen influence were investigated by in situ tests through synchrotron X-ray tomography. Intergranular and quasi-cleavage fractures were induced by hydrogen, and strain localization by the presence of cracks was not observed by 3D strain mapping. This result suggests that the strain localization at the crack tip is smaller than the measurement limit of 3D strain mapping. The average crack-tip-opening displacements, which are one of the crack driving forces specified by fracture mechanics, directly measured from the tomographic slice were 0.14 and 0.23 m for intergranular cracks and quasi-cleavage cracks, respectively. The crack driving force of the intergranular and quasi-cleavage cracks was small. The local deformation behavior at the crack tips was analyzed based on fracture mechanics. The local deformation field of the crack tip, which was characterized using the Rice-Drugan-Sham (RDS) solution rather than the Hutchinson-Rice-Rosengren (HRR) solution, was located within 20 m of the crack tip, and its size was limited. The results of this work clarify that the intergranular and quasi-cleavage crack growth are caused by small driving forces; however, this behavior is not perfectly brittle, accompanying local deformation at the crack tip.

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A new criterion for brittle-to-ductile fracture transition

Cited by 27 publications

References 29 publications

Direct measurement procedure for three-dimensional local crack driving force using synchrotron X-ray microtomography

Direct measurement procedure for three-dimensional local crack driving force using synchrotron X-ray microtomography

Elevated Temperature Fracture of Particulate‐reinforced Aluminum Part I: Fracture Toughness

Local Deformation and Fracture Behavior of High-Strength Aluminum Alloys Under Hydrogen Influence

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