Investigation on the Weibull parameters identification for local approach application in the ductile to brittle transition regime

Esposito, Luca; Gentile, Domenico; Bonora, Nicola

doi:10.1016/j.engfracmech.2006.07.002

Cited by 12 publications

(8 citation statements)

References 35 publications

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“…(16)) and therefore decreases the uniform strain to failure. The highest influence of strain hardening parameters is observed for ρ=2; however, the effect is in practice smaller than that, since most realistic values for brittle metals and engineering ceramics give ρ between 5 and 20 (roughly, ρ=3-20 for ceramics, ρ=8-20 for powder metallurgy steels, ρ>30 for wrought steels) [20][21][22][28][29][30][31][32][33][34][35][36]. We now examine more systematically the influence exerted by the five dimensionless parameters governing the problem: n, m, ρ, γ and φ, taking n between 0 and 0.5 and m between 0 and 0.1, the Weibull modulus ρ between 5 and 10 (above 10 the ductile phase influence becomes negligible), and γ between 0 and 1.…”

Section: Resultsmentioning

confidence: 99%

Tensile elongation of unidirectional or laminated composites combining a brittle reinforcement with a ductile strain and strain-rate hardening matrix

Cohades¹,

Mortensen²

2014

Acta Materialia

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We use the long-wavelength model of Hutchinson and Neale (Hutchinson JW, Neale KW. Acta Metall 1977;25:839) and Ghosh (Ghosh AK. Acta Metall 1977;25:1413) to estimate the uniform tensile elongation of two-phase composites deforming quasistatically according to the equistrain rule of mixtures, in which one phase is ductile while the other fractures progressively according to twoparameter Weibull statistics. We use shear-lag models in the literature to quantify load transfer from the ductile phase to the fractured brittle phase, to estimate the influence of matrix strain and strain-rate hardening, of brittle phase fracture characteristics, and of phase volume and strength ratios, on the composite strain to failure as dictated by the onset of unstable necking. Calculations show that strain and strain-rate hardening of the ductile phase do relatively little to increase the ductility of the composite. Two parameters play a dominant role, namely the brittle phase Weibull modulus and a dimensionless parameter describing load transfer across the two phases. The main practical implication of this analysis is that, to produce reasonably ductile two-phase composites, the best strategy is to aim for small layer thicknesses. IntroductionMany composite materials combine a ductile matrix with a brittle reinforcement: ceramic or carbon fibre reinforced metals fall in this category, as do some laminated metal composites and many other layered materials (such as thin film structures or ceramic-coated metals) [1][2][3][4]. When such composites are strained in tension the brittle phase develops cracks that cut its fibres or layers in two along a plane normal to the applied load; in laminated composites these are known as "tunnel cracks". Final fracture of the material may then happen in one of two ways. One is sudden brittle failure, caused by a propagative localization of internal damage that cuts abruptly the entire specimen in two; many strongly bonded ceramic or carbon fibre reinforced composites fail in this way [5][6][7], as do some particle reinforced composites [8]. Alternatively, internal damage accumulates stochastically throughout the material, in gradual and uncorrelated fashion. The composite is then likely to fail by strain localization, reaching its ultimate tensile strength at a smooth maximum along its stress-strain curve, and sometimes deforming significantly thereafter, while deformation concentrates in a portion of the sample's gauge length. Weakly bonded fibre reinforced composites (e.g., [5]), ceramic particle reinforced metals (e.g., [8,9]), two-phase metal alloys [10] or laminated metal composites [11] can all fail in this way. Strain hardening and strain-rate hardening then both play an important role: even small increases in a ductile material's strain hardening rate, or in its strain-rate sensitivity, can noticeably increase the tensile elongation when it is governed by the onset of strain localization.

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Section: Resultsmentioning

confidence: 99%

Tensile elongation of unidirectional or laminated composites combining a brittle reinforcement with a ductile strain and strain-rate hardening matrix

Cohades¹,

Mortensen²

2014

Acta Materialia

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“…Later Xia and Shih [13] defined the process zone as the region surrounding the crack tip where the maximum principal stress is k-times the yield stress, being k an arbitrary number between 1 and 3, often assumed 2.5. Recently Esposito et al [23] suggested to limit the process zone as the region where the equivalent plastic strain is larger than r y /E, at the given temperature, and the stress triaxiality, defined as the ratio between the mean stress and the equivalent Mises stress, is positive. In the present work, a criterion that combines the Xia and Shih and Esposito et al criteria was used, ½r 1 P 2:5r y &½e p eq P r y ðTÞ=EðTÞ&½r m =r eq P 0 ð 3Þ…”

Section: Cleavage Fracture Modelingmentioning

confidence: 99%

The effect of subcritical ductile crack growth on cleavage fracture probability in the transition regime using continuum damage mechanics simulation

Moattari

Sattari-Far

Bonora

2016

Theoretical and Applied Fracture Mechanics

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“…Therefore, this study will focus on this particular geometry. In former studies [4,5,11,12,14], the identification of micro-mechanical ductile failure parameters was required. This identification is time consuming and requires additional specific experiments and/or micro-structural investigations.…”

Section: Introductionmentioning

confidence: 99%

“…The 2D modeling developed in [5], was improved with 3D modeling in [11] and independently in [12]. The selected ductile damage model in [11] is based on computational cells but uses a modified Lemaitre approach developed in [13]; in [12] the Rousselier model [7] is used.…”

Section: Introductionmentioning

confidence: 99%

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Effect of prior crack growth on cleavage fracture of low toughness precracked Charpy specimens

Scibetta

2010

Journal of Nuclear Materials

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Investigation on the Weibull parameters identification for local approach application in the ductile to brittle transition regime

Cited by 12 publications

References 35 publications

Tensile elongation of unidirectional or laminated composites combining a brittle reinforcement with a ductile strain and strain-rate hardening matrix

Tensile elongation of unidirectional or laminated composites combining a brittle reinforcement with a ductile strain and strain-rate hardening matrix

The effect of subcritical ductile crack growth on cleavage fracture probability in the transition regime using continuum damage mechanics simulation

Effect of prior crack growth on cleavage fracture of low toughness precracked Charpy specimens

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