Fracture properties of interfacially doped Nb-A12O3 bicrystals: I, fracture characteristics

Korn, D.; Elssner, G.; Cannon, R. M.; Rühle, M.

doi:10.1016/s1359-6454(02)00193-3

Cited by 58 publications

(67 citation statements)

References 62 publications

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“…Thus, diffusion bonding at 1300-1400°C, accomplished with very flat and clean bonding surfaces under UHV conditions, has yielded interfaces with fracture energies of 90 J/m 2 using 99.9% pure Nb. 18,19 Possible explanations for the lower toughness in the present case may be a much higher yield strength for the present polycrystalline niobium due to impurity uptake during bonding and/or a decrease in the work of attraction, W at , due to copper adsorbed at the interface allowing interface failure at lower toughness values.…”

Section: 38mentioning

confidence: 77%

“…18,19,42 While the strain rate sensitivity of niobium is expected to play a role in reducing deformation during fast fracture, no evidence of deformation was found at the critical fracture initiation point where the loading rate was moderate and more deformation should be expected.…”

Section: 38mentioning

confidence: 99%

“…All these values are markedly higher than found after UHV diffusion bonding using cleaner Nb single crystals at 1400°C. 18,19 Using the classical relation…”

Section: E′mentioning

confidence: 99%

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Fracture and Fatigue Behavior at Ambient and Elevated Temperatures of Alumina Bonded with Copper/Niobium/Copper Interlayers

Kruzic

Marks

Yoshiya

et al. 2002

Journal of the American Ceramic Society

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Interfacial fracture toughness and cyclic fatigue-crack growth properties of joints made from 99.5% pure alumina partial transient-liquid phase bonded using copper/niobium/copper interlayers have been investigated at both room and elevated temperatures, and assessed in terms of interfacial chemistry and microstructure. The mean interfacial fracture toughness, G c , was found to decrease from 39 to 21 J/m 2 as temperature was raised from 25° to 1000°C, with failure primarily at the alumina/niobium interfaces. At room temperature, cyclic fatigue-crack propagation occurred at both the niobium/alumina interface and in the alumina adjacent to the interface, with the fatigue threshold, ∆G TH , ranging from 20 -30 J/m 2 ; the higher threshold values in that range resulted from a predominantly near-interfacial (alumina) crack path. During both fracture and fatigue failure, residual copper at the interface deformed and remained adhered to both sides of the fracture surface, acting as a ductile second phase, while separation of the niobium/alumina interface appeared relatively brittle in both cases. The observed fracture and fatigue behavior is considered in terms of the respective roles of the presence of ductile copper regions at the interface which provide toughening, extrinsic toughening due to grain bridging during crack propagation in the alumina, and the relative crack propagation resistance of each crack path, including the effects of segregation at the interfaces found by Auger spectroscopy.

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Section: 38mentioning

confidence: 77%

Section: 38mentioning

confidence: 99%

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Fracture and Fatigue Behavior at Ambient and Elevated Temperatures of Alumina Bonded with Copper/Niobium/Copper Interlayers

Kruzic

Marks

Yoshiya

et al. 2002

Journal of the American Ceramic Society

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“…Dimple formation between two decohered interfaces must therefore contribute the majority of the local work of fracture for this system. Such interfacial embrittlement effects were explained by Rice and Wang [82] and are receiving increasing attention for grainboundary fracture [34] or for fracture along metal/ ceramic interfaces [83][84][85].…”

Section: Microstructural Dependence Of Fracture and Toughening In Thementioning

confidence: 99%

Fracture of aluminium reinforced with densely packed ceramic particles: link between the local and the total work of fracture

Miserez

2004

Acta Materialia

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Model composites of pure Al reinforced with 50% ceramic particles are produced by infiltration. The composite fracture energy is measured by J -integral testing. Marked R-curve behaviour is found. The J-R curves exhibit a break in their slope at a well-defined point. This point is shown to denote the onset of macroscopic crack propagation and is used to assess the composite toughness.Toughness reaches values as high as 40 MPa ffiffiffiffi m p . Quantitative metallography and stereoscopic reconstructions of fracture surfaces are used to estimate the local work of fracture in the process zone. The measured (total) fracture energy is about ten times the estimated local fracture energy, for all composites. The main contribution to their total fracture energy is thus from plastic dissipation around the crack-tip; however, the toughness is still dictated by the local fracture energy. This study hence experimentally substantiates the ''valve'' concept in fracture mechanics.

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“…Experiments on ceramic-metal interfaces have shown quasi-static crack growth of a crack along the interface in the presence of plasticity [3][4][5][6]. In these studies, the interface crack remained relatively sharp (not significant blunting) and the estimated stress level needed to result in atomistic/microscopic decohesion is about 10 times the tensile yield stress [7].…”

Section: Introductionmentioning

confidence: 99%

Mode I and mixed mode crack-tip fields in strain gradient plasticity

Goutianos

2011

International Journal of Non-Linear Mechanics

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To cite this version:Stergios Goutianos.Mode I and mixed mode crack-tip fields in strain gradient plasticity.International Journal of Non-Linear Mechanics, Elsevier, 2011, 46 (9) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractStrain gradients develop near the crack-tip of Mode I or mixed-mode cracks.A finite strain version of the phenomenological strain gradient plasticity theory of Fleck-Hutchinson (2001) is used here to quantify the effect of the material length scales on the crack-tip stress field for a sharp stationary crack under Mode I and mixed-mode loading. It is found that for material length scales much smaller than the scale of the deformation gradients, the predictions converge to conventional elastic-plastic solutions. For length scales sufficiently large, the predictions converge to elastic solutions. Thus, the range of length scales over which a strain gradient plasticity model is necessary is identified. The role of each of the three material length scales, incorporated in the multiple length scale theory, in altering the near-tip stress field is systematically studied in order to quantify their effect.

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Fracture properties of interfacially doped Nb-A12O3 bicrystals: I, fracture characteristics

Cited by 58 publications

References 62 publications

Fracture and Fatigue Behavior at Ambient and Elevated Temperatures of Alumina Bonded with Copper/Niobium/Copper Interlayers

Fracture and Fatigue Behavior at Ambient and Elevated Temperatures of Alumina Bonded with Copper/Niobium/Copper Interlayers

Fracture of aluminium reinforced with densely packed ceramic particles: link between the local and the total work of fracture

Mode I and mixed mode crack-tip fields in strain gradient plasticity

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