Residual strain and the fracture stress-grain size relationship in brittle solids

Clarke, F.J.P.

doi:10.1016/0001-6160(64)90181-6

Cited by 86 publications

(11 citation statements)

References 5 publications

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“…Their conclusions are, in some ways, contrary to the idea that the strength change of polycrystalline materials that consist of anisotropic crystals primarily are governed by the formation of grain-boundary microcracks. 8,9,35,[64][65][66][67] Although a large decrease in fracture strength should be caused by the grain-boundary microcracking, before the formation of apparent microcracks, some degradation of the grain boundary (because of internal stresses and/or a change in chemistry) may have occurred and influenced the fracture toughness and, thus, the fracture strength. 8,68,69 These effects should vary from material to material and also be strongly dependent on the irradiation conditions; therefore, general performance (such as dependency on fluence or volume expansion) cannot be predicted easily for a variety of ceramics.…”

Section: (2) Bending or Compressive Strength And Fracture Toughnessmentioning

confidence: 99%

Effects of Neutron Irradiation on the Mechanical Properties of Magnesium Aluminate Spinel Single Crystals and Polycrystals

Yano

1999

Journal of the American Ceramic Society

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The effect of fast neutron irradiation on the mechanical properties of magnesium aluminate spinel single crystals and polycrystals, such as bending strength, fracture toughness, Young's modulus, and hardness, was summarized based on the reported data. Essentially, the changes in these properties are dependent on the nature and concentration of neutron-irradiation-induced defects. Furthermore, the efficiency of damage accumulation is known to be dependent on temperature. Spinel shows superior resistance to the formation of defect aggregates, and the recombination of point defects occurs efficiently under neutron irradiation; therefore, the change in mechanical properties is not critical, up to very high neutron fluences, and the spinel maintains its structural integrity.

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Section: (2) Bending or Compressive Strength And Fracture Toughnessmentioning

confidence: 99%

Effects of Neutron Irradiation on the Mechanical Properties of Magnesium Aluminate Spinel Single Crystals and Polycrystals

Yano

1999

Journal of the American Ceramic Society

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“…The inverse relation between ac and~ is evident from (2.4). The energy balanc'e argument leading to (2.4) has often been used to determine a critical grain size for spontaneous cracking (Clarke, 1964;Davidge and Green, 1968;Kuszyk and Bradt, 1973;Cleveland and Bradt, 1978;Evans, 1978). Equations (2.1-2.4) may now be combined to calculate the fraction q of grain facets which are likely to fracture during cooling.…”

Section: Vol 115 July 1993mentioning

confidence: 99%

The Influence of Grain Size on the Toughness of Monolithic Ceramics

Bower

Ortiz

1993

Journal of Engineering Materials and Technology

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Experiments have shown that there may be an optimal grain size which maximizes the toughness of polycrystalline ceramics. In this paper, we attempt to develop a theoretical model which can predict the effect of grain size on the toughness of ceramics. We assume that three principal mechanisms affect the toughness of the material: distributed microcracking; crack trapping by tough grains; and frictional energy dissipation as grains are pulled out in the wake of the crack. The grain size influences these mechanisms in several ways. The energy dissipated due to frictional crack bridging increases with the size of the bridging grains, tending to improve toughness. However, as the grain size increases, the density of microcracks in the solid also increases, which eventually weakens the material. In addition, the level of inter-granular residual stress is also reduced by microcracking, which as a detrimental effect on the toughening due to bridging. We have developed a simple model to quantify these effects. However, the model does not predict the dramatic loss of strength which has been observed to occur beyond a critical grain size. We have therefore proposed an alternative explanation for the apparent decrease in toughness in coarse grained ceramics. Calculations indicate that in a coarse grained material, the main contribution to toughness is due to frictional crack bridging. However, to produce this toughening, the bridging zone must be over 500 grains long. In practice, the length of the bridging zone in a coarse grained solid may be comparable to the dimensions of the specimen used to measure its toughness. Under these conditions, it is not appropriate to use the concept of a geometry independent toughness to characterize the strength of the specimen. We have therefore developed a simple model of a double cantilever beam fracture specimen, which accounts for the effects of large scale bridging. Using this model, we are able to predict the apparent decrease in toughness measured in coarse grained specimens.

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“…These internal stresses, induced by the anisotropy of thermal contraction between adjacent grains, can promote spontaneous cracking along grain facets (e.g., Clarke, 1964;Matsuo and Sasaki, 1966;Davidge and Green, 1968;Kuszyk and Bradt, 1973;Cleveland and Bradt, 1978;Evans, 1978;Blenctell and Coble, 1982;Yu and Evans, 1985;Fredrich and Wong, 1986). The occurrence ofmicrocracking has been found to depend on the scale of the microstructure in that there exists a critical grain size in single-phase systems below which grain boundary microfracture is essentially suppressed (Matsuo and Sasaki, 1966;Evans, 1978;Rice and Pohanka, 1979).…”

Section: Introductionmentioning

confidence: 99%

Statistical Properties of Residual Stresses and Intergranular Fracture in Ceramic Materials

Ortiz

Suresh

1993

Journal of Applied Mechanics

122

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Residual strain and the fracture stress-grain size relationship in brittle solids

Cited by 86 publications

References 5 publications

Effects of Neutron Irradiation on the Mechanical Properties of Magnesium Aluminate Spinel Single Crystals and Polycrystals

Effects of Neutron Irradiation on the Mechanical Properties of Magnesium Aluminate Spinel Single Crystals and Polycrystals

The Influence of Grain Size on the Toughness of Monolithic Ceramics

Statistical Properties of Residual Stresses and Intergranular Fracture in Ceramic Materials

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