The effect of microcracking upon the Poisson's ratio for brittle materials

Case, Eldon D.

doi:10.1007/bf02396943

Cited by 31 publications

(11 citation statements)

References 24 publications

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“…During the first cycle, we calculate a permanent decrease in

\frac{v_{P}}{v_{CWI}}

from 1.84 to 1.34 (Figure ) due to thermal microcracking. We note that a

\frac{v_{P}}{v_{S}}

ratio of less than

\sqrt{2} \approx 1.41

results in a negative Poisson's ratio and, although theoretically plausible (Case, ; Walsh, ), is rare among isotropic materials. Homand‐Etienne and Houpert () also found a negative Poisson's ratio for two thermally microcracked granites (Senones Granite and Remiremont Granite heated to 200–600°C); they suggested that residual stresses during cooling are the cause of this unexpected mechanical behavior.…”

Section: Discussionmentioning

confidence: 75%

Thermal Cracking in Westerly Granite Monitored Using Direct Wave Velocity, Coda Wave Interferometry, and Acoustic Emissions

et al. 2018

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To monitor both the permanent (thermal microcracking) and the nonpermanent (thermo‐elastic) effects of temperature on Westerly Granite, we combine acoustic emission monitoring and ultrasonic velocity measurements at ambient pressure during three heating and cooling cycles to a maximum temperature of 450°C. For the velocity measurements we use both P wave direct traveltime and coda wave interferometry techniques, the latter being more sensitive to changes in S wave velocity. During the first cycle, we observe a high acoustic emission rate and large—and mostly permanent—apparent reductions in velocity with temperature (P wave velocity is reduced by 50% of the initial value at 450°C, and 40% upon cooling). Our measurements are indicative of extensive thermal microcracking during the first cycle, predominantly during the heating phase. During the second cycle we observe further—but reduced—microcracking, and less still during the third cycle, where the apparent decrease in velocity with temperature is near reversible (at 450°C, the P wave velocity is decreased by roughly 10% of the initial velocity). Our results, relevant for thermally dynamic environments such as geothermal reservoirs, highlight the value of performing measurements of rock properties under in situ temperature conditions.

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“…During the first cycle, we calculate a permanent decrease in

\frac{v_{P}}{v_{CWI}}

from 1.84 to 1.34 (Figure ) due to thermal microcracking. We note that a

\frac{v_{P}}{v_{S}}

ratio of less than

\sqrt{2} \approx 1.41

Section: Discussionmentioning

confidence: 75%

Thermal Cracking in Westerly Granite Monitored Using Direct Wave Velocity, Coda Wave Interferometry, and Acoustic Emissions

et al. 2018

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“…From these assumptions, E may be calculated from the measured V l as (2) where ρ is the mass density of the specimen and ν is Poisson's ratio. However, ν is also a function of microcracking, depending upon if the microcracks are open or have been compressed closed [26,27]. For open microcracks, the relative changes in E and ν were approximated for small changes by Walsh [26], with good agreement with experiments [27], as (3) where the subscript 0 denotes the initial (uncycled) value.…”

Section: Discussionmentioning

confidence: 76%

In-situ, non-destructive acoustic characterization of solid state electrolyte cells

Schmidt

Sakamoto

2016

Journal of Power Sources

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Solid-state electrolytes such as cubic Li 6.25 Al 0.25 La 3 Zr 2 O 12 (LLZO) can enable solid-state batteries, metallic lithium anodes and higher voltage cathodes. However, the stability of cubic LLZO is affected by current density. In beta alumina solid electrolyte, microstructural failure was caused by Na dendrite penetration, and was shown to be a function of the fracture toughness, K IC . The relationship between dendrite penetration and K IC indicates electronic failure is related to creation of microstructural damage, and the microstructural damage may be used as an indicator of imminent electronic failure.To monitor microstructural damage during cycling, we developed a non-invasive, in-situ cell monitoring apparatus to help to correlate mechanical stability with Li-ion current density in LLZO. A pulse-echo transducer was integrated into all solid-state Li-LLZO-Li cells. The capability enables the characterization of microscopic inhomogeneities through the careful measurement of changes to the elastic moduli. The elastic moduli and fracture toughness have been previously reported for dense (>99%) specimens, but monitoring of the relative change in moduli during cycling has not been explored. In this study, an acoustic monitoring method is presented to monitor LLZO specimens during cycling.

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“…These discrepancies suggested the existence of internal strains inside the specimens. Further, the smaller elastic moduli of two-phase porcelains also suggested the existence of internal strains or cracks 14,15) . The degree of transparency of T-C porcelains decreased with an increase in cristobalite content.…”

Section: Discussionmentioning

confidence: 99%

Effect of Polymorphism of SiO2 Addition on Mechanical Properties of Feldspathic Porcelains

et al. 2008

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The present study aimed to investigate the effects of SiO2 polymorphism on the mechanical properties of feldspathic porcelains. Seven kinds of experimental feldspathic porcelains were prepared using chemical reagents; three types of low-fusing feldspathic glasses and four types of two-phase porcelains by adding 10 or 20 mass% of fused silica (T-F) or cristobalite (T-C). Flexural strength and fracture toughness of these porcelains were evaluated. Flexural strengths of two-phase porcelains did not show any significant increase when compared with those of single-phase glasses. On the other hand, fracture toughnesses of porcelains with cristobalite showed a significant increase when compared with those of single-phase glasses. Circumferential cracks were observed in the porcelains with cristobalite. These results suggested that cristobalite could strengthen fracture toughness of feldspathic porcelains, but not flexural strength.

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The effect of microcracking upon the Poisson's ratio for brittle materials

Cited by 31 publications

References 24 publications

Thermal Cracking in Westerly Granite Monitored Using Direct Wave Velocity, Coda Wave Interferometry, and Acoustic Emissions

Thermal Cracking in Westerly Granite Monitored Using Direct Wave Velocity, Coda Wave Interferometry, and Acoustic Emissions

In-situ, non-destructive acoustic characterization of solid state electrolyte cells

Effect of Polymorphism of SiO2 Addition on Mechanical Properties of Feldspathic Porcelains

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