Crack propagation in alkaline-earth fluorides

Becher, P. F.; Freiman, Stephen W.

doi:10.1063/1.325433

Cited by 36 publications

(10 citation statements)

References 8 publications

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“…The fracture surface energy of single crystals is typically of order 0.3-1.1 Jm -2 (Becher and Freiman 1978;White et al 1988). Accordingly, in the present simulations the crystalline or grain fracture toughness, c xtal , for both calcite and dolomite was assumed to be 0.5 Jm -2 , and isotropic.…”

Section: Finite-element Simulationsmentioning

confidence: 99%

Microcracking in calcite and dolomite marble: microstructural influences and effects on properties

Shushakova¹,

Fuller²,

Siegesmund³

2012

Environ Earth Sci

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Microstructure-based finite-element analysis with a microcracking algorithm was used to simulate an actual degradation phenomenon of marble structures, i.e., microcracking. Both microcrack initiation and crack propagation were characterized, as were their dependence on lattice preferred orientation (LPO), grain shape preferred orientation (SPO), grain size, marble composition (calcite and dolomite) and grain-boundary fracture toughness. Two LPOs were analyzed: a random orientation distribution function and an orientation distribution function with strong directional crystalline texture generated from a MarchDollase distribution. Three SPOs were considered: equiaxed grains; elongated grains and a mixture of equiaxed and elongated grains. Three different grain sizes were considered: fine grains of order 200 lm (only calcitic marble); medium size grains of order 1 mm (calcitic and dolomitic marbles); and large grains of order 2 mm (only dolomitic marble). The fracture surface energy for the grain boundaries, c ig , was chosen to be 20 and 40 % of the fracture surface energy of a grain, c xtal , so that both intergranular and transgranular fracture were possible. Studies were performed on these idealized marble microstructures to elucidate the range of microcracking responses. Simulations were performed for both heating and cooling by 50°C in steps of 1°C. Microcracking results were correlated with the thermoelastic responses, which are indicators related to degradation. The results indicate that certain combinations of LPO, SPO, grain size, grain-boundary fracture toughness and marble composition have a significant influence on the thermal-elastic response of marble. Microstructure with the smallest grain size and the highest degree of SPO and LPO had less of a tendency to microcrack. Additionally, with increasing SPO and LPO microcracking becomes more spatially anisotropic. A significant observation for all microstructures was an asymmetry in microcracking upon heating and cooling: more microcracking was observed upon cooling than upon heating. Given an identical microstructure and crystallographic texture, calcite showed larger thermal stresses than dolomite, had an earlier onset of microcracking upon heating and cooling, and a greater microcracked area at a given temperature differential. Thermal expansion coefficients with and without microcracking were also determined.

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Section: Finite-element Simulationsmentioning

confidence: 99%

Microcracking in calcite and dolomite marble: microstructural influences and effects on properties

Shushakova¹,

Fuller²,

Siegesmund³

2012

Environ Earth Sci

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“…In their article on the cleavage of the alkaline earth fluorides, Becher and Freiman [46] also report several fracture toughness values for dense, transparent polycrystalline fluorite (CaF2). Values from 1.6 to 3.6 MPa m 1/2 were reported.…”

Section: Fracture Toughnesses Of Polycrystalline Aggregatesmentioning

confidence: 99%

Single crystal cleavage of brittle materials

1994

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Cleavage of brittle single crystals is reviewed and the historical criteria for the phenomenon are critically examined. Previously proposed criteria, including those based on crystal structure (crystal growth planes, the planes bounding the unit cell, and planar atomic packing) and crystal properties (ionic charge of possible cleavage planes, bond density, elastic modulus, arid surface free energy), are found to be applicable only to particular crystals or to isostructural groups, but each lacks universal application. It is concluded that the fracture toughness (Kit) of the crystallographic planes is the most appropriate criterion. Measurements reveal that the 'cleavage toughnesses' of brittle single crystals are usually about 1 MPa m |/2 or less.Measurements of the fracture toughnesses of brittle polycrystalline aggregates are then compared to the single crystal cleavage values in those instances where reliable results are available for the same crystal structures. Polycrystalline toughnesses are consistently higher, in part because of the lack of continuity of cleavage cracks through the polycrystalline aggregates. However, the increment of toughness increase is only 1-2 MPa m 1/2. The role of grain texture or preferred crystal orientation is also addressed. It is concluded that polycrystalline aggregate toughnesses are often highly anisotropic and that the values for intensely oriented microstructures may approach those for single crystal cleavage.

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“…Second, this approach which would decrease with time, as was observed for some of the InP loading conditions. 4 This behavior was attributed to assumes that, for any applied K I , there is a corresponding nonzero v governed by Eq. (1); this is in direct conflict with Fig.…”

Section: Methodsmentioning

confidence: 99%

Double Cantilever Beam Measurements of Crack Growth in Indium(III) Phosphide

Braun

White

1997

Journal of the American Ceramic Society

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Crack growth measurements in InP crystals were con-Cracks which resulted from this procedure were typically 1/4 to 1/3 the total length of the specimen, and extended through the ducted using an applied-moment, double cantilever beam entire specimen thickness. Precracked specimens were glued to (DCB) geometry. Controlled, smooth crack growth was aluminum arms with a fast-acting commercial glue (Duro observed in water; however, the crack growth velocities Super Glue, Loctite Corp., Cleveland, OH). were not constant for constant applied stress intensity (K I ).The specimens were used in applied-moment DCB 2 tests to More importantly, there was no clear functional depeninvestigate the crack growth behavior of InP in water. Specidence of the crack growth rate (v) on K I . mens were dead-weight loaded and, in the applied-moment DCB geometry, experienced a constant stress intensity for a I. Introductiongiven load, independent of crack length. Crack lengths were monitored through a traveling microscope at a resolution of E NVIRONMENTALLY enhanced crack growth can limit the life-Ϸ6 m. Crack velocities were determined by measuring time of brittle materials. It is important, therefore, to deterchange in crack length over measured time intervals. Only one mine the relationship between crack velocity, in a particular environment, distilled water, was used for the DCB tests. The environment, and the stress intensity at the crack tip. Typically, cracks were immersed in a glass container filled with water quantitative determination of a material's susceptibility to enviduring the measurements. The sides of the container were optironmentally enhanced crack growth is obtained by evaluating cally polished to permit crack length measurements. the crack growth parameter, N, which is defined in the empirical relation between crack growth rate (v) and stress intensity factor (K I ): III. Results and DiscussionThe InP specimens showed very unusual crack growth behavior. At times, crack velocities were constant over the where A is an adjustable parameter. 1 The larger N is, the less time interval measured; at other times, crack velocities were susceptible the system is to environmentally enhanced fracture. observed either to increase or to decrease at constant K I . For More generally, traditional views of crack growth assume a most loads, however, no crack growth was observed. Figure 2 steady-state process in which v is described by a single parameshows data from a typical specimen; the open circles denote ter, K I , regardless of the specific functional dependence. In this actual crack velocity measurements at different stress intensity communication, we report results of double cantilever beam (DCB) measurements to determine the relationship between crack tip velocity and stress intensity for single-crystal InP in liquid water. InP is a III-V semiconductor of technological interest due to its infrared optical properties. InP has the same structure (zinc blende) and similar bonding to GaAs. It was initially expected, therefore, that th...

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Crack propagation in alkaline-earth fluorides

Cited by 36 publications

References 8 publications

Microcracking in calcite and dolomite marble: microstructural influences and effects on properties

Microcracking in calcite and dolomite marble: microstructural influences and effects on properties

Single crystal cleavage of brittle materials

Double Cantilever Beam Measurements of Crack Growth in Indium(III) Phosphide

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