Anisotropy of deformation and fracture processes in sapphire surface

Voloshin, A. V.; Dolzhenkova, E. F.; Litvinov, L. A.

doi:10.3103/s106345761505007x

Cited by 15 publications

(6 citation statements)

References 3 publications

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“…The atomic density of C-plane is significantly higher than that of M-plane, 0.2254 and 0.1199 at/Å, respectively. 30…”

Section: Methodsmentioning

confidence: 99%

“…Figure 1(b) and (c) shows the crystal lattices of sapphire viewed from the [0001]and ½10 10 directions, respectively. The atomic density of C-plane is significantly higher than that of M-plane, 0.2254 and 0.1199 at/Å , respectively 30.…”

mentioning

confidence: 86%

“…29 Besides, the C- and A-planes of sapphire exhibit the greatest anisotropy in scratching hardness, and the C-plane demonstrates the highest resistance to surface fracture. 30 However, the ground surface roughness of A-plane is lower than that of C-plane because the machining-induced cracks on C-plane are at a larger angle to the machined surface compared with that on A-plane. 31 This study preliminarily stated the influence of crack orientation on the machined surface roughness for different crystal planes of sapphire.…”

Section: Introductionmentioning

confidence: 99%

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Investigation into the anisotropy of cross-grinding surface quality in C- and M-planes of sapphire

Wang

Guo

Zhao

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part B:

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Sapphire is an important material for optical applications, but the anisotropy of key properties makes it difficult to obtain uniform ground surface. In this work, cross-grinding experiments were first conducted on C- and M-planes of sapphire to investigate the dependence of the ground surface quality on crystal orientation. Then, scratching tests were performed along the specific crystal orientations to explain the formation mechanism of the anisotropic grinding patterns. The results showed that the surface roughness distribution on C-plane is of a threefold symmetry, while one axis of symmetry for M-plane. The damage pits on C-plane possess lower aspect ratio than that on M-plane. By combining the scratching-induced fracture features with the contact-induced deformation theory of sapphire, it was found that the propagation of the primary cracks in sapphire is accompanied by activating different deformation systems. The material removal on C-plane is dominated by the shallow lateral cracks, which propagate parallel to the ground surface and result in shallow and wide pits. However, the deep lateral cracks play an important role on M-plane, which intersect with the ground surface and cause deep and dense defects. The non-uniformity of the ground surface is attributed to the appearance of radial cracks for C-plane, while it is associated with the number of the available deformation systems for M-plane.

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“…The atomic density of C-plane is significantly higher than that of M-plane, 0.2254 and 0.1199 at/Å, respectively. 30…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Investigation into the anisotropy of cross-grinding surface quality in C- and M-planes of sapphire

Wang

Guo

Zhao

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…Therefore, there is a high demand for a method for efficiently machining it with no surface and subsurface damage and without the drawbacks of the current techniques. Sapphire shows a high anisotropic behavior; therefore, the effect of its crystal orientation on the machining is also another challenge for this material [9][10][11]. Machining sapphire in ductile mode has been reported by a few researchers.…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermal Softening on Anisotropy and Ductile Mode Cutting of Sapphire Using Micro-Laser Assisted Machining

Mohammadi

Patten

2017

Journal of Micro and Nano-Manufacturing

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Ceramics and semiconductors have many applications in optics, micro-electro-mechanical systems, and electronic industries due to their desirable properties. In most of these applications, these materials should have a smooth surface without any surface and subsurface damages. Avoiding these damages yet achieving high material removal rate in the machining of them is very challenging as they are extremely hard and brittle. Materials such as single crystal silicon and sapphire have a crystal orientation or anisotropy effect. Because of this characteristic, their mechanical properties vary significantly by orientation that makes their machining even more difficult. In previous works, it has been shown that it is possible to machine brittle materials in ductile mode. In the present study, scratch tests were accomplished on the monocrystal sapphire in four different perpendicular directions. A laser is transmitted to a diamond cutting tool to heat and soften the material to either enhance the ductility, resulting in a deeper cut, or reducing brittleness leading to decreased fracture damage. Results such as depth of cut and also nature of cut (ductile or brittle) for different directions, laser powers, and cutting loads are compared. Also, influence of thermal softening on ductile response and its correlation to the anisotropy properties of sapphire is investigated. The effect of thermal softening on cuts is studied by analyzing the image of cuts and verifying the depth of cuts which were made by using varying thrust load and laser power. Macroscopic plastic deformation (chips and surface) occurring under high contract pressures and high temperatures is presented.

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“…Beyond the referenced-above consideration of hardness-determined elastic deformation behavior of sapphire, its hardness properties have been investigated to relate with abrasive wear resistance [25]. Tribological concern has been with chemomechanical aspects of sapphire crystal, …”

Section: Applicationsmentioning

confidence: 99%

Crystal Indentation Hardness

2017

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Abstract:There is expanded interest in the long-standing subject of the hardness properties of materials. A major part of such interest is due to the advent of nanoindentation hardness testing systems which have made available orders of magnitude increases in load and displacement measuring capabilities achieved in a continuously recorded test procedure. The new results have been smoothly merged with other advances in conventional hardness testing and with parallel developments in improved model descriptions of both elastic contact mechanics and dislocation mechanisms operative in the understanding of crystal plasticity and fracturing behaviors. No crystal is either too soft or too hard to prevent the determination of its elastic, plastic and cracking properties under a suitable probing indenter. A sampling of the wealth of measurements and reported analyses associated with the topic on a wide variety of materials are presented in the current Special Issue.

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Anisotropy of deformation and fracture processes in sapphire surface

Cited by 15 publications

References 3 publications

Investigation into the anisotropy of cross-grinding surface quality in C- and M-planes of sapphire

Investigation into the anisotropy of cross-grinding surface quality in C- and M-planes of sapphire

Effect of Thermal Softening on Anisotropy and Ductile Mode Cutting of Sapphire Using Micro-Laser Assisted Machining

Crystal Indentation Hardness

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