Anisotropy in the hardness and friction of calcium fluoride crystals

O'Neill, J. B.; Redfern, B. A. W.; Brookes, C. A.

doi:10.1007/bf00755582

Cited by 27 publications

(9 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The friction coefficients measured with the sharp stylus in [1 0 0] and [1 1 0] directions were 0.20 and 0.23, respectively. Similar frictional anisotropy at room temperature (0.62 vs. 0.64) was reported by O'Neill et al [10] They explained the stronger friction in the softer [1 1 0] direction by plowing with the stylus through the hills of displaced material.…”

Section: Friction Experimentssupporting

confidence: 83%

“…3(b). In the Knoop indentation experiment at CaF 2 (1 1 1) by O'Neill et al [10], similar slip pattern was observed with optical microscopy only on one side of the indenter set with the long diagonal placed along the <1 -1 0> direction.…”

Section: Indentation Experimentssupporting

confidence: 57%

“…The slip patterns observed are explained by the {1 0 0}<0 1 1> slip. The small Knoop hardness in <1 -1 0> directions at the (0 0 1) face [10] is also explained by the relative easiness of the slip.…”

Section: Indentation Experimentsmentioning

confidence: 93%

“…Steijn [9] discussed plastic deformation during sliding wear at CaF 2 (1 1 1) surface by analyzing distribution of dislocations formed. O'Neill et al [10] studied anisotropy in Knoop hardness and friction at (0 0 1) and (1 1 1) surfaces. These workers observed cracks and dislocation etch pits with optical microscopy.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Participation of {1 0 0}<0 1 1> Slip System in Sliding Friction at (0 0 1), (1 1 1) and (1 1 0) Surfaces of Fluorite (CaF2) Crystal

2012

View full text Add to dashboard Cite

Indentation experiments and friction measurements were performed at three low index faces of fluorite (CaF 2) crystal. Deformation patterns were analyzed by observing step structures with atomic force microscopy (AFM). Upon indentation at (0 0 1) surface, {1 0 0}<0 1 1> slip steps were formed at limited parts of the surface near the compressed area, where horizontal shear stress is added to vertical one. Upon indentation at (1 1 1) surface, the surface was split into 6 sectors separated by {1 1 1} cleavage lines. Steps formed on each sector were also explained by the {1 0 0}<0 1 1> slip. The signs of steps suggest that the steps in three alternate sectors were formed by vertical compression, and the steps in the other sectors were formed mainly by horizontal compression. The slip mechanism was explained by a simple mechanical model. Upon scratching the (0 0 1) surface in [1 0 0] direction, only steps in [1 0 0] direction, not in [0 1 0] direction, were formed outside the wear track. Scratch on (1 1 1) surface activated the slip in three possible directions selectively, depending upon the scan directions of the stylus. Slip did not occur easily at (1 1 0) surface, where slip can occur in five directions close to each other. Frictional anisotropy was discussed in relation to the slip system.

show abstract

Section: Friction Experimentssupporting

confidence: 83%

Section: Indentation Experimentssupporting

confidence: 57%

Section: Indentation Experimentsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Participation of {1 0 0}<0 1 1> Slip System in Sliding Friction at (0 0 1), (1 1 1) and (1 1 0) Surfaces of Fluorite (CaF2) Crystal

2012

View full text Add to dashboard Cite

show abstract

“…Noteworthy assessments of different crystal hardness anisotropy measurements have been reported by Brookes [263], Sargent and Page [264]. Individual crystal anisotropy measurements and analyses have been obtained on many crystals, including the following ones: calcium fluoride [265]; calcium and sodium nitrate [266]; MgO [267]; LaB 6 [268]; energetic (explosives) [269]; anthracene [270]; rare earth garnets [271]; magnesium sulphate hepta-hydrate [272]; gamma-TiAl [273]; and, a nickel base superalloy [274]. A result from the latter reference is shown in the square-framed spherically-modified indentation of Fig.…”

Section: Crystal Hardness and Plastic Anisotropymentioning

confidence: 99%

Elastic, Plastic, Cracking Aspects of the Hardness of Materials

Armstrong

Elban

Walley

2013

Int. J. Mod. Phys. B

View full text Add to dashboard Cite

The hardness properties of materials are tracked from early history until the present time. Emphasis is placed on the hardness test being a useful probe for determining the local elastic, plastic and cracking properties of single crystal, polycrystalline, polyphase or amorphous materials. Beginning from connection made between individual hardness pressure measurements and the conventional stress–strain properties of polycrystalline materials, the newer consideration is described of directly specifying a hardness-type stress–strain relationship based on a continuous loading curve, particularly, as obtained with a spherical indenter. Such effort has received impetus from order-of-magnitude improvements in load and displacement measuring capabilities that are demonstrated for nanoindentation testing. Details of metrology assessments involved in various types of hardness tests are reviewed. A compilation of measurements is presented for the separate aspects of Hertzian elastic, dislocation-mechanics-based plasticity and indentation-fracture-mechanics-based cracking behaviors of materials, including elastic and plastic deformation rate effects. A number of test applications are reviewed, most notably involving the hardness of thin film materials and coatings.

show abstract

Microindentation hardness of oriented chain‐extended polyethylene

Baltà‐Calleja

Bassett

1977

J. polym. sci., C Polym. symp.

View full text Add to dashboard Cite

SYNOPSISThe Knopp and Vickers microindentation hardnesses of oriented chain-extended polyethylene (cold-drawn, then hydrostatically annealed at 5-35 kbar) have been measured to establish correlations with some of the morphological features previously investigated (lamellar thickness, orientation). The irreversible deformation increases with time under load and tends towards a characteristic limiting value for each annealing temperature. This limiting value of microhardness is an increasing function of annealing temperature, TA, and consequently of chain extension, I . A conspicuous feature of the investigated oriented polyethylene samples is the clear anisotropy exhibited by the indentation pattern. The Vickers microhardness is a maximum when the indenter diagonal lies parallel to the fiber direction and minimum when normal to it. The opposite occurs for the Knoop case. This contrary behavior is due to the shape difference between the two indenters coupled with the high anisotropy of the material. This behavior supports morphological experiments and is a further illustration of the value of this technique in polymer textural studies. mainly a consequence of high orientation of polymer chains in both crystalline and noncrystalline regions. For anisotropic polymers, for instance, there are different hardness values depending on the direction of test. For uniaxially aligned chains there are at least two values of MH: parallel and perpendicular

show abstract

Anisotropy in the hardness and friction of calcium fluoride crystals

Cited by 27 publications

References 14 publications

Participation of {1 0 0}<0 1 1> Slip System in Sliding Friction at (0 0 1), (1 1 1) and (1 1 0) Surfaces of Fluorite (CaF2) Crystal

Participation of {1 0 0}<0 1 1> Slip System in Sliding Friction at (0 0 1), (1 1 1) and (1 1 0) Surfaces of Fluorite (CaF2) Crystal

Elastic, Plastic, Cracking Aspects of the Hardness of Materials

Microindentation hardness of oriented chain‐extended polyethylene

Contact Info

Product

Resources

About