**7. Wear and polishing mechanism formed in the use of sandpaper**

It is the name of grinding product formed as a result of covering abrasive grains on sandpaper, paper or on a cloth with a binding agent. Sandpaper is widely used for abrading and polishing of surfaces that are made of metal, glass, porcelain, stone, wood…etc. materials.

When glass machine profile is analyzed, it will be seen that abrading is done with abrasive grains that are lined at different positions. Effective factors in abrading process are; disc grain shape, solidity and height, its angle to the surface, applied load and form of bonding material and so the life of paper.

Contact angle of abrasive grain and surface is the most significant effective factor on wear as is given in the definition of adhesive wear.

Abrasive grains make cutting, friction and break through movements in different amounts according to the edge structure and location. Most of the studies focus on chip formation with cutting and occasions according to this.

Chip on the surface that is created by abrasive grain is given in Figure 21 in a simplified way.

In Figure 22, chip formation on brittle material is presented. Simplified chip formation model show that change of shape generally occurs in narrow space at shear plane or in an area called shear area (Figure 21). Permanent change of shape is complex in this area. But it is probably in the shape of hydrostatic component tensile type that will stay on the new surface. Namely, crack that will enable the formation of new surface is tension crack.

Theories on Rock Cutting, Grinding and Polishing Mechanisms 205

**Figure 21.** Chip formation model (Samuels, 1971).

204 Tribology in Engineering

materials.

way.

that is formed as a result of abrading.

secondary importance in removing material.

processes that will create smooth surfaces.

material and so the life of paper.

is given in the definition of adhesive wear.

with cutting and occasions according to this.

According to Regiani et al. (2000), basic mechanisms in material wear are; grains breaking, smashing, formation of ductile chip, and spalling. Wear of these types of materials are affected from various variables. Viscosity of used liquid, applied force on the disc, type of the disc and small scaled form of the material that is abraded are the most important of these. Small scaled form of the material has a significant effect on the development of crack

Regiani et al. (2000) stated that small scaled formation whose shape and crystal lengths of crystals that form the material are more enduring to wear than homogenous small scaled formation whose shape and whose crystal grains' lengths are similar. Again, according to Regiani et al. (2000), intrusion, gaps and crystal grain limits behave like borders for crack progress at each type of abrading process. Used liquid, size and type of disc have the

As a result, volumetric wear according to different operations haven't been revealed yet. Complete understanding of wear will enable the development of productive abrading

It is the name of grinding product formed as a result of covering abrasive grains on sandpaper, paper or on a cloth with a binding agent. Sandpaper is widely used for abrading and polishing of surfaces that are made of metal, glass, porcelain, stone, wood…etc.

When glass machine profile is analyzed, it will be seen that abrading is done with abrasive grains that are lined at different positions. Effective factors in abrading process are; disc grain shape, solidity and height, its angle to the surface, applied load and form of bonding

Contact angle of abrasive grain and surface is the most significant effective factor on wear as

Abrasive grains make cutting, friction and break through movements in different amounts according to the edge structure and location. Most of the studies focus on chip formation

Chip on the surface that is created by abrasive grain is given in Figure 21 in a simplified

In Figure 22, chip formation on brittle material is presented. Simplified chip formation model show that change of shape generally occurs in narrow space at shear plane or in an area called shear area (Figure 21). Permanent change of shape is complex in this area. But it is probably in the shape of hydrostatic component tensile type that will stay on the new

surface. Namely, crack that will enable the formation of new surface is tension crack.

**7. Wear and polishing mechanism formed in the use of sandpaper** 

**Figure 22.** Discontinuous chip creation on brittle material surface (Boothroyd, 1975)

According to Boathroyd (1975), contact angle between abrasive grain and surface is very significant in the process of abrading in order to determine chip formation. on the other hand, deformation distribution of chip area is also affected from this contact angle.

As a result, there is a limiting contact angle for abrasive grains and grinding tip cuts a chip on this angle while it grooves under it. When abraded surfaces are analyzed, it was seen that very few of the scratches are formed as a result of cutting of material in the shape of chip (Samuels, 1971). Abrasive grain grooves on contact points on material surface mostly by breaking through and friction but it removes small amount of material. Very few of them create chips with grating movement and this is more effective in removing material.

Theories on Rock Cutting, Grinding and Polishing Mechanisms 207

[1] Archard, J.F., 1953, Contact and Rubbing of Flat Surfaces, Journal of Applied Physics,

[3] Boathroyd G., 1975, Fundamentals of Metal Machining and Machine Tools, Scripta

[4] Bortolussi, A., Ciccu, R., Manca, P.P. and Massacci, G., 1994, Computer Simulation of Diamond-Wire Cutting of Hard Rock and Abrassive Rock, IMM, Vol. 103, August, pp.

[6] Chandrasekar, S. and Farris, T.N., 1997, Machining and Surface Finishing of Brittle

[7] Chen, X. and Rowe, W. B., 1996, Analysis and Simulation of the Grinding Process. Part 2 Mechanics of Grinding, International Journal of Machine Tools and Manufacture, Vol:

[9] Kato, K., Hokkirigawa, K., Kayabo, T. and Endo, Y., 1986, Three Dimensional Shape

[10] Konstanty, J., 2002, Theoretical Analysis of Stone Sawing With Diamonds, Journal of

[11] Lawn, B.R. and Swain, M.V., 1975, Microfracture Beneath Point Indentations in Brittle

[12] Moore, D.F., 1975, Principles and Application of Tribology, Mechanical Engineering

[13] Ozcelik Y., Kulaksiz S., Cetin M.C., 2002, Assessment of the wear of diamond beads in the cutting of different rock types by the ridge regression, Journal of Materials

[14] Regiani, I., Fortulan, C. A. and Purquerio, B.M., 2000, Abrasive Machining of Advanced

[15] Salmon, S. C., 1992, Modern Grinding Process Technology, McGrawHill Inc.

[16] Samuels, L.E., 1971, Metallographic Polishing by Mechanical Methods, American

[17] Suh, N. P. and Saka, N., 1978, Fundamentals of Tribology, Proceedings of the Internatonal Conference on the Fundamentals of Tribology, M.I.T. press, pp. 400-405 [18] Summers, J.D., 1994, An Introductory Guide to Industrial Tribology, Mechanical

[19] Wang, C.Y. and Clausen, R., 2002, Marble Cutting with Single Point Cutting Tool and Diamond Segments, International Journal of Machine Tools & Manufacture, Vol.42,

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[5] Bowden, F.P. and Hughes, T. P., 1937, Proc. Roy. Soc., p. 575

[8] Coes, L., 1971, Abrasives, Springer-Verlag, New York, p. 177

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Solids, Journal of Material Science, 10, pp. 113-122

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pp 83-101

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**8. References** 

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A55-A128.

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Rapid material wear is ensured by applying high loads and low decreasing speed in proportion to high amounts of cutting points, namely by low wear speed of sandpaper. These factors ensure high abrading speed and prevent formation of smooth and shiny surface.

Another intended purpose of sandpaper and cloth is polishing. Mechanism in polishing process is in fact very similar to abrading. It can be said that force affecting each abrasive grain determines depth and width of scratches on the surface of basic material. So, in order to make polishing operations on abraded surfaces, very low loads should be applied on abrasive grain and abrasive grain's height should be very low. Although sandpaper is used in the first step of polishing that is made with sandpaper, polishing cloth (Figure 23) is used in the last step in order to lessen the scratch depth and form shinier surfaces.

**Figure 23.** Mechanical polishing mechanism of abrasive grain that is clung on the polishing cloth fibre

As can be seen in Figure 23, abrasive grains in polishing cloth is inside the fibers of cloth. Grains affect on the material surface only with elastic force and ensure the creation of narrower and shallow scratches. In this way, shinier surfaces are achieved.
