Title of Invention	"A NOVEL VISCOELASTIC MEDIA USED FOR NANO-FINISHING OF MATERIALS AND A PROCESS FOR THE PREPARATION THEREOF"
Abstract	This invention relates to a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process comprising of viscoelastic material, 1 -90% by weight of abrasive particles (with respect to the said viscoelastic material) and 1-50% by weight of processing oil (with respect to the said viscoelastic material). Further, a process for preparation of viscoelastic media comprising steps of: mixing of 1-90% by weight of abrasive particles and 1-50% by weight of processing oil in viscoelastic material in a two-roll mill such as herein described.

Title of Invention

"A NOVEL VISCOELASTIC MEDIA USED FOR NANO-FINISHING OF MATERIALS AND A PROCESS FOR THE PREPARATION THEREOF"

Abstract

This invention relates to a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process comprising of viscoelastic material, 1 -90% by weight of abrasive particles (with respect to the said viscoelastic material) and 1-50% by weight of processing oil (with respect to the said viscoelastic material). Further, a process for preparation of viscoelastic media comprising steps of: mixing of 1-90% by weight of abrasive particles and 1-50% by weight of processing oil in viscoelastic material in a two-roll mill such as herein described.

Full Text	FIELD OF INVENTION This invention relates to a novel viscoelastic media used for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof. It can be used for grinding, deburring, radiusing, leveling of surface, polishing, etc, on flat / contour / three dimensional edge(s) / surface(s) / feature(s), both in external and internal surface (s). BACKGROUND OF INVENTION The higher level of surface finish, surface integrity and controlled corner/edge radii improves the performance as well as its life [Rhoades, L. J., (1988), "Abrasive flow machining," Manufacturing engineering, pp 75-78; Inasaki, I., Tonshoff, H. K., and Howes, T. D., (1993), "Abrasive machining in future", Annals of the CIRP, Vol.42/2, pp 723-732]. Generally, abrasive process has been proven to be inefficient for finishing or deburring for inaccessible domains. Researchers in mid - 60's at EXTRUDEHONE, USA came out with new process "Abrasive Flow Machining" which could solve this problem. Mccarty [Mccarty, R. W., U.S. Pat. No. 3,521,412, July 21, 1970] in his invention used silicon putty as a media. The three ingredients in his composition were 1) G.E. silicon putty SS-91 grade - 35%, isopropyl stearate (softner) - 3%, silicon grease (adds lubricity) - 2%, silicon carbide abrasives #120 grade - 60%. 2) Silicon putty - 1 pounds, aluminum oxide (100 gran size) - 6 pounds, methyl phenyl silicon fluid - 1 ounces (125 centistoke, G.E. Co.), tetrafluoroethylene powder - 2 ounces. 3) Kneaded rubber (isobutene) - 1 pounds, aluminum oxide (100 grains size) - 4 pounds, silicon fluid - 3 ounces, Teflon powder - 1 ounces.Rhoades et al [Rhoades, L. J., (1990), "Method of finishing machining the surface of irregularly shaped fluid passages", U.S. Pat. No. 4,936,057; Rhoades, L. J., (1991), "Process and apparatus of abrading by extrusion", U.S. Pat. No. 4,996,796; Rhoades, L. J., (1991), "Process for abrasive flow machining using multiple cylinders", U.S. Pat. No. 5,076,027; Rhoades, L. J., (1992), "Abrasive flow machining with an in situ viscous plastic medium", U.S. Pat. No. 5,125,191; Rhoades, L. J., (2003), "Method and apparatus for the region of intersection between a branch outlet and a passageway in a body", U.S. Pat. No. 6,503,126 Bl; Rhoades, L. J., Kohut, T. A., Nokovich, N. P., and Yanda, D. W., (1991), "Reversible unidirectional abrasive flow machining", U. S. Pat. No. 5,070,652; Rhoades, L. J., Kohut, T. A., Nokovich, N. P., and Yanda, D. W., (1994), "Unidirectional abrasive flow machining", U. S. Pat. No. 5,367,833; Rhoades, L. J., Nokovich, N. P., Kohut, T. A., and Johnson, F. E., (1991), "Method of controlling flow resistance in fluid orifice manufacture", U. S. Pat. No. 5,054,247] in his invention used dry pulverulent: Guar gum, 50 to 75 percent; boric acid 30 to 40 percent; borax 1.0 to 2.5 percent; high molecular weight polysaccharide 0.25 to 0.60 percent (as indicated by the trade designation B-1459 in Ahrabi patent) by weight. The water, oil and abrasive were the other ingredients of media. A sample percentage range of ingredients by volume are: precursor - 1, water - 2 to 50, silicon oil - 0 to 10, grit - 0 to 50. Along with the media varying abrasives in the size of 6 to 10 microns were used. He also invented a new method for finishing machining of irregular shape fluid passages and multi cylinder AFM. Davis and Fletcher [Davies, P. J., Fletcher, A. J., ( 1995), "The assessment of the Theological characteristics of various polyborosiloxane/grit mixtures as utilized in the abrasive flow machining process', Journal of mechanical engineering science: Proc Instn. Mech. Engrs, Vol 209, pp 409-418] also used PBS/silicon carbide mixture of different viscosity and concluded that the relation between number of cycles and both the temperature and pressure drop across the die are dependent upon medium type and abrasives-polyborosiloxane(PBS) ratio. They found that average viscosity and pressure drop decreases as abrasives-polyborosiloxane ratio increases, irrespective of mesh size and type of PBS. The mesh size has minimal effect on Theological parameters. Fletcher and Fioravanti [Flether, A. J., Fioravanti, A., (1996), "Polishing and Honing Processes: An Investigation of the thermal Properties of Mixture of Polyborosiloxane and Silicon carbide abrasive", Proc. Instn Mech. Engrs, Part C: Journal of Mechanical Engineering Science, Vol.210,pp. 255-265] investigated for the polyborosiloxane (PBS) and silicon carbide abrasive mixture that the thermal conductivity of the composite sharply increases when concentration of abrasives reached 50 percent by mass. The surface heat transfer coefficient at the interface between the media and die is a primarily function of abrasive concentration, whereas the mesh size and polymer type have very slight influence. The theoretical, semi-empirical and empirical models are also derived by them for the thermal properties as a function of material composition and temperature. Liebke et al [Liebke, R. W., Dawson, D. R., Fredette, M. A., and Goodstein, M. B., (1997), "Method of removing excess overlay coating from within colling holes of aluminide coated gas turbine engine components", U. S. Pat. No. 5,702,288] invented the application of abrasive flow machining for removing excess overlay coating from within cooling holes of aluminide coated gas turbine engine components. For that they have used extrude Hone corporation media #831-G-1 for abrasive slurry. Klein [Klein, E. J., (1998), "Apparatus and method for polishing lumenal prostheses", U. S. Pat. No. 5,788,558] invented the application of abrasive flow machining for deburring and rounding edges and polishing surfaces of radially expansible luminal prostheses, such as stents and grafts are provided. The slurry used by him is mixture of polyborosiloxanes, silicon oil and abrasives. Perry [Perry, W. B., (1998), "Method and apparatus for controlling the diameter and geometry of an orifice with an abrasive slurry", U.S. Pat. No. 5,807,163; Perry W. B (2000), "Abrasive liquid slurry for polishing and radiusing a microholes", U.S. Pat. No. 6,132,482] invented a new method and its apparatus for controlling orifice size and form geometry with abrasive slurry. Perry used abrasive, rheological additives and fluid media such as cutting fluids, honing fluids and the like, which are distinct from semisolid polymer composition. Perry et al [Perry, W. B., Liam, O., and Wright, M., (2001), "System for controlling the size and surface geometry of an orifice", U.S. Pat. No. 6,306,011 Bl] invented system for controlling the size and surface geometry of an orifice. Shaw [Shaw, J. S., (2001), "Free flow abrasive hole polishing", U.S. Pat. No. 6,234,872 Bl] invented a free flow hole polishing system for improving air flow which resulted better cooling efficiency. The slurry used was of abrasive and water only. Jain et al [Jain, V. K., Ranganatha, C, and Muralidhar, K. (2001), "Evaluation of rheological properties of medium for AFM process", Machining science and technology, Vol.5 (2), pp 151-170] used mixture of commercial grade sealing putty, varnish oil and abrasive as AFM media and studied the effect of temperature of media, concentration and mesh size of abrasives on the viscosity. Gilmore and Rhoades [Gilmore, J. R., and Rhoades, L. J., (2005), "Abrasive polishing composition", U.S. Pat. No. 6,918,937 B2; Gilmore. J. R, Rhoades. L. J (2003), "Abrasive polishing apparatus", U. S. Pat. No. 6,544,110 B2; Gilmore, J. R., and Rhoades, L. J., (2003), "Self-forming tooling for an 0rbital polishing machine and method for producing the same", U. S. Pat. No. 6,645,056 Bl] invented improved orbital AFM with abrasive viscoelastic medium, which had a composition of "a viscoelastic poly (boro-siloxane) polymer carrier having a static viscosity from about 5X103 to 5X105 centipoises; a particulate abrasive; an optional inert filler in an amount of up to about 25% by weight of said medium; optional plasticizing lubricant up to 25% by weight of said medium; abrasive types : alumina, silica, garnet, silicon'carbide, diamond, tungsten carbide and mixtures. By using the above composition Gilmore and Rhoades were able to achieve 0.2 micro-inches Ra in tool steel dies in two stages. First boron carbide abrasive composition was used and second time 2\|um diamond abrasive was used. The second example is of polishing a plurality of forged aluminum 3D complex shape component and achieved Ra is 20 to 25 micro-inches from 100 to 120 micro-inches initial Ra. Third example is of cast aluminum automotive wheel with complex shape and its initial Ra 145 to 175 micro-inches whereas achieved Ra is 20 to 25 micro-inches. Inventor said that for this invention polymer gels, particularly hydrogels, non-aqueous polymer formulations and poly (borosiloxanes) can be adapted. In another invention, Gilmore and Rhoades [Gilmore, J. R., Rhoades, L. J., (2005), "Abrasive polishing composition", U.S. Pat. No. 6,918,937 B2] invented abrasive polishing apparatus as well as self - forming tool for orbital polishing machine and method. Agrawal et al [Agrawal, A., Jain, V. K., and Muralidhar, K., (2005), "Experimental determination of viscosity of abrasive flow machining media", International Journal of Manufacturing Technology and Management, v 7, n 2-4, 2005, pp 142-156] studied viscosity of commercial media with the help of fabricated viscometer based on the principle of visco-elasticity. Raju et al [Raju, H. P., Narayanasamy, K., Srinivasa, Y. G., and Krishnamurthy, R., (2005), "Characteristics of extrude honed SG iron internal primitives", Journal of materials processing technology, Vol.166, pp 455-464] used grade (40) of silicone polymer as carrier medium with silicon abrasives for extrude honing of SG cast iron 600. OBJECTS OF THE INVENTION An object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof in which the media is very cost effective (max Rs. 300/Kg) as compared to known high cost existing commercial media (Rs. 2, 50, OOO/- per kg). Another object of this invention is to propose a novel viscoelastic media for nano-fmishing of materials through abrasive flow machining process and a method of manufacture thereof to obtain surface finish of workpiece at nanoscale. Still another object of this invention is to propose a novel viscoelastic media for nano-fmishing of materials through abrasive flow machining process and a method of manufacture thereof in which the media can be used to machine all types of materials i.e. very hard metal to soft metal including composite materials. Yet further object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof which can be used for all types of existing abrasive flow machining processes. Still further object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof utilizing less number of ingredients, which are easily available at very low cost. Yet another object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof in which fabrication for media is simple and quite cost effective, which can employ all types of abrasive flow machining processes. Still another object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof in which the fabrication method is safe, non toxic and environmental friendly and useful for all types of abrasive flow machining processes. Still further object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof, which can efficiently work for abrasive machining processes. Further objects and advantages of this invention will be more apparent from the ensuing description. STATEMENT OF INVENTION According to this invention there is provided a novel viscoelastic media for nano-fmishing of materials through abrasive flow machining process comprising of viscoelastic material, 1-90% by weight of abrasive particles (with respect to the said viscoelastic material) and 1-50% by weight of processing oil (with respect to the said viscoelastic material). Further according to this invention there is provided a process for preparation of viscoelastic media comprising steps of:mixing of 1-90% by weight of abrasive particles and 1-50% by weight of processing oil in viscoelastic material in a two-roll mill such as herein described. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Further objects and advantages of thiis invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein: Fig. 1 shows a schematic diagram of two-way abrasive flow machining type in house fabricated setup that is used for present invention. Fig. 2 shows AFM image of carbon-carbon workpiece before machining, which is high performance composite material. The surface roughness is ~ 353 nm. Fig. 3 shows AFM image of carbon-carbon workpiece after machining. The surface roughness is -22 nm. It is in the nano-scale. The improvement of surface roughness of carbon-carbon composite is -94%. Fig. 4 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is ~ 16 nm. The improvement of surface roughness of carbon-carbon composite is -96%. Fig. 5 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is ~ 33nm. The improvement of surface roughness of carbon-carbon composite is -91%. Fig. 6 shows Another AFM image of carbon-carbon workpiece after machining. The surface roughness is ~ 24 nm. The improvement of surface roughness of carbon-carbon composite is -93%. Fig. 7 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is -34 nm. The improvement of surface roughness of carbon-carbon composite is -90%. Fig. 8 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is - 9 nm. The improvement of surface roughness of carbon-carbon composite is -98%. Fig. 9 shows AFM image of En8 workpiece before machining. The surface roughness is ~ 740 nm Fig. 10 shows AFM image of En8 workpiece after machining (1800 cycles). The surface roughness is ~ 50nm. The improvement of surface roughness of En8 high performance material is -87%. Fig. 11 shows AFM image of Aluminium workpiece before machining. The surface roughness is -365 nm Fig. 12 shows AFM image of Aluminium workpiece after machining (100 cycles). The surface roughness is ~ lOnm. The improvement of surface roughness is -97%. Figure 13 shows Effect of number of cycles on improvement of Ra using various loading of abrasive particle. (A: Aluminium and B: En8) Figure 14 shows Effect of number of cycles on improvement of Ra for carbon-carbon composites Figure 15 shows Effect of number of cycles on improvement of Ra using various sizes of abrasive particle (A En8 and B: carbon-carbon composites) Figure 16 shows Effect of number of cycles on improvement of Ra using various loading of process oil. (A: Aluminium and B: En8) Figure 17 shows Effect of viscbelastic media on Ra (A: Aluminium; B En8) Figure 18 shows Effect of operating pressure on Ra Figure 19: shows Effect of shear rate on viscosity of viscoelastic media-1 (D 33% abrasive 1,D 50% abrasive 1, D33% abrasive 2, D 50% abrasive 2 Figure 20: shows Modulus-strain- plot of viscoelastic media Figure 21: shows (A) Effect of abrasive loading, (B) process oil (C) temperature and (D) particle size on creep compliance of viscoelastic media-1 DETAIL DESCRIPTION OF INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS According to this invention, media comprises of viscoelastic material/s, abrasive particle/s and process oil/s and mixture thereof. Viscoelastic media is selected from the groups comprising of natural rubber, polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber, ethylene-propylene rubber, ethylene-propylene diene-monomer rubber, butyl rubber, halobutyl rubber, nitrile rubber, hydrogenated nitrile rubber, polysulfide rubber, polyacrylic rubber, neoprene rubber, hypalon rubber, silicone rubber, fluorocarbon rubber, polyurethane rubber, thermoplastic elastomer, and mixture thereof. Abrasive particle is selected from the group comprising of alumina, silicone carbide, diamond powder, boron carbide, silica, garnet, tungsten carbide, etc. wherein particle size of the abrasive particle varies from 5 nm to 75jam. Process oil is selected from the group comprising of paraffmic oil, naphthenic oil, aromatic oil, vegetable oil, and mixture thereof. Mixing of abrasive particle/s, and process oil/s in viscoelastic material/s is carried out using two-roll mill having rolls of 150 mm in diameter at a temperature of 50 to 125QC depending on the type of viscoelastic material. The speed of front roll is in between 10 to 34 rpm and friction ratio between front and rear roll is 1:1.1 to 1: 1.5. The clearance between rolls is adjustable from 0.1 to 12 mm. During mixing, at first the viscoelastic material/s is/are fed into the nip gap of two roll to get a thin sheet. Then abrasive particles in powder form are added slowly followed by process oil. The batch is cut % of the distance across the roll with the help of a knife, and held the knife at this position until the bank just disappears. This process is continued for about 10 minutes. The materials falling through the nip is collected carefully from the tray and returned back to the mix. The mixing cycle is concluded by passing the rolled batch endwise through the mill six to eight times with an opening of 0.2 mm to improve the dispersion. Finally, the mixed compound is passed four times through the mill at a setting of 0.1 mm, folding it back on itself each time. The batch is removed and kept on the glass sheet, in a closed container to prevent absorption of moisture from the air for 24 hours. This media is used in the AFM (Fig. 1) setup for machining. Set-up details The experiments are conducted on a set-up as shown in Fig.l. The surface roughness is measured by "Surftest SJ 301" of "Mitutoyo" make and Atomic force microscopy [PicoScan 5.3.1, Molecular Imaging, USA; Cantilever: NSC36(A)(gold coated) from MikroMasch at Force constant: 1.0 N/m and Frequency: 110 KHZ]. During the experiment, the stroke length is 40 mm and the reduction ratio (Fixture passage diameter / bore diameter) is 0.274. The surface roughness is reported in terms of improvement in percentage and calculated by the following formula: A f InitialRa-FinalRa _.in_ Average improvement (%) = X100 Initial Ra ) The experimental results are reproducible within ±10%. Workpieces are selected from the group of materials i.e., Inconel, Monel, Titanium and its alloy, Al and its alloy, Mg and its alloy, Stainless steel, Cermet i.e., TiCN - Ni, WC-Co, ceramics ie., all oxide ceramics (Alumina, ZrO), all non oxide ceramics (WC, SiC, B4C, CBN, PCBN), carbon-carbon composites, particulate reinforced metal matrix composites, long fiber reinforced metal matrix composites, nanoparticles reinforced metal matrix composites, particulate reinforced ceramic matrix composites, long fiber reinforced ceramic matrix composites, nanoparticles reinforced ceramic matrix composites, particulate reinforced polymer matrix composites, long fiber reinforced polymer matrix composites, nanoparticles reinforced polymer matrix composites, etc. ADVANTAGES; (1) The best surface roughness using suitable combination of viscoelastic media, abrasive particle and process oil is ~9nm for high performance carbon- carbon composite. (2) The improvement of surface finish is -98%. The pressure used in abrasive flow machining process (Figl) is less than 3 MPa. (3) The stroke length used in abrasive flow machining is less than 40 mm. (4) The number of cycles required to achieve nanofmishing varies from 10 to 300 depending on the material and initial surface roughness. (5) The finishing operation is carried out at room temperature. (6) The media used in abrasive flow machining (Fig 1) is repressible. The effect of abrasive concentration and number of cycles on surface roughness has been studied for carbon-carbon composites and two very common materials En8 and aluminum. Representative plots are shown in Fig 13 for aluminium and En8. The overall trend of experimental results in Fig 13 shows that with increasing the concentration of abrasives, percentage improvement in surface finishing increases. This is because with increasing abrasives percentage, more numbers of abrasive grains means more cutting edges per unit area comes in contact with the specimen/workpiece. These contribute for removing more picks from surface and more improvement in surface finish revealed. During this study it is also observed that vary high percentage of abrasives (more then 78% abrasive) reveals less improvement. The responsible factors for these may be: 1) higher percentage of abrasive particles increases viscosity of media which causes difficulty to flow. 2) very low percentage of carrier no longer remains efficient to act as binder. The same Figs. 13 also show that effect of number of cycles is positive effect on average percentage improvement in surface roughness but with diminishing nature. This is because at initial stage the numbers and comparative heights of peaks are larger but as cycles increases peaks is no longer as previous. The both Figs. 13 (A) and (B) also furnish that media gives higher average percentage improvement in case of aluminum compared to ENS because of its softness. Same trend is also observed for carbon-carbon composites as shown in Fig. 14. ' The effect of abrasive particle size and number of cycles on surface roughness has been studied for same carbon-carbon, En8 and aluminum materials. The overall trend of experimental results in Fig. 15 shows that with increased mesh size of abrasives reveals lower average percentage improvement in surface roughness. Higher the mesh size means smaller the grain size and small grains are less efferent to penetrate in specimen surface means less amount of material removal per stroke. So the percentage improvement in Ra is less. But effect of individual mesh size is different on both materials that is because of their material properties it self and its initial Ra. It is observed that media containing below 9% oil by weight is not flowing for present used set-up and tooling system. So the experiment started from 9% oil. The Fig. 16 indicates that as the oil percentage increases the amount of percentage improvement in Ra decreases. This is due to reduction in viscosity of media because added oil acts as softener/ plasticizer. From this Fig 16 it is also clear media that have more then 14 % oil gives very low percentage improvement. Five different types of media based on natural rubber (NR), butyl rubber (IIR), ethylene propylene diene monomer rubber (EPDM), silicone and styrene butadiene rubber (SBR) have been used to.see the performance of media. Fig. 17 shows that for initial number of cycles (1/3 of total cycles) improvement is higher compared to next 2/3 number of cycles. Again it is observed that the surface finish improvement is approximately 17, 16, 35, 58 and 70% for aluminum work piece whereas 6, 11, 31, 40 and 50% for En8 is given by these media respectively. The media with viscoelastic carriers NR, IIR, EPDM, silicon and SBR gives higher improvement on both the work pieces (Al, En8, carbon-carbon composites, etc) respectively. The main reason is their chemical structures. Fig. 18 shows the effect of pressure on improvement in Ra for 450 cycles. In case of pressure as varying parameter, it is observed that below 3 MPa media flow is very difficult for used system. Fig 18. indicates that the improvement in Ra is increased when pressure increases from 3 MPa to 5 MPa. This occurs because under higher pressure media is compressed more due to elasticity nature and grains comes closer to each other, ultimately this action contributing to transmit the force from source to the specimen. Viscosity plays a major role to give the surface finish of material. It is observed from Fig. 19 for 33% and 50% SiC filled media that the reduction of viscosity in the range of 0-100 s-1 shear rate is 98% and 97% respectively. For alumina it is 96% and 97%. Graph also shows that up to the 20 to 25 s-1 shear rate there is an 87% to 90% reduction in a viscosity and in letter stage of shear rate only 7 to 10% reduction is taking place. It is found that alumina gives more viscosity compared to SiC under the same experimental conditions. For example, at 70 s-1 shear rate the instantaneous viscosity are approximately 312, 393, 423 and 461 Pa.s for 33% SiC, 50% SiC, 33% A12O3 and 50% A12O3 respectively. It is also observed that alumina and SiC have same trend for change of viscosity with respect to the change in shear rate. The viscosity difference at particular shear rate is because of the difference in surface characteristics of both the abrasives. Apart from this when percentage loading is increased, means volume fraction increases, the flow resistance against the applied shear force increases. For any material Young's modulus, which is a basic material property is needed to characterize the material in target application. In AFM, media is deformed, it is worth to study the effect of strain on the modulus of selected viscoelastic carriers in their virgin form. The modulus at various deformations is calculated from equation given below and presented in graphical from in Fig. 20. Fig. 20 shows the effect of strain on modulus of various virgin viscoelastic carriers at a temperature of 25°C and strain rate of 0.189 s-1 under tensile mode. Media 1 shows low modulus. It gives modulus 0.05, 0.07, 0.08 and 0.09 MPa at 25, 50, 75 and 100% strain respectively. The curve of media 1, within the experiment range of straifi shows overall modulus increment of 80%. After media 1 next higher modulus is observed for media 2, it gives 0.16, 0.23, 0.28 and 0.31 MPa at 25, 50, 75 and 100% strain. This data shows that media 2 has 207% higher modulus compared to media 1. It shows 99% overall increment in modulus form 25 to 100% strain. The media 3 is giving 0.18, 0.26, 0.31 and 0.33 MPa at 25, 50, 75 and 100% strain. It shows 78% improvement in modulus when the strain is changed from 25 to 100%. For media 4 it is observed that the behavioral trend is same but and overall improvement is 49% in modulus for 25 to 100 % strain increment. The media 5 offers highest modulus in selected rubbers, for example its modulus is 700% higher compared to the media 1 at 25% strain. From above discussion and Fig. 20 it is also seen that as modulus increases for the respective percentage strain, the overall modulus improvement, over the strain from 25 to 100% range reduces for example 99, 78, 48 and 23% for media 2, media 3, media 4, and media 5. The above study shows the selected viscoelastic carriers have very good modulus (28 to 700% at 25% strain) compared to commercial media. This is the positive signal, which implies that selected rubbers can be a substitute of present viscoelastic carrier. During AFM process stresses are acting on the media. To understand this situation the creep compliance is measured for these media. Because the media is a viscoelastic material, it creeps (long-time continues deformation) under the influence of constant stress (less than the short-time yield value). And this creeps, fully or partly recoverable with respect to the time. That is why the creep test has been conducted and effect of time on creep compliance has been measured. Fig. 21 shows the effect of abrasive loading, process oil, temperature and particle size on creep compliance of viscoelastic media. In Fig. 21 (A) it can be seen that the 33% loaded abrasive sample has highest 3.15X10-5 Pa-1 creep compliance at approximate near to zero creep time and that portion of curve is more vertical compared to other (as loading increases this segment is slanting towards right side). This shows that at low percentage abrasive loaded sample gives more pure elastic deformation compared to other higher loaded abrasive samples. After that, 33% loaded curve shows the viscous deformation with respect to time. Same nature has been found for all other samples. In viscous part, e.g at 29.5 s creep time, creep compliance of 33, 50 and 80% loaded samples are 5.3X10-4, 2.75X10-4 and 5.18X10-5 Pa-1 respectively. It implies that for particular time period under constant stress the more deformation is taking place in case of low percentage loaded abrasives and that is obvious. Because at higher loading of abrasive particle, higher is the modulus and lower will be the deformation. At the same time higher percentage of abrasive reduced the elasticity. So the recovery is also reduced. The result of exercise infers that higher the abrasive loading lower is the creep compliance with respect to the creep time. 47% change in abrasive loading causes approximately 90% change in creep compliance. The graph (Fig. 21 (B)) shows that 20% oil based sample gives lowest (7.8X10-6 Pa-1) creep compliance means it has lowest straining for particular creep time. This is the expected result, because oil acts as softener and it is promoting the strain that is why higher oil content gives high creep compliance. At 40 s creep time, 33, 43 and 50% oil percentage based samples gives 628, 144, 12670% increment in creep compliance. Means higher the oil content, higher will be the viscous flow and less elastic flow (less recovery). This shows that oil percentage is predominant factor for the behavior of media. Fig.21 (C) shows that at 25°C, creep'compliance is 1.4X10-5 Pa-1 at near zero time. For subsequent higher temperatures (40, 55, and 7QOC), it reduces which infers that at lower temperature sample has higher modulus, which is obvious and gives higher creep compliance. For example in this study at approximate 10 s creep time, creep compliance increases by 90, 245 and 502% for 40, 55 and 70°C temperatures respectively. This happens due to breaking, reduction in entanglement of chain, reduction in viscosity, which promotes more deformation and ultimately high creep compliance. The results in Fig.21 (D) indicate that creep compliance for 240 mesh size is 3.9X10-5 pa-i at creep time near zero. For 400, 800, and 1000 mesh size this values are 3.5X10-5, 2.04X10-5 and 1.17X1O5 Pa-i respectively. So increased mesh size contributing to decline the creep compliance. And decline percentage is 10, 48 and 70% compared to 240 mesh size for 400, 800 and 1000 mesh respectively. This happens because of increase in the surface area between filler and matrix material. That causes higher modulus means lower straining and ultimately low creep compliance. Results disclose that smaller the particle size lower will be the creep compliance and change in mesh size from 240 to 1000, the creep compliance is reduced by 70%. APPLICATION The precision manufacturing industries those who are dealing with debrruring, polishing, removing recast layers, radiusing for various soft materials like aluminium and hard metals like steel including high performance composites with special reference to carbon-carbon composites A) Aerospace Industry a) Various operation purpose like; finishing of holes, improvement of the mechanical fatigue strength of blades/hubs, polishing, radiusing of air craft engines b) Reconditioning of aircraft engines. B) Automotive Industry c) To improve the surface of intake and exhaust manifolds as well as cylinder heads, which improve the horse power efficiency and air/fluid flow. d) To remove stress riser factors like burrs from gears and ultimately improve the life. e) To improve the performance of diesel injectors/nozzle. f) Same way it is used for the parts of watercraft, motorcycles, Karts and cycles, which contribute to improvement in performance. C) Dies and mold Industries g) To remove the recast layer, surface polishing, deburring, corner/edge radii at production stage of dies or mold it self. h) To clean the dies or molds as well as for reconditioning at daily bases also. D) Medical applications: Various parts are geometrically corrected because its trapping leads chances of bacteria and viruses. E) Polishing of parts like; valves, fittings, tubes, flow meters etc. Example: 1 to 300 gm (interval of 10 gm) abrasive particle/s (variable), 1 to 80 gm processing oil/s, are mixed in 370 gm rubber/s by two roll mixing mill. The mixing of abrasives particles and process oil in viscoelastic media is carried out on open two-roll mill (150 mm diameter roll, 7.5 HP) with friction ratio of 1: 1.1 and temperature of 50 to 75°C. The clearance between rolls is adjustable from 0.2 mm to 8 mm. The mixing is performed as per the ASTM D 3182-89 with mastication (break down of the molecular chain) of viscoelastic carrier. This is essential because it improves the acceptability of viscoelastic carrier for abrasives and additives (if any) and ultimately promotes the uniform dispersion. The batch is cut 3A of the distance across the roll with the help of knife, and holds the knife at this position until the bank just disappears. Next successive % cuts are made from alternate ends of the roll, allowing 20 sec between each cut. After sufficient mastication the pre-decided abrasive is added evenly across the roll at uniform rate. The total oil quantity is added alternatively in small - small quantity with abrasive. The falling material is collected carefully and is added back to the mix. For ensuring uniform dispersion, batch is passed six to eight times through mill with opening of 0.8 mm, and finally passed four times with opening of 6 mm. The percentage ingredient by weight of ingredient is calculated using equation given below 0/ c _• i • j- . (Weight of perticular ingredient "j 1AA % of perticular ingredient = - xioo ^ Total weight of compund ) The specimens prepared from different categories of materials are En8, Aluminium, carbon-carbon composites, etc. The En8 is chosen from ferrous and hard group whereas aluminum is chosen from soft and nonferrous material. In addition to this carbon-carbon is chosen from high performance engineering materials used in high temperature. All samples are made of same size and shape. So only one fixture can do for all samples at a time and comparative evaluation becomes possible. The specimens are prepared by precision machining and free from any kind of surface. For correct interpretation of results initially, surface of specimens ground simultaneously so the roughness values comes within ±10%. Every specimen has been cleaned by acetone before and after use, and no misleading results reveal there of. First of all media has been filled in lower cylinder (Fig. 1) by keeping the position of piston in top and in upper cylinder piston has been kept in bottom position. After filling of sufficient amount of media the fixture has been set (Fig. 1) with dummy workpiece and run at required pressure for few numbers of cycles so there is uniform filling of media. In the next stage of exercise, fixture has been taken out and again some amount of media has been filled again, if required. Now the actual specimens (prior cleaned by acetone and measured surface roughness) has been put into fixture and fixed on setup. The required pressure for particular set of experiment has been set and setup is run for required number of cycles. After completion, the specimens acre taken out and cleaned with acetone and surface measurement has been done. The same cycle has been repeated for next set of experiment. During experiment reduction ratio (fixture passage diameter / bore diameter) is 0.306 and stroke length is kept 40 mm (approximate). The measured surface roughness is reported in terms of improvement in percentage and calculated by the following formula; .... (Initial Ra- Final Ra^l ... Average improvement (%) = x 100 Initial Ra ) Surface roughness is measured by Atomic force microscope (PicoScan 5.3.1, Molecular Imaging, USA. Cantilever: NSC36(A)(gold coated) from MikroMasch. Force constant: 1.0 N/m, Frequency: 110 kHZ). It is to be noted that the formulation of the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant formulations are intended to be within the scope of the present invention, which is further set forth under the following claims: WE CLAIM; 1. A novel viscoelastic media for nano-finishing of materials through abrasive flow machining process comprising of viscoelastic material, 1-90% by weight of abrasive particles (with respect to the said viscoelastic material) and 1-50% by weight of processing oil (with respect to the said viscoelastic material). 2. A process for preparation of viscoelastic media comprising steps of: mixing of 1-90% by weight of abrasive particles and 1-50% by weight of processing oil in viscoelastic material in a two-roll mill such as herein described. 3. A process for preparation of viscoelastic media as claimed in claim 2 wherein the mixing is carried out at 50-12 5°C and at a friction ratio of 1:1.1-1:1.5 with speed of front roll in between 10-34 rpm using two roll mixing mill. 4. The media as claimed in Claim 1 wherein the abrasive particles and processing oil imbedded viscoelastic matrix is prepared by mixing the media and other compounding ingredients by other methods such as internal mixing kneader, intermix and banbary mixer 5. The media and process as claimed in Claim 1 or 2 wherein the viscoelastic media is selected from the group comprising of natural rubber, polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber, ethylene-propylene rubber, ethylene-propylene diene-monomer rubber, butyl rubber, halobutyl rubber, nitrile rubber, hydrogenated nitrile rubber, polysulfide rubber, polyacrylic rubber, neoprene rubber, hypalon rubber, silicone rubber, fluorocarbon rubber, polyurethane rubber, thermoplastic elastomer, and mixture thereof. 6. The media and process as claimed in Claim 5 wherein the viscoelastic matrix natural rubber is selected from the group comprising of standard malaysian rubber (SMR) L, SMR CV, SMR WF, SMR GP, SMR LV, SMR 5, SMR 10, SMR 20, SMR 50, technically specified rubbers (TSR) 5, TSR 10, TSR 20, TSR 50, technically classified rubber, oil extended natural rubber, deproteinized natural rubber, peptized natural rubber, skim natural rubber, superior processing natural rubber, heveaplus MG rubber, epoxidized natural rubber, thermoplastic natural rubber, and mixture thereof; the elastomer matrix styrene-butadiene rubber is selected from the group comprising of solution styrene-butadiene rubber i.e., SBR 2305, SBR 2304, emulsion styrene-butadiene rubber i.e., cold SBR 1500, cold SBR 1502, hot SBR 100, and mixture thereof; the elastomer matrix polybutadiene rubber is selected from the group comprising of cisamer-01, cisamerl220, BR 9000, BR 9004A, BR 9004B, low molecular weight 1, 3 poly butadiene, and mixture thereof; the elastomer matrix butyl rubber is selected from the group comprising of IIR-1751, IIR-1751F, I1R-745, Exxon butyl 007, Exxon butyl 065, Exxon butyl 068, Exxon butyl 165, Exxon butyl 268, Exxon butyl 269, Exxon butyl 365, polysar butyl 100, polysar butyl 101, polysar butyl 101-3, polysar butyl 301, polysar butyl 402, and mixture thereof; the elastomer matrix ethylene-propylene rubber is selected from the group comprising of dutral-CO-034, dutral-CO-038, dutral-CO-043, dutral-CO-054, dutral-CO-058, dutral-CO-059, dutral-CO-055, and mixture thereof; the elastomer matrix ethylene-propylene-diene-monomer. rubber is selected from the group comprising of ethylene-propylene-dicyclopentadiene rubber, ethylene-propylene-ethylidenenorbornene rubber, ethylene-propylene-1, 4 hexadiene rubber, and mixture thereof; the elastomer matrix halobutyl rubber is selected from the group comprising of Exxon chlorobutyl 1065, Exxon chlorobutyl 1066, Exxon chlorobutyl 1068, Polysar chlorobutyl 1240, Polysar chlorobutyl 1255, Exxon bromobutyl 2222, Exxon bromobutyl 2233, Exxon bromobutyl 2244, Exxon bromobutyl 2255, Polysar bromobutyl X2, Polysar bromobutyl 2030, and mixture thereof; the elastomer matrix nitrile rubber is selected from the group comprising of Krynac-2750, Nipol-1053, Nipol-1032, Paracril-C, Chemigum-N-3, Krynac-5075, and mixture thereof; the elastomer matrix hydrogenated nitrile rubber is selected from the group comprising of zetpol-1010, zetpol-1020, zetpol-2010, zetpol-2020, therban, and mixture thereof; the elastomer matrix polyacrylic rubber is selected from the group comprising of hycar-4051, hycar-4052, hycar-4054, vamac-B-124, and mixture thereof; the elastomer matrix neoprene rubber is selected from the group comprising of neoprene-AC, neoprene-AD, neoprene-ADG, neoprene-AF, neoprene-AG, neoprene-FB, neoprene-GN, neoprene-GNA, neoprene-GRT, neoprene-GS, neoprene-GW, neoprene-W, neoprene-W-MI, neoprene-WB, neoprene-WD, neoprene-WHY, neoprene-WHV-100, neoprene-WHV-200, neoprene-WHV-A, neoprene-WK, neoprene-WRT, neoprene-WX, neoprene-TW, neoprene-TW-100, neoprene-TRT, and mixture thereof; the elastomer matrix hypalon rubber is selected from the group comprising of hypalon-20, hypalon-30, hypalon-LD-999, hypalon-40S, hypalon-40, hypalon-4085, hypalon-623, hypalon-45, hypalon-48S, hypalon-48, and mixture thereof; the elastomer matrix silicone rubber is selected from the group comprising of silicone MQ, silicone MPQ, silicone MPVQ, silicone FVQ, and mixture thereof; the elastomer matrix fluorocarbon rubber is selected from the group comprising of viton-LM, viton-C-10, viton-A-35, viton-A, viton-A-HF, viton-E-45, viton-E-60, viton-E-60C, viton-E403, viton-B-50, viton-B, viton-B-70, viton-910, viton-GLT, viton-GF, viton-VTR-4730, DAI-EL-G-101, DAI-EL-701, DAI-EL-751, DAI-EL-702, DAI-EL-704, DAI-EL-755, DAI-EL-201, DAI-EL-501, DAI-EL-801, DAI-EL-901, DAI-EL-902, tecnoflon-FOR-LHF, tecnoflon-NMLB, tecnoflon-NML, tecnoflon-NMB, tecnoflon-NM, tecnoflon-NH, tecnoflon-FOR-45-45BI, tecnoflon-FOR- 70-70BI, tecnoflon-FOR-45-C-CI, tecnoflon-FOR-60K-KI, tecnoflon-FOR-50E, tecnoflon-TH, tecnoflon-TN-50, tecnoflon-TN, tecnoflon-FOR-THF, tecnoflon-FOR-TF-50, tecnoflon-FOR-TF, fluorel-2145, fluorel-FC-2175, Huorel-FC-2230, fluorel-FC-2178, fiuorel-FC-2170, fluorel-FC-2173, fluorel-FC-2174, fluorel-FC-2177, fluorel-FC-2176, fhiorel-FC-2180, fluorel-FC-81, fluorel-FC-79, fluorel-2152, fluorel-FC-2182, fluorel-FC-2460, nuorel-FC-2690, fluorel-FC-2480, and mixture thereof, the elastomer matrix polyurethane rubber (polyether and polyester type) is selected from the group comprising of FMSC-1035, FMSC-1035T, FMSC-1040, FMSC-1050, FMSC-1060, FMSC-1066, FMSC-1070, FMSC-1075, FMSC-1080-SLOW, FMSC-1080-FAST, FMSC-1085, FMSC-1090-FAST, FMSC-1090-SLOW, and mixture thereof; the elastomer matrix thermoplastic elastomer (polyurethane, polyester, polyamide, styrene-butadiene-styrene, blends, etc) is selected from the group comprising of SBS 1401, SBS 4402, SBS 4452, SBS 1301, SBS 1401-1, SBS 4303, estane-55103, hytrel-40xy, hytrel-63xy, hytrel-72xy, gaflex-547, pebax-2533, pebax-6333, TPR-1600, TPR-1900, TPR-2800, TELCAR-340, SOMEL-301, SOMEL-601, santoprene, cariflex-TR, solprene-400, stereon, and mixture thereof; the elastomer matrix polysulfide elastomer is selected from the group comprising of thiakol-A, thiakol-B, thiakol-FA, thiakol-ST, and mixture thereof; 7. The media and process as claimed in Claim 1 or 2 wherein the abrasive particles are selected from the group comprising of alumina, silicone carbide, diamond powder, boron carbide, silica, garnet, tungsten carbide, etc and mixture thereof. . 8. The media and process as claimed in Claim 1 or 2 wherein the process oil is selected from the group comprising of paraffinic oil, naphthenic oil, aromatic oil, vegetable oil, and mixture thereof. 9. A novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof substantially as herein described and illustrated.

Full Text

FIELD OF INVENTION
This invention relates to a novel viscoelastic media used for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof. It can be used for grinding, deburring, radiusing, leveling of surface, polishing, etc, on flat / contour / three dimensional edge(s) / surface(s) / feature(s), both in external and internal surface (s).
BACKGROUND OF INVENTION
The higher level of surface finish, surface integrity and controlled corner/edge radii improves the performance as well as its life [Rhoades, L. J., (1988), "Abrasive flow machining," Manufacturing engineering, pp 75-78; Inasaki, I., Tonshoff, H. K., and Howes, T. D., (1993), "Abrasive machining in future", Annals of the CIRP, Vol.42/2, pp 723-732]. Generally, abrasive process has been proven to be inefficient for finishing or deburring for inaccessible domains. Researchers in mid - 60's at EXTRUDEHONE, USA came out with new process "Abrasive Flow Machining" which could solve this problem.
Mccarty [Mccarty, R. W., U.S. Pat. No. 3,521,412, July 21, 1970] in his invention used silicon putty as a media. The three ingredients in his composition were 1) G.E. silicon putty SS-91 grade - 35%, isopropyl stearate (softner) - 3%, silicon grease (adds lubricity) - 2%, silicon carbide abrasives #120 grade - 60%. 2) Silicon putty - 1 pounds, aluminum oxide (100 gran size) - 6 pounds, methyl phenyl silicon fluid - 1 ounces (125 centistoke, G.E. Co.), tetrafluoroethylene powder - 2 ounces. 3) Kneaded rubber (isobutene) - 1 pounds, aluminum oxide (100 grains size) - 4 pounds, silicon fluid - 3 ounces, Teflon powder - 1 ounces.Rhoades et al [Rhoades, L. J., (1990), "Method of finishing machining the surface of irregularly shaped fluid passages", U.S. Pat. No. 4,936,057; Rhoades, L. J., (1991), "Process and apparatus of abrading by extrusion", U.S. Pat. No. 4,996,796; Rhoades, L. J., (1991), "Process for abrasive flow machining using multiple cylinders", U.S. Pat. No. 5,076,027; Rhoades, L. J., (1992), "Abrasive flow machining with an in situ viscous plastic medium", U.S. Pat. No. 5,125,191; Rhoades, L. J., (2003), "Method and apparatus for the region of intersection between a branch outlet and a passageway in a body", U.S. Pat. No. 6,503,126 Bl; Rhoades, L. J., Kohut, T. A., Nokovich, N. P., and Yanda, D. W., (1991), "Reversible unidirectional abrasive flow machining", U. S. Pat. No. 5,070,652; Rhoades, L. J., Kohut, T. A., Nokovich, N. P., and Yanda, D. W., (1994), "Unidirectional abrasive flow machining", U. S. Pat. No. 5,367,833; Rhoades, L. J., Nokovich, N. P., Kohut, T. A., and Johnson, F. E., (1991), "Method of controlling flow resistance in fluid orifice manufacture", U. S. Pat. No. 5,054,247] in his invention used dry pulverulent: Guar gum, 50 to 75 percent; boric acid 30 to 40 percent; borax 1.0 to 2.5 percent; high molecular weight polysaccharide 0.25 to 0.60 percent (as indicated by the trade designation B-1459 in Ahrabi patent) by weight. The water, oil and abrasive were the other ingredients of media. A sample percentage range of ingredients by volume are: precursor - 1,

water - 2 to 50, silicon oil - 0 to 10, grit - 0 to 50. Along with the media varying abrasives in the size of 6 to 10 microns were used. He also invented a new method for finishing machining of irregular shape fluid passages and multi cylinder AFM.
Davis and Fletcher [Davies, P. J., Fletcher, A. J., ( 1995), "The assessment of the Theological characteristics of various polyborosiloxane/grit mixtures as utilized in the abrasive flow machining process', Journal of mechanical engineering science: Proc Instn. Mech. Engrs, Vol 209, pp 409-418] also used PBS/silicon carbide mixture of different viscosity and concluded that the relation between number of cycles and both the temperature and pressure drop across the die are dependent upon medium type and abrasives-polyborosiloxane(PBS) ratio. They found that average viscosity and pressure drop decreases as abrasives-polyborosiloxane ratio increases, irrespective of mesh size and type of PBS. The mesh size has minimal effect on Theological parameters.
Fletcher and Fioravanti [Flether, A. J., Fioravanti, A., (1996), "Polishing and Honing Processes: An Investigation of the thermal Properties of Mixture of Polyborosiloxane and Silicon carbide abrasive", Proc. Instn Mech. Engrs, Part C: Journal of Mechanical Engineering Science, Vol.210,pp. 255-265] investigated for the polyborosiloxane (PBS) and silicon carbide abrasive mixture that the thermal conductivity of the composite sharply increases when concentration of abrasives reached 50 percent by mass. The surface heat transfer coefficient at the interface between the media and die is a primarily function of abrasive concentration, whereas the mesh size and polymer type have very slight influence. The theoretical, semi-empirical and empirical models are also derived by them for the thermal properties as a function of material composition and temperature.
Liebke et al [Liebke, R. W., Dawson, D. R., Fredette, M. A., and Goodstein, M. B., (1997), "Method of removing excess overlay coating from within colling holes of aluminide coated gas turbine engine components", U. S. Pat. No. 5,702,288] invented the application of abrasive flow machining for removing excess overlay coating from within cooling holes of aluminide coated gas turbine engine components. For that they have used extrude Hone corporation media #831-G-1 for abrasive slurry.
Klein [Klein, E. J., (1998), "Apparatus and method for polishing lumenal prostheses", U. S. Pat. No. 5,788,558] invented the application of abrasive flow machining for deburring and rounding edges and polishing surfaces of radially expansible luminal prostheses, such as stents and grafts are provided. The slurry used by him is mixture of polyborosiloxanes, silicon oil and abrasives.

Perry [Perry, W. B., (1998), "Method and apparatus for controlling the diameter and geometry of an orifice with an abrasive slurry", U.S. Pat. No. 5,807,163; Perry W. B (2000), "Abrasive liquid slurry for polishing and radiusing a microholes", U.S. Pat. No. 6,132,482] invented a new method and its apparatus for controlling orifice size and form geometry with abrasive slurry. Perry used abrasive, rheological additives and fluid media such as cutting fluids, honing fluids and the like, which are distinct from semisolid polymer composition.
Perry et al [Perry, W. B., Liam, O., and Wright, M., (2001), "System for controlling the size and surface geometry of an orifice", U.S. Pat. No. 6,306,011 Bl] invented system for controlling the size and surface geometry of an orifice.
Shaw [Shaw, J. S., (2001), "Free flow abrasive hole polishing", U.S. Pat. No. 6,234,872 Bl] invented a free flow hole polishing system for improving air flow which resulted better cooling efficiency. The slurry used was of abrasive and water only.
Jain et al [Jain, V. K., Ranganatha, C, and Muralidhar, K. (2001), "Evaluation of rheological properties of medium for AFM process", Machining science and technology, Vol.5 (2), pp 151-170] used mixture of commercial grade sealing putty, varnish oil and abrasive as AFM media and studied the effect of temperature of media, concentration and mesh size of abrasives on the viscosity.
Gilmore and Rhoades [Gilmore, J. R., and Rhoades, L. J., (2005), "Abrasive polishing composition", U.S. Pat. No. 6,918,937 B2; Gilmore. J. R, Rhoades. L. J (2003), "Abrasive polishing apparatus", U. S. Pat. No. 6,544,110 B2; Gilmore, J. R., and Rhoades, L. J., (2003), "Self-forming tooling for an 0rbital polishing machine and method for producing the same", U. S. Pat. No. 6,645,056 Bl] invented improved orbital AFM with abrasive viscoelastic medium, which had a composition of "a viscoelastic poly (boro-siloxane) polymer carrier having a static viscosity from about 5X103 to 5X105 centipoises; a particulate abrasive; an optional inert filler in an amount of up to about 25% by weight of said medium; optional plasticizing lubricant up to 25% by weight of said medium; abrasive types : alumina, silica, garnet, silicon'carbide, diamond, tungsten carbide and mixtures. By using the above composition Gilmore and Rhoades were able to achieve 0.2 micro-inches Ra in tool steel dies in two stages. First boron carbide abrasive composition was used and second time 2|um diamond abrasive was used. The second example is of polishing a plurality of forged aluminum 3D complex shape component and achieved Ra is 20 to 25 micro-inches from 100 to 120 micro-inches initial Ra. Third example is of cast aluminum automotive wheel with complex shape and its initial Ra 145 to 175 micro-inches whereas achieved Ra is 20 to 25 micro-inches. Inventor said that for this invention polymer gels, particularly hydrogels, non-aqueous polymer formulations and poly (borosiloxanes) can be adapted.

In another invention, Gilmore and Rhoades [Gilmore, J. R., Rhoades, L. J., (2005), "Abrasive polishing composition", U.S. Pat. No. 6,918,937 B2] invented abrasive polishing apparatus as well as self - forming tool for orbital polishing machine and method.
Agrawal et al [Agrawal, A., Jain, V. K., and Muralidhar, K., (2005), "Experimental determination of viscosity of abrasive flow machining media", International Journal of Manufacturing Technology and Management, v 7, n 2-4, 2005, pp 142-156] studied viscosity of commercial media with the help of fabricated viscometer based on the principle of visco-elasticity.
Raju et al [Raju, H. P., Narayanasamy, K., Srinivasa, Y. G., and Krishnamurthy, R., (2005), "Characteristics of extrude honed SG iron internal primitives", Journal of materials processing technology, Vol.166, pp 455-464] used grade (40) of silicone polymer as carrier medium with silicon abrasives for extrude honing of SG cast iron 600.
OBJECTS OF THE INVENTION
An object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof in which the media is very cost effective (max Rs. 300/Kg) as compared to known high cost existing commercial media (Rs. 2, 50, OOO/- per kg).
Another object of this invention is to propose a novel viscoelastic media for nano-fmishing of materials through abrasive flow machining process and a method of manufacture thereof to obtain surface finish of workpiece at nanoscale.
Still another object of this invention is to propose a novel viscoelastic media for nano-fmishing of materials through abrasive flow machining process and a method of manufacture thereof in which the media can be used to machine all types of materials i.e. very hard metal to soft metal including composite materials.
Yet further object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof which can be used for all types of existing abrasive flow machining processes.
Still further object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof utilizing less number of ingredients, which are easily available at very low cost.

Yet another object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof in which fabrication for media is simple and quite cost effective, which can employ all types of abrasive flow machining processes.
Still another object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof in which the fabrication method is safe, non toxic and environmental friendly and useful for all types of abrasive flow machining processes.
Still further object of this invention is to propose a novel viscoelastic media for nano-finishing of materials through abrasive flow machining process and a method of manufacture thereof, which can efficiently work for abrasive machining processes.
Further objects and advantages of this invention will be more apparent from the ensuing description.
STATEMENT OF INVENTION
According to this invention there is provided a novel viscoelastic media for nano-fmishing of materials through abrasive flow machining process comprising of viscoelastic material, 1-90% by weight of abrasive particles (with respect to the said viscoelastic material) and 1-50% by weight of processing oil (with respect to the said viscoelastic material).
Further according to this invention there is provided a process for preparation of viscoelastic media comprising steps of:mixing of 1-90% by weight of abrasive particles and 1-50% by weight of processing oil in viscoelastic material in a two-roll mill such as herein described.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of thiis invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig. 1 shows a schematic diagram of two-way abrasive flow machining type in house fabricated setup that is used for present invention.
Fig. 2 shows AFM image of carbon-carbon workpiece before machining, which is high performance composite material. The surface roughness is ~ 353 nm.
Fig. 3 shows AFM image of carbon-carbon workpiece after machining. The surface roughness is -22 nm. It is in the nano-scale. The improvement of surface roughness of carbon-carbon composite is -94%.
Fig. 4 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is ~ 16 nm. The improvement of surface roughness of carbon-carbon composite is -96%.

Fig. 5 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is ~ 33nm. The improvement of surface roughness of carbon-carbon composite is -91%.
Fig. 6 shows Another AFM image of carbon-carbon workpiece after machining. The surface roughness is ~ 24 nm. The improvement of surface roughness of carbon-carbon composite is -93%.
Fig. 7 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is -34 nm. The improvement of surface roughness of carbon-carbon composite is -90%.
Fig. 8 shows another AFM image of carbon-carbon workpiece after machining. The surface roughness is - 9 nm. The improvement of surface roughness of carbon-carbon composite is -98%.
Fig. 9 shows AFM image of En8 workpiece before machining. The surface roughness is ~ 740 nm
Fig. 10 shows AFM image of En8 workpiece after machining (1800 cycles). The surface roughness is ~ 50nm. The improvement of surface roughness of En8 high performance material is -87%.
Fig. 11 shows AFM image of Aluminium workpiece before machining. The surface roughness is -365 nm
Fig. 12 shows AFM image of Aluminium workpiece after machining (100 cycles). The surface roughness is ~ lOnm. The improvement of surface roughness is -97%.
Figure 13 shows Effect of number of cycles on improvement of Ra using various loading of abrasive particle. (A: Aluminium and B: En8)
Figure 14 shows Effect of number of cycles on improvement of Ra for carbon-carbon composites
Figure 15 shows Effect of number of cycles on improvement of Ra using various sizes of abrasive particle (A En8 and B: carbon-carbon composites)
Figure 16 shows Effect of number of cycles on improvement of Ra using various loading of process oil. (A: Aluminium and B: En8)
Figure 17 shows Effect of viscbelastic media on Ra (A: Aluminium; B En8)
Figure 18 shows Effect of operating pressure on Ra
Figure 19: shows Effect of shear rate on viscosity of viscoelastic media-1 (D 33%
abrasive 1,D 50% abrasive 1, D33% abrasive 2, D 50% abrasive 2
Figure 20: shows Modulus-strain- plot of viscoelastic media

Figure 21: shows (A) Effect of abrasive loading, (B) process oil (C) temperature and (D) particle size on creep compliance of viscoelastic media-1
DETAIL DESCRIPTION OF INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
According to this invention, media comprises of viscoelastic material/s, abrasive particle/s and process oil/s and mixture thereof. Viscoelastic media is selected from the groups comprising of natural rubber, polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber, ethylene-propylene rubber, ethylene-propylene diene-monomer rubber, butyl rubber, halobutyl rubber, nitrile rubber, hydrogenated nitrile rubber, polysulfide rubber, polyacrylic rubber, neoprene rubber, hypalon rubber, silicone rubber, fluorocarbon rubber, polyurethane rubber, thermoplastic elastomer, and mixture thereof. Abrasive particle is selected from the group comprising of alumina, silicone carbide, diamond powder, boron carbide, silica, garnet, tungsten carbide, etc. wherein particle size of the abrasive particle varies from 5 nm to 75jam. Process oil is selected from the group comprising of paraffmic oil, naphthenic oil, aromatic oil, vegetable oil, and mixture thereof.
Mixing of abrasive particle/s, and process oil/s in viscoelastic material/s is carried out using two-roll mill having rolls of 150 mm in diameter at a temperature of 50 to 125QC depending on the type of viscoelastic material. The speed of front roll is in between 10 to 34 rpm and friction ratio between front and rear roll is 1:1.1 to 1: 1.5. The clearance between rolls is adjustable from 0.1 to 12 mm. During mixing, at first the viscoelastic material/s is/are fed into the nip gap of two roll to get a thin sheet. Then abrasive particles in powder form are added slowly followed by process oil. The batch is cut % of the distance across the roll with the help of a knife, and held the knife at this position until the bank just disappears. This process is continued for about 10 minutes. The materials falling through the nip is collected carefully from the tray and returned back to the mix. The mixing cycle is concluded by passing the rolled batch endwise through the mill six to eight times with an opening of 0.2 mm to improve the dispersion. Finally, the mixed compound is passed four times through the mill at a setting of 0.1 mm, folding it back on itself each time. The batch is removed and kept on the glass sheet, in a closed container to prevent absorption of moisture from the air for 24 hours. This media is used in the AFM (Fig. 1) setup for machining.
Set-up details
The experiments are conducted on a set-up as shown in Fig.l. The surface roughness is measured by "Surftest SJ 301" of "Mitutoyo" make and Atomic force microscopy [PicoScan 5.3.1, Molecular Imaging, USA; Cantilever: NSC36(A)(gold coated) from MikroMasch at Force constant: 1.0 N/m and

Frequency: 110 KHZ]. During the experiment, the stroke length is 40 mm and the reduction ratio (Fixture passage diameter / bore diameter) is 0.274. The surface roughness is reported in terms of improvement in percentage and calculated by the following formula:
A f InitialRa-FinalRa _.in_
Average improvement (%) = X100
Initial Ra )
The experimental results are reproducible within ±10%. Workpieces are selected from the group of materials i.e., Inconel, Monel, Titanium and its alloy, Al and its alloy, Mg and its alloy, Stainless steel, Cermet i.e., TiCN - Ni, WC-Co, ceramics ie., all oxide ceramics (Alumina, ZrO), all non oxide ceramics (WC, SiC, B4C, CBN, PCBN), carbon-carbon composites, particulate reinforced metal matrix composites, long fiber reinforced metal matrix composites, nanoparticles reinforced metal matrix composites, particulate reinforced ceramic matrix composites, long fiber reinforced ceramic matrix composites, nanoparticles reinforced ceramic matrix composites, particulate reinforced polymer matrix composites, long fiber reinforced polymer matrix composites, nanoparticles reinforced polymer matrix composites, etc.
ADVANTAGES;
(1) The best surface roughness using suitable combination of viscoelastic media,
abrasive particle and process oil is ~9nm for high performance carbon- carbon
composite.
(2) The improvement of surface finish is -98%.
The pressure used in abrasive flow machining process (Figl) is less than 3 MPa.
(3) The stroke length used in abrasive flow machining is less than 40 mm.
(4) The number of cycles required to achieve nanofmishing varies from 10 to 300
depending on the material and initial surface roughness.
(5) The finishing operation is carried out at room temperature.
(6) The media used in abrasive flow machining (Fig 1) is repressible.
The effect of abrasive concentration and number of cycles on surface roughness has been studied for carbon-carbon composites and two very common materials En8 and aluminum. Representative plots are shown in Fig 13 for aluminium and En8. The overall trend of experimental results in Fig 13 shows that with increasing the concentration of abrasives, percentage improvement in surface finishing increases. This is because with increasing abrasives percentage, more numbers of abrasive grains means more cutting edges per unit area comes in contact with the specimen/workpiece. These contribute for removing more picks from surface and more improvement in surface finish revealed. During this study it is also observed that vary high percentage of abrasives (more then 78% abrasive) reveals less improvement. The responsible factors for these may be: 1) higher percentage of abrasive particles increases viscosity of media which causes difficulty to flow. 2) very low percentage of carrier no longer remains efficient to act as binder. The same Figs. 13 also show that effect of number of cycles is

positive effect on average percentage improvement in surface roughness but with
diminishing nature. This is because at initial stage the numbers and comparative
heights of peaks are larger but as cycles increases peaks is no longer as previous.
The both Figs. 13 (A) and (B) also furnish that media gives higher average
percentage improvement in case of aluminum compared to ENS because of its
softness. Same trend is also observed for carbon-carbon composites as shown in
Fig. 14. '
The effect of abrasive particle size and number of cycles on surface roughness has been studied for same carbon-carbon, En8 and aluminum materials. The overall trend of experimental results in Fig. 15 shows that with increased mesh size of abrasives reveals lower average percentage improvement in surface roughness. Higher the mesh size means smaller the grain size and small grains are less efferent to penetrate in specimen surface means less amount of material removal per stroke. So the percentage improvement in Ra is less. But effect of individual mesh size is different on both materials that is because of their material properties it self and its initial Ra.
It is observed that media containing below 9% oil by weight is not flowing for present used set-up and tooling system. So the experiment started from 9% oil. The Fig. 16 indicates that as the oil percentage increases the amount of percentage improvement in Ra decreases. This is due to reduction in viscosity of media because added oil acts as softener/ plasticizer. From this Fig 16 it is also clear media that have more then 14 % oil gives very low percentage improvement.
Five different types of media based on natural rubber (NR), butyl rubber (IIR), ethylene propylene diene monomer rubber (EPDM), silicone and styrene butadiene rubber (SBR) have been used to.see the performance of media. Fig. 17 shows that for initial number of cycles (1/3 of total cycles) improvement is higher compared to next 2/3 number of cycles. Again it is observed that the surface finish improvement is approximately 17, 16, 35, 58 and 70% for aluminum work piece whereas 6, 11, 31, 40 and 50% for En8 is given by these media respectively. The media with viscoelastic carriers NR, IIR, EPDM, silicon and SBR gives higher improvement on both the work pieces (Al, En8, carbon-carbon composites, etc) respectively. The main reason is their chemical structures.
Fig. 18 shows the effect of pressure on improvement in Ra for 450 cycles. In case of pressure as varying parameter, it is observed that below 3 MPa media flow is very difficult for used system. Fig 18. indicates that the improvement in Ra is increased when pressure increases from 3 MPa to 5 MPa. This occurs because under higher pressure media is compressed more due to elasticity nature and grains comes closer to each other, ultimately this action contributing to transmit the force from source to the specimen.

Viscosity plays a major role to give the surface finish of material. It is observed from Fig. 19 for 33% and 50% SiC filled media that the reduction of viscosity in the range of 0-100 s-1 shear rate is 98% and 97% respectively. For alumina it is 96% and 97%. Graph also shows that up to the 20 to 25 s-1 shear rate there is an 87% to 90% reduction in a viscosity and in letter stage of shear rate only 7 to 10% reduction is taking place. It is found that alumina gives more viscosity compared to SiC under the same experimental conditions. For example, at 70 s-1 shear rate the instantaneous viscosity are approximately 312, 393, 423 and 461 Pa.s for 33% SiC, 50% SiC, 33% A12O3 and 50% A12O3 respectively. It is also observed that alumina and SiC have same trend for change of viscosity with respect to the change in shear rate. The viscosity difference at particular shear rate is because of the difference in surface characteristics of both the abrasives. Apart from this when percentage loading is increased, means volume fraction increases, the flow resistance against the applied shear force increases.
For any material Young's modulus, which is a basic material property is needed to characterize the material in target application. In AFM, media is deformed, it is worth to study the effect of strain on the modulus of selected viscoelastic carriers in their virgin form. The modulus at various deformations is calculated from equation given below and presented in graphical from in Fig. 20.
Fig. 20 shows the effect of strain on modulus of various virgin viscoelastic carriers at a temperature of 25°C and strain rate of 0.189 s-1 under tensile mode. Media 1 shows low modulus. It gives modulus 0.05, 0.07, 0.08 and 0.09 MPa at 25, 50, 75 and 100% strain respectively. The curve of media 1, within the experiment range of straifi shows overall modulus increment of 80%. After media 1 next higher modulus is observed for media 2, it gives 0.16, 0.23, 0.28 and 0.31 MPa at 25, 50, 75 and 100% strain. This data shows that media 2 has 207% higher modulus compared to media 1. It shows 99% overall increment in modulus form 25 to 100% strain. The media 3 is giving 0.18, 0.26, 0.31 and 0.33 MPa at 25, 50, 75 and 100% strain. It shows 78% improvement in modulus when the strain is changed from 25 to 100%. For media 4 it is observed that the behavioral trend is same but and overall improvement is 49% in modulus for 25 to 100 % strain increment. The media 5 offers highest modulus in selected rubbers, for example its modulus is 700% higher compared to the media 1 at 25% strain. From above discussion and Fig. 20 it is also seen that as modulus increases for the respective percentage strain, the overall modulus improvement, over the strain from 25 to 100% range reduces for example 99, 78, 48 and 23% for media 2, media 3, media 4, and media 5. The above study shows the selected viscoelastic carriers have very good modulus (28 to 700% at 25% strain) compared to commercial media. This is the positive signal, which implies that selected rubbers can be a substitute of present viscoelastic carrier. During AFM
process stresses are acting on the media. To understand this situation the creep compliance is measured for these media.
Because the media is a viscoelastic material, it creeps (long-time continues deformation) under the influence of constant stress (less than the short-time yield value). And this creeps, fully or partly recoverable with respect to the time. That is why the creep test has been conducted and effect of time on creep compliance has been measured. Fig. 21 shows the effect of abrasive loading, process oil, temperature and particle size on creep compliance of viscoelastic media. In Fig. 21 (A) it can be seen that the 33% loaded abrasive sample has highest 3.15X10-5 Pa-1 creep compliance at approximate near to zero creep time and that portion of curve is more vertical compared to other (as loading increases this segment is slanting towards right side). This shows that at low percentage abrasive loaded sample gives more pure elastic deformation compared to other higher loaded abrasive samples. After that, 33% loaded curve shows the viscous deformation with respect to time. Same nature has been found for all other samples. In viscous part, e.g at 29.5 s creep time, creep compliance of 33, 50 and 80% loaded samples are 5.3X10-4, 2.75X10-4 and 5.18X10-5 Pa-1 respectively. It implies that for particular time period under constant stress the more deformation is taking place in case of low percentage loaded abrasives and that is obvious. Because at higher loading of abrasive particle, higher is the modulus and lower will be the deformation. At the same time higher percentage of abrasive reduced the elasticity. So the recovery is also reduced. The result of exercise infers that higher the abrasive loading lower is the creep compliance with respect to the creep time. 47% change in abrasive loading causes approximately 90% change in creep compliance.
The graph (Fig. 21 (B)) shows that 20% oil based sample gives lowest (7.8X10-6 Pa-1) creep compliance means it has lowest straining for particular creep time. This is the expected result, because oil acts as softener and it is promoting the strain that is why higher oil content gives high creep compliance. At 40 s creep time, 33, 43 and 50% oil percentage based samples gives 628, 144, 12670% increment in creep compliance. Means higher the oil content, higher will be the viscous flow and less elastic flow (less recovery). This shows that oil percentage is predominant factor for the behavior of media.
Fig.21 (C) shows that at 25°C, creep'compliance is 1.4X10-5 Pa-1 at near zero time. For subsequent higher temperatures (40, 55, and 7QOC), it reduces which infers that at lower temperature sample has higher modulus, which is obvious and gives higher creep compliance. For example in this study at approximate 10 s creep time, creep compliance increases by 90, 245 and 502% for 40, 55 and 70°C temperatures respectively. This happens due to breaking, reduction in entanglement of chain, reduction in viscosity, which promotes more deformation and ultimately high creep compliance.
The results in Fig.21 (D) indicate that creep compliance for 240 mesh size is 3.9X10-5 pa-i at creep time near zero. For 400, 800, and 1000 mesh size this
values are 3.5X10-5, 2.04X10-5 and 1.17X1O5 Pa-i respectively. So increased mesh size contributing to decline the creep compliance. And decline percentage is 10, 48 and 70% compared to 240 mesh size for 400, 800 and 1000 mesh respectively. This happens because of increase in the surface area between filler and matrix material. That causes higher modulus means lower straining and ultimately low creep compliance. Results disclose that smaller the particle size lower will be the creep compliance and change in mesh size from 240 to 1000, the creep compliance is reduced by 70%.
APPLICATION
The precision manufacturing industries those who are dealing with debrruring, polishing, removing recast layers, radiusing for various soft materials like aluminium and hard metals like steel including high performance composites with special reference to carbon-carbon composites
A) Aerospace Industry
a) Various operation purpose like; finishing of holes, improvement of
the mechanical fatigue strength of blades/hubs, polishing, radiusing
of air craft engines
b) Reconditioning of aircraft engines.
B) Automotive Industry
c) To improve the surface of intake and exhaust manifolds as well as
cylinder heads, which improve the horse power efficiency and
air/fluid flow.
d) To remove stress riser factors like burrs from gears and ultimately
improve the life.
e) To improve the performance of diesel injectors/nozzle.
f) Same way it is used for the parts of watercraft, motorcycles, Karts
and cycles, which contribute to improvement in performance.
C) Dies and mold Industries
g) To remove the recast layer, surface polishing, deburring,
corner/edge radii at production stage of dies or mold it self.
h) To clean the dies or molds as well as for reconditioning at daily bases also.
D) Medical applications: Various parts are geometrically corrected because its
trapping leads chances of bacteria and viruses.
E) Polishing of parts like; valves, fittings, tubes, flow meters etc.
Example: 1 to 300 gm (interval of 10 gm) abrasive particle/s (variable), 1 to 80 gm processing oil/s, are mixed in 370 gm rubber/s by two roll mixing mill. The mixing of abrasives particles and process oil in viscoelastic media is carried out
on open two-roll mill (150 mm diameter roll, 7.5 HP) with friction ratio of 1: 1.1 and temperature of 50 to 75°C. The clearance between rolls is adjustable from 0.2 mm to 8 mm. The mixing is performed as per the ASTM D 3182-89 with mastication (break down of the molecular chain) of viscoelastic carrier. This is essential because it improves the acceptability of viscoelastic carrier for abrasives and additives (if any) and ultimately promotes the uniform dispersion. The batch is cut 3A of the distance across the roll with the help of knife, and holds the knife at this position until the bank just disappears. Next successive % cuts are made from alternate ends of the roll, allowing 20 sec between each cut. After sufficient mastication the pre-decided abrasive is added evenly across the roll at uniform rate. The total oil quantity is added alternatively in small - small quantity with abrasive. The falling material is collected carefully and is added back to the mix. For ensuring uniform dispersion, batch is passed six to eight times through mill with opening of 0.8 mm, and finally passed four times with opening of 6 mm.
The percentage ingredient by weight of ingredient is calculated using equation given below
0/ c _• i • j- . (Weight of perticular ingredient "j 1AA
% of perticular ingredient = - xioo
^ Total weight of compund )
The specimens prepared from different categories of materials are En8, Aluminium, carbon-carbon composites, etc. The En8 is chosen from ferrous and hard group whereas aluminum is chosen from soft and nonferrous material. In addition to this carbon-carbon is chosen from high performance engineering materials used in high temperature. All samples are made of same size and shape. So only one fixture can do for all samples at a time and comparative evaluation becomes possible. The specimens are prepared by precision machining and free from any kind of surface. For correct interpretation of results initially, surface of specimens ground simultaneously so the roughness values comes within ±10%. Every specimen has been cleaned by acetone before and after use, and no misleading results reveal there of.
First of all media has been filled in lower cylinder (Fig. 1) by keeping the position of piston in top and in upper cylinder piston has been kept in bottom position. After filling of sufficient amount of media the fixture has been set (Fig. 1) with dummy workpiece and run at required pressure for few numbers of cycles so there is uniform filling of media. In the next stage of exercise, fixture has been taken out and again some amount of media has been filled again, if required. Now the actual specimens (prior cleaned by acetone and measured surface roughness) has been put into fixture and fixed on setup. The required pressure for particular set of experiment has been set and setup is run for required number of cycles. After completion, the specimens acre taken out and cleaned with acetone and surface measurement has been done. The same cycle has been repeated for next set of experiment. During experiment reduction ratio (fixture passage diameter / bore diameter) is 0.306 and stroke length is kept 40 mm (approximate). The measured surface roughness is reported in terms of improvement in percentage and calculated by the following formula;
.... (Initial Ra- Final Ra^l ...
Average improvement (%) = x 100
Initial Ra )
Surface roughness is measured by Atomic force microscope (PicoScan 5.3.1,
Molecular Imaging, USA. Cantilever: NSC36(A)(gold coated) from MikroMasch.
Force constant: 1.0 N/m, Frequency: 110 kHZ).
It is to be noted that the formulation of the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant formulations are intended to be within the scope of the present invention, which is further set forth under the following claims:

WE CLAIM;
1. A novel viscoelastic media for nano-finishing of materials through abrasive
flow machining process comprising of viscoelastic material, 1-90% by
weight of abrasive particles (with respect to the said viscoelastic material)
and 1-50% by weight of processing oil (with respect to the said viscoelastic
material).
2. A process for preparation of viscoelastic media comprising steps of:
mixing of 1-90% by weight of abrasive particles and 1-50% by weight of
processing oil in viscoelastic material in a two-roll mill such as herein
described.
3. A process for preparation of viscoelastic media as claimed in claim 2
wherein the mixing is carried out at 50-12 5°C and at a friction ratio of
1:1.1-1:1.5 with speed of front roll in between 10-34 rpm using two roll
mixing mill.
4. The media as claimed in Claim 1 wherein the abrasive particles and
processing oil imbedded viscoelastic matrix is prepared by mixing the
media and other compounding ingredients by other methods such as
internal mixing kneader, intermix and banbary mixer
5. The media and process as claimed in Claim 1 or 2 wherein the viscoelastic
media is selected from the group comprising of natural rubber,
polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber,
ethylene-propylene rubber, ethylene-propylene diene-monomer rubber,
butyl rubber, halobutyl rubber, nitrile rubber, hydrogenated nitrile rubber,
polysulfide rubber, polyacrylic rubber, neoprene rubber, hypalon rubber,
silicone rubber, fluorocarbon rubber, polyurethane rubber, thermoplastic
elastomer, and mixture thereof.
6. The media and process as claimed in Claim 5 wherein the viscoelastic
matrix natural rubber is selected from the group comprising of standard
malaysian rubber (SMR) L, SMR CV, SMR WF, SMR GP, SMR LV, SMR 5,
SMR 10, SMR 20, SMR 50, technically specified rubbers (TSR) 5, TSR 10,
TSR 20, TSR 50, technically classified rubber, oil extended natural rubber,
deproteinized natural rubber, peptized natural rubber, skim natural
rubber, superior processing natural rubber, heveaplus MG rubber,
epoxidized natural rubber, thermoplastic natural rubber, and mixture
thereof; the elastomer matrix styrene-butadiene rubber is selected from the
group comprising of solution styrene-butadiene rubber i.e., SBR 2305, SBR
2304, emulsion styrene-butadiene rubber i.e., cold SBR 1500, cold SBR
1502, hot SBR 100, and mixture thereof; the elastomer matrix
polybutadiene rubber is selected from the group comprising of cisamer-01,

cisamerl220, BR 9000, BR 9004A, BR 9004B, low molecular weight 1, 3 poly butadiene, and mixture thereof; the elastomer matrix butyl rubber is selected from the group comprising of IIR-1751, IIR-1751F, I1R-745, Exxon butyl 007, Exxon butyl 065, Exxon butyl 068, Exxon butyl 165, Exxon butyl 268, Exxon butyl 269, Exxon butyl 365, polysar butyl 100, polysar butyl 101, polysar butyl 101-3, polysar butyl 301, polysar butyl 402, and mixture thereof; the elastomer matrix ethylene-propylene rubber is selected from the group comprising of dutral-CO-034, dutral-CO-038, dutral-CO-043, dutral-CO-054, dutral-CO-058, dutral-CO-059, dutral-CO-055, and mixture thereof; the elastomer matrix ethylene-propylene-diene-monomer. rubber is selected from the group comprising of ethylene-propylene-dicyclopentadiene rubber, ethylene-propylene-ethylidenenorbornene rubber, ethylene-propylene-1, 4 hexadiene rubber, and mixture thereof; the elastomer matrix halobutyl rubber is selected from the group comprising of Exxon chlorobutyl 1065, Exxon chlorobutyl 1066, Exxon chlorobutyl 1068, Polysar chlorobutyl 1240, Polysar chlorobutyl 1255, Exxon bromobutyl 2222, Exxon bromobutyl 2233, Exxon bromobutyl 2244, Exxon bromobutyl 2255, Polysar bromobutyl X2, Polysar bromobutyl 2030, and mixture thereof; the elastomer matrix nitrile rubber is selected from the group comprising of Krynac-2750, Nipol-1053, Nipol-1032, Paracril-C, Chemigum-N-3, Krynac-5075, and mixture thereof; the elastomer matrix hydrogenated nitrile rubber is selected from the group comprising of zetpol-1010, zetpol-1020, zetpol-2010, zetpol-2020, therban, and mixture thereof; the elastomer matrix polyacrylic rubber is selected from the group comprising of hycar-4051, hycar-4052, hycar-4054, vamac-B-124, and mixture thereof; the elastomer matrix neoprene rubber is selected from the group comprising of neoprene-AC, neoprene-AD, neoprene-ADG, neoprene-AF, neoprene-AG, neoprene-FB, neoprene-GN, neoprene-GNA, neoprene-GRT, neoprene-GS, neoprene-GW, neoprene-W, neoprene-W-MI, neoprene-WB, neoprene-WD, neoprene-WHY, neoprene-WHV-100, neoprene-WHV-200, neoprene-WHV-A, neoprene-WK, neoprene-WRT, neoprene-WX, neoprene-TW, neoprene-TW-100, neoprene-TRT, and mixture thereof; the elastomer matrix hypalon rubber is selected from the group comprising of hypalon-20, hypalon-30, hypalon-LD-999, hypalon-40S, hypalon-40, hypalon-4085, hypalon-623, hypalon-45, hypalon-48S, hypalon-48, and mixture thereof; the elastomer matrix silicone rubber is selected from the group comprising of silicone MQ, silicone MPQ, silicone MPVQ, silicone FVQ, and mixture thereof; the elastomer matrix fluorocarbon rubber is selected from the group comprising of viton-LM, viton-C-10, viton-A-35, viton-A, viton-A-HF, viton-E-45, viton-E-60, viton-E-60C, viton-E403, viton-B-50, viton-B, viton-B-70, viton-910, viton-GLT, viton-GF, viton-VTR-4730, DAI-EL-G-101, DAI-EL-701, DAI-EL-751, DAI-EL-702, DAI-EL-704, DAI-EL-755, DAI-EL-201, DAI-EL-501, DAI-EL-801, DAI-EL-901, DAI-EL-902, tecnoflon-FOR-LHF, tecnoflon-NMLB, tecnoflon-NML, tecnoflon-NMB, tecnoflon-NM, tecnoflon-NH, tecnoflon-FOR-45-45BI, tecnoflon-FOR-

70-70BI, tecnoflon-FOR-45-C-CI, tecnoflon-FOR-60K-KI, tecnoflon-FOR-50E, tecnoflon-TH, tecnoflon-TN-50, tecnoflon-TN, tecnoflon-FOR-THF, tecnoflon-FOR-TF-50, tecnoflon-FOR-TF, fluorel-2145, fluorel-FC-2175, Huorel-FC-2230, fluorel-FC-2178, fiuorel-FC-2170, fluorel-FC-2173, fluorel-FC-2174, fluorel-FC-2177, fluorel-FC-2176, fhiorel-FC-2180, fluorel-FC-81, fluorel-FC-79, fluorel-2152, fluorel-FC-2182, fluorel-FC-2460, nuorel-FC-2690, fluorel-FC-2480, and mixture thereof, the elastomer matrix polyurethane rubber (polyether and polyester type) is selected from the group comprising of FMSC-1035, FMSC-1035T, FMSC-1040, FMSC-1050, FMSC-1060, FMSC-1066, FMSC-1070, FMSC-1075, FMSC-1080-SLOW, FMSC-1080-FAST, FMSC-1085, FMSC-1090-FAST, FMSC-1090-SLOW, and mixture thereof; the elastomer matrix thermoplastic elastomer (polyurethane, polyester, polyamide, styrene-butadiene-styrene, blends, etc) is selected from the group comprising of SBS 1401, SBS 4402, SBS 4452, SBS 1301, SBS 1401-1, SBS 4303, estane-55103, hytrel-40xy, hytrel-63xy, hytrel-72xy, gaflex-547, pebax-2533, pebax-6333, TPR-1600, TPR-1900, TPR-2800, TELCAR-340, SOMEL-301, SOMEL-601, santoprene, cariflex-TR, solprene-400, stereon, and mixture thereof; the elastomer matrix polysulfide elastomer is selected from the group comprising of thiakol-A, thiakol-B, thiakol-FA, thiakol-ST, and mixture thereof;
7. The media and process as claimed in Claim 1 or 2 wherein the abrasive
particles are selected from the group comprising of alumina, silicone
carbide, diamond powder, boron carbide, silica, garnet, tungsten carbide,
etc and mixture thereof. .
8. The media and process as claimed in Claim 1 or 2 wherein the process oil
is selected from the group comprising of paraffinic oil, naphthenic oil,
aromatic oil, vegetable oil, and mixture thereof.
9. A novel viscoelastic media for nano-finishing of materials through abrasive
flow machining process and a method of manufacture thereof substantially
as herein described and illustrated.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=NJkfxoBaSLdAbm/+U743ng==&loc=+mN2fYxnTC4l0fUd8W4CAA==

« Previous Patent

Next Patent »

Patent Number

268746

Indian Patent Application Number

591/DEL/2007

PG Journal Number

38/2015

Publication Date

18-Sep-2015

Grant Date

15-Sep-2015

Date of Filing

19-Mar-2007

Name of Patentee

INDIAN INSTITUTE OF TECHNOLOGY KANPUR

Applicant Address

KANPUR-208016, (U.P) AN INDIAN INSTITUTE

Inventors:

#	Inventor's Name	Inventor's Address
1	JANAKARAJAN RAMKUMAR	ADVANCED NANO ENGINEERING MATERIALS LABORATORY, DEPARTMENT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE PROGRAMME; INDIAN INSTITUTE OF TECHNOLOGY KANPUR;KANPUR-20816,UP,INDIA
2	KAMAL KRISHNA KAR	ADVANCED NANO ENGINEERING MATERIALS LABORATORY, DEPARTMENT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE PROGRAMME; INDIAN INSTITUTE OF TECHNOLOGY KANPUR;KANPUR-20816,UP,INDIA
3	PIYUSHKUMAR BIPINCHANDRA TAILOR	ADVANCED NANO ENGINEERING MATERIALS LABORATORY, DEPARTMENT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE PROGRAMME; INDIAN INSTITUTE OF TECHNOLOGY KANPUR;KANPUR-20816,UP,INDIA

PCT International Classification Number

B24B1/00; B24B21/00; B24B1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA