Efficiency of Teflon Sliding Surface

Transcription

1 Internatial Journal of Sports Science 2013, 3(6): DOI: /j.sports Efficiency of Tefl Sliding Surface Evgeniy A. Bogoslov 1, Nikolay P. Gerasiov 2, Maxi P. Danilaev 1, Sergey A. Mikhailov 1, Yury E. Polsky 1, Olga Y. Bogoolova 1,* 1 Departent of Engineering and Technology, Tupolev s Kazan Natial Research Technical University (KNRTU-KAI), Kazan, , Russian Federati 2 Departent of Physical educati, Tupolev s Kazan Natial Research Technical University (KNRTU-KAI), Kazan, , Russian Federati Abstract A coparative analysis of cross-country skis sliding surfaces ade of ultra-high-olecular-weight polyethylene, pure Tefl and Tefl with special cductive filler are presented in this paper. It is shown that the use of Tefl sliding surface increases the distance by 20-27%, and decreases the distance tie by 20%. Sliding efficiency of cross-country skis with Tefl sliding surface is higher than of cross-country skis with ultra-high-olecular-weight polyethylene sliding surface in wide range of teperatures (-15;0 C) and high snow huidity (~97%). Keywords Sliding Surface of Skis, Skis Sliding, Tefl 1. Introducti Sliding surface of odern skis is ade of ultra-high-olecular-weight polyethylene with various additives[1]. Before each ctest the sliding surface is being waxed to iprove the sliding quality[2,3]. Today the ost widely used type of gliding wax is fluorine-ctained wax[4]. However, wax fluorine coatings are being destroyed during skis exploitati, even with use of odern coating technologies. That causes the repetiti of coating procedure before each race[5]. Because of absence of single proven gliding wax selecti ethod and of ipartial quantitative gliding wax effectiveness test, not always the serviceen can choose the right wax, that worsens the results of sporting events. Today there is an active search for gliding waxes copositis and the coating technologies that can iprove the effectiveness of cross-country skis sliding. Use of gliding waxes has a nuber of restrictis[6,7,8], because waxes: - work at a short range of teperatures and air and snow huidity; - depend a snow type and its structure; - can t provide the sae effectiveness of skis sliding coplex tracks with variable track cditis, such as teperature and huidity, snow structure etc.; - require the choice of a gliding wax before each race. As a result, a new type of sliding surface is needed to * Correspding author: likebog@gail.co (Olga Y. Bogoolova) Published line at Copyright 2013 Scientific & Acadeic Publishing. All Rights Reserved provide effective sliding in wide range of track cditis without gliding waxes. For analysis of skis sliding a snow a co theory of snow crystals elting, based heat eissi during fricti and forati of elted water fil between the skis sliding surface and the snow surface, is used[9]. According to this theory, two types of sliding cditis exist: hydrodynaic and quasihydrodynaic. Hydrodynaic cditi works at snow teperature above -5 C and is characterized by big aount of elted water between the sliding surface and the snow surface; as a result, surfaces are copletely separated. Quasihydrodynaic cditi works at teperature below -5 C and is characterized by sall aount of elted water; as a result, top points of undulatis of skis sliding surface and snow surface begin to cnect, and part of the pressure is transferred to these top points. Following the theory of sliding a elted water fil, it is necessary in both cditis to use the sliding surface with high hardness (sliding surface aterial ust be harder than snow crystals), water repellency (adhesi between the sliding surface and the snow decreases with the increase of water repellency) and low theral cductivity (low theral cductivity of the sliding surface saves the heat eitted fro fricti; this heat produce additial aounts of gliding lubricant elted water). Coparative analysis of odern aterials used for aking the cross-country skis sliding surface and Tefl is presented in Table 1. Table 1 shows that the use of sliding surface ade of pure Tefl, as well as of filled cductive aterial (such as PTFE CSC 1,2), provides low fricti ratio and good cductivity. The latter reoves the proble of static

2 Internatial Journal of Sports Science 2013, 3(6): charges[10,11] that takes place during the exploitati of skis with Tefl sliding surface. On the e hand, low fricti ratio and weak adhesi of Tefl provide effective sliding of cross-country skis in wide range of track cditis. On the other hand, low adhesi leads to restrictis in use of this aterial for aking the skis sliding surface, because it doesn t provide the necessary adhesive strength between olith Tefl coating and skis base[12]. The ai of this study is experiental testing of sliding efficiency of cross-country skis with Tefl sliding surface. 2. Technology A plasa-cheical technology of nanostructured polyer coatings forati in two-phase gas flows with use of plasa at atospheric pressure has been developed In Tupolev s Kazan Natial Research Technical University (KNRTU-KAI). This technology provides Tefl tape surface odificati that iparts high adhesive properties and ensures solid cnecti with ski base[13,14]. A plasa-cheical technology of nanostructured polyer coatings forati in two-phase gas flows with use of plasa at atospheric pressure is based the initiati of grafting radical polyerizati reacti of surface olecules of Tefl with oer olecules that for a thin layer (up to oolecular thickness, but not ore than 100 n). It results in breaking of cheical bds and generati of free radicals (including lg-lived radicals) that undergo cheical and recobinati transforatis, Material Тeral cductivity (W/*K) such as cross-linking, creati of double-bds and polar groups etc. With use of that a thin layer of a different polyer aterial is fored e side of a Tefl sliding surface. Polyer olecules are covalently attached to Tefl surface olecules. Moer (or ix of oers) and carrier-gas are chosen based their ability to perfor the radical (or ani/cati) polyerizati of oer or ix of oers by nucleati of radicals (or anis/catis). Afterwards, Tefl tape s odified side is being attached to the surface by any known ethod. The secd side reains unodified. This allows the use of high water repellency and low adhesi of the outer side of Tefl coating. Structure chart of the experiental setup is shown Figure 1. Figure 1. Table 1. Coparative Analysis of Modern Sliding Surface Materials and Tefl Breaking strength (MPa) Сtact angle Hardness (Shore D) Structure chart of the experiental setup Volue resistivity (Ω*) Static fricti ratio Dynaic fricti ratio Tefl 100% 0, ,08-0,1 0, Tefl + 1,2% cductive filler 0,24 > > ,08-0,1 0,06-0,08 UHMWPE 1 (P-TexR 4000) 0,4 ~ ,3 105 ~0,17 ~0,15 UHMWPE 2 (P-TexR ,4 ~ ,7 106 ~0,15 ~0,13 Electra) Carb (wax) 0,1 Swix LF4 (-10/-20оС) (wax) 47,8 0,12 Star wax Na8 (-8/-20оС) (wax) 50,4 0,15 Table 2. The results of adhesi strength testing Adherent aterials Adherence cditis Interlainar Destructi type Saple Rupture load, Base Flexible Glue Р, strength, On adherent Т, С width, Р, kn aterial aterial kg/s 2 τ, in On glue layer F, kn/ aterials 1 Wood Tefl ED ,05 0,095 2, Wood Tefl ED ,05 0,105 2, Wood Tefl ED ,05 0,1 2, Wood Tefl ED ,05 0,1 2, Wood Tefl ED ,05 0,1 2,2 + -

3 226 Evgeniy A. Bogoslov et al.: Efficiency of Tefl Sliding Surface Polyer fil 1 was pulled by the stretch rolls 2 through the discharge chaber 3 and oer depositi chaber 4. The discharge chaber is ade of two electrodes: plane and needle. The distance between electrodes is varied fro 1 to 2 c with 10% accuracy. For extensi of radicals lifetie scale the surface of polyer fil and for stabilizati of cora discharge inert gas (Ar) inputs 5 were ade in side walls of the discharge chaber. Gas csupti through the side walls inputs was ~0.5 c 3 /sec. Moer particles were ejected into oer depositi chaber 4 with the ejector 7. Arg was used as the carrier gas 8 for creati of two-phase gas flow. The discharge chaber was installed in the exit nozzle of the ejector 7 to provide the possibility of oer particles charging in the cora discharge. Power source s output voltage of the discharge chabers ranged between 0 and 50kV with 5% accuracy. Two-phase (oer particles and inert gas) gas flow s csupti was regulated by reducer 9, installed in the entrance of the ixing chaber. Polyer fil speed was deterined by drive assebly 10 at ~15s. The distance l between the discharge chaber and oer depositi chabers was chosen according to radicals lifetie scale the surface of polyer fil, l~1s. In experiental studies a styrene was used as oer that creates a thin cohesive layer after polyerizati. Styrene was chosen because of its ability to perfor radical polyerizati with forati of copolyer with surface olecules of polyer (Tefl) fil. The testing of adhesi strength between olith Tefl tape and ski base took place a testing stand iitating the ski work in the Laboratory of strength of KNRTU-KAI (Figure 2). Figure 2. Testing stand iitating the ski work The adhesi strength was tested after cycles of bending that correspds to ore than a 1000 k of skiing. The results showed no signs of adhesi failure. The adhesi interlainar strength was tested the tearing achine IR Loading rate was /in. At least five saples were prepared fro a 1,5 thick Tefl tape, the size of saples was 50x125. The saples were pasted in the wooden bricks. An epoxy-diane glue (ED-8) was applied a 110 length; ends of a saple were fixed in the tearing achine s claws. Interlainar strength was defined by the forula: P F = (1) b, where Р average load of tape delainati, N; b glue layer thickness,. An arithetical ean of interlainar strengths of all saples was taken as a test result. Based a gathered data, the adhesi strength of surfaces interactis was estiated. The results of testing are shown in Table 2. Thus, adhesi interlainar strength between odified Tefl tape and wooden brick was at least 2 kh/ (kg/s). To estiate the efficiency of Tefl coating of a skis sliding surface, a nuber of experients downhill distance with and without skier were perfored. 3. Experients A series of experients downhill distance of weighted skis were ade in the end of a winter seas to gain a rough estiate of sliding effectiveness of cross-country skis with Tefl sliding surface. The experients were ade without a skier. The schee is shown Figure 3. Figure 3. The schee of an experient downhill distance of weighted skis On the Figure 3: 1 start point; 2 finish point of a ski with waxed sliding surface; 3 finish point of a ski with sliding surface with pasted-in 50 icr thick Tefl fil; 4 finish point of a ski with sliding surface with pasted-in 1 thick Tefl tape; H slope height (H~1,5-2 ); L1 distance of a ski with waxed sliding surface; L1+L2 distance of a ski with sliding surface with pasted-in Tefl fil; L1+L2+L3 - a ski with sliding surface with pasted-in Tefl tape. The experiental cditis were: - air teperature: ~0 C; - snow teperature: ~-5 C; - relative air huidity: ~80%; - stable waterlogged snow cover. Eighty-five experients downhill distance were ade in total, using the schee, shown Figure 2. It is worth nothing that thickness of cross-country skis is usually 1 to 1,5, so using of 50 icr thick fil was necessary ly for optiizati of pasting-in technology. The results are presented in Table 3 (noralized velocity V 0 was calculated coparatively to the velocity of ski with waxed sliding surface).

4 Internatial Journal of Sports Science 2013, 3(6): Table 3. The results of experients downhill distance (without a skier) Ski sliding surface with pasted-in Ski with sliding surface with Paraeter Ski with waxed sliding surface 50 icr thick Tefl fil pasted-in 1 thick Tefl tape Weighted ski s ass, kg 6,5 6,5 6,5 Surface area, s L1=20±0,01 L1+L2=25,5±0,01 L1+L2+L3=27,5±0,01 tie, s T 1 =17,4 ± 0,04 T 2 =14,0 ± 0,04 T 3 =14,6 ± 0,04 Average velocity, /s V 1 =1,15±0,01 V 2 =1,82±0,01 V 3 =1,88±0,01 Noralized velocity, V 0 V 0 =V 1 /V 1 =1 V 0 =V 2 /V 1 =1,6 V 0 =V 3 /V 1 =1,7 Skis 1 (UHMWPE) Table 4. The results of experients downhill distance (with a skier) Skis 2 (Tefl) Skis 3 (PTFE+1,2% of cductive filler) III I II III II I III II I III II I III II I at different teperatures to realize two types of sliding cditis: hydrodynaic and quasihydrodynaic. Eighty-five experients downhill distance were ade in total, using the schee, shown Figure 3. The sliding efficiency was judged by skier s distance. During experients, estiatis of tie and distance easuring inaccuracies were ade. Measuring inaccuracy: of distance δ 1 ~1% of distance tie δ 2 ~1%. Figure 4. Cross-country skis with SS ade of: 1 PTFE+1,2% of cductive filler; 2 Tefl-4; 3 - UHMWPE The experiental results analysis shows that the use of Tefl as a sliding surface iproves the distance by 20-27% and also iproves distance tie speed by 20% that indicates the increase of skis sliding efficiency. For ore thorough experiental research a test cross-country skis for skate skiing with three different types of a sliding surface (SS) were ade (Figure 4): 1) SS ade of ultra-high-olecular-weight polyethylene with gliding wax for appropriate weather cditis (skis 1); 2) SS ade of pure PTFE (Tefl) (skis 2); 3) SS ade of PTFE+1,2% of cductive filler (skis 3). Experiental studies took place in a tie period fro January 11th, 2013 to January 21st, 2013 using the schee, shown Figure 3. Test skis were preliinary echanically treated; all three pairs had the sae pattern arked the sliding surface. Experients were cducted Figure 5. Experient downhill distance (with a skier) The results of five experients (Figure 5) are presented in Table 4. The results of other eighty experients were siilar to the presented five and with the sae easuring inaccuracies, so they are not presented for cciseness. The results show that skis 2 and 3 had the lgest distance and highest speed. The distance advantage was 2-9 coparing to skis 1. Skis 2 and 3 were winning by turns, depending the weather cditis

5 228 Evgeniy A. Bogoslov et al.: Efficiency of Tefl Sliding Surface 4. Cclusis The results analysis shows that: - the use of Tefl SS not ly increases the distance by 20-27%, but also decrease the distance tie by 20%; which is the evidence of increase of sliding efficiency; - efficiency of sliding of test skis with Tefl SS depends a weather cditis. A coparative analysis of experiental results shows that sliding efficiency of cross-country skis with Tefl SS is higher than of cross-country skis with waxed UHMWPE SS in wide range of teperatures (-15;0 C) and high snow huidity (~97%). The results coply with the theoretical analysis of sliding of skis with Tefl SS. Thereby, use of Tefl SS is proising for different sports equipent, such as sledge, snowboards etc. ACKNOWLEDGEMENTS Authors acknowledge Y.F.Zolotov, a professor of a Physical educati departent of KNRSU-KAI, for his help in preparati and aking of the experients. REFERENCES [1] C.Staboulides, P.Englezos, S.G.Hatzikiriakos, Ice fricti of ultra-high olecular weight polyethylene: The effects of fluorine additives and plasa (PECVD) treatent, Tribology Internatial, vol. 57, pp , Jan [2] N.P.Gerasiov, Y.F.Zolotov. Ski training a Physical culture classes in high school. Methodological guide. Kazan, [3] V.I.Aparin, A.P.Bezrukov, B.A.Gubatenko, E.A.Dukhovsky, A.Y.Lyapunov, N.N.Rozhkova, Ski wax, RU Patent , Apr. 27, [4] I.Rogowski, D.Leard, J.-Y.Gauvrit, P.Lanteri, Influence of fluorine-based additive ctent the physical and physicocheical properties of ski gliding wax, Cold regi science and Technology, vol. 49(2), pp , Aug [5] L.Kuzin. Surface sliding fricti of skis: nature, paths and ethods of iproveent. All-Russian scientific-practical cference Modern syste of sports training in biathl. Osk, [6] L.Kuzin, M.Tinnsten, The ctainati, wettability and gliding ability of ski running surfaces, Science and Nordic skiing, pp [7] L.Kuzin, M.Tinnsten, Dirt absorpti the ski running surface quantificati and influence the gliding ability, Sports Engineering, vol.9(3), pp [8] L.Kuzin, M.Tinnsten, Estiati of dirt attracti running surfaces of cross-country skis, The Ipact of Technology Sport II, pp , [9] V.A.Balakin, O.V. Pereverzeva, Frictial heating and elting of sliding surfaces, Journal of Fricti and Wear c/c Trenie i Iznos, (4): p [10] M.Yekta-Fard, A.B.Pter, Factors affecting the wettability of polyer surfaces, Journal of Adhesi Science and Technology, vol.6, pp , [11] G.Sandford, Perfluoroalkanes, Tetrahedr, vol.59(4), pp , [12] A.D.Zi. Adhesi of fils and coatings. Moscow, [13] Y.E.Polsky, S.A.Mikhailov, M.P.Danilaev, Methods of polyer fils odificati (optis) and device for its realisati, RU Patent , Jan. 10, [14] E. A. Bogoslov, M.P.Danilaev, M. V. Efiov, S.A. Mikhailov, Y.E.Polskii, K.V.Faizullin Experiental Studies of a Method of Forati of Multilayer Polyer Fils with Given Physicocheical Properties of Individual Layers// Protecti of Metals and Physical Cheistry of Surfaces, 2013, Vol. 49, No. 3, pp