1、l I I 2000FTM5 Systematic Investigations on the Influence of Viscosity Index Improvers on EHL-Film Thickness by: B.-R. Hhn, K. Michaelis K. Michaelis, Chief Engineer; F. Kopatsch, Research Engineer Gear Research Center (FZG), Technical University of Munich, Boltzmannstr. 15, 85748 Garching, Germany
2、Nomenclature (tJM = (9, + 9J2) A C C 1, E2 E FN G L Mw P R SSI U VI W b deformed area of disk capacitor capacitance of disk capacitor thermal correction factor acc. MurchMlson Youngs modulus of contact bodies reduced Youngs modulus normal force EHL-parameter of elasticity thermal load factor acc. Mu
3、rchMlson 131 weight average molecular weight polymer-correction-factor reduced radius of curvature shear-stability-index EHL-parameter of velocity viscosity-index EHL-parameter of load deformed Hertzian contact width tip circle base circle pitch circle frequency of resonance circuit measured lubrica
4、nt film thickness minimum film thickness calculated acc. Dowson/Higginson 6 film thickness in the parallel gap calculated acc. ErtellGrubin 7,9 disk width Hertzian contact pressure radius of curvature of contact bodies slip ratio (s = 7 - vJvl) surface velocity of contact bodies hydrodynamic velocit
5、y (v, = vl + v2) pressure-viscosity coefficient temperature coefficient of dynamic viscosity shear rate relative dielectric coefficient of the oil electric field constant (so = 8,8542. 1-12 C/(Vm) dynamic viscosity dynamic viscosity at bulk temperature temperature average bulk temperature i31 (v2 C
6、Y u .- pitting-test PT C/9/90 I I L 1 PIE1 H ,/- F i 8 C D E poth of contact Fig. 16. Calculated film thicknesses of test oils . 1 H at pitting-test conditions. pitting-test PT C/9/90 I t 1 - .- El B C D E poth of contact Fig. 17. Calculated film thicknesses of test oils . 2L at pitting-test conditi
7、ons. With these gear data, the film thickness can be calculated along the path of contact of a gear mesh. An example is shown in Fig. 16. The film thickness hO,thermal,pol,r which was calculated acc. ErteVGrubin 7, 91 with thermal correction acc. MurchMiilson I 31 and polymer-correction-factor P, is
8、 plotted against the path of contact of a C-PT-type gear pair for the conditions of the standard pitting-test PT C/9/90 for the test oils . 1 H with short-chain polymers and high concentrations. The relevant tooth bulk temperature was assumed to be constant at 100C. Without using the polymer-correct
9、ion-factor P, the film thicknesses of all polymer-containing oils would be calculated equal to that one of M240. With using the polymer-correction-factor P, the calculated film thicknesses of the polymer-containing oils represent the actually measured values better (see Fig. 8). Another calculation
10、example in Fig. 17 shows the film thicknesses of the test oils . 2L with the long- chain polymers in low concentration. Again, calcu- lation would provide film thicknesses equal to M240 for all polymer containing oils without using the polymer-correction-factor. With using the factor, the calculated
11、 film thicknesses show much better correlation with the measured ones (see Fig. 9). 6 Conclusions The lubricant film thicknesses of a number of polymer-containing oils and their base oils were measured systematically in a twin disk test rig. The investigated polymers were polyalkylmethacrylates (PMA
12、), polyisobutylenes (PIB), olefin-copolymeres (OCP), styrene-butadiene-copolymeres (SBC) and star-shaped styrene-isoprene-copolymeres (STAR) in with two different molecular weights each. In addition, the base oil viscosity and the concentration of the polymers in the base oil were varied. For inform
13、ation about the shear stability of the polymers, the temporary and the permanent viscosity loss by shearing were determined separately from each other by means of HTHS-viscosity measurements and KRL-shear stability tests. All polymer containing oils formed lower film thicknesses than a straight mine
14、ral oil of the same kinematic viscosity v, over a wide range of operating conditions. Short-chain polymers in high concentration in the base oil turned out to be significantly more effective in the contact than long- chain polymers in low concentration with same viscosities. Polymers, which thickeni
15、ng power is mainly based on the formation of network structures, such as SBC, proved poor film forming properties. A correction-factor P was derived from the test results, by which the accuracy of film thickness calculation can be improved significantly for polymer- containing oils. The application
16、of the correction- factor is demonstrated and its practical use is exemplified by calculating the film thicknesses of some polymer-containing oils in a gear contact. 7 Acknowledgement This research project was sponsored by the Deut- sche Wissenschaftliche Gesellschaft fr Erdl, Erdgas und Kohle e.V.
17、(DGMK) within the Arbeits- gemeinschaft industrieller Forschungsvereinigun-gen e.V. (AiF) by funds of the German Bundesministeri- um fr Wirtschaft (BMWi). 8 References 11 ASTM D4624-93: Standard Test Method for Measuring Apparent Viscosity by Capillary Viscometer at High Temperature and High Shear-R
18、ates. ASTM-Standard, 1998. Bartz, W.-J.: Bewertung des reversiblen und irreversiblen Viskosittsverlustes von Mehr- bereichslen. Tribologie und Schmierungs- technik, 41. Jahrgang, 4/1994, S. 214-218. CEC L-45-A-99: Viscosity Shear Stability Test Procedure for the Tapered Roller Bearing Test Rig, 1999
19、. CEC L-37-T-85: Shear Stability of Polymer- Containing Oils (FZG Spur Gear Test Rig), 2 3 4 i 51 1986. DIN/ISO 2909: Berechnung des Viskositts- index aus der kinematischen Viskositt. Juli 1979. Dowson, D.; Higginson, G.R.: Elastohydrody- namic Lubrication. Oxford. Pergamon Press, 1966. Ertel-Mohren
20、stein, A.: Die Berechnung der hydrodynamischen Schmierung gekrmmter Oberflchen unter hoher Belastung und Rela- tivbewegung. VDI-Fortschrittsbericht Reihe 1, Nr. 115, 1984. FVA-Informationsblatt zum Forschungsvorha- ben Nr 2/IV: Pittingtest - Einflu des Schmier- Stoffes auf die Grbchenlebensdauer ein
21、satz- gehrteter Zahnrder im Einstufen- und im Lastkollektivversuch, 1997. Grubin, A.N .; Vinogradova, J .E. : Investigation of the contact machine components. Cent. Sci. Res. Inst. Tech. Mech. Eng. Moscow, Book No. 30, 1949. Kopatsch, F.: Systematische Untersuchungen zum Einflu von polymeren Zustzen
22、 auf die EHD-Schmierfilmdicke. DGMK-Forschungs- bericht Nr. 466-01, 1999. Mann, U.: Messung von Schmierfilmdicken im EHD-Kontakt. Einflu verschiedener Grundle und Viskositts-lndex-Verbesserer. DGMK- Forschungsbericht Nr. 466, 1995. Mitsui, H.; Spikes, H.A.: Predicting EHD Film Thickness of Lubricant
23、 Polymer Solutions. Tribology Transactions, Vol. 41, 1, 1998, pp. 1 - 10. Murch, L.E.; Wilson, W.R.D.: A Thermal Elastohydrodynamic Inlet Zone Analysis. Trans. ASME F, J. Lubr. Techn. 97, 2, 1975, Simon, M.: Messung von elasto-hydrody- namischen Parametern und ihre Auswirkung auf die Grbchentragfhig
24、keit vergteter Scheiben und Zahnrder. Disc. TU Mnchen, 1984. Smeeth, M.; Spikes, H.A.; Gunsel, S.: The Formation of Viscous Surface Films by Poly- mer Solutions: Boundary or Elastohydrodyna- mic Lubrication? Tribology Transactions, Vol. Smeeth, M.; Spikes, H.A.; Gunsel, S.: Boun- dary Film Formation by Viscosity Index Impro- vers. Tribology Transactions, Vol. 39, 3, 1996, pp. 212-216. 39, 3, 1996, pp. 720-725. pp. 726-734. 11
