Friction and Lubrication in Mechanical Design Episode 2 Part 4 ppsx

0.06 0.05 0.04 0.03 cc 0.02 0.01 0.00 1 1 1 1 1 1 0 .oo 0.05 0.10 0.15 0.20 0.25 0.30 f Figure 7.34 Calculated coefficient of friction vs. slidingjrolling ratio for different rolling speeds, T = 26°C (78.8"F), steel-steel contact, ground surfaces, S = 0.3 pm (12pin.), W = 378,812N/m (2160 lbf/in.), 10W30 oil, R = 0.0234m (0.92 in.). 0.06 0.05 0.04 0.03 cc 0.02 0.01 0.00 0.05 0.10 0.15 0.20 0.25 0.30 f Figure 7.35 Calculated coefficient of friction vs. sliding/rolling ratio for different normal loads, T = 26°C (78.8"F), steel-steel contact, ground surfaces, S = 0.3 pm (12pin.), U = 3.2m/sec (216 in./sec), IOW30 oil, R = 0.0234m (0.92 in.). 305 f Figure 7.36 Calculated coefficient of friction vs. sliding/rolling ratio for different effective radii, T = 26°C (78.8"F), steel-steel contact, ground surfaces, S = 0.3 pm (12pin.), W = 378,812N/m (2160 lbf/in.), 10W30 oil, U1 = 3.2m/s (126 in./sec). 0.08 I I I 1 I 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 I I I 1 I 0.00 0.05 0.10 0.1 5 0.20 0.25 0.30 f Figure 7.37 Calculated coefficient of friction vs. slidinglrolling ratio for different viscosity, steel-steel contact, ground surfaces, S = 0.3 pm (12 pin.), W = 378,8 12 N/m (2160 lbf/in.), IOW30 oil, U1 = 3.2m/s (126 in./sec), R = 0.0234m (0.92 in.). 306 RoNingISliding Contacts 307 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 Stainless Steel (S.S) - Steel-Bronze Steel-Ceramic _ Steel-Steel I I I I I Stainless Steel (S.S) Steel-Ceramic _ Steel-Steel - Steel-Bronze - I I I I I 0.00 0.05 0.1 0 0.1 5 0.20 025 0.30 f Figure 7.38 Calculated coefficient of friction vs. sliding/rolling ratio for different materials, T = 26°C (78.8”F), ground surfaces, S = 0.3 pm (12 pin.), W = 378,812 N/m (2160 lbf/in.), 10W30 oil, U1 = 3.2 m/s (126 in./sec), R = 0.0234m (0.92 in.). S = 0.03 pm (12pin.), W = 378,812N/m (2160lbf/in.), 10W30 oil, U1 = 3.2 m/sec (126 in./sec), R = 0.0234 m (0.92 in.). REFERENCES 1. 2. 3. 4. 5. 6. Palmgren, A., Ball and Roller Bearing Engineering, S. H. Burbank, Philadelphia, 1945. Tabor, D., “The Mechanism of Rolling Friction,” Phil. Mag., Vol. 43, 1952, pp. 1055 and Vol. 45, 1954, p. 1081. Rabinowicz, E., Friction and Wear of Materials, John Wiley and Sons, New York, NY, 1965. Dowson, D., and Higginson, G. R., Elastohydrodynamic Lubrication, Pergamon, Oxford, 1977. Grubin, A. N., Book No. 30, English Translation DSIR, 1949. Dowson, D., and Whitaker, A. V., “A Numerical Procedure for the Solution of the Elastohydrodynamic Problem of Rolling and Sliding Contacts Lubricated 308 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. Chapter 7 by a Newtonian Fluid,” Proc. Inst. Mech. Engrs, 1965-1966, Vol. 180, Part 3b, Trachman, E. G., and Cheng, H. S., “Traction in EHD Line Contacts for Two Synthesized Hydrocarbon Fluids,” ASLE Trans., 1974, Vol. 17(4), pp. 27 1-279. Hirst, W., and Moore, A. J., “Non-newtonian Behavior in EHD Lubrication,“ Proc. Roy. Soc. Lond. A., 1974, Vol. 337, pp. 101-121. Johnson, K. L., and Cameron, R., “Shear Behavior of EHD Oil Films at High Rolling Contact Pressures,” Proc. Inst. Mech. Engrs, 1967-1968, Vol. 182, Pt. 1, No. 14. Plint, M. A., “Some Recent Research on the Perbury Variable-Speed Gear,” Proc. Inst. Mech. Engrs, 1965-1966, Vol. 180, Pt. 3B. Crook, A. W., “The Lubrication of Rollers, Part Ill,” Phil. Trans. Roy. Soc. Lond., Ser. A, 1961, Vol. 254, p. 237. Conry, T. F., “Thermal Effects on Traction in EHD Lubrication,” J. Lubr. Technol., Oct. 1981, pp. 533-538. Bair, S., and Winer, W. O., “Regimes of Traction in Concentrated Contact Lubrication,” ASME Trans., Vol. 104, July 1982, pp. 382-386. Plint, M. A., “Traction in Elastohydrodynamic Contacts,” Proc. Inst. Mech. Engrs, 1967-1968, Vol. 182, Pt. 1, No. 1 14, pp. 300-306. Dyson, A., “Frictional Traction and Lubricant Rheology in Elastohydrodynamic Lubrication,” Phil. Trans. Roy. Soc. Lond., 1970, Vol. 266, No. 1170. Sasaki, T., Okamura, K., and Isogal, R., “Fundamental Research on Gear Lubrication,” Bull. JSME, 1961, Vol. 4(14). Drozdov, Y. N., and Gavrikov, Y. A., “Friction and Scoring under the Conditions of Simultaneous Rolling and Sliding of Bodies,” Wear, 1968, Vol. 11. O’Donoghue, J. P., and Cameron, A., “Friction and Temperature in Rolling Sliding Contacts,’’ ASLE Trans., 1966, Vol. 9, pp. 186-194. Benedict, G. H., and Kelley, B. W., “Instantaneous Coefficients of Gear Tooth Friction,” ASLE Trans., 1961, Vol. 4, pp. 59-70. Misharin, J. A., “Influence of the Friction Conditions on the Magnitude of the Friction Coefficient in the Case of Rolling with Sliding,” Int. Conf. on Gearing. Proc., Sept. 1958. Ku, P. M., Staph, H. E., and Carper, H. J., “Frictional and Thermal Behavior of the Sliding-Rolling Concentrated Contacts,” ASME Trans., J. Lubr. Technol., Jan. 1978, Vol. 100. Li. Y., “An Investigation on the Effects of the Properties of Coating Materials on the Tribology Behavior of Sliding/Rolling Contacts,” Ph.D. Thesis, Univ. of Wisconsin, 1987. Rashid, M. K., and Seireg, A., “Heat Partition and Transient Temperature Distribution in Layered Concentrated Contacts,” ASME Trans., J. Tribol., July 1987, Vol. 109, pp. 49604502. Hsue, E. Y., “Temperature and Surface Damage under Lubricated Sliding1 Rolling Contacts,” Ph.D. Thesis, University of Wisconsin-Madison, 1984. p. 57. RollinglSliding Contacts 309 25. Wilson, W. R. D., and Sheu, S., “Effect of Inlet Shear Heating Due to Sliding and EHD Film Thickness,’’ J. Lubr. Technol., April 1983, Vol. 105. 26. Cameron, A., Basic Lubrication Theory, Longman Group, London, England, 1970. 27. Juvinall, R. C., Fundamentals of Machine Component Design, John Wiley & Sons, New York, NY, 1983. 8.1 INTRODUCTION Wear can be defined as the progressive loss of surface material due to normal load and relative motion. This generally leads to degradation of the surface, loss of component functionality, and in many situations, to catastrophic failure. The wear of mechanical components has been estimated to cost the U.S. economy between 6% and 7% of the gross national product. Understanding the wear process and its control is, therefore, of major practical importance. The highly complex nature of the wear process has made it difficult to develop generalized procedures for predicting its occurrence and intensity. Even wear tests under seemingly controlled conditions, are not always reproducible. It is not unusual that repeated tests may give wear rates which differ by orders of magnitude. Surface damage or wear can manifest itself in many forms. Among these are the commonly used terminology: pitting, frosting, surface fatigue, sur- face cracking, fretting, blistering, plastic deformation, scoring, etc. Wear types include elastic wear, plastic wear, delamination wear, abrasive wear, adhesive wear, corrosive wear, cavitation erosion, etc. The occurrence of a particular type of wear depends on many factors, which include the geome- try of the surfaces, the nature of surface roughness, the applied load, the rolling and sliding velocities. Other important factors which influence wear are the environmental temperature, moisture, and chemical conditions, as well as the mechanical, thermal, chemical, and metalurgical properties of the surface layer and bulk material. The microstructure of the surface layer, its 310 Wear 31 I ductility, the microhardness distribution in it, and the existence of vacancies and impurities also play critical parts in the wear process. Furthermore, wear is highly influenced by the physical, thermal, and chemical properties of the lubricant, the regime of lubrication, the mutual overlap between the rubbing surfaces, and the potential for removal of the chemical layers and debris generated in the process. This chapter provides a conceptual evaluation of this extremely complex phenomenon, and presents guidelines for its prediction and control. Although the mechanism of wear is not fully understood, designers of machine components have to rely on judgement and empirical experiences to improve the functional life of their design. The success of their judgement depends on their depth of understanding of which factors are relevant to a particular situation, and which are only accessories. It is interesting to note that with all the modern tools of experimenta- tion and computation, generalized wear design procedures that would pro- duce practical results are still beyond our reach. We have therefore to rely on thoughtful interpretation of accumulated data and observations. One such poignant observation was documented 2000 years ago by the Roman philosophical poet Titus Caras Lucretius [l]: He said, A ring is worn thin next to a finger with continual rubbing. Dripping water hollows a stone, a curved plow share, iron though it is, dwindles imperceptibly in the furrow. We see the cobblestones of the highway worn by the feet of many wayfarers. The bronze statues by the city gates show their right hands worn thin by the touch of all travelers who have greeted them in passing. We shall see that all these are being diminished since they are worn away. But to perceive what particles drop off at any particular time is a power grudged to us by our ungenerous sense of sight. 8.2 CLASSIFICATION OF WEAR MECHANISMS It has not yet been possible to devise a single classification of the different types of wear. Some of the mechanisms by which rubbing surfaces are damaged are [2]: Mechanical destruction of interlocking asperities; Surface fatigue due to repeated mechanical interaction between asperi- ties or the variation of pressure developed in the lubrication; Failure due to work hardening and increasing brittleness caused by deformation; Flaking away of oxide films; 312 Chapter 8 Mechanical damage due to atomic or molecular interactions; Mechanical destruction of the surface due to the high temperatures Adhesion or galling; Corrosion; Abrasion due to the presence of loose particles; Cutting or ploughing of a soft material by a harder rough surface; Erosion produced by impinging fluid or fluids moving with high rate of produced by frictional heating; shear. The treatment in this chapter attempts to formulate general concepts about the nature of wear, which can be readily associated with practical experience and to provide equations which can be used for design purposes based on these concepts. The broad categories to be considered are: Frictional wear Surface fatigue due to contact pressure Microcutting Thermal wear Delamination wear Abrasive wear Corrosion or chemical wear Erosion wear 8.3 FRICTIONAL WEAR In the broad category of frictional (or adhesive) wear considered in this section, it is assumed that the material removal is the result of the mechan- ical interaction between the rubbing surfaces at the real area of contact. It has been shown in Chapter 4 that the real area of contact is approximately proportional to the normal load under elastic contact condition. The pro- portionality constant is a function of the material properties, the asperity density, the radius of the asperities, and the root mean square of the asperity height. The wear volume per unit sliding distance has been evaluated according to this concept by several investigations. Their results are illustrated in the following. Archard [3, 41, as well as Burwell and Strang [5], proposed wear equa- tions of the following form: Wear 313 where V = wear volume L = sliding distance P = applied load oy = yield stress of the softer material K = proportionality constant depending on the material combination and test conditions (wear coeficient) H,,, = microhardness of the softer material Results obtained by Archard from dry tests where the end of a cylinder 6mm diameter was rubbed against a ring of 24mm diameter under a 400g load at a speed of 1.8m/sec are given in Table 8.1. Rabinowicz [6, 71 gave a similar equation: Table 8.1 Dry Wear Coefficients for Different Material Pairs Sliding against hardened tool steel unless otherwise stated Wear coefficient, K ( 103 kg/cm2) Microhardness, H,,, Mild steel on mild steel 60/40 brass Teflon 70/30 brass Perspex Bakelite (moulded) type 5073 Silver steel Beryllium copper Hardened tool steel Stellite Ferritic stainless steel Laminated bakelite type 292/16 Moulded bakelite type 11085/1 Tungsten carbide on mild steel Moulded bakelite type 547/1 Polyet hylene Tungsten carbide on tungsten carbide 7 x 10-’ 1.7 10-~ 7 x 10-6 7.5 x 10-6 3.7 x 10-‘ 1.3 10-~ 5.5 x 10-’ 1.7 10-~ 7.5 10-7 4 x 10-6 3 10-~ 1.3 10-~ 1 x 10-6 6x 10-4 2.5 x 10-’ 6 x 10-5 1.5 x 10-6 18.6 9.5 0.5 6.8 2.0 2.5 32 21 85 69 25 3.3 3.0 18.6 2.9 0.17 130 314 Chapter 8 where Y = wear volume (in.3) L = sliding distance (in.) A = surface area (in.2) P = applied load (lb) U,, = yield strength of the softer material (psi) h = depth of wear of the softer material (in.) k = wear coefficient Values of k for different material combinations are given in Table 8.2. The depth of wear of the harder material hh, can be calculated from: 2 $=(&) (8.3) For conditions where the load and or the surface temperature are high enough to cause plastic deformation, the wear rate as calculated from Eqs (8.1) and (8.2) can be several orders of magnitude higher (in the order of Table 8.2 Wear Coefficients, k, for Metal Combinations Metal combination k x 10-4 Metal combination k x 10-4 Cu vs. Pb Ni vs. Pb Fe vs. Ag Ni vs. Ag Fe vs. Pb A1 vs. Pb Ag vs. Pb Mg vs. Pb Zn vs. Pb Ag vs. Ag A1 vs. Zn A1 vs. Ni A1 vs. Cu A1 vs. Ag A1 vs. Fe Fe vs. Zn Ag vs. Zn Ni vs. Zn 0.1 0.2 0.7 0.7 0.7 1.4 2.5 2.6 2.6 3.4 3.9 4.7 4.8 5.3 6.0 8.4 8.4 11.0 Zn vs. Zn Mg vs. AI Zn vs. cu Fe vs. Cu Ag vs. Cu Pb vs. Pb Ni vs. Mg Zn vs. Mg A1 vs. A1 Cu vs. Mg Ag vs. Mg Mg vs. Mg Fe vs. Mg Fe vs. Ni Fe vs. Fe Cu vs. Ni cu vs. cu Ni vs. Ni 11.6 15.6 18.5 19.1 19.8 23.8 28.6 29.1 29.8 30.5 32.5 36.5 38.5 59.5 77.5 81.0 126.0 286.0 [...]... 41 40LL 41 50 4 620 5 130LL 821 4 8 620 52 100 Carpenter 1 1 annealed Hampden steel annealed HYCC( HA) HYCC(PM) Ketos Nitralloy G Rexalloy AA Star Zenith annealed Nickel alloys Invar “36” annealed H,M,80 annealed Monel C Hm (yl mm y (psi x 1 0 ~ ) 27 0 29 6 22 4 25 2 27 0 27 0 22 4 29 6 58 63 40 50 58 58 40 63 I99 46 8 27 0 397 359 160 I80 3 84 27 6 24 2 26 0 22 0 21 6 746 22 0 33 106 58 90 80 27 32 82. 5 65 47 55 40 40 ... Dry 0 .20 0 .26 A 0 .20 0 .23 B 0 .20 0 11 Dry 0 .20 0.38 Sintered iron G ~1 0 .20 0 .21 0. 54 0 .23 Dry 0 .20 0 .47 A 0 .20 0 .20 B 0. 54 0.19 Dry 0 .20 0. 34 A 0. 54 0.15 B 0. 54 0.15 A B Sintered ironcopper Sintered steel 3 02 vs stainless steel 3 02 Dry 0 .20 1. 02 A 0 .20 0.16 B 321 44 0 c 0 .20 Dry 0 .20 A 0. 54 B 0. 54 Dry 0 .20 A 0. 54 B 0 .20 0.15 1 .47 0.15 0. 14 0.90 0.13 0.15 3 02 vs steel 1 045 Dry 0 .20 0.71 A 0 .20 0.16... 3 02 vs aluminum alloy 1 12 Aluminum Dry A B 195 Aluminum Dry A B 355 Aluminum 3 02 vs plastic Delrin Nylatron G Polyethylene Dry A B Dry A B Dry A B Dry A €3 G p 0. 54 0.89 0. 54 0. 14 0. 54 0. 14 0 .20 0.83 0. 54 0. 14 0. 54 0. 14 0 .20 0.93 0. 54 0.15 0. 54 0. 14 0 .20 0 .20 0 .20 1.33 0.16 0.19 0 .20 0 .20 0 .20 0.99 0.15 0.15 0 .20 0. 54 0. 54 0 .20 0. 54 0. 54 0 .20 0. 54 0. 54 1.16 0 .20 0. 14 1.17 0.15 0. 14 1.1 1 0.17 0 .20 ... 150 40 22 6 40 26 2 340 27 0 29 6 396 350 75 58 63 90 80 26 9 58 1 84 30 27 0 1 84 58 40 55 Material (tg/ y mm (psi x 1 0 ~ ) H m ~ Copper alloys Brass Be-Cu Cu-Ni Phosphor-Bronze Aluminum alloys 43 aluminum 1 12 aluminum 195 aluminum 22 0 aluminum 355 aluminum 356 aluminum Sintered materials Sintered brass 1 7.5 min Sintered brass 2 7.0-7.5 Sintered bronze 1 ASTM B2 02- 58T Sintered bronze 2 ASTM B255-61T Sintered... 1 0.17 0 .20 0. 54 0. 54 0. 54 0. 54 0. 54 0. 54 0. 54 0. 54 0. 54 0.36 0.15 0.18 0.57 0 .22 0 . 24 0 .26 0.17 0.17 3 24 Chciptcr X Continued Table 8 .4 ~ Material Oila p Dry B 0. 54 0. 54 0. 54 0.09 0.15 0.1 1 Dry A B Teflon G 0. 54 0. 54 0. 54 0.60 0 .27 0 .27 41 40 LL 0 .20 0 .20 0.70 0 .22 0.19 521 00 0.78 0 .23 0.13 0. 72 0.18 0.16 "Oil A Socony Vacuum Gargole PE797 (Paraffin type; VI = 105) b 0 1 B Esso Standard Millcot K-50... 7.5 min Sintered iron 2 7.3 min Sintered iron 3 7.0 rnin Sintered iron copper I 7.1 copper infil - 15% 5.8-6 .2 - 20 % Sintered steel 1 7.0 rnin Stainless 3 161 Sintered steel 2 7.0 rnin 115 199 171 I66 17.9 31 35 27 60.7 117 96.8 1 24 .5 90.5 62 I 8 15 15 18 14 8 115 17.9 96 74 I35 22 .5 I50 25 180 31.5 150 25 110 17.9 22 0 I90 40 33 22 0 40 150 25 32 I Wear 1000 1 0 100 1000 10000 100000 Yield Point in shear,... 0.57 0 .21 0.17 0.60 0 .21 0.16 0.78 0.18 0.16 Material Oila G P Ni trallo y-G G Dry A B Dry A B 0 .20 0 .20 0 .20 0 .20 0. 54 0 .20 0.63 0.15 0.13 0.73 0.13 0.13 Dry A B 0 .20 0. 54 0 .20 0.63 0. 12 0. 12 Dry 0 .20 A 0 .20 B 0 .20 Dry 0 .20 A 0 .20 B 0. 54 521 00 vs copper alloy Cu-Ni Dry 0 .20 A 0. 54 B 0. 54 PhorphorusDry 0 .20 Bronze A A 0 .20 B 0. 54 521 00 vs aluminum alloy 1 12 Aluminum Dry 0 .20 A 0. 54 B 0 .20 195 Aluminum... 0 .20 0 .45 0 .20 1060 Dry A B 0 .20 0 .20 0 .20 41 40 LL Dry A B 0 .20 0 .20 0 .20 521 00 Dry A B 0 .20 0 .20 0 .20 Carpenter 1 1, special steel, annealed Hampden steel, annealed, oil wear HYCC (HA) Dry 0 .20 A 0 .45 B 0 .45 Dry 0. 54 A 0. 54 B 0. 54 Dry 0 .20 A 0. 54 B 0. 54 HYCC (PM) Dry - 0.13 0. 12 0. 62 0.13 0.11 0. 64 0 .20 0 .20 0 .20 0.16 0.17 Dry 0 .20 A 0. 54 B 0. 54 0.67 0.18 0.15 A B Ketos 0.67 0.15 0.17 0.73 0. 14 0 .21 0.57... vs stainless steel Dry A B 3 02 0. 54 A Dry 0. 54 Dry A B 44 0 c 0 .20 0 .20 B 32 1 0 .20 0 .20 0. 54 Material G p Dry 0 .20 0 .20 0 .20 0 .20 0 .20 0.66 A 0 .20 0. 12 0.73 0 .22 B Dry Brass vs steel 1 045 Oila 0 .20 0 .20 0 . 24 0.80 A B Dry A B 0 .20 0 .26 0. 54 0 .20 ~ ~ i I (a) Figure 8.5 (b) Coefficient of mutual overlap (a) K,,,,,, = 1; (b) Kn,,,, 0  325 Wear Motion of follower Cam and follower Length o strokg f 4 q Reciprocatingball... Dry 0 .20 A 0. 54 B 0. 54 355 Aluminum Dry 0 .20 A 0. 54 B 0. 54 521 00 vs sintered materials Sintered brass Dry 0 .20 A 0 .20 B 0 .20 1 .28 0 . 24 0.18 0.73 0. 12 0. 14 Rexalloy AA Star Zenith steel annealed red wear 521 00 vs steel Carpenter free cot invar “36” annealed Monel C 1 .23 0 .2 1 0.15 0.67 0.19 0.16 1.08 0 .25 0.15 1.07 0.17 0.13 1 .21 0.13 0 .20 0. 32 0 .2 1 0.16 Wear Table 8 .4 323 Continued Material Oila Sintered . alloys Invar “36” annealed H,M,80 annealed Monel C 27 0 29 6 22 4 25 2 27 0 27 0 22 4 29 6 I99 46 8 27 0 397 3 59 160 I80 3 84 27 6 24 2 26 0 22 0 21 6 746 22 0 22 6 26 2 340 27 0 29 6. 3 02 Dry 0 .20 A 0 .20 B 0 .20 32 1 Dry 0 .20 A 0. 54 B 0. 54 44 0 c Dry 0 .20 A 0. 54 B 0 .20 3 02 vs. steel 1 045 Dry 0 .20 A 0 .20 B 0. 54 I060 Dry 0 .20 A 0. 54 B 0 .20 . 0 .20 0.78 0 .20 0 .23 0. 54 0.13 0 .20 0. 72 0 .20 0.18 0. 54 0.16 Brass vs. steel 1 045 Dry 0 .20 0.66 A 0 .20 0 .20 B 0 .20 0. 12 41 40 LL Dry 0 .20 0.73 A 0 .20 0 .22 B 0 .20