Thông tin tài liệu
TABLE 23-2 Journal bearing design practices Bearing modulus (minimum) Diameter Maximum pressure, P clearance Viscosity, 1 Viscosity, S 00 ¼ 1 n P S 00 ¼ n 0 P ratio Machinery Bearing kgf/mm 2 kpsi MPa ¼ c d Ratio L d cP Pa s 10 3 USCSU SI Units, 109 Automobile Main 0.56–1.19 0.8–1.7 5.50–11.70 — 0.1–1.8 7 7 15 36.3 and aircraft Crankpin 1.06–2.47 1.5–3.5 10.40–24.40 0.7–1.4 to to 10 24.2 engines Wrist pin 1.62–3.62 2.3–5.0 15.00–34.80 1.5–2.2 8 8 8 19.3 Gas and oil Main 0.49–0.85 0.7–1.2 4.85–8.35 0.001 0.6–2.0 20 20 20 48.4 engines (four- Crankpin 0.90–1.27 1.4–1.8 8.80–12.40 <0.001 0.6–1.5 to to 10 24.2 stroke) Wrist pin 1.27–1.55 1.8–2.2 12.40–15.20 <0.001 1.5–2.0 65 65 5 12.1 Gas and oil Main 0.35–0.56 0.5–0.8 3.42–5.50 0.001 0.6–2.0 20 20 25 60.4 engines (two- Crankpin 0.70–1.06 1.0–1.5 6.85–10.40 <0.001 0.6–1.5 to to 12 29.0 stroke) Wrist pin 0.85–1.07 1.2–1.8 8.35–12.50 <0.001 1.5–2.0 65 65 10 24.2 Marine steam Main 0.35 0.5 3.42 <0.001 0.7–1.5 30 30 20 48.4 engines Crankpin 0.42 0.6 4.14 <0.001 0.7–1.2 40 40 15 36.3 Wrist pin 1.06 1.5 10.40 <0.001 1.2–1.7 30 30 10 24.2 Stationary, Main 0.28 0.4 2.75 <0.001 1.0–2.0 60 60 20 48.4 slow-speed Crankpin 1.06 1.5 10.40 <0.001 0.9–1.3 80 80 6 14.5 steam engines Wrist pin 1.27 1.8 12.50 <0.001 1.2–1.5 60 60 5 12.1 Stationary, Main 0.17 0.25 1.66 <0.001 1.5–3.0 15 15 25 60.4 high-speed Crankpin 0.42 0.6 4.14 <0.001 0.9–1.5 30 30 6 14.5 steam engines Wrist pin 1.27 1.8 12.50 <0.001 1.3–1.7 25 25 5 12.1 Steam Driving axle 0.39 0.55 3.72 0.001 1.6–1.8 100 100 30 72.5 locomotives Crankpin 1.40 2.0 13.70 <0.001 0.7–1.1 40 40 5 12.1 Wrist pin 2.82 4.0 27.60 <0.001 0.8–1.3 30 30 5 12.1 Reciprocating Main 0.17 0.25 1.66 <0.001 1.0–2.2 30 30 30 72.5 pumps and Crankpin 0.42 0.6 4.14 <0.001 0.9–1.7 to to 20 48.4 compressors Wrist pin 0.70 1.0 6.85 <0.001 1.5–2.0 80 80 10 24.2 Railway cars Axle 0.35 0.45 3.42 0.001 1.8–2.0 100 100 50 120.9 Steam Main 0.07–0.19 0.1–0.275 0.69–1.87 0.001 1.0–2.0 2–16 2–16 100 241.8 turbines Generators, Rotor 0.07-0.14 0.1-0.2 0.69-1.37 0.0013 1.0–2.0 25 25 200 483.5 motors, centrifugal pumps Gyroscope Rotor 0.60 0.85 5.90 0.0013 — 30 30 55 133.0 Transmission Light, fixed 0.08 0.025 0.17 0.001 2.0–3.0 25 25 100 241.8 shafting Self-aligning 0.106 0.15 1.04 0.001 2.5–4.0 to to 30 72.5 Heavy 0.106 0.15 1.04 0.001 2.0–3.0 60 60 30 72.5 Cotton mill Spindle 0.0007 0.001 0.0069 0.005 — 2 2 10000 24177.5 Machine tools Main 0.21 0.3 2.06 0.001 1.0–1.4 40 40 40 96.7 Punching and Main 2.82 4.0 27.80 0.001 1.0–2.0 100 100 — — shearing Crankpin 5.62 8.0 55.60 0.001 1.0–2.0 100 100 — — machine Rolling mills Main 2.11 3.0 20.60 0.0015 1.1–1.5 50 50 10 24.2 Key: ð 1 Þ¼absolute viscosity, Pa s (cP); n ¼ speed, rpm; n 0 ¼ speed, rps; P ¼ pressure, N/m 2 or MPa (psi); MPa ¼megapascal ¼10 6 N/m 2 ;Pa¼ Pascal ¼ 1 N/m 2 ; 1 psi ¼ 6894.757 Pa; 1 kpsi ¼ 6.89475 MPa; USCSU ¼ US Customary System units. DESIGN OF BEARINGS AND TRIBOLOGY 23.15 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY TABLE 23-3 Values of factor C 1 in Eq. (23-23) Lubrication Workmanship Attendance Operating condition Constant C 1 Oil bath or flooded High grade First class Clean and protected 1 Oil, free drop (constant feed) Good Fairly good Favorable (ordinary condition) 2 Oil cup or grease (intermittent feed) Fair Poor Exposed to dirt, grit or other unfavorable conditions 4 TABLE 23-4 Values of factor C 2 in Eq. (23–23) Type of bearing Constant C 2 Rotating journals, such as rigid bearing and crankpins 1 Oscillating journals, such as rigid wrist pin and Pintle blocks 1 Rotating bearings lacking ample rigidity, such as eccentric and the like 2 Rotating flat surfaces lubricated from the center to the circumference, such as annular step or pivot bearings 2 Sliding flat surfaces wiping over the guide ends, such as reciprocating crossheads; use 2 for relatively long guides and 3 for short guides 2–3 Sliding or wiping surfaces lubricated from the periphery or outer wiping edge, such as marine thrust bearings and worm gears 3–4 Long power-screw nuts and similar wiping parts over which it is difficult to effect a uniform distribution of lubricant or load 4–6 r + w c 2 0 0 0 h w φ B A D E e e (a) Stand still r 0’ 0’ 0’ α’ β ω θ r + c 2 w (b) At start (c) Running FIGURE 23-8 Behaviour of a journal in its bearing. 23.16 CHAPTER TWENTY-THREE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY BEARING PRESSURE (Fig. 23-9) General Electric Company’s formula for bearing pressure in the design of motor and generator bearing Victor Tatarinoff’s equation for safe operating load Victor Tatarinoff’s equation for permissible unit pressure P a ¼ 6:2 10 5 3 ffiffiffiffiffiffi v m p SI ð23-24aÞ where P a in N/m 2 and v m in m/s P a ¼ 15:5 3 ffiffiffiffiffiffi v m p USCS ð23-24bÞ where P a in psi and v m in ft/min P a ¼ 0:0635 3 ffiffiffiffiffiffi v m p Customary Metric ð23-24cÞ where P a in kgf/mm 2 and v m in m/s W ¼ 1 nd 3 ðL=dÞ 2 127ð10 6 Þh 1 þ L d USCS ð23-25aÞ where 1 in cP, n in rpm, L, d, h, and c in in, W in lbf W ¼ n 0 d 3 ðL=dÞ 2 0:295h 1 þ L d SI ð22-25bÞ where in Pa s, n 0 in rps, L, d, h, and c in m, W in N P ¼ 1 n 0 3175ð10 4 Þ 2 L L þd USCS ð23-26aÞ where P in psi, 1 in cP, n in rpm, L and d in in P ¼ 13:5 n 0 2 L L þd SI ð23-26bÞ where P in Pa, in Pa s, n 0 in rps, and L and d in m Particular Formula Oil film pressure o e = E C c n Without groove With groove d + c Line of centers or line joining 0 (centre of bearing) and 0’ (centre of jouurnal) I L θ Pmax P max φ h max P min p h o = h min w Bearing Journal Oil inlet θ PO θ FIGURE 23-9 Oil film pressure distribution in the full journal bearing. DESIGN OF BEARINGS AND TRIBOLOGY 23.17 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY H. F. Moore’s equation for critical pressure The critical unit pressure for any given velocity should not exceed according to Louis Illmer Stribeck’s equation for the critical pressure when the speed does not exceed 2.5 m/s (500 ft/min) Stribeck’s equation for the critical pressure when the speed exceeds 2.5 m/s (500 ft/min) For permissible Pv values For values S 00 for various combinations of journal bearing materials, abrasion pressure for bearings, allowable bearing pressures for semi-fluid lubricants and diametral clearances in bearing dimensions. P c ¼ 7:23 10 5 ffiffiffi v p SI ð23-27aÞ where P c in N/m 2 and v in m/s P c ¼ 0:0737 ffiffiffi v p Customary Metric ð23-27bÞ where P c in kgf/mm 2 and v in m/s P c ¼ 7:5 ffiffiffi v p USCS ð23-27cÞ where P c in psi and v in ft/min P c ¼ 4:6 10 6 3 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi v m t 288:5 r SI ð23-28aÞ where P c in N/m 2 , v m in m/s, and t in K P c ¼ 0:47 3 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi v m t 15:5 r Customary Metric ð23-28bÞ where P c in kgf/mm 2 , v m in m/s, and t in 8C P c ¼ 140 3 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi v m t 15:5 r USCS ð23-28cÞ where P c in psi, v m in ft/min, t in 8F P c ¼ 9:7 10 5 ffiffiffi v p SI ð23-28dÞ where P c in N/m 2 and v in m/s P c ¼ 10 ffiffiffi v p USCS ð23-28eÞ where P c in psi and v in ft/min P c ¼ 0:0986 ffiffiffi v p Customary Metric ð23-28f Þ where P c in kgf/mm 2 and v in m/s P c ¼ 2:9 10 6 ffiffiffi v p SI ð23-28gÞ where P c in N/m 2 and v in m/s P c ¼ 30 ffiffiffi v p USCS ð23-28hÞ where P c in psi and v in ft/min P c ¼ 0:296 ffiffiffi v p Customary Metric ð23-28iÞ where P c in kgf/mm 2 and v in m/s Refer to Table 23-5 for allowable pressures for reci- procating motion. Refer to Table 23-6. Refer to Tables 23-7 to 23-10. Particular Formula 23.18 CHAPTER TWENTY-THREE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY TABLE 23-5 Allowable bearing pressure, reciprocating motion Pressure, P Type of bearing Type of machinery psi MPa Steam engine, stationary 35–60 0.24–0.412 Steam engine, marine 55–100 0.378–0.688 Crosshead f Steam engine, locomotive 70–90 0.48–0.62 Gas and oil engines, stationary 40–70 0.275–0.48 Compressors and pumps 50–90 0.342–0.62 Trunk pin f Gas and oil engines, stationary 20–25 0.136–0.172 Automotive and aircraft engines 25–40 0.172–0.275 TABLE 23-6 Permissible Pv values Values Class of bearing or journal psi ft/s N/m s Mill shafting, with self-aligning cast-iron bearings, grease, or imperfect oil-lubrication, maximum value 12,000 4.210 5 Mill shafting, self-aligning ring-oiled babbitt bearings, maximum 24,000 8.4510 5 Self-aligning ring-oiled bearings, continuous load in one direction 35,000–40,000 12.310 5 to 1410 5 Crankshaft journals with bronze bearings 22,000 7.710 5 Crankshaft bearings with babbitted bearings, maximum 59,000 20.810 5 For excellent radiating condition 133,000 46.510 5 Key: US Customary unit: P ¼ pressure, psi, v ¼ velocity, ft/s; SI unit: P ¼ pressure, N/m 2 , v ¼ velocity, m/s TABLE 23-7 Values S 00 for various combinations of journal bearing materials Bearing-modulus S 00 ¼ 1 n P S 00 ¼ n 0 P Shaft Bearing Metric SI 10 9 Hardened and ground steel Babbitt 28,500 48.5 Machined, soft steel Babbitt 36,000 61.2 Hardened and ground steel Plastic bronze 42,700 72.6 Machined, soft steel Plastic bronze 35,800 60.9 Hardened and ground steel Rigid bronze 56,900 96.7 Machined, soft steel Rigid bronze 71,100 120.8 DESIGN OF BEARINGS AND TRIBOLOGY 23.19 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY TABLE 23-8 Abrasion pressures for bearings Pressure Materials in contact psi MPa Remarks Hardened tool steel on lumen or phosphor bronze 10,000 68.8 Values applies to rigid, polished and accurately fitted rubbing surface 0.50 C machine steel on lumen or phosphor bronze 8,000 55.0 When not worn to a fit or well lubricated reduce to 4.22 kgf/mm 2 (41.4 MPa) Hardened tool steel on hardened tool steel 7,000 48.0 0.50 C machine steel or wrought iron on genuine hard babbitt 6,000 41.5 Cast iron on cast iron (close grained or chilled) 4,500 31.0 Case-hardened machine steel on case-hardened machine steel 4,000 27.5 0.30 C machine steel on cast iron (close-grained) 3,500 24.0 0.40 C machine steel on soft common babbitt 3,000 20.6 Soft machine steel on machine steel (not case- 2,000 13.8 hardened) Machine steel on lignum vitae (water-lubricated) 1,500 10.2 TABLE 23-9 Allowable bearing pressures for semifluid lubrication Allowable pressure, P a Bearing material Journal material psi MPa Lumen of phosphor bronze Hardened tool steel 2500 17.30 Hardened steel Hardened alloy steel 2000 14.40 Hard babbitt SAE 1050 steel 1500 10.30 Bronze Hardened alloy steel 1300 8.90 Cast iron Cast iron 1100 7.58 Bronze Alloy steel 850 5.90 Babbit, soft SAE 1040 steel 750 5.20 Bronze Mild steel, smooth finish 540 3.70 Bronze Mild steel, ordinary finish 400 2.75 Bronze Cast iron 400 2.75 Cast iron Mild steel 350 2.40 Lignum vitae, water lubricated Mild steel 350 2.40 23.20 CHAPTER TWENTY-THREE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY IDEALIZED JOURNAL BEARING (Figs. 23-8 and 23-9) The diametral clearance ratio or relative clearance Attitude or eccentricity ratio or eccentricity coefficient Oil film thickness at any position For position of minimum oil thickness and max oil film pressure Minimum oil film thickness The minimum oil film thickness variable ¼ c d ð23-29Þ " ¼ 2e c ¼ 1 2h min d ð23-30Þ Refer to Fig. 23-10 for ". h ¼ c 2 ð1 þ " cos Þð23-31Þ Refer to Figs. 23-11 and 23-11A h min ¼ h o ¼ c 2 ð1 "Þð23-32Þ ¼ 2h min c ¼ð1 "Þð23-33Þ Refer to Figs. 23-12 to 23-14 and 23-15 for . Particular Formula TABLE 23-10 Diametral clearance in bearings dimension in micrometers (1 lm ¼ 10 6 m) Diametral clearances, c in lm Particular about bearing and journal d ¼ 12 d ¼ 25 d ¼ 50 d ¼ 100 d ¼ 140 Precision spindle, hardened and ground steel, lapped into bronze bearingv m < 25 m/s; P < 500 psi (3.43 N/m 2 ); 0.2–0.4 mmrms 7–19 19–38 38–63 63–88 88–125 Precision spindle, hardened and ground steel, lapped into bronze bearingv m > 25 m/s; P > 500 psi (3.43 N/m 2 ); 0.2–0.4 mmrms 13–25 25–50 50–75 75–113 113–163 Electric motors and generators, ground journals i n broached or reamed bronze or babbitt bearings; 0.4–0.8 mmrms 13–38 25–50 38–85 50–100 75–150 General machinery, intermittent or continuous motion, turned or cold-rolled journal in reamed and bored bronze or babbitt bearings; 0.8–1.5 mmrms 50–100 63–113 75–125 100–175 125–200 Rough machinery, turned or cold-rolled steel journals in poured babbitt bearings; 1.5–3.8 mmrms 77–150 125–225 200–300 275–400 350–500 Automotive crankshaft Babbitt-lined bearing 38 63 Cadmium silver copper 50 75 Copper lead 36 88 DESIGN OF BEARINGS AND TRIBOLOGY 23.21 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY 0 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 0.10 0.20 0.30 0.40 Attitude, ε 0 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 0.010 0.020 0.030 0.040 Attitude, ε Reynolds Petroff Lightly loaded bearing Beyond this point S = 1 59 . 36 Bearing characteristic number, S = ηn P 1 ψ 2 (a) Moderately and lightly loaded bearing Bearing characteristic number, S = ηn’ P 1 ψ 2 (b) Heavily loaded bearing FIGURE 23-10 Variation of attitude " of full journal bearing with characteristic number S. [Radzimosvksy 4 ] 0 0 10 20 30 40 50 60 70 80 90 100 0.01 0.02 0.04 0.060.080.1 0.2 0.4 0.6 0.81.0 2 4 6 8 10 Bearing Characteristic Number, S = ηn’ P 1 ψ 2 Position of Minimum Oil Film Thickness, deg φ L d = ∞ 1 2 1 4 1 FIGURE 23-11 Position of minimum oil film thickness vs. bearing characteristic number S for full journal bearing. (Refer to Fig. 23-9 for definition of .) [Boyd and Raimondi 5 ] 23.22 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY 0 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 12 46 810 246 810 2 246 810 3 BEARING CHARACTERISTIC NUMBER S’ = 60ηn’ P 1 ψ 2 MINIMUM FILM THICKNESS VARIABLE, δ FIGURE 23-12 Minimum oil film thickness variable based on no side flow. [Boyd and Raimondi 5 ] 0 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 . 0 0 . 10 0 . 20 0 . 30 BEARING CHARACTERISTIC NUMBER ηn’ P 1 ψ 2 S = REYNOLDS PETROFF LIGHTLY LOADED BEARING 2n min c δ = FIGURE 23-13 Variation of minimum oil film thickness variable of full journal bearing with S. 23.23 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY The safe oil film thickness for a bearing in good condition and v m 1 m/s (200 ft/min) The thickness of oil film where the pressure is maxi- mum or minimum The resultant pressure distribution around a journal bearing excluding P o the oil film pressure at the point where ¼ 0or ¼ 2 The pressure at any point (Figs. 23-8 and 23-9) The load carrying capacity of the bearing [Fig. 23-8 (panel c)] The bearing characteristic number or Sommerfeld number For Sommerfeld number S h min ¼ h o ¼ 2:37 10 5 v 0:4 m A 0:2 SI ð23-34aÞ where h min in m, A in m 2 , and v m in m/s h min ¼ 0:0015v 0:4 m A 0:2 Customary Metric ð23-34bÞ where h min in mm, A in mm 2 , and v m in m/s h min ¼ 0:000026v 0:4 m A 0:2 USCS ð23-34cÞ where h min in in, A in in 2 , and v m in in ðhÞ PðmaxÞ ¼ k ¼ 2cð1 " 2 Þ 2 þ" 2 ð23-35Þ PðminÞ P r ¼ðP P o Þ ¼ 12U 2 d "ð2 þ" cos Þsin ð2 þ" 2 Þð1 þ" cos Þ 2 ð23-36Þ P ¼ P r þ P o ð23-37Þ W ¼ UL 2 2" ð2 þ" 2 Þ ffiffiffiffiffiffiffiffiffiffiffiffiffi 2 " 2 p ! ð23-38Þ S ¼ n 0 P 1 2 ð23-39Þ Refer to Tables 23-10 to 23-12 for Sommerfeld numbers S for full and partial bearings. 0 040 60 S C L 10 6 MINIMUM FILM THICKNESS VARIABLE, δ 80 VALUE OF 120 160 200 240 280 320 360 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 FIGURE 23-14 Variation of minimum oil film thickness variable with S=C L . Particular Formula 23.24 CHAPTER TWENTY-THREE Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. DESIGN OF BEARINGS AND TRIBOLOGY [...]... factor, CW 1.0 DESIGN OF BEARINGS AND TRIBOLOGY CHAPTER TWENTY-THREE DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY Particular Formula 1.0 Friction factor, CF 23.41 ∈=0.2 ∈=0.4 ∈=0.6 0.9 120 Centrally loaded partial journal bearings 0.8 SLIDER ∈=0.8 0 1 2 Length in direction of motion Axial length 3 = 4 FIGURE 23-31 Leakage factors for friction force for 1208 centrally loaded partial journal... FIGURE 23-23 Variation of coefficient of friction variable = with S for 3608 partial journal bearing µ Coefficient of friction variable, ψ 5 30 µ Coefficient of friction variable, ψ µ Coefficient of friction variable, ψ 6.5 6.0 DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY Particular 23.37 Formula 2 Coefficient of Friction Variable, λµ = µ/ψ 102 5... 0.093 0 .119 Machine oil 0.099 0 .115 Soapstone (powdered) 0.169 0.306 Mica (powdered) 0.257 0.305 Boron (not a lubricant) 0.482 0.710 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ð23-48Þ DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF... B/L = 1 0 B/L = 2 0 B/L = 4 0 B/L = 3 0 360… Journal bearings 2.0 0.20 FIGURE 23-38 Variation of attitude " with S for 3608 partial journal bearing Attitude, ε 1.0 0.9 0.8 DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY Particular 23.45 Formula 6.0 Coefficient of friction variable, 5.0 Representative experimental Dividing line 4.0 Sommerfeld 3.0... 0.23 0.22 4Q d 2 n0 L See Key and Source under Table 23 -11 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY Particular 23.31 Formula 10 Factor CL 8 6 4 2 0 0 1 2 Ratio,... Thickness Variables, δ = 1.0 DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website 23.25 DESIGN OF BEARINGS AND TRIBOLOGY 23.26 CHAPTER TWENTY-THREE Particular Formula n P where... ψ2 0.5 60 Partial journal bearings 0.15 ηn’ 1 Bearing characteristic number, S = P ψ2 0.05 60 Partial journal bearings 2.0 0.20 FIGURE 23-20 Variation of coefficient of friction variable = with S for 608 partial journal bearing µ Coefficient of friction variable, ψ µ Coefficient of friction variable, ψ 0 10 20 0 0 1 2 3 4 0 0.10 1.0 ηn’ Bearing characteristic number, S = P 0.5 B/L = 1.0 120 Partial journal... DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY 23.27 TABLE 23 -11 Dimensionless performance parameters for full journal bearings with side flow Values of L=d ratio For maximum load For minimum friction L d 0.25 0.27 0.03 0.5 0.43 0.12 1 0.66 0.6 1.0 0.53 0.3 Qs Q csp T0 P P Pmax 3.45 3.76 4.37 4.99 5.60 5.91 6.12 — 0 0.180 0.330 0.567 0.746 0.884 0.945 0.984 1.0 1 1287.0 611. 0... given at the website DESIGN OF BEARINGS AND TRIBOLOGY DESIGN OF BEARINGS AND TRIBOLOGY Particular 23.39 Formula Load leakage factor according to Kingsbury6 CW ¼ W W1 ð23-52Þ Refer to Fig 23-28 for CW Load leakage factor CW as a function of B=L ratio for a slider bearing having q ¼ ðh1 =h2 Þ À 1 ¼ 1 or h1 ¼ 2h2 Refer to Table 23-16 Load leakage factor for 1208, centrally loaded partial bearing according... 42.7 25.9 11. 6 — 0.456 0.438 0.389 0.321 0.237 0.178 0 .112 0 1 36.6 18.1 8.20 4.43 2.17 1.24 0.550 0 3.29 3.32 3.15 2.80 2.18 1.70 1.19 — 0 0.124 0.225 0.386 0.530 0.684 0.787 0.899 1.0 — 149.0 77.2 40.5 27.0 19.0 15.1 10.6 0 — 0.431 0.424 0.389 0.336 0.261 0.203 0.136 0 90.0 72.43 58.25 43.98 35.65 27.42 21.29 13.49 0 1 14.5 7.44 3.60 2.16 1.27 0.855 0.461 0 3.20 3 .11 2.75 2.24 1.57 1 .11 0.694 . 31.0 Case-hardened machine steel on case-hardened machine steel 4,000 27.5 0.30 C machine steel on cast iron (close-grained) 3,500 24.0 0.40 C machine steel on soft common babbitt 3,000 20.6 Soft machine. 0.1 0.0147 21.51 0.653 0.388 0 21.2 0. 311 0.97 0.03 0.00406 13.86 0.399 0 .118 0 42.3 0.199 1.0 0 0 0 0 0 0 1 0 a See Key and Source under Table 23 -11. DESIGN OF BEARINGS AND TRIBOLOGY 23.29 Downloaded. 25–50 50–75 75 113 113 –163 Electric motors and generators, ground journals i n broached or reamed bronze or babbitt bearings; 0.4–0.8 mmrms 13–38 25–50 38–85 50–100 75–150 General machinery, intermittent
Ngày đăng: 11/08/2014, 10:23
Xem thêm: Machine Design Databook 2010 Part 11 potx
