1、I . AGMA SLL-A 94 0687575 0003433 408 M AGMA 911-A94 AMERICAN GEAR MANUFACTURERS ASSOCIATION Design Guidelines for Aerospace Gearing I J AGMA INFORMATION SHEET (This Information Sheet is NOT an AGMA Standard) AGMA 911-A 94 m Ob87575 0003434 344 m AGMA 911-A94 AGMA 91 1-A94, Design Guidelines for Aer
2、ospace Gearing CAUTION NOTICE: AGMA standards are subject to constant improvement, revision, or withdrawal as dictated by experience. Any person who refers to any AGMA Technical Publication should be sure that the publication is the latest available from the Association on the subject matter. Tables
3、 or other self-supporting sections may be quoted or extracted in their entirety. Credit lines should read: Extracted from AGMA 911-A94, Information Sheet - Design Guidelines for Aerospace Gearing, with the permission of the publisher, the American Gear Manufacturers Association, 1500 King Street, Su
4、ite 201, Alexandria, Virginia 2231 41. ABSTRACT: This Information Sheet covers current gear design practices as they are applied to airvehicles and spacecraft. The material included goes beyond the design of gear meshes and presents the broad spectrum of factors which combine to produce a working ge
5、ar system, whether it be a power transmission or special purpose mechanism. Although a variety of gear types, such as wormgears, face gears and various proprietary tooth forms are used in aerospace applications, this document covers only spur, helical, and bevel gears. Copyright O 1994 by American G
6、ear Manufacturers Association Published by American Gear Manufacturers Association i500 King Street, Suite 201, Alexandria, Virginia, 22314 A r ISBN: 1-55589-629-4 AGHA 911-A 94 0687575 0003435 280 AGMA 911-A94 Contents Page Foreword vi 1 Scope . 1 1.1 Application . 1 1.2 References., . 1 2 Applicat
7、ion . 1 3 Definitions and symbols 2 3.1 Definitions . 2 3.2 Symbols . 2 4 Design approach 5 Design requirements and goals 5 Identify design criteria . 6 4.3 Preliminary design 8 4.4 Detail design 12 4.1 4.2 5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Lubrication 15 Cooling vs . l
8、ubrication requirements 15 Lubricants . 15 Distribution systems 18 Lubrication system design considerations . 19 Filtration 21 Oil pumps . 21 Lube system condition monitoring 23 Environmental issues . 24 Ambient temperature effects . 24 Ambient pressure effects 25 Attitude effects 25 Contaminant eff
9、ects (water. corrosives. dirt. dust. and sand) . 26 VibratiodShock effects . 26 Fire resistance requirements 29 Electromagnetic effects . 29 Nuclear. biological. and chemical (NEC) effects 29 7 7.1 7.2 7.4 7.5 Vibration and noise . 30 Causes of gear vibration 30 Consequences of vibration 31 Analyzin
10、g vibration problems 35 VibrationlNoise reduction techniques . 37 8 Load Capacity . 39 8.1 Introduction . 39 8.2 Spur, helical. and bevel gear tooth breakage and surface durability . 41 8.3 Spur. helical. and bevel gear scuffing (scoring) -flash temperature index 45 9 Gear materials and heat treatme
11、nt . 47 9.1 Class and grade definitions 47 9.2 Mechanical properties 47 7.3 Design 32 iii AGMA 911-A94 AGMA SII-A 94 Ob87575 O003436 117 Contents. continued 9.3 9.4 9.5 9.6 9.7 9.8 9.9 9.1 o 9.11 9.12 9.13 Cleanliness . 48 Heat treatment . 48 Microstructure . 48 Hardenability 48 Dimensional stabilit
12、y 48 Pre-machining stock removal 48 Ferrous gearing 48 Non-ferrous gearing 49 Material grades and heat treatment . 49 Gear surface hardening . 49 Gear through hardening . 53 10 Surface treatment 54 10.1 Introduction . 54 10.2 Shot peening 55 10.3 Surface coatings . 60 10.4 Ion implantation of gears
13、61 11.1 Introduction . 63 11.2 Spur and helical gears 63 11.3 Bevel gears . 64 11.4 Stress relief treatment 67 12 Gear inspection 68 12.1 General . 68 12.2 Spur and helical involute gears 68 12.3 Bevel gears . 69 13 Rocket - Propeller gearboxes reduce engine speed to propeller speed; - Fan gearboxes
14、 allow the use of optimum turbine and fan speeds for maximum effi- ciency; - Helicopter transmissions. A system of gearboxes and shafting to drive the helicopter rotors from the engine(s); - Mechanical interconnection between engines allow for independent engine opera- tion on multi-engine systems;
15、1 AGMA 911-A94 AGMA 711-A 94 - Accessory drive gearboxes drive accessory devices, such as generators, fuel pumps, hy- draulic pumps, oil pressure and scavenge pumps, blowers, alternators, etc: - Auxiliary/secondary power units (APU/ SPU) consist of an auxiliary turbine engine inte- grated with a gea
16、rbox to provide power for main engine starting, electrical services, emergency hydraulic power, cabin air conditioning, etc.; - Actuators. A general class of geared devices used tocause a position change of an object. The objects may include aerodynamic control sur- faces, winch cables, doors, landi
17、ng gear, or telerobotic arms. Actuators are distinguished from most aerospace gearing in that they only move on command; - Space systems. A specialized grouping of power (as in rocket turbo-pump drives), and ac- tuator type devices which have been designed to be compatible with the unique rigors of
18、outer- space environments. These include the high power, short life rocket applications as well as the long life satellite or space plaform systems. 3 Definitions and symbols 3.1 Definitions. Symbol Ob83575 0003442 410 The terms used, wherever applicable, conform to the following standards: ANSI Y1
19、0.3-1 968, Letter Symbols for Quantities Used in Mechanics of Solids AGMA 1 O1 2-F90, Gear Nomenclature, Definitons of Terms with Symbols AGMA 904-889, Metric Usage 3.2 Symbols. The symbols used in this information sheet are shown in table 1. NOTE - The symbols and definitions used in this informati
20、on sheet may differ from other AGMA publications. The user should not assume that fa- miliar symbols can be used without a careful study of these definitions. SI (metric) units of measure are shown in parenthe- ses in table 1 and in the text. Where equations re- quire a different format or constant
21、for use with SI units, a second expression is shown after the first, indented, in smaller type, and with “M included in the equation number. hample .( 11) st=- wt Ka - pd Ks KB K, Kx F J The second expression uses SI units. Table 1 - Symbols used in equations Name Center distance Application factor
22、for pitting resistance Surface condition factor for pitting resistance Hardness ratio factor for pitting resistance Life factor for pitting resistance Load distribution factor for pitting resistance Elastic coefficient Reliability factor for pitting resistance Size factor for pitting resistance Unit
23、s First ,quation 9 12 12 18 18 12 12 18 12 Reference paragraph 8.2.2 8.2.2 8.2.2 8.2.8 8.2.8 8.2.2 8.2.2 8.2.8 8.2.2 (continued) 2 iymbol AGMA 711-A 74 m Ob87575 0003443 357 m Table 1 (continued) AGMA 911-A94 Name Temperature factor for pitting resistance Dynamic factor for pitting resistance Lubric
24、ant specific heat Pinion operating pitch diameter Reduced modulus of elasticity Face width Effective or net face width Oil film thickness Heat generated at design point Film thickness, minimum Geometry factor for pitting resistance Geometry factor for bending strength Contact load factor for pitting
25、 resistance External application factor for bending strength Rim thickness factor Life factor for bending strength Load distribution factor for bending strength Reliability factor for bending strength Size factor for bending strength Temperature factor for bending strength Dynamic factor for bending
26、 strength Lengthwise curvature factor for bevel gear bending strength Lubricant flow rate Module ( = 25.4/Pd ) Gear ratio (never less than 1 .O) Number of standard deviations Pinion speed Transmitted power Units - BTUAbm OF (kJNl K) in (mm) ib/in2(Nlmr+) in (mm) in (mm) in (mm) BTU/min (kJ/min) - Fi
27、rst quation 18 12 8 10 4 9 12 1 8 4 12 11 9 11 11 13 11 13 11 13 11 11 8 11 M 9 14 9 9 leference laragraph 8.2.8 8.2.2 5.1.2 8.1.2 4.2.4 8.1.2 8.2.2 4.2.4 5.1.2 4.2.4 8.2.2 8.2.1 8.1.2 8.2.1 8.2.1 8.2.7 8.2.1 8.2.7 8.2.1 8.2.7 8.2.1 8.2.1 5.1.2 8.2.1 8.1.2 8.2.7 8.1.2 8.1.2 (continued) 3 AGMA 911-A
28、94 m Ob87575 0003444 293 m AGMA 911-A94 Symbol Table 1 (concluded) Name Diametral pitch ( = 25.4/m) Reliability constant Allowable contact stress number Allowable bending stress number Contact stress number Bending stress number Working contact stress number Working bending stress number Inlet oil t
29、emperature Outlet oil temperature Contact temperature Flash temperature Bulk temperature Speed parameter Average rolling speed Entraining velocity Load parameter Unfi tangential load Normal unit load Tangential tooth load Load sharing factor Pressure viscosity coefficient Specific film thickness vis
30、cosity Absolute viscosity Coefficient of variation or standard deviation Normal relative radius of curvature Composite surface roughness Surface roughness of pinion, gear Units in- - Win2 (MPa) Win2 (MPa) Ib/in2 (MPa) Ib/in2 (MPa) Ib/in2 (MPa) Ib/in2 (MPa) OF (“C) OF (“C) OF (“C) OF (“C) OF (“C) - i
31、dsec (mdsec) ids (ds) - Ib/in (N/mm) Ib/in (N/mm) Ib (NI - in2/lb (l/MPa) idin (mmlmm) reyns (kPa s) reyns (kPa s) - in (mm) Pin uIm) Pin Olm) First 3q uat io n 11 14 18 13 12 11 18 13 8 8 19 19 19 6 1 6 7 1 7 11 7 5 2 1 6 14 1 2 3 Reference paragraph 8.2.1 8.2.7 8.2.8 8.2.7 8.2.2 8.2.1 8.2.8 8.2.7
32、5.1.2 5.1.2 8.3.1 8.3.1 8.3.1 4.2.4 4.2.4 4.2.4 4.2.4 4.2.4 4.2.4 8.2.1 4.2.4 4.2.4 4.2.4 4.2.4 4.2.4 8.2.7 4.2.4 4.2.4 4.2.4 4 ALMA 911-A 94 Ob87575 0003445 12T 4 Design approach 4.1 Design requirements and goals The design procedure begins with a definition of the application, requirements, and go
33、als for the project. It is sometimes difficult to clearly define all aspects of the project at the start, but a complete tabulation of the following parameters should be made to provide a working definition of the project. 4.1 .I Power/speed and torquelposition The complete range of power and speed
34、or toque and position (actuators) must be tabulated including a definition of growth capability. A duty cycle definition is required for calculation of life. Within these parameters a design point must be selected for sizing purposes. 4.1.2 Gear ratio and direction of rotation Gear ratio must be spe
35、cified with an indication of allowable deviation. Input and output directions of rotation are required and are important in selection of the hand of helix or hand of spiral for thrust direction and lubrication considerations. 4.1.3 Life A clear definition of required gear and bearing system life mus
36、t be provided. Life is defined at a specified survival level. 4.1.4 Weight System weight is critical in aerospace applications. A value for gear system weight should be specified as dry gearbox weight or gearbox plus lubrication system weight. 4.1.5 Sire limitations In most applications, gearbox loc
37、ation and maxi- mum envelope will be defined. These details must be made available to the designer. 4.1.6 Reliability Reliability requirements are typically specified in terms of mean time between failure (MTBF). A historical data base of typical component reliability will permit calculation of syst
38、em reliability. New products are more difficult to characterize. Tech- niques to quantify reliability levels must be specified for a new gearbox system. AGMA 91 1 -A94 4.1.7 Maintainability Guidelines for field service work, space require- ments, and tool limitations must be specified early in the p
39、roject. 4.1.8 Cost Aerospace gearing is generally more costly than commercial gearing because of the necessary performance, quality and traceability requirements. Life cycle cost is often established at the start of the project as a goal or as a requirement. Lae cycle cost is defined as the total co
40、st of ownership of a system over its operating life. 4.1.9 Efficiency In most aerospace applications, gearbox efficiency is an important design consideration because it influences system weight and power requirements. Efficiency requirements and goals will provide the designer a clear indication of
41、the project objectives and may affect key decisions in the design process. 4.1 .IO Altituddattitude requirements Altitude and attitude specifications are required for lubrication system design, since oil pump and oil passage design are dependent on these parame- ters. In lieu of any specific applica
42、tion data MIL-E-8593C provides general requirements for aerospace applications. 4.1 .i1 Externally generated gearbox loads Extemal loads can be generated by rotor loads, flight maneuvers, gravity and gyroscopic effects, hard or crash landing requirements, or vibration, as applicable. All must be con
43、sidered in the design of the gearbox housing, mounts and their effects on misalignment of bearings and gears within the gearbox. Typical loads are given in MlL-E-8593C. 4.1.12 Mount locations Mount locations must be specified to allow design and analysis of the housing and internal structure under e
44、xternal loading conditions. Mount location requirements may also affect maintainability con- siderations. 4.1 .I3 Loss of lubricant All military and some commercial aircraft have requirements for operation with loss of lubricant , typically specifying a time and power level of operation after loss o
45、f lubricant. These require- 5 AGMA 911-A94 AGMA 711-A 74 Ob87575 0003446 066 = ments must be known to allow the design of a suitable lubrication system. 4.1 .I4 Test requirements Test requirements are sometimes different than those used to design the gearbox. If an unusual test is required it can af
46、fect the gearbox design. 4.1.15 Noise requirements The recent trend in air vehicle specification has been to require meeting specified internal noise levels in cabin and cockpit. 4.2 Identify design criteria It is sometimes difficult to clearly define design objectives or goals of a gearbox or gears
47、et. Proper identification of design criteria requires application of many disciplines such as elastohydrodynamics, involutometry, geometry, stress analysis, system dynamics, materials, kinematics, vibration, heat transfer, processes, manufacturing, economics, etc. Each of the above disciplines requi
48、res that design limits be imposed such as: - Stress limits; - Scuffing (scoring); - Minimum oil film thickness; - Type of mounts, deflections and locations; -Weight and Cost; - Vibration; - Noise. The design criteria which have the largest influence on the final configuration are as follows. 4.2.1 A
49、llowable contact stress The tooth contact (Hertz) stress limit depends on the type of application, required service life, proper- ties of materials used, and the shape of the tooth surfaces near the point of contact before the load transfer begins. 4.2.1.1 Power transmission In high pitch linevelocity gearsets, thedistributionof dynamic load is required for accurate determination of tooth contact stress. A method for calculation of contact stresses, along with allowable limits, is given in ANSVAGMA 2001-888. 4.2.1.2 Actuator gearing Actuator gears are subject
