1、 SAE Manual on Design and Application of Helical and Spiral Springs 1997 Edition SAE HS-795 INTERNATIONAL IBI Society of Automotive Engineers, Inc. Warrendale, Pa. All technical reports, including standards approved and practices recommended, are advisory only. Their use by anyone engaged in industr
2、y or trade or their use by governmental agencies is entirely voluntary. There is no agreement to adhere to any SAE Standard or Recommended Practice, and no commitment to conform to or be guided by any technical report. In formulating and approving technical reports, the Technical Board, its councils
3、, and committees will not investigate or consider patents which may apply to the subject matter. Prospective users of the report are responsible for protecting themselves against liability for infringement of patents, trademarks, and copyrights. Copyright O 1997 Society of Automotive Engineers, Inc.
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6、.50. Coil Spring Subcommittee E.H. Judd (Chairman) Joseph A. Fader Mike Holly John M. Jaloszynski Stephen L. Kaye Yuyi Lin Gordon D. Millar Arthur M. Peach James H. Schindler Kenny E. Siler Richard Tiefenbruck Retired Rockwell Suspension Systems General Motors Corp. Barnes Group Inc. Rockwell Suspen
7、sion Systems University of Missouri at Columbia Stelco Inc. Chrysler Corp. Ford Motor Co. Ford Motor Co. Moog Automotive . 111 Introduction The Manual on Design and Application of Helical and Spiral Springs was Originally published in 1943 under the title “Manual on Design and Application of Helical
8、 Springs for Ordnance” at the behest of the U.S. Ordnance Department. The wide accep- tance of the manual has resulted in five revisions over the years. In 1982, SI units were incorporated in accordance with SAE Technical Board Standards. In the latest revision, the basic layout of the manual is unc
9、hanged. However, some of the tables have been changed in Chapters 2 and 4, and entire sections have been rewritten in Chapters 2,4, and 5. As in previous editions, the Spring Committee wishes to emphasize that the manual is not encyclopedic in coverage but is confined to a concise and simple account
10、 of the essentials involved in the design and application of helical and spiral springs. It is presented in the hope that it will be helpful to the engineer and the designer in two ways: as a means toward the better appreciation of the nature of the spring problems that one encounters in ones work,
11、and more specifically as a ready ref- erence and guide. I wish to thank the members of the Spring Committee and the Coil Spring Subcommittee for their help and guidance in this latest revision of the manual, which would not have been pos- sible without their contributions. E.H. Judd V Table of Conte
12、nts LETTER SYMBOLS . 1 CONVERSION TABLE . 2 CHAPTER 1-FUNDAMENTAL CONSIDERATIONS 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . Energy . 3 Definitions 3 Energy Capacity of Different Spring Types 3 Space Limitations . 4 Nested Springs 4 Static Versus Dynamic Loading 8 Natural Frequency . 10 Residual Stresses . 11 S
13、hot Peening . 11 Presetting 12 Temperature Effects on Springs 13 Fatigue Durability . 14 Common Causes of Spring Failure . 15 Surface Protection . 16 Protection from Mildly Corrosive Environment . 16 Electroplating 16 Effect of Finish on Environment . 17 Techniques for Minimizing Hydrogen Embrittlem
14、ent CHAPTER 24PRING MATERIALS 1 . 2 . 3 . 4 . 5 . 6 . Material Selection . 19 Cold Wound Spring Material 19 Ferrous Wire . 19 Hard Drawn Carbon Spring Wire-SAE 5113 . 19 Music Spring Wire-SAE 5178 19 . 19 Oil Tempered Carbon Valve Spring Wire-SAE 535 1 . 20 20 Annealed Wires (SAE 1065 Thru 5.0 mm; S
15、AE 1566 Over 5.0 20 Alloy Steel Spring Wires-SAE 5132 and SAE 5157 20 Stainless Steel Wire-SAE 5230 and SAE 5217 20 Copper Alloys . 20 Spring Brass 20 Phosphor Bronze . 20 Beryllium Copper . 20 Silicon Bronze 21 Nickel Alloy Wires, SAE 5470 . 21 Inconel 600 . 21 Inconel X-750 . 21 Monel 400 . . 21 M
16、onel K-500 Superalloys . Oil Tempered Carbon Spring Wire-SAE 53 16 . Hard Drawn Valve Spring Wire-SAE 5172 vii 7 . Spring Steel for Flat Spiral Springs 21 Flat Wire . 21 Hot Coiled Spring Materials . 22 Corrosion Resistance 22 Material Handbooks 23 strip 21 8 . 9 . 10 . CHAPTER 3-COLD WOUND HELICAL
17、AND SPIRAL SPRINGS A . B . C . D . E . HELICAL COMPRESSION SPRINGS 1 . General 33 2 . Spring Details . 33 Terminology and Types of Ends . 33 Wire Diameter (d) . 33 Free Length (L, ) . 34 Number of Coils (N) . 34 Helix of Coil . 35 Solid Length (L, ) . : 35 Load (P) 35 Rate (R) . 35 HELICAL EXTENSION
18、 SPRINGS 1 . General 35 2 . Types of Ends . 35 3 Stress Concentrations in End Coils 35 4 . Position of Hooks . 37 6 . Initial Tension . 38 7 Spring Design 39 TOLERANCES FOR HELICAL COMPRESSION AND EXTENSION SPRINGS 1 . General 39 2 . Coil Diameter 42 3 . Free Length . 42 4 . Load 42 5 . Rate . 43 6
19、. Solid Length 43 7 . Number of Coils 45 8 . Squareness and Parallelism of Ends . 46 HELICAL TORSION SPRINGS 1 . General 46 2 . Effect of Direction of Coiling and Beneficial Residual Stress . 46 3 . Support of Torsion Springs . 46 4 . Types of Ends and End Stresses . 47 5 . Specifications 47 6 . Des
20、ign Formulae . 47 7 . Design Stresses . 47 8 . Commercial Tolerances 47 Coil Diameter 48 Wire Diameter . 48 Position of Ends 48 FLAT SPIRAL SPRINGS 1 . General 48 2 . Spring Materials 49 3 . Design Formulae . 50 Coil Diameter (D) . 33 . . 5 . Specifications 37 . . . v111 CHAPTER two typical examples
21、 are whether the spring actuates an engine valve or a circuit breaker. For most spring applications, the deflection F can be con- sidered as proportional to the load P, provided the elastic limit of the material is not exceeded. Not all springs, however, have linear load deflection diagrams. Notably
22、 in this class are disk or Belleville and volute springs. Where accurate load deflec- tion characteristics are a factor, changes in coil diameter and non-axial force components must be considered. If the spring is considered as having a constant load-deflection rate R, with load P expressed in terms
23、 of N (newton) and deflection F ex- pressed in terms of m (meter), then the energy stored by the spring at deflection F or load P can be expressed in terms of J (Joule = N.m) as follows: PF p2 RF Energy = - = - = - 2 2R 2 However, in this Manual, F is expressed as mm and R as N/mm; this requires tha
24、t the denominator in the energy formula be multiplied by lo3 so as to convert mm into m, thereby allowing the energy still to be expressed as J. The stored energy will then be expressed as follows: (JI R F, 2x10 -210 -210 - PF - P2 Energy = The need for this conversion arises wherever lengths are ex
25、pressed in mm, as in d, D, F, L, and also where compound terms involving a length dimension are used, such as R (Nmm) and E, G, S (MPa = N/mm2). There are four mathematical symbols in this Manual where the length factor has not been converted to mm. They are the symbols for density - y (kg/m3), stan
26、dard acceleration of grav- ity - g (9.81 m/s2), and velocity under dynamic loading - c and v (ms). Therefore, the reader must be alert to apply the correct conversion factor where a formula contains both converted and unconverted factors, as in Sections 2 and 3 of this Chapter. The preceding formula
27、e are based on the fact that the de- flection starts from the free length or free position depending upon the type,of spring. Generally the spring is given some initial deflection F, upon assembly into its application which develops the load PI. From this point, the increase of the load to its maxim
28、um value P, will cause the spring to be deflected through a distance or “stroke” (F, - F,) to the maximum deflec- tion F,. The subsequent decrease in load to Pl will return the spring to its assembled length. In such instances, the energy to be absorbed by the spring during the cycle is: P +P (PZ2 -
29、 Pl) Energy = ( F2 - FI) = 2x10 2 x io3 - R(F2 - F:) - 2x10 (J) Energy Capacity of Different Spring Types The general problem for the designer is to know the over- all energy capacity required of the spring and to relate this to the maximum stress in the spring. It has been established in fundamenta
30、l studies that the energy capacity of a spring for a given maximum stress increases in direct proportion to the vol- ume of the active spring material. For each type of spring, the energy capacity per unit volume of active material represents the basic index for the efficient utilization of the spri
31、ng mate- rial. This Manual deals with helical compression and extension springs, in which the spring wire is principally subjected to tor- sional stress, and with torsion and flat spiral springs, in which the spring wire is principally subjected to bending stress. The two formulae expressing the spe
32、cific energy capacity for these spring types are as follows: For springs subject to torsional stress: Energy =u- S2 Volume G For springs subject to bending stress: Energy =u- S2 Volume E 3 where: U = 1/2 for material under uniform stress, therefore most efficient utilization of material possible; ap
33、- proached by a thin-walled tube used as a torsion bar spring (under torsional loading) and by a ring spring (under compression) U = 1/4 for round wire torsion bar springs and coil springs U = U6.5 for square wire coil springs U = 1/6 for rectangular cross sections in uniform circular bending U = 1/
34、8 for round cross sections in uniform circular bending The formulae indicate that the specific energy capacity in- creases withthe square of the maximum stress which the mate- rial can withstand without permanent set. Specific energy capacity is also inversely proportional to the modulus of elastici
35、ty of the material. It is for these reasons that there is a constant search for materials and fabricating pro- cesses which will permit springs to be highly stressed. In many applications, density of material is an important factor in mass reduction. As for the type of springs to incorporate the hig
36、hest pos- sible energy capacity, the formulae are not conclusive in them- selves, because the maximum design stresses vary with the type of spring and material, as the diagrams in the later chapters of this Manual show. A comparison of different configurations on the basis of volume of metal can be
37、made by selecting suitable stress values for each configuration and solving the appropriate energyholume equations. When other than metallic materials are considered for mass reduction, the comparisons should be made by converting the energy/volume equations to energy/mass equations. The principal s
38、pring types treated in this manual can be arranged in descending order of their specific energy capaci- ties: 1. Round wire compression springs. 2. Flattened round wire or rectangular wire compression 3. Round wire extension springs. 4. Square wire compression springs. 5. Torsion springs and flat sp
39、iral springs with rectangular 6. Square wire extension springs. 7. Torsion springs and flat spiral springs with round wire springs. wire section. section. Space Limitations Frequently it is valuable to determine early in the design of a particular spring configuration the maximum volume of spring ma
40、terial which can be used within a given space. For a flat spiral spring, the solution depends only upon the required clearance between coils and on the space required for the inner fastening device. For round wire compression and extension springs, the curves in Fig. 1.1 will determine if the space
41、is approximately adequate. The curves represent “space efficiency factors” VIV, where Vis the volume of active spring material (the inac- tive end coils are ignored), and V, is the volume of the cylindn- cal space in which the spring is contained when solid. The curves are plotted against “spring in
42、dex” (C = D/d). Two types of spring application are considered. One type is springs under a static load throughout their life with only infrequent further deflection, such as a steam boiler safety valve spring. In such a spring, the entire (round) wire surface is as- sumed to be under uniform torsio
43、nal stress. For this spring the space efficiency factor is: KC - v v, (c + i)* Other springs are expected to withstand a great number of load cycles which subject the wire to large stress ranges, as in most engine valve springs. In such a spring, where the maxi- mum stress range is the criterion for
44、 failure, the higher stresses near the inside of the coil, due to wire curvature and direct shear, become more critical. This is usually taken into account by multiplication of the torsional stress with a “stress correction factor” greater than 1 .O and dependent upon the spring index C. The “Wahl f
45、actor” an alkaline cleaner pro- duces a thicker, hard, tight coating; if an acid is used, the coat- ing is coarse and very thick. A uniform coating depends on good cleaning and chemical control. This phosphate coating is a ba- sis for the subsequent coating with a rust preventive oil, wax, grease, o
46、r organic finish providing good protection from corro- sion. The mechanism of these coatings is the ability of the minute pits, surface irregularities, and the crystalline structure of the zinc and iron phosphate crystals to retain the subsequent coat- ing, thereby providing maximurn corrosion prote
47、ction. The phos- phating process must be tailored to protect the spring from acid pickling, both in the precleaning sequence and during the phos- phate process by controlling the free acid ratio. When the end use of the spring is in a mildly corrosive atmosphere, a black oxide finish provides some d
48、egree of cor- rosion protection. A black oxide coating provides some of the same mechanics to hold rust preventive materials as the zinc and iron phosphate coatings, but with an overall lesser degree of protection. When black oxide coatings are applied they have the advantage of Gausing very slight,
49、 if any, dimensional changes and no hydrogen embrittlement. Frequently, it is advantageous to use precoated spring wire where mildly corrosive conditions are encountered. These wires are coated by dipping into molten metal or by electroplating. They may be coated and then drawn to size, or they may be coated at the finished size. Cadmium, tin, and zinc are the met- als employed for the wire coating process. The commercial importance of the process is considerable because the parts formed from such wires may be used immediately without
