(碟簧-英语版-2013) DIN2093_2013_12_EN

DIN 2093

ICS 21.160

D

Supersedes

DIN 2093:2013-02

Disc springs –

Quality specifications –Dimensions,

English translation of DIN 2093:2013-12

Tellerfedern –

Qualitätsanforderungen –Maße,

Englische Übersetzung von DIN 2093:2013-12Rondelles ressorts –Exigences de qualité –Dimensions,

Traduction anglaise de DIN 2093:2013-12

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56Document comprises 18 pages

Translation by DIN-Sprachendienst.

In case of doubt, the German-language original shall be considered authoritative.

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No part of this translation may be reproduced without prior permission of

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04.142099813 DIN 2093:2013-12

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Foreword

This document has been prepared by Working Committee NA 026-00-02 AA Tellerfedern of the Normen-ausschuss Federn, Stanzteile und Blechformteile (NAFS) (Springs, Stamped Parts and Moulded Parts Standards Committee) in DIN.

Since this edition is a corrected edition of DIN 2093:2006-03, the Amendments clause from the 2006 edition is reproduced here. In the meantime, the ISO 31 series of standards has been replaced by the ISO 80000 series.

Further information about NAFS can be found at www.nafs.din.de. Amendments

This standard differs from DIN 2093:1992-01 as follows:

a) examples of designation for springs produced by turning (G) and for springs produced by fine blanking (F)

are no longer included (see Clause 4); b) Clause 4 now includes the assignment of springs to series A, B or C based on the h0/t ratio;

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56c) in Clause 7, new values of Ftand of stresses σII,σIII,σOM have been specified;

d) the standard has been editorially revised to take account of the new style rules for standards. Quantities,

symbols, units and signs have been aligned with the International System of Units (SI) as in ISO 31. The following corrections have been made to the DIN 2093:2006-03 edition: a) Corrigendum 1 from July 2007 has been incorporated;

b) in Figure 6 (Fatigue life of not shot peened disc springs with 1,25 mm ≤ t ≤ 6 mm) the maximum stress has

been corrected to 1 250 MPa; c) the drawings have been reworked to reflect the new principles on which they are based; d) normative references have been updated.

The following corrections have been made to the DIN 2093:2013-02 edition:

a) in Table 1, column “σIII”, the value 1 419 for De 25 disc springs in Group 2 has been corrected to 1 091; b) in Table 1, column “σOM”, the value −1 562 for De 25 disc springs in Group 2 has been corrected to

−1 622; Previous editions

DIN 2093: 1957-05, 1967-04, 1978-04, 1990-09, 1992-01, 2006-03, 2013-02 DIN 2093 Corrigendum 1: 2007-07

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DIN 2093:2013-12

1 Scope

This standard specifies the set of requirements that ensure the correct functioning of disc springs. These include requirements relating to the materials and manufacturing process, tolerances on dimensions and spring forces, and also the permissible relaxation and fatigue life of such springs as a function of stress. All requirements specified here are minimum requirements. This standard covers three dimensional series of disc springs.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

DIN 2092:2006, Disc springs — Calculation

DIN 50969, Testing of high strength steel building elements for resistance to hydrogen induced brittle fracture and advice on the prevention of such fracture

DIN EN 1654, Copper and copper alloys — Strip for springs and connectors

DIN EN 10083-1, Steels for quenching and tempering — Part 1: General technical delivery conditions

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56DIN EN 10083-2, Steels for quenching and tempering — Part 2: Technical delivery conditions for unalloyed quality steels

DIN EN 10083-3, Steels for quenching and tempering — Part 3: Technical delivery conditions for alloy steels DIN EN 10089, Hot rolled steels for quenched and tempered springs — Technical delivery conditions

DIN EN 10132-4, Cold rolled narrow steel strip for heattreatment — Technical delivery conditions — Part 4: Spring steels and other applications

DIN EN 10151, Stainless steel strip for springs — Technical delivery conditions DIN EN ISO 3269, Fasteners — Acceptance inspection

DIN EN ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method

DIN EN ISO 6507-2, Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing machines

DIN EN ISO 6507-3, Metallic materials — Vickers hardness test — Part 3: Calibration of reference blocks DIN EN ISO 6507-4, Metallic materials — Vickers hardness test — Part 4: Tables of hardness values DIN EN ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method (scales A, B, C, D, E, F, G, H, K, N, T)

DIN EN ISO 6508-2, Metallic materials — Rockwell hardness test — Part 2: Verification and calibration of testing machines and indenters (scales A, B, C, D, E, F, G, H, K, N, T)

DIN EN ISO 6508-3, Metallic materials — Rockwell hardness test — Part 3: Calibration of reference blocks (scales A, B, C, D, E, F, G, H, K, N, T)

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DIN 2093:2013-12

3 Terms and definitions

Disc springs are annular coned elements that offer resistance to a compressive load applied axially. They may be designed as single disc springs or as disc springs stacked in parallel or in series, either singly or in multiples. They may be subjected to both static and fatigue loading, and may have flat bearings.

In this standard, disc springs are divided into three groups and three dimensional series. Classification into groups is based on the manufacturing process, which is a function of the material thickness. The assignment of disc springs to dimensional series is governed by the h0/t ratio.

4 Dimensions and designations

4.1 General

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56

a) without flat bearings: Group 1 Group 2

b) with flat bearings:

Group 3

Figure 1 — Single disc spring of group 1, 2 or 3 (sectional view), including the relevant points

of loading

Designation of a disc spring of dimensional series A with an outer diameter De of 40 mm:

Disc spring DIN 2093 — A 40

4.2 Disc spring groups

Group 1 2 3 t < 1,25 1,25 ≤ t ≤ 6 > 6 < t ≤ 14 With flat bearings and reduced thickness No No Yes 4.3 Dimensional series

Series A B C h0/t ~ 0,40 ~ 0,75 ~ 1,30 4

DIN 2093:2013-12

5 Symbols, units and descriptions

Symbol De Di Unit mm mm mm MPa N N N N mm mm N/mm Nmm mm mm mm mm mm mm mm mm MPa MPa MPa MPa MPa MPa Outer diameter of spring Inner diameter of spring Description D0 Diameter of centre of rotation Modulus of elasticity Spring load Design spring load when spring is in the flattened position Test load for length Lt or lt Relaxation Length of springs stacked in series or in parallel, in the initial position Design length of springs stacked in series or in parallel, in the flattened position Number of cycles to failure Spring rate Energy capacity of spring Initial cone height of springs without flat bearings h0=l0−t ′=l0−t′ Initial cone height of springs with flat bearings h0E F Fc Ft ∆F L0 Lc N R W h0 Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56h′0 i l0 lt Number of disc springs or packets stacked in series Free overall height of spring in its initial position Test length of disc spring lt=l0−0,75h0 Deflection of single disc spring Spring deflections related to spring loads F1,F2,F3... Thickness of single disc spring Reduced thickness of single disc spring with flat bearings (group 3) Poisson’s ratio Design stress Design stresses at the points designated II, III, OM (see Figure 1) Fatigue stress related to the deflection of springs subject to fatigue loading Maximum fatigue stress Minimum fatigue stress Permanent range of fatigue stress Theoretical centre of rotation of disc spring cross-section (see Figure 1) Lever arms Mean surface roughness s s1,s2,s3... t t' µ σ σII,σIII,σOM σh σO σU σH=σO−σU P V,V' Ra 5

DIN 2093:2013-12

6 Spring material

Springs complying with this standard shall be made from steel as specified in DIN EN 10083, DIN EN 10089 or DIN EN 10132-4. Carbon steel shall only be used for the manufacture of group 1 springs (see also Table 4).

NOTE The design of disc springs made from steel as above shall be based on a modulus of elasticity E of 206 000 MPa.

The modulus of elasticity and strength property of other materials (e.g. stainless steel for springs in accordance with DIN EN 10151, copper alloys (spring bronze) in accordance with DIN EN 1654) will likely be different. The values given for F and σ in Tables 1 to 3 then cease to apply. In such cases it is recommended the spring manufacturer be consulted.

7 Spring dimensions, nominal sizes, design values

7.1 Dimensional series A

Disc springs with

hDe ≈ 18; 0 ≈ 0,4; E = 206000 MPa; µ = 0,3 ttTable 1

Group De h12 Di H12 t or (t')a 0,4 0,5 0,7 0,8 0,9 1 1,1 1,25 1,5 1,5 1,75 2 2,25 2,5 3 3 3,5 4 5 5 6 6 8 (7,5) 8 (7,5) 10 (9,4) 10 (9,4) 12 (11,25) 12 (11,25) 14 (13,1) h0 0,2 0,25 0,3 0,3 0,35 0,4 0,45 0,5 0,55 0,65 0,7 0,8 0,9 1 1,1 1,3 1,4 1,6 1,7 2 2,2 2,5 2,6 3,2 3,5 4 4,2 5 5,6 l0 0,6 0,75 1 1,1 1,25 1,4 1,55 1,75 2,05 2,15 2,45 2,8 3,15 3,5 4,1 4,3 4,9 5,6 6,7 7 8,2 8,5 10,6 11,2 13,5 14 16,2 17 19,6 Ft 210 325 660 797 1 013 1 254 1 521 1 929 2 926 2 841 3 871 5 187 6 500 7 716 11 976 11 388 15 025 20 535 33 559 31 354 48 022 43 707 85 926 85 251 138 331 125 417 183 020 171 016 248 828 lt s ≈ 0,75 h0 0,45 0,56 0,77 0,87 0,99 1,1 1,21 1,37 1,64 1,66 1,92 2,2 2,47 2,75 3,27 3,32 3,85 4,4 5,42 5,5 6,55 6,62 8,65 8,8 10,87 11 13,05 13,25 15,4 σIIIb 1 218 1 218 1 382 1 308 1 301 1 295 1 290 1 296 1 091 1 274 1 296 1 332 1 328 1 296 1 418 1 274 1 296 1 332 1 453 1 295 1 418 1 239 1 326 1 284c 1 338 1 201c 1 227 1 137c 1 221c σOM s = h0 −1 605 −1 595 −1 666 −1 551 −1 555 −1 558 −1 560 −1 534 −1 622 −1 562 −1 570 −1 611 −1 595 −1 534 −1 659 −1 565 −1 524 −1 594 −1 679 −1 558 −1 663 −1 505 −1 708 −1 675 −1 753 −1 576 −1 611 −1 489 −1 596 Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:561 2 3 8 10 12,5 14 16 18 20 22,5 25 28 31,5 35,5 40 45 50 56 63 71 80 90 100 112 125 140 160 180 200 225 250 4,2 5,2 6,2 7,2 8,2 9,2 10,2 11,2 12,2 14,2 16,3 18,3 20,4 22,4 25,4 28,5 31 36 41 46 51 57 64 72 82 92 102 112 127 a The values specified for t are nominal values. In the case of springs with flat bearings (cf. group 3 in Clause 4), the desired spring b c load F (where s ≈ 0,75 h0) is to be obtained by reducing the thickness of single disc springs t which then gives the value t'. In the case of dimensional series A and B, t' ≈ 0,94 · t, and in the case of dimensional series C, t' ≈ 0,96 · t. The values specified apply for the largest calculated tensile stress on the lower edges of the spring. The values specified apply for the largest calculated tensile stress at the point designated III. 6

DIN 2093:2013-12

7.2 Dimensional series B

Disc springs with

hDe ≈ 28; 0 ≈ 0,75; E = 206000 MPa; µ = 0,3 tt

Table 2 Group De h12 Di H12 t or (t')a 0,3 0,4 0,5 0,5 0,6 0,7 0,8 0,8 0,9 1 1,25 1,25 1,5 1,75 2 2 2,5 2,5 3 3,5 3,5 4 5 5 6 6 8 (7,5) 8 (7,5) 10 (9,4) h0 0,25 0,3 0,35 0,4 0,45 0,5 0,55 0,65 0,7 0,8 0,9 1 1,15 1,3 1,4 1,6 1,75 2 2,3 2,5 2,8 3,2 3,5 4 4,5 5,1 5,6 6,5 7 l0 0,55 0,7 0,85 0,9 1,05 1,2 1,35 1,45 1,6 1,8 2,15 2,25 2,65 3,05 3,4 3,6 4,25 4,5 5,3 6 6,3 7,2 8,5 9 10,5 11,1 13,6 14,5 17 Ft 118 209 294 279 410 566 748 707 862 1 107 1 913 1 699 2 622 3 646 4 762 4 438 7 189 6 725 10 518 14 161 13 070 17 752 29 908 27 920 41 008 37 502 76 378 70 749 119 050 lt s ≈ 0,75 h0 0,36 0,47 0,59 0,6 0,71 0,82 0,94 0,96 1,07 1,2 1,47 1,5 1,79 2,07 2,35 2,4 2,94 3 3,57 4,12 4,2 4,8 5,87 6 7,12 7,27 9,4 9,62 11,75 σIII 1 312 1 281 1 114 1 101 1 109 1 114 1 118 1 079 1 023 1 086 1 187 1 073 1 136 1 144 1 140 1 092 1 088 1 055 1 142 1 114 1 049 1 090 1 149 1 101 1 109 1 035 1 254 1 176 1 244 σOM s = h0 −1 505 −1 531 −1 388 −1 293 −1 333 −1 363 −1 386 −1 276 −1 238 −1 282 −1 442 −1 258 −1 359 −1 396 −1 408 −1 284 −1 360 −1 246 −1 363 −1 363 −1 235 −1 284 −1 415 −1 293 −1 333 −1 192 −1 409 −1 267 −1 406 1 Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:562 3 8 10 12,5 14 16 18 20 22,5 25 28 31,5 35,5 40 45 50 56 63 71 80 90 100 112 125 140 160 180 200 225 250 4,2 5,2 6,2 7,2 8,2 9,2 10,2 11,2 12,2 14,2 16,3 18,3 20,4 22,4 25,4 28,5 31 36 41 46 51 57 64 72 82 92 102 112 127 a The values specified for t are nominal values. In the case of disc springs with flat bearings (cf. Group 3 in Clause 4), the desired spring load F (where s ≈ 0,75 h0) is to be obtained by reducing the thickness of single disc springs t which then gives the value t'. In the case of dimensional series A and B, t' ≈ 0,94 · t and in the case of dimensional series C, t' ≈ 0,96 · t. 7

DIN 2093:2013-12

7.3 Dimensional series C

Disc springs with

hDe ≈ 40; 0 ≈ 1,3; E = 206000 MPa; µ = 0,3 tt

Table 3

Group De h12 Di H12 t or (t')a 0,2 0,25 0,35 0,35 0,4 0,45 0,5 0,6 0,7 0,8 0,8 0,9 1 1,25 1,25 1,5 1,8 2 2,25 2,5 2,7 3 3,5 3,8 4,3 4,8 5,5 6,5 (6,2) 7 (6,7) h0 0,25 0,3 0,45 0,45 0,5 0,6 0,65 0,8 0,9 1 1,05 1,15 1,3 1,6 1,6 1,95 2,35 2,6 2,95 3,2 3,5 3,9 4,5 4,9 5,6 6,2 7 7,1 7,8 l0 0,45 0,55 0,8 0,8 0,9 1,05 1,15 1,4 1,6 1,8 1,85 2,05 2,3 2,85 2,85 3,45 4,15 4,6 5,2 5,7 6,2 6,9 8 8,7 9,9 11 12,5 13,6 14,8 Ft 39 58 151 123 154 214 254 426 600 801 687 832 1 017 1 891 1 550 2 622 4 238 5 144 6 613 7 684 8 609 10 489 15 416 17 195 21 843 26 442 36 111 44 580 50 466 lt s ≈ 0,75 h0 0,26 0,32 0,46 0,46 0,52 0,6 0,66 0,8 0,92 1,05 1,06 1,19 1,32 1,65 1,65 1,99 2,39 2,65 2,99 3,3 3,57 3,97 4,62 5,02 5,7 6,35 7,25 8,27 8,95 σIII 1 034 965 1 278 1 055 1 009 1 106 1 063 1 227 1 259 1 304 1 130 1 078 1 063 1 253 1 035 1 218 1 351 1 342 1 370 1 286 1 235 1 218 1 318 1 249 1 238 1 201 1 247 1 137 1 116 σOM s = h0 −1 003 − 957 −1 250 −1 018 − 988 −1 052 −1 024 −1 178 −1 238 −1 282 −1 077 −1 042 −1 024 −1 227 −1 006 −1 174 −1 315 −1 295 −1 311 −1 246 −1 191 −1 174 −1 273 −1 203 −1 189 −1 159 −1 213 −1 119 −1 086 1 Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:562 3 8 10 12,5 14 16 18 20 22,5 25 28 31,5 35,5 40 45 50 56 63 71 80 90 100 112 125 140 160 180 200 225 250 4,2 5,2 6,2 7,2 8,2 9,2 10,2 11,2 12,2 14,2 16,3 18,3 20,4 22,4 25,4 28,5 31 36 41 46 51 57 64 72 82 92 102 112 127 a The values specified for t are nominal values. In the case of disc springs with flat bearings (cf. Group 3 in Clause 4), the desired spring load F (where s ≈ 0,75 h0) is to be obtained by reducing the thickness of single disc springs t which then gives the value t'. In the case of dimensional series A and B, t' ≈ 0,94 · t, and in the case of dimensional series C, t' ≈ 0,96 · t. 8

DIN 2093:2013-12

8 Manufacture

8.1 Manufacturing process and surface quality

Disc springs shall be manufactured as specified in Table 4.

Table 4 — Prescribed manufacturing processes and surface quality

Surface roughnessa Surface roughnessa on upper and bottom on outer and inner Manufacturing process surfaces, edges, µm µm Stamping, cold forming, edge rounding Stampingb, cold forming, De und Di turning, edge rounding or fine blankingc, cold forming, edge rounding Cold or hot forming, turning on all sides, edge rounding or Stampingb, cold forming, De and Di turning, edge rounding or fine blankingc, cold forming, edge rounding Ra < 3,2 Ra < 12,5 Group Material as in 1 DIN EN 10132-4 Ra < 6,3 Ra < 6,3 DIN EN 10132-4 2 Ra < 6,3 Ra < 3,2 DIN EN 10132-4 Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56Ra < 12,5 Ra < 12,5 DIN EN 10083 DIN EN 10089 3 Ra < 12,5 Ra < 12,5 DIN EN 10132-4 Ra < 12,5 Ra < 12,5 DIN EN 10132-4 a The values specified do not apply to shot peened springs. b Stamping without D and D turning is not permitted. eic Fine blanking in accordance with VDI Guideline 2906 Part 5: Clean cut min. 75 %, scar category 2, tear off max. 25 %. 8.2 Heat treatment

To ensure satisfactory fatigue life with minimum relaxation, the hardness of disc springs shall lie within the

range of 42 HRC to 52 HRC.

For group 1 disc springs, the hardness shall be determined according to Vickers (425 HV10 to 510 HV10). After heat treatment, the disc spring shall not exhibit a depth of decarburization exceeding 3 % of its thickness.

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DIN 2093:2013-12

8.3 Shot peening

In order to increase the values given in Figures 5 to 7, shot peening is recommended. This procedure shall be the subject of agreement between customer and manufacturer.

8.4 Presetting

After heat treatment, each disc spring shall be loaded until it is in the flat position.

After loading the disc spring with twice its test load Ft, the tolerances for the spring load as specified in Table 7 shall be met.

8.5 Surface treatment and corrosion protection

The surface shall be free from defects such as scars, cracks and corrosion.

Whether and which corrosion protection is to be provided shall be a function of the particular spring application. Suitable corrosion protection includes phosphating, black finishing, and the application of protective metallic coatings such as zinc or nickel. This shall be agreed between customer and manufacturer. Galvanizing processes using aqueous solutions that are currently available may not preclude the risk of hydrogen embrittlement. Disc springs with a hardness exceeding 40 HRC are more prone to the risk of hydrogen embrittlement than softer springs. Particular care shall therefore be taken when selecting the material, manufacturing process, heat treatment and surface treatment (cf. DIN 50969). When ordering disc springs with galvanic surface protection it is advisable to consult the spring manufacturer.

For disc springs with dynamic loading galvanic surface protection should be avoided and processes used in which inclement effects do not occur.

Phosphating and oiling is the standard corrosion protection for disc springs.

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:569 Tolerances

9.1 Tolerances on diameter

De: tolerance class h12

Coaxiality tolerance for De ≤ 50 : 2 · IT11 Coaxiality tolerance for De > 50 : 2 · IT12 Di: tolerance class H12

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DIN 2093:2013-12

9.2 Tolerances on thickness

Table 5

Group 1 t 0,2 ≤ t ≤ 0,6 0,6 < t < 1,25 1,25 ≤ t ≤ 3,8 3,8 < t ≤ 6,0 6,0 < t ≤ 14,0 Tolerances +0,02−0,06 +0,03−0,09 +0,04−0,12 +0,05−0,15 ± 0,10 2 3

9.3 Tolerances on free overall height l0

Table 6

Group 1 t t < 1,25 1,25 ≤ t ≤ 2,0 Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56Grenzabmaße +0,10−0,05 +0,15−0,08+0,20−0,10 2 2,0 < t ≤ 3,0 3,0 < t ≤ 6,0 +0,30−0,15 3

6,0 < t ≤ 14,0 ± 0,30 9.4 Tolerances on spring load

9.4.1 Single disc springs

The spring load Ft shall be determined at test length lt = l0 − 0,75 h0. The measurement is taken while loading between flat plates, using a suitable lubricant. The flat plates shall be hardened, ground and polished.

Table 7

Group 1 3 t t < 1,25 1,25 ≤ t ≤ 3,0 3,0 < t ≤ 6,0 6,0 < t ≤ 14,0 Tolerances for Ft at lt = l0 − 0,75 h0 % +25−7,5 +15−7,5 +10−5 ± 5

To comply with the specified load tolerances, it may be necessary to exceed the tolerance values specified for l0 and t.

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DIN 2093:2013-12

9.4.2 Springs stacked in series

Figure 2 — Loading and unloading curves obtained from testing springs stacked in series

Ten single disc springs stacked in series shall be used to determine the deviation in load between the loading curve and the unloading curve.

Prior to testing, the disc spring shall be compressed to twice its test load Ft. The individual disc springs shall be centred by a mandrel in compliance with Clause 13. The clearance between disc springs and mandrel shall be as specified in Table 9. The flat plates shall meet the requirements specified in 9.4.1.

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56At Lt = L0 − 7,5 h0 the spring load determined for the unloading curve shall make up at least the minimum percentages specified in Table 8 of the spring load determined for the loading curve (see also Figure 2).

Table 8 — Minimum spring load at unloading, as a percentage of the spring load at loading at Lt

Group 1 2 3

A 90 92,5 95 Series B C 85 87,5 90 9.5 Clearance between disc spring and guiding element

A guiding element is necessary to keep the disc spring in position. This should be preferably a mandrel. In the case of external positioning, a sleeve is preferred.

Table 9 — Recommended clearance between disc spring and guiding element

Di or De Up to 16 Over 16 up to 20 Over 20 up to 26 Over 26 up to 31.5 Over 31.5 up to 50 Over 50 up to 80 Over 80 up to 140 Over 140 up to 250 Total clearance 0,2 0,3 0,4 0,5 0,6 0,8 1,0 1,6 12

DIN 2093:2013-12

10 Creep and relaxation

All disc springs lose load during usage. Depending on the application, this is expressed by creep or relaxation. Both creep and relaxation are largely a result of the stress distribution over the cross-section of the disc spring. Its influence can be estimated on the basis of the design stress σOM (see DIN 2092, Clause 10). Creep is defined as the further decrease in length of the disc spring with time ∆l when subjected to a constant load. Relaxation is defined as the decrease in load with time ∆F when the disc spring is compressed to a constant length.

For disc springs under static load, the guideline values for relaxation illustrated in Figures 3 and 4 should not be exceeded.

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56

Figure 3 — Permissible relaxation for disc springs made of carbon steel in accordance

with DIN EN 10132-4

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DIN 2093:2013-12

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56Figure 4 — Permissible relaxation for disc springs made of alloy steel in accordance

with DIN EN 10089 and DIN EN 10132-4

If the ambient temperature exceeds 100 °C, the spring manufacturer should be consulted.

11 Permissible stresses

11.1 Static and rarely alternating loading

For disc springs made of steels according to DIN EN 10089 or DIN EN 10132-4, which are subject to static loading or to moderate fatigue conditions, the design stress σOM at maximum deflection shall not exceed 1 600 MPa.

Higher stresses may cause a higher loss of spring load (see Clause 10).

11.2 Dynamic loading

Minimum initial deflection to avoid cracking:

Disc springs subject to fatigue loading shall be designed and installed in such a way that the initial deflection is s1 ≈ 0,15 h0 to s1 ≈ 0,20 h0 in order to avoid cracking at the upper inner edge, point I (see Figure 1) as a result of residual stresses from the presetting process. 11.2.1 Permissible loading

Figures 5 to 7 illustrate the fatigue life of disc springs subject to dynamic loading that have not been shot peened. They specify guideline values for the permanent range of stress σH as a function of the minimum

655

stress σU at three different numbers of stress cycles, namely where N ≤ 2 · 10, N = 10 und N = 5 · 10.

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DIN 2093:2013-12

Intermediate values for other numbers of stress cycles may be estimated based on this information.

The information given in Figures 5 to 7 represents the results of laboratory testing using fatigue testing equipment capable of producing sinusoidal loading cycles and the statistical results obtained for a 99 % probability of fatigue life. The figures are valid for single disc springs and stacks with I ≤ 10 disc springs stacked in series. Test conditions are: room temperature, disc springs preloaded from s1 ≈ 0,15 h0 to s1 ≈ 0,20 h0, surface hardened and perfectly processed inner and outer guidance.

To ensure the expected fatigue life of disc springs, they shall be protected from mechanical damage and other 65:01 61-70-4102-1001357966.rNfL-8247894.rNdK-HbmG eguezrhafneneihcS rüf emetsyS ESMERB-RRONK-htueB-daolnwoD-nemroNadverse conditions.

Figure 5 — Fatigue life of not shot peened disc springs with t < 1,25 mm

Figure 6 — Fatigue life of not shot peened disc springs with 1,25 mm ≤ t ≤ 6 mm

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DIN 2093:2013-12

Figure 7 — Fatigue life of not shot peened disc springs with 6 mm < t ≤ 14 mm

It should be noted that stress cycles in practice are generally not sinusoidal in form. Any additional type of loads (e.g. sudden dynamic loading, shock loads and resonance) will shorten the fatigue life.

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:56In this case the values given in the above figures shall be converted by appropriate factors of safety; the spring manufacturer should be consulted where necessary.

NOTE Reliable information regarding the fatigue life is not available for disc springs made from materials other than those specified here, for disc springs consisting of more than ten single disc springs stacked in series, for other unfavourable arrangements of stacks of springs, nor for springs subjected to chemical or thermal effects, although some relevant information is usually obtainable from the spring manufacturer.

In the case of stacks with a highly degressive load/deflection curve (dimensional series C) and a large number of single disc springs stacked in series, an uneven deflection of the single disc springs can be expected. This effect is caused by friction between the disc springs and the guiding element and dimensional tolerances. Disc springs at the moving end of the stack deflect more than the others. This will result in a shorter fatigue life than shown in Figures 5 to 7.

The fatigue life of disc springs can be prolonged considerably by additional shot peening.

12 Testing

Determination of the properties covered in 12.1 and 12.2 shall be the subject of agreement between customer and manufacturer.

12.1 Check of dimensions and other spring characteristics

The specifications given in DIN EN ISO 3269 shall be applied in addition to the characteristics and quality levels specified in Table 10.

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Table 10

Spring characteristics Major characteristics Spring load F (s ≈ 0,75 h0) Outer diameter De Inner diameter Di Minor characteristics Free overall height in initial position l0 Spring thickness t or t' Surface roughness Ra

1 AQL value 1,5 12.2 Hardness testing

Vickers hardness testing shall be carried out according to DIN EN ISO 6507-1 to DIN EN ISO 6507-4. Rockwell hardness testing shall be carried out according to DIN EN ISO 6508-1 to DIN EN ISO 6508-3. The indentation shall be made on the upper surface of the disc spring, at a point that lies centrally between the inner and outer edges.

Normen-Download-Beuth-KNORR-BREMSE Systeme für Schienenfahrzeuge GmbH-KdNr.4987428-LfNr.6697531001-2014-07-16 10:5613 Other relevant requirements

Where possible, the guiding element and the support plate shall be made from case hardened materials, with a case depth of ≈ 0,8 mm, and have a minimum hardness of 60 HRC. The surface of the guiding element should be smooth and perfectly finished. It shall be permitted to use unhardened guiding elements where the disc spring is subject to static loading.

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DIN 2093:2013-12

Bibliography

DIN 4000-11, Tabular layouts of article characteristics for springs

DIN 59200, Flat products of steel — Hot rolled wide flats — Dimensions, mass, tolerances on dimensions, shape and mass

DIN EN 10048, Hot rolled narrow steel strip — Tolerances on dimensions and shape

DIN EN 10051, Continuously hot rolled strip and plate/sheet cut from wide strip of non-alloy and alloy steels — Tolerances on dimensions and shape

DIN EN 10140, Cold rolled narrow steel strip — Tolerances on dimensions and shape

DIN EN 12476, Phosphate conversion coatings of metals — Method of specifying requirements

DIN EN ISO 11124-1, Preparation of steel substrates before application of paints and related products — Specifications for metallic blast cleaning abrasives — Part 1: General introduction and classification DIN EN ISO 26909, Springs — Vocabulary

DIN ISO 2162-1, Technical products documentation — Springs — Part 1: Simplified representation

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