DEUTSCHE NORM
March 2006
D
DIN 2093
Supersedes DIN 2093:1992-01
ICS 21.160
Disc springs – Quality specifications – Dimensions Tellerfedern – Qualitätsanforderungen – Maße s . i y G p A ! o g s c a e s m i g h n t e a f D h o S c f n o M i S o t f e c u o s d a o s e c r s p o n i e r p r d , u e 3 t t p a y d e e n p h a u s p e e m b c o t n c o e r a r n f e t l e i n l i r r w o N f I y y p D l o o n t o c s g d i n e i t h d t T r i o m c r c e A p
Document comprises
18 pages
Translation by DIN-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text.
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DIN 2093:2006-03
Foreword This standard has been prepared by the Ausschuss Federn (Springs Standards Committee). *)
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.
c)
In clause 7, new values of F t and of stresses
d)
The standard has been editorially revised to take account of the new style rules for standards. Symbols, units and quantities have been aligned with the International System of Units (SI) as in ISO 31.
σ II, σ III and σ OM have
been specified.
Previous editions DIN 2093: 1957-07, 1967-04, 1978-04, 1990-09, 1992-01
*) This English translation also includes amendments from Corrigendum DIN 2093:2006-03 Ber 1:2007-08. These are
identified by a footnote.
2
DIN 2093:2006-03
1
Scope
This standard specifies requirements for the materials, manufacturing process, dimensions and tolerances for disc springs. It includes graphs showing the permissible relaxation and the 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 reference documents are indispensable for the application of this document. 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, Quenched and tempered steels — Technical delivery conditions for special steels DIN EN 10083-2, Quenched and tempered steels — Technical delivery conditions for unalloyed quality steels DIN EN 10083-3, Quenched and tempered steels — Technical delivery conditions for boron 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 heat treatment — 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 (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)
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.
3
DIN 2093:2006-03
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 4.1
Dimensions and designation General
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
4.3
Disc spring groups Group
t
1
< 1,25
With flat bearings and reduced thickness No
2
1,25 ≤ t ≤ 6
No
3
> 6 < t ≤ 14
Yes
Dimensional series
**) See *) on page 2.
4
Dimensional series
h0/t
A B C
∼ 0,40 ∼ 0,75 ∼1,30
DIN 2093:2006-03
5
Symbols, units and descriptions Symbol
Unit
Description
De
mm
Outer diameter of spring
Di
mm
Inner diameter of spring
D0
mm
Diameter of centre of rotation
E
MPa
Modulus of elasticity
F
N
Spring load
F c
N
Design spring load when spring is in the flattened position
F t
N
Test load for length Lt or l t
N
Relaxation
∆ F
L0
mm
Length of springs stacked in series or in parallel, in the initial position
Lc
mm
Design length of springs stacked in series or in parallel, in the flattened position Number of cycles to failure
N R
N/mm
Spring rate
W
N mm
Energy capacity of spring
h0
mm
Initial cone height of springs without flat bearings, h0 = l 0 − t
h0′
mm
Initial cone height of springs with flat bearings, h′0 = l 0 − t' Number of disc springs or packets stacked in series
i l 0
mm
Free overall height of spring in its initial position
l t
mm
Test length of spring, l t = l 0 − 0,75 h0
s
mm
Deflection of single disc spring
s1, s2 , s3 ...
mm
Spring deflections related to spring loads F 1, F 2, F 3…
t
mm
Thickness of single disc spring
t ′
mm
Reduced thickness of single disc spring with flat bearings (group 3) Poisson’s ratio
µ σ
MPa
Design stress
σ II, σ III, σ OM
MPa
Design stresses at the points designated II, III, OM (see Figure 1)
σ h
MPa
Fatigue stress related to the deflection of springs subject to fatigue loading
σ O
MPa
Maximum fatigue stress
σ U
MPa
Minimum fatigue stress
σ H = σ O − σ U
MPa
Permanent range of fatigue stress
P
Theoretical centre of rotation of disc spring cross section (see Figure1)
V , V ′
Lever arms
Ra
Mean surface roughness
5
DIN 2093:2006-03
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 to consult the spring manufacturer.
7
Spring dimensions, nominal sizes, design values
7.1
Dimensional series A
Disc springs with
De t
≈ 18;
h0 t
≈ 0,4; E =
206 000 MPa; µ = 0,3 Table 1
Group
1
2
3
6
De
Di
h12
H12
t or (t ′)a
h0
l 0
F t
l t
σ IIIb
σ OM
s = h0
s ≈ 0,75 h0
8 10 12,5 14
4,2 5,2 6,2 7,2
0,4 0,5 0,7 0,8
0,2 0,25 0,3 0,3
0,6 0,75 1 1,1
210 325 660 797
0,45 0,56 0,77 0,87
1218 1218 1382 1308
−1 605
16 18 20 22,5 25 28 31,5 35,5
8,2 9,2 10,2 11,2 12,2 14,2 16,3 18,3
0,9 1 1,1 1,25 1,5 1,5 1,75 2
0,35 0,4 0,45 0,5 0,55 0,65 0,7 0,8
1,25 1,4 1,55 1,75 2,05 2,15 2,45 2,8
1013 1254 1521 1929 2926 2841 3871 5187
0,99 1,1 1,21 1,37 1,64 1,66 1,92 2,2
1301 1295 1290 1296 1419 1274 1296 1332
−1 555
40 45 50 56 63
20,4 22,4 25,4 28,5 31
2,25 2,5 3 3 3,5
0,9 1 1,1 1,3 1,4
3,15 3,5 4,1 4,3 4,9
6500 7716 11976 11388 15025
2,47 2,75 3,27 3,32 3,85
1328 1296 1418 1274 1296
−1 595
4 5 5 6 6 8 (7,5) 8 (7,5) 10 (9,4)
1,6 1,7 2 2,2 2,5 2,6 3,2 3,5
20535 33559 31354 48022 43707 85926 85251 138331
4,4 5,42 5,5 6,55 6,62 8,65 8,8 10,87
1332 1453 1295 1418 1239 1326 1 284c 1338
−1 594
71 80 90 100 112 125 140 160
36 41 46 51 57 64 72 82
5,6 6,7 7 8,2 8,5 10,6 11,2 13,5
−1 595 −1 666 −1 551
−1 558 −1 560 −1 534 −1 562 −1 562 −1 570 −1 611
−1 534 −1 659 −1 565 −1 524
−1 679 −1 558 −1 663 −1 505 −1 708 −1 675 −1 753
DIN 2093:2006-03
Table 1 (concluded) Group
3
t or (t ′)a
De
Di
h12
H12
180
92
200 225 250
102 112 127
h0
l 0
F t
l t
σ IIIb
σ OM
s = h0
s ≈ 0,75 h0
10 (9,4)
4
14
125417
11
1 201c
−1 576
12 (11,25) 12 (11,25) 14 (13,1)
4,2 5 5,6
16,2 17 19,6
183020 171016 248828
13,05 13,25 15,4
1227 1 137c 1 221c
−1 611 −1 489 −1 596
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 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 . b
The values specified apply for the largest calculated tensile stress on the lower edges of the spring.
c
The values specified apply for the largest calculated tensile stress at the point designated III.
7.2
Dimensional series B
Disc springs with
De t
≈ 28;
h0 t
≈ 0,75; E =
206 000 MPa; µ = 0,3 Table 2
Group
De
Di
h12
H12
t or (t ′)a
h0
l 0
F t
l t
σ III
σ OM
s = h0
s ≈ 0,75 h0
8 10 12,5 14 16
4,2 5,2 6,2 7,2 8,2
0,3 0,4 0,5 0,5 0,6
0,25 0,3 0,35 0,4 0,45
0,55 0,7 0,85 0,9 1,05
118 209 294 279 410
0,36 0,47 0,59 0,6 0,71
1312 1281 1114 1101 1109
−1 505
18 20 22,5 25 28 31,5 35,5 40 45 50
9,2 10,2 11,2 12,2 14,2 16,3 18,3 20,4 22,4 25,4
0,7 0,8 0,8 0,9 1 1,25 1,25 1,5 1,75 2
0,5 0,55 0,65 0,7 0,8 0,9 1 1,15 1,3 1,4
1,2 1,35 1,45 1,6 1,8 2,15 2,25 2,65 3,05 3,4
566 748 707 862 1 107 1913 1699 2622 3646 4 762
0,82 0,94 0,96 1,07 1,2 1,47 1,5 1,79 2,07 2,35
1114 1118 1079 1023 1086 1187 1073 1136 1144 1140
−1 363
56 63 71 80 90
28,5 31 36 41 46
2 2,5 2,5 3 3,5
1,6 1,75 2 2,3 2,5
3,6 4,25 4,5 5,3 6
4 438 7189 6725 10518 14161
2,4 2,94 3 3,57 4,12
1092 1088 1055 1142 1114
−1 284
51 57 64 72 82 92
3,5 4 5 5 6 6
2,8 3,2 3,5 4 4,5 5,1
13070 17752 29908 27920 41008 37502
4,2 4,8 5,87 6 7,12 7,27
1049 1090 1149 1101 1109 1035
−1 235
−1 531 −1 388 −1 293 −1 333
1
2
100 112 125 140 160 180
6,3 7,2 8,5 9 10,5 11,1
−1 386 −1 276 −1 238 −1 282 −1 442 −1 258 −1 359 −1 396 −1 408
−1 360 −1 246 −1 363 −1 363
−1 284 −1 415 −1 293 −1 333 −1 192
7
DIN 2093:2006-03
Table 2 (concluded)
Group
3
De
Di
h12
H12
200 225 250
t or (t ′)a
h0
l 0
F t
l t
σ III
s = h0
s ≈ 0,75 h0
102 112 127
8 (7,5) 8 (7,5) 10 (9,4)
5,6 6,5 7
13,6 14,5 17
76378 70749 119050
σ OM
9,4 9,62 11,75
1254 1176 1244
−1 409 −1 267 −1 406
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
7.3
× t ,
and in the case of dimensional series C, t ′ ≈ 0,96
× t .
Dimensional series C
Disc springs with
De t
≈ 40;
h0 t
≈ 1,3; E =
206 000 MPa; µ = 0,3 Table 3
Group
1
2
3
De
Di
h12
H12
t or (t ′)a
h0
l 0
F t
l t
σ III
σ OM
s = h0
s ≈ 0,75 h0
8 10 12,5 14 16 18
4,2 5,2 6,2 7,2 8,2 9,2
0,2 0,25 0,35 0,35 0,4 0,45
0,25 0,3 0,45 0,45 0,5 0,6
0,45 0,55 0,8 0,8 0,9 1,05
39 58 151 123 154 214
0,26 0,32 0,46 0,46 0,52 0,6
1034 965 1278 1055 1009 1106
20 22,5 25 28 31,5 35,5 40 45 50 56 63 71
10,2 11,2 12,2 14,2 16,3 18,3 20,4 22,4 25,4 28,5 31 36
0,5 0,6 0,7 0,8 0,8 0,9 1 1,25 1,25 1,5 1,8 2
0,65 0,8 0,9 1 1,05 1,15 1,3 1,6 1,6 1,95 2,35 2,6
1,15 1,4 1,6 1,8 1,85 2,05 2,3 2,85 2,85 3,45 4,15 4,6
254 426 600 801 687 832 1017 1891 1550 2622 4238 5144
0,66 0,8 0,92 1,05 1,06 1,19 1,32 1,65 1,65 1,99 2,39 2,65
1063 1227 1259 1304 1130 1078 1063 1253 1035 1218 1351 1342
−1 024
80 90 100 112 125
41 46 51 57 64
2,25 2,5 2,7 3 3,5
2,95 3,2 3,5 3,9 4,5
5,2 5,7 6,2 6,9 8
6613 7684 8609 10489 15416
2,99 3,3 3,57 3,97 4,62
1370 1286 1235 1218 1318
−1 311
140 160 180 200 225 250
72 82 92 102 112 127
3,8 4,3 4,8 5,5 6,5 (6,2) 7 (6,7)
4,9 5,6 6,2 7 7,1 7,8
8,7 9,9 11 12,5 13,6 14,8
17195 21843 26442 36111 44580 50466
5,02 5,7 6,35 7,25 8,27 8,95
1249 1238 1201 1247 1137 1116
−1 203
−1 003 −
957
−1 250 −1 018 −
988
−1 052
−1 178 −1 238 −1 282 −1 077 −1 042 −1 024 −1 227 −1 006 −1 174 −1 315 −1 295
−1 246 −1 191 −1 174 −1 273
−1 189 −1 159 −1 213 −1 119 −1 086
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
8
× t ,
and in the case of dimensional series C, t ′ ≈ 0,96
× t .
DIN 2093:2006-03
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
Group
Manufacturing process
1
Stamping, cold forming, edge rounding
2
Stamping b, cold forming, De and Di turning, edge rounding or fine blankingc, cold forming, edge rounding
3
Surface roughness a Surface roughness on on upper and bottom outer and inner edges, in µm surfaces, in µm
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
Material as in
Ra < 3,2
Ra < 12,5
DIN EN 10132-4
Ra < 6,3
Ra < 6,3
DIN EN 10132-4
Ra < 6,3
Ra < 3,2
DIN EN 10132-4
Ra < 12,5
Ra < 12,5
DIN EN 10083 DIN EN 10089
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. e i c Fine blanking in accordance with VDI Richtlinie (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.
9
DIN 2093:2006-03
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 of its test load F t, 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 protections include 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. Phosphating and oiling is the standard corrosion protection for disc springs.
9 9.1
Tolerances 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
9.2
Tolerances on thickness Table 5 Group 1
t
Tolerances
0,2 ≤ t ≤ 0,6
+ 0,02 − 0,06
0,6
< t < 1,25
1,25 2 3,8 3
**) See *) on page 2.
10
6,0
≤ t ≤ 3,8
+ 0,03 − 0,09 + 0,04 − 0,12
< t ≤ 6,0**)
+ 0,05 − 0,15
< t ≤ 14,0
± 0,10
DIN 2093:2006-03
9.3
Tolerances on free overall height, l 0 Table 6 Group
t
Tolerances
1
t < 1,25
+ 0,10 − 0,05
1,25 ≤ t ≤ 2,0 2
3
9.4 9.4.1
+ −
0,15 0,08 0,20 0,10
2,0
< t ≤ 3,0
+ −
3,0
< t ≤ 6,0
+ 0,30 − 0,15
6,0 < t ≤ 14,0
± 0,30
Tolerances on spring load Single disc springs
The spring load F t shall be determined at test length l t = l 0 − 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 Tolerances for F t Group
t
1
t < 1,25
2
1,25 ≤ t ≤ 3,0 3,0
3
< t ≤ 6,0
6,0 < t ≤ 14,0
at l t = l 0 − 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 l 0 and t . 9.4.2
Springs stacked in series
Figure 2 — Loading and unloading curves obtained from testing springs stacked in series
11
DIN 2093:2006-03
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, F t. 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. At 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
A
1 2 3
9.5
Dimensional series B 90 92,5 95
C 85 87,5 90
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
Total clearance
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
0,2 0,3 0,4 0,5 0,6 0,8 1,0 1,6
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 σ OM (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.
12
DIN 2093:2006-03
Figure 3 — Permissible relaxation for disc springs made of carbon steel in accordance with DIN EN 10132-4
13
DIN 2093:2006-03
Figure 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, σ OM , 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.
14
DIN 2093:2006-03
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, σ H, as a function of the minimum stress, σ U, at three different numbers of stress cycles, N , namely where N ≤ 2 × 106, N = 105, and N = 5 × 105. 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 adverse conditions.
Figure 5 — Fatigue life of not shot peened disc springs with t < 1,25 mm
15
DIN 2093:2006-03
Figure 6 — Fatigue life of not shot peened disc springs with 1,25 mm
≤ t ≤
6 mm
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. In 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.
16
DIN 2093:2006-03
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 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. Table 10 Spring characteristics
AQL value
Major characteristics Spring load, F (where s ≈ 0,75 h0) Outer diameter, De Inner diameter, Di
1
Minor characteristics Free overall height in initial position, l 0 Spring thickness, t or t' Surface roughness, Ra
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, and Rockwell hardness testing 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.
13 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 2093:2006-03
Bibliography
DIN 4000-11, Tabular layouts of article characteristics for springs DIN 59200, Hot rolled wide steel flats — Dimensions, mass and tolerances DIN EN 10048, Hot-rolled narrow steel strip — Tolerances on dimensions and shape DIN EN 10051, Continuously hot-rolled uncoated plate, sheet and strip of non-alloy and alloy steels — Tolerances of 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 ISO 2162-1, Technical products documentation — Springs — Part 1: Simplified representation DIN ISO 2162-3, Technical product documentation — Springs — Part 3: Vocabulary
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