ISO 18137:2015

INTERNATIONAL ISO
STANDARD 18137
First edition
2015-08-01
Leaf springs — Technical
specifications
Ressorts à lames — Spécifications techniques
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Spring types . 2
6 Technical requirements . 7
6.1 Materials . 7
6.2 Tolerances of spring dimensions and shapes . 7
6.2.1 Span . 7
6.2.2 Assembled spring width . . 7
6.2.3 Spring end width . 8
6.2.4 Eye inner diameter and bush inner diameter . 8
6.2.5 Flank bending . 8
6.2.6 Perpendicularity and parallelism of the spring eye. 9
6.3 Requirements for characteristic .10
6.3.1 Spring rate .10
6.3.2 Design camber .10
6.3.3 Fatigue .10
6.4 Requirements for manufacturing .10
6.4.1 Hardness .10
6.4.2 Decarburization .10
6.4.3 Shot peening .10
6.4.4 Presetting .11
6.4.5 Lubricant and surface protection .11
6.4.6 Surface conditions .11
7 Designation .11
Annex A (informative) Test methods of leaf springs .12
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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on the ISO list of patent declarations received (see www.iso.org/patents).
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assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 227, Springs.
iv © ISO 2015 – All rights reserved

INTERNATIONAL STANDARD ISO 18137:2015(E)
Leaf springs — Technical specifications
1 Scope
This International Standard specifies the technical specifications for leaf springs.
This International Standard is applicable to leaf springs for road vehicle (hereinafter simply “springs”).
The leaf springs for other vehicle may refer to this International Standard.
2 Normative references
The following referenced 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.
ISO 683-14, Heat-treatable steels, alloy steels and free-cutting steels — Part 14: Hot-rolled steels for
quenched and tempered springs
ISO 3887, Steels — Determination of depth of decarburization
ISO 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method
ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method
ISO 16249, Springs — Symbols
ISO 18265, Metallic materials — Conversion of hardness values
ISO 26909, Springs — Vocabulary
ISO 26910-1, Springs — Shot peening — Part 1: General procedures
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 26909 and Table 1 apply.
4 Symbols
For the purposes of this document, the symbols and units given in ISO 16249 and Table 1 apply.
Table 1 — Terms, symbols and units
Term Symbol Unit Meaning
Spring end width b mm Width of the spring eye or sliding end.
A
Assembled spring
b mm Width of the assembly in the range of U-clamping.
E
width
Perpendicular distance from the surface where tensile stress is
generated in use, of the uppermost leaf at the centre pin or the
Camber C mm
centre bolt, to the straight line connecting the centers of both
eyes or connecting the load-supporting points of the spring.
Free camber C mm Camber when free or at zero load.
Design camber C mm Camber under design (nominal) load.
d
Table 1 (continued)
Term Symbol Unit Meaning
Eye inner diameter d mm Inner diameter of the spring eye.
A
Eye bush inner diam-
d mm Inner diameter of the spring eye bush.
i
eter
Load F N Total spring force.
Design load F N Design (nominal) load of the spring.
d
Maximum test load F N Maximum test force of the spring.
max.t
Height H mm The overall height of the spring.
Free height H mm Height when free or at zero load.
Design height H mm Height under design (nominal) load.
d
Span l mm Distance between the load-supporting points of the spring.
Free Span l mm Span when free or at zero load.
Fixed half span l mm Length of the span between the fixed end and the centre.
A
Length of the span between the load-supporting points of the
Straight span l mm
ST
spring when the first leaf is straight.
Fixed half straight Length of the span between the fixed end and the centre when
l mm
ST,A
span the first leaf is straight.
Spring rate R N/mm Force required to deflect the spring by one unit of deflection.
Change of the vertical position of the centre pin or the centre
Deflection s mm bolt against the line connecting the centers of both eyes or
connecting both load-supporting points of the spring.
Design deflection s mm The deflection under the design load.
d
Maximum test deflec-
s mm The deflection under the maximum test load.
max,t
tion
Flank bending δ mm Side bending deformation of the leaf.
5 Spring types
The most common spring types are shown in the following.
2 © ISO 2015 – All rights reserved

l
F
l
F
F
l
l
d
A
A
B
ST,A
ST
A
Key
b spring end width F total spring load
A
b assembled spring width F , F loads at eye A or eye B
E A B
C camber l span
d eye inner diameter l fixed half span
A A
d eye bush inner diameter l straight span
i ST
H height l fixed half straight span
ST,A
Figure 1 — Multi-leaf spring with eyes
C
H
b
E
l
l
A
a) Multi-leaf parabolic spring with eyes
Key
l span
l fixed half span
A
l
l
A
b) Single leaf parabolic spring with eyes
Key
l span
l fixed half span
A
Figure 2 — Parabolic spring with eyes
Key
l span
l fixed half span
A
Figure 3 — Multi-leaf spring with one eye and one sliding end
4 © ISO 2015 – All rights reserved

Key
l span
l fixed half span
A
Figure 4 — Parabolic spring with one eye and one sliding end
Key
l span
Figure 5 — Multi-leaf spring with sliding ends
Key
l span
Figure 6 — Parabolic spring with sliding ends
Key
l span
l fixed half span
A
Figure 7 — Two-stage progressive multi-leaf spring with helper spring
Key
l span
l fixed half span
A
Figure 8 — Two-stage progressive parabolic spring with helper spring
l
l
A
Key
l span
l fixed half span
A
Figure 9 — Two-stage rate parabolic spring with auxiliary spring
6 © ISO 2015 – All rights reserved

l
l
A
Key
l span
l fixed half span
A
Figure 10 — Progressive (rate) spring
6 Technical requirements
6.1 Materials
Unless otherwise agreed by the purchaser and the supplier, the springs should be made from the hot
rolled spring flat bar conforming to ISO 683-14.
6.2 Tolerances of spring dimensions and shapes
6.2.1 Span
The tolerances of the straight span and the fixed half straight span should be in accordance with Table 2.
Table 2 — Tolerances of span
Dimensions in millimetres
Straight s
...