SIST EN 13906-1:2014

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Zylindrische Schraubenfedern aus runden Drähten und Stäben - Berechnung und Konstruktion - Teil 1: DruckfedernRessorts hélicoïdaux cylindriques fabriqués à partir de fils ronds et de barres - Calcul et conception - Partie 1: Ressorts de compressionCylindrical helical springs made from round wire and bar - Calculation and design - Part 1 : Compression springs21.160VzmetiSpringsICS:Ta slovenski standard je istoveten z:EN 13906-1:2013SIST EN 13906-1:2014en,fr,de01-januar-2014SIST EN 13906-1:2014SLOVENSKI
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SIST EN 13906-1:2014



EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 13906-1
July 2013 ICS 21.160 Supersedes EN 13906-1:2002English Version
Cylindrical helical springs made from round wire and bar - Calculation and design - Part 1 : Compression springs
Ressorts hélicoïdaux cylindriques fabriqués à partir de fils ronds et de barres - Calcul et conception - Partie 1: Ressorts de compression
Zylindrische Schraubenfedern aus runden Drähten und Stäben - Berechnung und Konstruktion - Teil 1: Druckfedern This European Standard was approved by CEN on 30 May 2013.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 13906-1:2013: ESIST EN 13906-1:2014



EN 13906-1:2013 (E) 2 Contents Foreword . 3 Introduction . 4 1 Scope . 5 2 Normative references . 5 3 Terms, definitions, symbols, units and abbreviated terms . 5 4 Theoretical compression spring diagram . 8 5 Design principles . 9 6 Types of Loading . 10 7 Stress correction factor k . 12 8 Material property values for the calculation of springs . 13 9 Calculation formulae . 14 10 Permissible torsional stresses . 19 Annex A (informative)
Examples of relaxation for cold coiled springs . 29 Bibliography . 35
SIST EN 13906-1:2014



EN 13906-1:2013 (E) 3 Foreword This document (EN 13906-1:2013) has been prepared by Technical Committee CEN/TC 407 “Project Committee - Cylindrical helical springs made from round wire and bar - Calculation and design”, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by January 2014, and conflicting national standards shall be withdrawn at the latest by January 2014. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 13906-1:2002. This European Standard has been prepared by the initiative of the Association of the European Spring Federation ESF. This European Standard constitutes a revision of EN 13906-1:2002 for which it has been technically revised. The main modifications are listed below:  updating of the normative references,  technical corrections. EN 13906 consists of the following parts, under the general title Cylindrical helical springs made from round wire and bar — Calculation and design:  Part 1: Compression springs;  Part 2: Extension springs;  Part 3: Torsion springs. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
SIST EN 13906-1:2014



EN 13906-1:2013 (E) 4 Introduction The revision of EN 13906 series have been initiated by the Association of the European Spring Federation – ESF – in order to correct the technical errors which are in the published standards and to improve them according to the state of the art. However, the revision of the figures is not take part of this work due to the lack of shared (mutual) data to update them. Nevertheless, the customers can have updated data from the manufacturers. SIST EN 13906-1:2014



EN 13906-1:2013 (E) 5 1 Scope This European Standard specifies the calculation and design of cold and hot coiled cylindrical helical compression springs with a linear characteristic, made from round wire and bar of constant diameter with values according to Table 1, and in respect of which the principal loading is applied in the direction of the spring axis. Table 1 Characteristic Cold coiled compression spring Hot coiled compression spring Wire or bar diameter d ≤ 20 mm 8 mm ≤ d ≤ 100 mm Number of active coils n ≥ 2 n ≥ 3 Spring index 4 ≤ w ≤ 20 3 ≤ w ≤ 12 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. EN 10270-1, Steel wire for mechanical springs — Part 1: Patented cold drawn unalloyed spring steel wire EN 10270-2, Steel wire for mechanical springs — Part 2: Oil hardened and tempered spring steel wire EN 10270-3, Steel wire for mechanical springs — Part 3: Stainless spring steel wire EN 10089, Hot-rolled steels for quenched and tempered springs — Technical delivery conditions EN 12166, Copper and copper alloys — Wire for general purposes EN ISO 2162-1:1996, Technical product documentation — Springs — Part 1: Simplified representation
(ISO 2162-1:1993) EN ISO 26909:2010, Springs — Vocabulary (ISO 26909:2009) ISO 26910-1, Springs — Shot peening — Part 1: General procedures 3 Terms, definitions, symbols, units and abbreviated terms 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in EN ISO 26909:2010 and the following apply. 3.1.1 spring mechanical device designed to store energy when deflected and to return the equivalent amount of energy when released [SOURCE: EN ISO 26909:2010, 1.1] 3.1.2 compression spring spring (1.1) that offers resistance to a compressive force applied axially [SOURCE: EN ISO 26909:2010, 1.2] SIST EN 13906-1:2014



EN 13906-1:2013 (E) 6 3.1.3 helical compression spring compression spring (1.2) made of wire of circular, non-circular, square or rectangular cross-section, or strip of rectangular cross-section, wound around an axis with spaces between its coils [SOURCE: EN ISO 26909:2010, 3.12] 3.2 Symbols, units and abbreviated terms Table 2 contains the symbols, units and abbreviated terms used in this European Standard. Table 2 (1 of 3) Symbols Units Terms a0 mm gap between active coils of the unloaded spring 2ieDDD+= mm mean diameter of coil De mm outside diameter of spring ∆De mm increase of outside diameter of the spring, when loaded Di mm inside diameter of spring d mm nominal diameter of wire (or bar) dmax mm upper deviation of d E N/mm² (MPa) modulus of elasticity (or Young’s modulus) F N spring force F1, F2 . N spring forces, for the spring lengths L1, L2. (at ambient temperature of 20C) Fc th N theoretical spring force at solid length Lc
NOTE The actual spring force at the solid length is as a rule greater than the theoretical force FK N buckling force Fn N spring force for the minimum permissible spring length Ln FQ N spring force perpendicular to the spring axis (transverse spring force) fe s-1
(Hz) natural frequency of the first order of the spring (fundamental frequency) G N/mm² (MPa) modulus of rigidity
k - stress correction factor (depending on D/d ) L mm spring length L0 mm nominal free length of spring L1, L2. mm spring lengths for the spring forces
F1, F2. SIST EN 13906-1:2014



EN 13906-1:2013 (E) 7 Table 2 (2 of 3) Symbols Units Terms Ln mm minimum permissible spring length (depending upon Sa) Lc mm solid length LK mm buckling length m mm mean distance between centres of adjacent coils in the unloaded condition (pitch) N - number of cycles up to rupture n - number of active coils nt - total number of coils R N/mm spring rate Rm N/mm² (MPa) minimum value of tensile strength RQ N/mm transverse spring rate Sa mm sum of minimum gaps between adjacent active coils at spring length Ln s mm spring deflection s1, s2 . mm spring deflections, for the spring forces
F1, F2 . sc mm spring deflection, for the solid length, Lc sh mm deflection of
spring (stroke ) between two positions sK mm spring deflection, for the buckling force FK (buckling spring deflection) sn mm spring deflection, for the spring force
Fn sQ mm transverse spring deflection, for the transverse force FQ vSt m/s impact speed W Nmm spring work, dDw= - spring index η
- spring rate ratio λ
- slenderness ratio υ - seating coefficient ξ
- relative spring deflection ρ kg/dm³ density τ N/mm² (MPa) uncorrected torsional stress (without the influence of the wire curvature being taken into account)
τ1, τ2 .
N/mm² (MPa) uncorrected torsional stress, for the
spring forces F1, F2 . τc N/mm² (MPa) uncorrected torsional stress, for the solid length Lc SIST EN 13906-1:2014



EN 13906-1:2013 (E) 8 Table 2 (3 of 3) Symbols Units Terms τkh N/mm² (MPa) corrected torsional stress range, for the stroke sh τk N/mm² (MPa) corrected torsional stress (according to the stress correction factor k) τk1, τk2 . N/mm² (MPa) corrected torsional stress, for the
spring forces F1, F2 . τkH (.) N/mm² (MPa) corrected torsional stress range in fatigue, with the subscript specifying the number of cycles to rupture or the number of ultimate cycles τkn N/mm² (MPa) corrected torsional stress, for the
spring force Fn τkO (.) N/mm² (MPa) corrected maximum torsional stress in fatigue, with the subscript specifying the number of cycles to rupture or the number of ultimate cycles τkU (.) N/mm² (MPa) corrected minimum torsional stress in fatigue, with the subscript specifying the number of cycles to rupture or the number of ultimate cycles
τn N/mm² (MPa) uncorrected torsional stress, for the
spring force Fn τSt N/mm² (MPa) impact stress τzul N/mm² (MPa) permissible static torsional stress 4 Theoretical compression spring diagram The illustration of the compression spring corresponds to Figure 4.1 from EN ISO 2162-1:1996. The theoretical compression spring diagram is given in Figure 1. SIST EN 13906-1:2014



EN 13906-1:2013 (E) 9
Figure 1 — Theoretical compression spring diagram 5 Design principles Before carrying out design calculations for a spring, the requirements to be met shall be considered, particularly taking into account and defining:  a spring force and corresponding spring deflection or two spring forces and corresponding stroke or a spring force, the stroke and the spring rate,  loading as a function of time: is static or dynamic,  in the case of dynamic loading the total number of cycles, N, to rupture,  operating temperature and permissible relaxation,
 transverse loading, buckling, impact loading,  other factors (e.g. resonance vibration, corrosion). SIST EN 13906-1:2014



EN 13906-1:2013 (E) 10 In order to optimise the dimensions of the spring by taking the requirements into account, sufficient working space should be provided when designing the product in which the spring will work. 6 Types of Loading
6.1 General Before carrying out design calculations, it should be specified whether they will be subjected to static loading, quasi-static loading, or dynamic loading. 6.2 Static and/or quasi-static loading
A static loading is:  a loading constant in time. A quasi-static loading is:  a loading variable with time with a negligibly small torsional stress range (stroke stress) (e.g. torsional stress range up to 0,1 × fatigue strength);  a variable loading with greater torsional stress range but only a number of cycles of up to 104. 6.3 Dynamic loading In the case of compression springs dynamic loading is: Loading variable with time with a number of loading cycles over 104 and torsional stress range greater than 0,1 × fatigue strength at: a) constant torsional stress range; b) variable torsional stress range. Depending on the required number of cycles N up to rupture it is necessary to differentiate the two cases as follows: c) infinite life fatigue in which the number of cycles  N
≥ 107 for cold coiled springs;  N
≥ 2 × 106 for hot coiled springs; In this case the torsional stress range is lower than the infinite life fatigue limit. d) limited life fatigue in which  N
< 107 for cold coiled springs;  N
< 2 × 106 for hot coiled springs. In this case the torsional stress range is greater than the infinite life fatigue limit but smaller than the low cycle fatigue limit. In the case of springs with a time- variable torsional stress range and mean torsional stress, (set of torsional stress combinations) the maximum values of which are situated above the infinite fatigue life limit, the service life can be calculated as a rough approximation with the aid of cumulative damage hypotheses. In such circumstances, the service life shall be verified by means of a fatigue test. SIST EN 13906-1:2014



EN 13906-1:2013 (E) 11 6.4 Operating temperature The data relating to the permissible loading of the materials used as given in Clause 10 apply at ambient temperature. The influence of temperature shall be taken into consideration especially in the case of springs with closely toleranced spring forces. At operating temperatures below -30°C the reduction of the notch impact strength shall also be taken into account. 6.5 Transverse loading If an axially loaded spring with parallel guided ends is additionally loaded perpendicular to its axis, transverse deflection with localised increase in torsional stress will occur, and this shall be taken into account in the calculation. 6.6 Buckling Axially loaded springs have a tendency to buckle depending on the slenderness ratio when they are compressed to a certain critical length. Consequently, their buckling behaviour shall be checked. An adequate safety against buckling shall be allowed for in the design of these springs, because the buckling limit is reached in practice sooner than calculated theoretically. Springs which cannot be designed with an adequate safety against buckling shall be guided inside a tube or over a mandrel. Friction will be the inevitable consequence, and damage to the spring will occur in the long run. It is therefore preferable to split up the spring into individual springs, which are safe against buckling, as far as possible, and to guide these springs via intermediate discs over a mandrel or in a tube. It shall always be borne in mind that the direction of the spring force does not coincide precisely with the geometric axis of the spring. Consequently, the spring will tend to buckle before the theoretical buckling limit has been attained. It is very difficult to allow for this effect by calculation. Buckling occurs in smooth progression. 6.7 Impact loading Additional torsional stresses will be generated in a spring, if one end of the spring is suddenly accelerated to a high speed, e.g. through shock or impact. This impact wave will travel through the successive coils of the spring and will be reflected at the other end of the spring. The level of this additional torsional stress depends on the speed with which the impact is delivered, but not on the dimensions of the spring. 6.8 Other factors 6.8.1 Resonance vibrations A spring is prone to resonance vibrations by virtue of the inert mass of its active coils and of the elasticity of the material. A distinction is made between vibrations of the first order (fundamental vibrations) and vibrations of higher order (harmonic vibrations). The frequency of the fundamental vibration is called the fundamental frequency, and the frequency of the harmonic vibrations are integral multiples thereof.
When calculating springs, subject to high frequency forced vibration, care shall be taken to ensure that the frequency of the forced vibration oscillation (excitation frequency) does not come into resonance with one of the natural frequencies of the spring. In the case of mechanical excitations (e.g. via cams), resonance may also occur if a harmonic component of the excitation frequency coincides with one of the natural frequencies of the spring. In cases of resonance, an appreciable increase in torsional stress will arise at certain individual points of the spring, known as nodes. In order to avoid such increases in torsional stress due to resonance phenomena, the following measurers are advised:  avoid integral ratios between excitation frequencies and natural frequencies;  select the natural frequency of the first order of the spring as high as possible; avoid resonance with the low harmonics of the excitation; SIST EN 13906-1:2014



EN 13906-1:2013 (E) 12  use springs with a progressive characteristic (variable pitch);  design the cam with a favourable profile (low peak value of the excitation harmonics);  provide for damping by means of spacers. 6.8.2 Corrosion influences, friction marks The service life of springs is adversely affected by corrosion influences, by friction and chafing marks. The service life of dynamically loaded springs in particular is reduced considerably by the influence of corrosion. Organic or inorganic coatings can be applied as a protection against corrosion. In the case of electroplated protective coatings, the risk of hydrogen embrittlement shall be borne in mind. Furthermore, various chrome-nickel steels or non-ferrous metals can be used depending on the risk of corrosion involved. Damage to the surface of the spring, in the form of fretting corrosion, will occur
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