1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 21181:2013Light conveyor belts Determination of the r e l a x e d e l a s t i c m o d u l u sBS EN ISO 21181:2013 BRITISH STANDARDNational forewordThis British Standard
2、 is the UK implementation of EN ISO 21181:2013. It supersedes BS EN ISO 21181:2006, which is withdrawn.The UK participation in its preparation was entrusted to T e c h n i c a l C o m m i t t e e P R I / 6 7 , C o n v e y o r b e l t s .A list of organizations represented on this committee can be ob
3、tained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2013. Published by BSI Standards Limited 2013.ISBN 978 0 580 77364 8 ICS 53.040.10 Complian
4、ce with a British Standard cannot confer immunityfrom legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2013.Amendments issued since publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE
5、NORM EN ISO 21181 February 2013 ICS 53.040.20 Supersedes EN ISO 21181:2006English Version Light conveyor belts - Determination of the relaxed elastic modulus (ISO 21181:2013) Courroies transporteuses lgres - Dtermination du module dlasticit relax (ISO 21181:2013) This European Standard was approved
6、by CEN on 12 February 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 st
7、andards 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
8、 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, Hungar
9、y, 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 COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management
10、 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 ISO 21181:2013: EBS EN ISO 21181:2013 EN ISO 21181:2013 (E) 3 Foreword This document (EN ISO 21181:2013) has been prepared by Technical
11、 Committee ISO/TC 41 “Pulleys andbelts (including veebelts)“ in collaboration with Technical Committee CEN/TC 188 “Conveyor belts” thesecretariat of which is held by SNV. This European Standard shall be given the status of a national standard, either by publication of an identicaltext or by endorsem
12、ent, at the latest by August 2013, and conflicting national standards shall be withdrawn atthe latest by August 2013. Attention is drawn to the possibility that some of the elements of this document may be the subject of patentrights. CEN and/or CENELEC shall not be held responsible for identifying
13、any or all such patent rights. This document supersedes EN ISO 21181:2006. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, CzechRepublic, Denm
14、ark, 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. Endorsement noti
15、ce The text of ISO 21181:2013 has been approved by CEN as EN ISO 21181:2013 without any modification. BS EN ISO 21181:2013ISO 21181:2013(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Symbols 25 Principle 26 Ap
16、paratus . 27 Test pieces . 27.1 Shape, dimensions, number and selection 27.2 Conditioning 38 Procedure. 39 Calculation and expression of results . 410 Test report . 6Bibliography 7BS EN ISO 21181:2013ISO 21181:2013(E)ForewordISO (the International Organization for Standardization) is a worldwide fed
17、eration 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 comm
18、ittee. 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.International Standards are drafted in accordan
19、ce with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires a
20、pproval by at least 75 % of the member bodies casting a vote.ISO 21181 was prepared by Technical Committee ISO/TC 41, Pulleys and belts (including veebelts), Subcommittee SC 3, Conveyor belts.This International Standard is based on EN 1723:1999, prepared by CEN/TC 188.This second edition cancels and
21、 replaces the first edition (ISO 21181:2005), of which it constitutes a minor revision.iv ISO 2013 All rights reservedBS EN ISO 21181:2013ISO 21181:2013(E)IntroductionMany applications for light conveyor belts require that the belt is initially tensioned and there is no subsequent change in belt len
22、gth by adjustment of any rollers. In such cases, the tensioning force in the belt changes throughout the life of the belt because of two effects: permanent stretch and relaxation of the belt, both of which change its real elastic modulus. It is vital to have a means of establishing the way in which
23、the tensioning forces change; and this test applies a cyclic stretching between two defined states of elongation over a large number of cycles. It has been found experimentally that the tensioning force drops in an exponential way. It is possible to measure the tensioning force and then to calculate
24、 what is defined in this International Standard as the “relaxed elastic modulus”. It is important to note that this is not a true elastic modulus, because it includes an element of permanent stretch; but, except in cases where the permanent stretch is relatively large, it is a measure of great pract
25、ical value in determining final tensioning forces. This International Standard is designed to meet the requirements for such applications. ISO 2013 All rights reserved vBS EN ISO 21181:2013BS EN ISO 21181:2013Light conveyor belts Determination of the relaxed elastic modulus1 ScopeThis International
26、Standard specifies a test method for the determination of the relaxed elastic modulus of light conveyor belts according to ISO 21183-1 or other conveyor belts where ISO 9856 is not applicable.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this docum
27、ent 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 7500-1, Metallic materials Verification of static uniaxial testing machines Part 1: Tensio
28、n/ compression testing machines Verification and calibration of the force-measuring systemISO 9856, Conveyor belts Determination of elastic and permanent elongation and calculation of elastic modulusISO 18573, Conveyor belts Test atmospheres and conditioning periodsISO 21183-1, Light conveyor belts
29、Part 1: Principal characteristics and applications3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1elastic modulusforce per unit of width of a conveyor beltNote 1 to entry: It is expressed in newtons per millimetre width of belt and is represente
30、d in ISO 9856 by the symbol M.Note 2 to entry: This definition of the term deviates from that normally used in engineering, which is expressed in units of stress, i.e. a force per unit of cross-section, and represented by the symbol E (see, for example, ISO 527-4).3.2elastic modulusforce in newtons
31、per unit of width required to extend a representative test piece of light conveyor belting by 1 % of its original lengthNote 1 to entry: The force is represented by the symbol k and, consequently, the elastic modulus is represented by the symbol k1%. This value is also called the “tensile force for
32、1 % elongation per unit of width” or “k1%value”. It is expressed in newtons per millimetre.Note 2 to entry: In EN 10002-1:2001, the symbol k is used to represent the coefficient of proportionality.3.3relaxed elastic moduluselastic modulus of a light conveyor belt after being cycled between predeterm
33、ined limits of extension for 500 cyclesNote 1 to entry: The k1%value of a new conveyor belt is higher than that of a used conveyor belt in which relaxation has taken place in service. The relaxation takes place following an exponential function.INTERNATIONAL STANDARD ISO 21181:2013(E) ISO 2013 All r
34、ights reserved 1BS EN ISO 21181:2013ISO 21181:2013(E)4 SymbolsFor the purposes of this document, the following symbols apply.FA, FBare the maximum and minimum tensile forces, respectively, in the test piece, in newtons;FA, FBare the specific values of FA, FBreferred to the width of the test piece, i
35、n newtons per mil-limetre;a is the value, in newtons per millimetre, of k1%for z = 1;b is the manufactured width of conveyor belt, in millimetres;r is the correlation coefficient;x is the variable in equation of straight line;y is the value of equation of straight line;z is the number of cyclic elon
36、gations.5 PrincipleA test piece is exposed to a cyclic elongation between two defined limits and the tensile force recorded as a function of the number of cycles. From that graph, the relaxed elastic modulus is determined by calculation through a logarithmic regression.6 Apparatus6.1 Tensile testing
37、 machine, capable of applying a load suitable for the strength of the test piece and with a force measuring system in accordance with ISO 7500-1:2004, class of machine 3 or better (e.g. class of machine 2), and also capable of applying the load in displacement-controlled cycles of 5 mm and with a fr
38、equency of 0,5 Hz (this frequency being realizable also with older, mechanically controlled dynamometers).7 Test pieces7.1 Shape, dimensions, number and selectionCut from the full thickness of the conveyor belt in the longitudinal direction five rectangular test pieces each (50 0,5) mm wide and havi
39、ng a length of 500 mm plus twice the length necessary for clamping in the jaws. Select the test pieces from the conveyor belt in accordance with Figure 1. The test piece shall not be tested sooner than five days after manufacture.2 ISO 2013 All rights reservedBS EN ISO 21181:2013ISO 21181:2013(E)Dim
40、ensions in millimetresbb/10 b/5 b/5 b/5 b/5 b/10Figure 1 Distribution of test piece selection7.2 ConditioningBefore testing, condition the test pieces in accordance with ISO 18573, Atmosphere B, for 24 h, except that, if the light conveyor belt (as specified in ISO 21183-1 ) consists of materials wi
41、th a high absorption of moisture, e.g. cotton or polyamide, condition the test piece for 48 h.8 ProcedurePlace the ends of the test piece between the jaws of the tensile testing machine (6.1) such that the test piece is straight without using force. Ensure that the free length between the jaws is 50
42、0 mm 1 mm and that there is no slippage of the test piece in the jaws during the test.Slippage can be minimized by rubbing rosin on the portion of the test piece that will be in the jaws, removing any excess rosin and enclosing both sides of the rosin-coated test piece with coarse emery cloth. The e
43、mery cloth should be folded over the ends of the test piece with the coarse side of the cloth next to the rosin-coated surfaces.Elongate the test piece cyclically, eithera) between 1 % and 2 % (5 mm and 10 mm) at a frequency of 0,5 Hz, orb) if the conveyor belt contains reinforcing elements with a h
44、igh elastic modulus (e.g. with reinforcing elements of aramid threads), between 0,5 % and 1 % (2,5 mm and 5 mm) at the same frequency of 0,5 Hz.NOTE For a), the same effect will be realized if the test piece is given an initial elongation of 1,5 %, corresponding to 7,5 mm, and a cyclic alteration of
45、 the elongation of 0,5 %, corresponding to 2,5 mm, is superposed at the same frequency. The average speed of deformation in the test piece will be 5 mm/s ( = 300 mm/min).Record the tensile force during 500 cyclic elongations as a function of the number of cycles. At the end of the test, measure the
46、permanent elongation by reducing the tensioning force to zero and measuring the distance between the jaws. If this elongation is equal to or exceeds 1 % of the initial length, this indicates that the method is unsuitable for such a belt type; in which case, use the method according to ISO 9856 inste
47、ad. ISO 2013 All rights reserved 3BS EN ISO 21181:2013ISO 21181:2013(E)YFAFB0X100 200 250 300 350400 500 600 700 800KeyX number of cycles, zY tensile force, F, NFigure 2 Tensile force as function of number of cyclic elongations9 Calculation and expression of resultsRead the forces FAand FBfor the nu
48、mber of cyclic elongations z = 250, z = 350, and z = 500 from the graph shown in Figure 2.Divide all of these forces by belt width (50 mm) to give the elastic moduli, as follows: =FFAAN/mm50(1a)4 ISO 2013 All rights reservedBS EN ISO 21181:2013ISO 21181:2013(E) =FFBBN/mm50(1b)If a cyclic elongation
49、between 1 % and 2 % has been applied, calculate the elastic modulus from the following formula:kFF1%ABN/mm= + 215,(2)If a cyclic elongation between 0,5 % and 1 % has been applied, calculate the elastic modulus from the following formula:kFF1%ABN/mm= + 2075,(3)From the three calculated k1%values and the corresponding number of cyclic elongations, determine the equation of a straight line of the form:yacx=+ (4)and subsequently carry out a logarithmic regression.For that, use a calculator which provides statistical
