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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 1723:2000 The Europ
2、ean Standard EN 1723:1999 has the status of a British Standard ICS 53.040.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Light conveyor belts Method of test for the determination of the relaxed elastic modulus Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:08:08
3、 GMT+00:00 2006, Uncontrolled Copy, (c) BSI This British Standard, having been prepared under the direction of the Sector Committee for Materials and Chemicals, was published under the authority of the Standards Committee and comes into effect on 15 January 2000 BSI 01-2000 ISBN 0 580 35057 6 BS EN
4、1723:2000 Amendments issued since publication Amd. No.DateComments National foreword This British Standard is the English language version of EN 1723:1999. The UK participation in its preparation was entrusted to Technical Committee PRI/67, Conveyor belts, which has the responsibility to: aid enquir
5、ers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on th
6、is committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled International Standards Correspondence Index, or
7、 by using the Find facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer imm
8、unity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 6, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Licensed Copy: sheffie
9、ldun sheffieldun, na, Sun Oct 29 11:08:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI CEN European Committee for Standardization Comite Europe en de Normalisation Europa isches Komitee fu r Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1999 CEN All rights of exploitation in any for
10、m and by any means reserved worldwide for CEN national Members. Ref. No. EN 1723:1999 E EUROPEAN STANDARDEN 1723 NORME EUROPE ENNE EUROPA ISCHE NORM August 1999 ICS 53.040.20 English version Light conveyor belts Method of test for the determination of the relaxed elastic modulus Courroies transporte
11、uses le ge res Me thode dessai pour la de termination du module de lasticite relaxe Leichte Fo rdergurte Pru fverfahren zur Bestimmung des relaxierten Elastizita tsmoduls This European Standard was approved by CEN on 8 January 1999. CEN members are bound to comply with the CEN/CENELEC Internal Regul
12、ations 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 Central Secretariat or to any CEN member. This Eu
13、ropean 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 Central Secretariat has the same status as the official versions. CEN members are the na
14、tional standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:08:08 GMT+00:00 2006, U
15、ncontrolled Copy, (c) BSI Page 2 EN 1723:1999 BSI 01-2000 Foreword This European Standard has been prepared by Technical Committee CEN/TC 188, Conveyor belts, the Secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an
16、 identical text or by endorsement, at the latest by February 2000, and conflicting national standards shall be withdrawn at the latest by February 2000. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this Euro
17、pean Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Contents Page Foreword2 Introduction3 1Scope3 2Normative references3 3Definitions and sym
18、bols3 4Principle4 5Apparatus4 6Test piece4 7Procedure4 8Calculation and expression of results5 9Test report6 Annex A (informative) Bibliography6 Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:08:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 3 EN 1723:1999 BSI 01-2000 Introduction Man
19、y applications for light conveyor belts require that the belt is initially tensioned and there is no subsequent change in belt length 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: both permanent stretch an
20、d relaxation of the belt changing its real elastic modulus. It is vital to have a means of establishing the way in which the tensioning forces will change and this test applies to a cyclic stretching between two defined states of elongation over a large number of cycles. It has been found experiment
21、ally that the tensioning force drops in an exponential way. It is possible to measure the tensioning force and then to calculate what is herein defined 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
22、 but, except in cases where the permanent stretch is relatively large, it is a measure of great practical value in determining final tensioning forces. This standard is designed to meet the requirements for such applications. 1 Scope This European Standard specifies a test method for the determinati
23、on of the relaxed elastic modulus of light conveyor belts as defined by EN 873 or other conveyor belts where ISO 9856 is unsuitable. 2 Normative references This European Standard incorporates by dated or undated references, provisions from other publications. These normative references are cited at
24、the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of t
25、he publication referred to applies. EN 873, Light conveyor belts Principal characteristics and applications. EN 10002-2, Metallic materials Tensile testing Part 2: Verification of the force measuring system of the tensile testing machines. ISO 471, Rubber Temperatures, humidities and times for condi
26、tioning and testing. ISO 554, Standard atmospheres for conditioning and/or testing Specifications. ISO 7500-1, Metallic materials Verification of static uniaxial testing machines Part 1: Tensile testing machines. ISO 9856, Conveyor belts Determination of elastic modulus. 3 Definitions and symbols Fo
27、r the purposes of this standard the following apply. 3.1 elastic modulus 1) (in conveyor belt technology). A force per unit of width of a conveyor belt. It is expressed in newtons per millimetre width of belt and is represented in ISO 9856 by the symbol M. NOTEThis definition of the term deviates fr
28、om that normally used in engineering which is expressed in units of stress, i.e. a force per unit of cross section and is represented by the symbol E; (see for example ISO 527-4). 2) (in light conveyor belt technology). The force in newtons per unit of width required to extend a representative test
29、piece of light conveyor belting by 1 % of its original length. 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 1 % elongation per unit of width or kl %value. It is expressed in newtons pe
30、r millimetre NOTEIn EN 10002-1:1991, the symbol k is used to represent the coefficient of proportionality. 3.2 relaxed elastic modulus used in light conveyor belt technology to describe the elastic modulus of a light conveyor belt after being cycled between predetermined limits of extension for 500
31、cycles NOTEThe 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. The following symbols are also used in this standard: FA, FBare the maximum and minimum tensile fo
32、rces respectively in the test piece in newtons; F9A, F9Bare the specific values of FA, FBreferred to the width of the test piece in newtons per millimetre; a is the value in newtons per millimetre of k1 % for z = 1; b is the manufactured width of the conveyor belt in millimetres: in equations (4) an
33、d (5), b is the slope of the straight line; r is the correlation coefficient; x is the variable in the equation of the straight line; y is the value of the equation of the straight line; z is the number of cyclic elongations. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:08:08 GMT+00:00
34、2006, Uncontrolled Copy, (c) BSI Page 4 EN 1723:1999 BSI 01-2000 b = manufactured width of the conveyor belt Figure 1 Distribution of test piece selection 4 Principle A test piece, cut from the full thickness of the conveyor belt in the longitudinal direction, is exposed to a cyclic elongation betwe
35、en two defined limits and the tensile force is recorded as a function of the number of cycles. From that graph, the relaxed elastic modulus is determined by calculation through a logarithmic regression. 5 Apparatus Tensile testing machine, capable of applying load suitable for the strength of the te
36、st piece and with a force measuring system in accordance with EN 10002-2, Class of machine 3 or better (e.g. Class of machine 2) as well as capable of applying the load in displacement-controlled cycles of 5 mm and with a frequency of 0.5 Hz (this frequency being realizable also with older, mechanic
37、ally controlled dynamometers). 6 Test piece 6.1 Shape, dimensions, number and selection Cut from the full thickness of the conveyor belt in the longitudinal direction five rectangular test pieces each (50 0,5) mm wide 3 (500 plus twice the length necessary for clamping in the jaws) mm long. Select t
38、he test pieces from the conveyor belt at places as shown in Figure 1. 6.2 Conditioning The test pieces shall be conditioned at (23 2) 8C and a relative humidity of (505) % in accordance with ISO471 and ISO 554. The climatizing time shall be: For light conveyor belts containing materials with a low a
39、bsorption of moisture, e.g. polyester, 24 h. For light conveyor belts containing materials with a high absorption of moisture e.g.cotton or polyamide, 48h. 7 Procedure The test pieces shall not be tested earlier than five days after manufacture of the conveyor belt. The test shall be carried out wit
40、h each of the test pieces defined in 6.1. Place the ends of the test piece between the jaws of the tensile testing machine in such a way that the test piece is straight without using force. The free length between the jaws shall be 500 mm 1 mm. There shall be no slippage of the test piece in the jaw
41、s during the test. NOTE 1Slippage 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 emery cloth should be folded over the ends of the test piece w
42、ith the coarse side of the cloth next to the rosin-coated surfaces. Elongate the test piece cyclically between 1 % and 2 % (5 mm and 10 mm) at a frequency of 0,5 Hz. Licensed Copy: sheffieldun sheffieldun, na, Sun Oct 29 11:08:08 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Page 5 EN 1723:1999 BSI 01-
43、2000 x5 Tensile force F y5 Number of cycles z Figure 2 Tensile force as a function of number of cyclic elongations NOTE 2The 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 the elongation of 0,5 %, correspondi
44、ng to 2,5 mm, is superposed at the same frequency. In both cases the average speed of deformation in the test piece will be 5mm/s (= 300mm/min). In cases of conveyor belts containing reinforcing elements with a high elastic modulus (e.g. with reinforcing elements of Aramid threads), the cyclic elong
45、ation of the test piece shall take place between 0,5 % and 1 % (2,5 mm and 5 mm) at the same frequency of 0,5 Hz. Record the tensile force during 500 cyclic elongations as a function of the number of cycles. At the end of the test measure the permanent elongation by reducing the tensioning force to
46、zero, and measuring the distance between the jaws. If this elongation is equal to or exceeds 1 % of the initial length, then this test is unsuitable for such a belt type and ISO 9856 shall be used instead. 8 Calculation and expression of results Read the forces FAand FBfor the number of cyclic elong
47、ations z = 250, z = 350 and z = 500 from the graph following Figure 2. Refer all these forces to the unit of belt width (50 mm): F9A=in newtons per millimetre1 FA 50 F9B=in newtons per millimetre1 FB 50 Calculate the elastic moduli belonging to F9Aand F9B. In case of having applied a cyclic elongati
48、on between 1 % and 2 %, calculate the elastic modulus from: k1 %=in newtons per millimetre2 F9A+ F9B 2 1,5 In case of having applied a cyclic elongation between 0,5 % and 1 %, calculate the elastic modulus from the following equation: k1 %=in newtons per millimetre3 F9A+ F9B 2 0,75 From the three ca
49、lculated k1 %, values and the corresponding numbers of cyclic elongations, the equation of a straight line of the form: y = a + bx4 is determined, with which a logarithmic regression is carried out subsequently. For that, a calculator is used which provides statistic functions. The x-values of the number couples to put in are the numbers of cyclic elongations given as natural logarithms (ln z). The y-values are the corresponding calculated k1 %values. Therefore, equation 4 reads: k1 %= a +
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