1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 5628:2012Paper and board Determination of bendingstiffness General principlesfor two-point, three-point andfour-point methodsBS ISO 5628:2012 BRITISH STANDARDNational fore
2、wordThis British Standard is the UK implementation of ISO 5628:2012. Itsupersedes BS7424:1991 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PAI/11, Methods of test for paper, board and pulps.A list of organizations represented on this committee can be
3、obtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 68216 2ICS 85.060Compliance with
4、 a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 29 February 2012.Amendments issued since publicationDate Text affectedBS ISO 5628:2012 ISO 2012Paper and board Determination of be
5、nding stiffness General principles for two-point, three-point and four-point methodsPapier et carton Dtermination de la rigidit la flexion Principes gnraux pour les mthodes deux points, trois points et quatre pointsINTERNATIONAL STANDARDISO5628Second edition2012-01-15Reference numberISO 5628:2012(E)
6、BS ISO 5628:2012ISO 5628:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm,
7、without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 5628:2012ISO 562
8、8:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Normative references . 13 Terms and definitions . 14 Symbols and units 15 Theory . 26 Different bending test methods . 36.1 Two-point bending method . 36.2 Three-point bending method 46.3 Calculation of bendin
9、g stiffness using the two-point and three-point methods . 56.4 Four-point bending method 67 Apparatus 78 Sampling and preparation of test pieces 88.1 Sampling 88.2 Conditioning . 88.3 Preparation of test pieces . 89 Procedure 810 Evaluation and calculation . 811 Test report . 9Bibliography .10BS ISO
10、 5628:2012ISO 5628:2012(E)ForewordISO (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 i
11、n 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 Commis
12、sion (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance 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 c
13、ommittees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall no
14、t be held responsible for identifying any or all such patent rights.ISO 5628 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps, Subcommittee SC 2, Test methods and quality specifications for paper and board.This second edition cancels and replaces the first edition (ISO 5628:1990)
15、, which has been technically revised.The main differences between this edition and the previous edition are the following: the equations for bending stiffness for two-point and three-point bending have been harmonized; geometrical conditions for test pieces have been added; some additional aspects o
16、f corrugated board have been added for four-point bending.iv ISO 2012 All rights reservedBS ISO 5628:2012ISO 5628:2012(E)IntroductionBending stiffness is regarded as an important property of paper and board, and a large number of test methods have been used for its determination. This is a result, i
17、n part at least, of the wide range in the bending stiffness of paper and board. For paper and board in the grammage range 50 g/m2to 500 g/m2, bending stiffness might vary by a factor of over 1 000. This wide variation is reflected in the design of instruments intended for the measurement of this pro
18、perty.A second factor to be taken into account is that, in general terms, bending stiffness (as defined here) can only be determined with accuracy within certain limits with regard to the degree of deformation imposed upon the test piece. These limits depend on the dimensions of the test piece and o
19、n the test method used.This International Standard is intended to enable the bending stiffness (as defined here) to be measured and described in a consistent way, despite the variations in material type and instrument design. It will be found that many commercially available instruments can be regar
20、ded as giving results in accordance with this International Standard for only part of the range of bending stiffness, or for only some of the materials for which they were originally designed. It is intended, therefore, that this International Standard will be used as the basis for preparing detaile
21、d methods for determining bending stiffness, using particular instruments. ISO 2012 All rights reserved vBS ISO 5628:2012BS ISO 5628:2012Paper and board Determination of bending stiffness General principles for two-point, three-point and four-point methods1 ScopeThis International Standard specifies
22、 three test methods for determining the bending stiffness of paper and paperboard. The test methods differ in the type of loading mode, thus giving rise to the two-point, three-point and four-point bending test methods.For paper and paperboard in a low thickness range, the two-point bending method a
23、nd the three-point bending method are suitable.For corrugated fibreboard and board with a higher thickness, the four-point bending method is recommended.The measurement conditions are defined in such a way that the test piece is not subjected to any significant permanent deformation during the test,
24、 nor is the range of validity of the equations for calculating the bending stiffness exceeded.In these bending tests, the test pieces of paper and board are regarded as “beams” as defined by the science of the strength of materials, see Reference 1.2 Normative referencesThe following referenced docu
25、ments 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.ISO 186, Paper and board Sampling to determine average qualityISO 187, Paper, b
26、oard and pulps Standard atmosphere for conditioning and testing and procedure for monitoring the atmosphere and conditioning of samplesISO 534, Paper and board Determination of thickness, density and specific volumeISO 3034, Corrugated fibreboard Determination of single sheet thickness3 Terms and de
27、finitionsFor the purposes of this document, the following terms and definitions apply.3.1bending stiffnessSbresistance that a test piece offers to bending, in the region of elastic deformationNOTE The theories used for the determination of bending stiffness are derived under the condition that the t
28、est piece is perfectly flat at the beginning of the test. In a real situation, the test piece always deviates from flatness. It is, however, not possible to give recommendations on the magnitude of such deviations (such as curl, twist, cockle or other deviations) that can be present and still produc
29、e a valid test.4 Symbols and unitsThe following symbols are used for the equations in this International Standard.INTERNATIONAL STANDARD ISO 5628:2012(E) ISO 2012 All rights reserved 1BS ISO 5628:2012ISO 5628:2012(E)Table 1 Symbols and unitsSymbol Unit Meaningb mm test piece width in the direction o
30、f the bending axisE MPa (N/mm2) modulus of elasticityf mm linear deflectionF N forcefmaxmm maximum linear deflectionI mm4second moment of inertial mm bending lengthl1mm distance in the four-point methodl2mm bending length in the four-point methodSbNmm bending stiffnesst mm test piece thickness (degr
31、ee) bending anglemax (degree) maximum bending angle % (mm/mm) strainmax% (mm/mm) maximum strain5 TheoryFor a beam of a homogeneous material, with equal thickness and a constant modulus of elasticity in the plane of the paper or board, the bending stiffness Sb(per unit width b) may be derived from th
32、e product of the modulus of elasticity, E, and the second moment of inertia, I, of the test piece, divided by the width, b, of the test piece as shown in Equation (1):Sb=EIb(1)From a testing point of view, the bending stiffness, Sb, may be evaluated in three principally different ways:a) From the ma
33、ximum slope of the curve achieved from recording force versus linear deflection (F/f), or force versus angular deflection (F/), see Figure 12. The rate of testing shall be reported.b) Applying a linear deflection or angular deflection and recording the force after a specified time2. This Internation
34、al Standard gives suggestions for maximum allowable deflections for the various beam-bending methods. The time of application shall be reported.c) Applying a force and recording the linear deflection or angular deflection after a specified time (References 2, 3, 5). This International Standard gives
35、 suggestions for maximum allowable deflections for the various beam-bending methods. The time of application shall be reported.NOTE Suggestions for allowable deflections only apply to principles b) and c).2 ISO 2012 All rights reservedBS ISO 5628:2012ISO 5628:2012(E)Key1 maximum slope of curve2 true
36、 curveF forcef linear deflection angular deflectionFigure 1 Schematic curve of force versus linear deflection or force versus angular deflection of a paper or board6 Different bending test methods6.1 Two-point bending methodThe two-point method is suitable for paper and low-thickness board. For corr
37、ugated board, the two-point method is not recommended.The bending according to the two-point bending method can be performed in two ways.In Figure 2, the beam-shaped test piece is clamped at one end and subjected to a force, F, acting perpendicular to the surface of the test piece at the start of th
38、e test, at a bending length, l, from the clamp. The linear deflection, f, of the test piece is the shift in the point of application of the force in the direction in which it acts.In Figure 3, the beam-shaped test piece is clamped at one end in a clamp that rotates and is subjected to a force, F, ac
39、ting perpendicular to the surface of the test piece at the start of the test, at a bending length, l, from the clamp. The bending angle, , is the angle through which the clamp is rotated during the test. ISO 2012 All rights reserved 3BS ISO 5628:2012ISO 5628:2012(E)KeyF force (in newtons)f linear de
40、flection (in millimetres)l bending length (in millimetres)Figure 2 Two-point methodKeyF force (in newtons)l bending length (in millimetres) bending angle (in degrees)Figure 3 Two-point method6.2 Three-point bending methodThe three-point method is suitable for paper and low-thickness board. For corru
41、gated board, the three-point method is not recommended.NOTE 1 It is possible to use the three-point bending method for corrugated board, if very long test pieces are used. The test method is not suitable for test pieces of recommended dimensions used for paper and board, due to the shear strain of t
42、he corrugated board2. The suitable dimensions depend on the material to be tested and no absolute values can be stated in this International Standard.The beam-shaped test piece is supported close to each end and is subjected to a force, 2F, in the centre perpendicular to the test-piece surface at th
43、e start of the test, see Figure 4.KeyF force (in newtons)f linear deflection (in millimetres)l bending length (in millimetres)Figure 4 Three-point methodThe distance between the two supporting anvils is now twice the bending length, l. The linear deflection, f, is the shift in the point of applicati
44、on of the force in the direction in which it acts.NOTE 2 The definitions of the force and bending length in the three-point test make the three-point test equal to two mirror images of the two-point test, thus making the calculation of bending stiffness and measurement conditions equal for these two
45、 tests.4 ISO 2012 All rights reservedBS ISO 5628:2012ISO 5628:2012(E)6.3 Calculation of bending stiffness using the two-point and three-point methods6.3.1 Bending stiffness determinationIf the linear deflection, f, and the force F are measured during the bending test, the bending stiffness, Sb, is c
46、alculated according to Equation (2):Sb=Fflb33(2)If the bending angle, , and force F are measured during the bending test, the bending stiffness, Sb, is calculated according to Equation (3):SFlbb=602pi (3)6.3.2 Geometrical requirementIt is assumed in Equations (2) and (3) that the bending occurs with
47、 negligible influence of inter-laminar shear strain. This strain depends theoretically on the ratio of inter-laminar shear stiffness to tensile stiffness and the ratio of the thickness to the bending length. In order to minimize the impact of inter-laminar shear strain on the result, the length l sh
48、all not be less than approximately 40 times the thickness of the test piece for paper and board, see Reference 2.In this International Standard, no particular requirement is stipulated for the width of the test piece. The choice of width has to be selected by the user and be suited for a particular
49、testing equipment. The width shall be reported.6.3.3 Allowable deflections and anglesThe test piece shall not suffer any significant permanent deformation during the bending test. Furthermore, there are requirements for the maximum deflection according to the beam-bending theory2. To comply with these requirements, Equations (4) to (7) apply.Experience has shown that the in-plane strain, , should not exceed approximately 0,2 % (max) in the outer layers of the test piece,
