ISO INTERNATIONAL STANDARD 5628 Third edition 2019-05 Paper and board Determination of bending stiffness - General principles for two-point, three-point and four- point methods Papier et carton -Détermination de la rigidité a la flexion - Principes genéraux pour les méthodes a deux points, a trois points et a quatrepoints Reference number ISO 5628:2019(E) osi @IS02019 IS0 5628:2019(E) COPYRIGHTPROTECTEDDOCUMENT @ IS0 2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +41 22 749 01 11 Fax: +41 22 749 09 47 Email: copyright@iso.org Website: www.iso.org Published in Switzerland i @ IS0 2019 - All rights reserved IS0 5628:2019(E) Contents Page Foreword ..iv Introduction. ..V 1 Scope. ..1 2 Normative references 3 Terms and definitions 4 Symbols and units ..2 5 Theory ..2 6 Different bending test methods ..3 6.1 Two-point bending method .3 6.2 Three-point bending method .4 6.3 Calculation of bending stiffness using the two-point and three-point methods. 5 6.3.1 Bending stiffness determination. .5 6.3.2 Geometrical requirement 5 6.3.3 Allowable deflections and angles .5 6.4 Four-point bending method. 6 6.4.1 Geometry .6 6.4.2 Calculation of bending stiffness 7 6.4.3 Measurement conditions .7 6.4.4 Geometrical and practical considerations .7 7 ..8 Apparatus 8 Sampling and preparation of test pieces ..8 8.1 Sampling ..8 8.2 Conditioning ..8 8.3 Preparation of test pieces ..8 9 Procedure ..8 10 Evaluation and calculation .9 11 Test report .9 Bibliography ..10 @ IS0 2019 - All rights reserved ii