ISO INTERNATIONAL STANDARD 18756 First edition 2003-12-01 Fine ceramics (advanced ceramics, advanced technical ceramics) Determination of fracture toughness of monolithic ceramics at room temperature by the surface crack in flexure (SCF) method Ceramiquestechniques-Determinationde latenacitea la rupturedes ceramiquesmonolithiquesatemperatureambianteparfissuration superficielle en flexion Reference number ISO 18756:2003(E) ISO @ ISO 2003 ISO18756:2003(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. ISO 2003 All 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, without permission in writing from either IsO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56.CH-1211Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland ii @ ISO 2003— All rights reserved ISO18756:2003(E) Contents Page Foreword. iv 1 Scope 2 Normative reference 3 Terms and definitions 4 Symbols. 5 Principle, 6 Apparatus 7 Testspecimens..... 7.1 Specimensize,preparationandedgechamfering 7.2 Number of specimens... 8 Procedure. 8.1 Introduction of theprecrackbyKnoop indentation... 8.2 Specimenfracture. 8.3 Cracksizemeasurement 12 8.4 Environmental effects... 8.5 Optional:EstimateofR-curvebehaviour 8.6 Optional:Referencematerials. 9 Calculation.. 10 Test report.... 15 AnnexA(informative)Environmentaleffects.. AnnexB (normative)Precrack characterization AnnexC(informative)R-curve estimationbytheScFmethod. AnnexD(normative)Chamfercorrectionfactors 27 Bibliography .. 29 @ ISO 2003—All rights reserved ili ISO18756:2003(E) Foreword IsO (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 International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/lEC 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 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 not be held responsible for identifying any or all such patent rights. ISO18756waspreparedbyTechnical CommitteeISO/TC206,Fineceramics iv @ISO2003-All rights reserved INTERNATIONAL STANDARD ISO18756:2003(E) Fine ceramics (advanced ceramics, advanced technical ceramics)Determinationoffracturetoughnessof monolithic ceramicsat roomtemperaturebythe surfacecrackinflexure (SCF) method Scope This International Standard describes a test method that covers the determination of fracture toughness of monolithic ceramic materials at room temperature by the surface crack in flexure (ScF) method. This International Standard is intended for use with monolithic ceramics and whisker- or particulate-reinforced ceramics that are regarded as macroscopically homogeneous. It does not include continuous-fibre reinforced ceramic composites. The test method is applicable to materials with either flat or rising crack growth resistan