DIN EN 14425-3-2010 Advanced technical ceramics - Test methods for determination of fracture toughness of monolithic ceramics - Part 3 Chevron notched beam (CNB) method German vers.pdf

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1、November 2010 Translation by DIN-Sprachendienst.English price group 10No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).I

2、CS 81.060.30!$l1_“1731460www.din.deDDIN EN 14425-3Advanced technical ceramics Test methods for determination of fracture toughness of monolithicceramics Part 3: Chevron notched beam (CNB) methodEnglish translation of DIN EN 14425-3:2010-11Hochleistungskeramik Prfverfahren zur Bestimmung der Bruchzhi

3、gkeit von monolithischer Keramik Teil 3: Verfahren fr Biegeproben mit Chevron-Kerb (CNB-Verfahren)Englische bersetzung von DIN EN 14425-3:2010-11Cramiques techniques avances Mthode dessai de dtermination de la tnacit la rupture des cramiquesmonolithiques Partie 3: Mthode de lprouvette entaille en ch

4、evronTraduction anglaise de DIN EN 14425-3:2010-11SupersedesDIN CEN/TS 14425-3:2003-11www.beuth.deDocument comprises pagesIn case of doubt, the German-language original shall be considered authoritative.1610.10 DIN EN 14425-3:2010-11 2 A comma is used as the decimal marker. National foreword This st

5、andard has been prepared by Technical Committee CEN/TC 184 “Advanced technical ceramics” (Secretariat: BSI, United Kingdom). The responsible German body involved in its preparation was the Normenausschuss Materialprfung (Materials Testing Standards Committee), Working Committee NA 062-02-91 AA Prfun

6、g von Hochleistungs-keramik Monolithische Werkstoffe. The DIN Standard corresponding to the International Standard referred to in this document is as follows: ISO 3611 DIN 863-1 Amendments This standard differs from DIN CEN/TS 14425-3:2003-11 as follows: a) the prestandard status has been changed to

7、 that of a full standard; b) the standard has been editorially revised. Previous editions DIN CEN/TS 14425-3: 2003-11 National Annex NA (informative) Bibliography DIN 863-1, Verification of geometrical parameters Micrometers Part 1: Standard design micrometer callipers for external measurement; conc

8、epts, requirements, testing EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 14425-3 June 2010 ICS 81.060.30 Supersedes CEN/TS 14425-3:2003English Version Advanced technical ceramics - Test methods for determination of fracture toughness of monolithic ceramics - Part 3: Chevron notched beam (CNB

9、) method Cramiques techniques avances - Mthode dessai de dtermination de la tnacit la rupture des cramiques monolithiques - Partie 3: Mthode de lprouvette entaille en chevron Hochleistungskeramik - Prfverfahren zur Bestimmung der Bruchzhigkeit von monolithischer Keramik - Teil 3: Verfahren fr Biegep

10、roben mit Chevron-Kerb (CNB-Verfahren) This European Standard was approved by CEN on 30 April 2010. 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-

11、to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN 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 un

12、der the responsibility of a CEN member into its own language and notified to the CEN 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, France, German

13、y, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG M

14、anagement Centre: Avenue Marnix 17, B-1000 Brussels 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14425-3:2010: EEN 14425-3:2010 (E) 2 Contents Page Foreword 31 Scope 42 Normative references 43 Terms and definitions .44 Prin

15、ciple, significance and use 45 Test apparatus .56 Test pieces .56.1 Material selection .56.2 Test piece dimensions 56.3 Sawn notch .67 Procedure .68 Calculation of results 79 Interferences and errors .810 Reporting 8Bibliography . 14DIN EN 14425-3:2010-11 EN 14425-3:2010 (E) 3 Foreword This document

16、 (EN 14425-3:2010) has been prepared by Technical Committee CEN/TC 184 “Advanced technical ceramics”, 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 identical text or by endorsement, at the latest by Decem

17、ber 2010, and conflicting national standards shall be withdrawn at the latest by December 2010. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such paten

18、t rights. This document supersedes CEN/TS 14425-3:2003. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Fin

19、land, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. DIN EN 14425-3:2010-11 EN 14425-3:2010 (E) 4 1 Scope This European Standard pr

20、ovides a test method for fracture toughness determination based on the chevron-notch method. For the purposes of this European Standard, the term monolithic includes particle and whisker reinforced advanced technical ceramics which can be regarded as macroscopically homogeneous. It does not include

21、long-fibre reinforced ceramics. 2 Normative references The following referenced documents 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) app

22、lies. EN 843-1:2006, Advanced technical ceramics Mechanical properties of monolithic ceramics at room temperature Part 1: Determination of flexural strength EN 1006, Advanced technical ceramics Monolithic ceramics Guidance on the selection of test pieces for the evaluation of properties EN ISO 7500-

23、1, Metallic materials Verification of static uniaxial testing machines Part 1: Tension/compression testing machines Verification and calibration of the force-measuring system (ISO 7500-1:2004) EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories (ISO/IEC

24、17025:2005) ISO 3611, Micrometer callipers for external measurement 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 chevron-notch test piece test piece in which a two coplanar saw cuts are made at an angle to each other part way through a tes

25、t piece to leave a remaining cross-section with a sharp tip from which a crack may be initiated in a controlled or semi-controlled manner 4 Principle, significance and use In the chevron-notched beam method, a crack is generated during the test from a sharp tip resulting when two coplanar notches ar

26、e cut in a test piece (see Figure 1). This overcomes the need to generate sharp planar cracks before commencing the test. During the test, the crack front widens as the crack propagates from the tip, resulting in an increase in the force required to maintain growth. Countering this, the test piece b

27、ecomes more compliant as the crack lengthens, and so the two effects result in a peak load being attained after some distance of propagation. The toughness is determined from the peak force applied. This test method employs the chevron notch in a flexural strength test piece, loaded in four-point be

28、nding geometry. The advantage is that it can be performed on standard flexural strength test pieces. DIN EN 14425-3:2010-11 EN 14425-3:2010 (E) 5 The test is most appropriate for homogeneous isotropic materials, but can be used with care on anisotropic materials subject to the geometry of fracture r

29、emaining valid. In materials which are inhomogeneous on the scale of the crack dimensions, a wide scatter of results and the development of invalid non-planar cracks may occur. In addition, the test is valid primarily for materials which do not show rising crack resistance with increasing crack leng

30、th. Since the crack width progressively increases as propagation occurs, the concurrent presence of rising crack resistance means that the crack front would no longer stay straight but would become convex, producing an uncertainty in the calculated results. It should be noted that this test employs

31、a slowly moving crack. The numerical value for the fracture toughness calculated from this method may not be the same as those from fast crack propagation tests, especially if the susceptibility to subcritical crack growth is significant. 5 Test apparatus 5.1 Flexural strength test apparatus of four

32、-point bending type, in accordance with the requirements in EN 843-1. 5.2 Mechanical testing machine, capable of accurate recording of load/displacement data for loads in the range 0 N to 500 N. The load shall be calibrated in accordance with EN ISO 7500-1. NOTE A stiff loading system (i.e. frame, l

33、oad cell and fixtures, etc.) is advantageous for this test. The compliance is ideally less than 5 10-5m/N (see 1). 5.3 Micrometer in accordance with ISO 3611 but measuring to an accuracy of 0,002 mm. 5.4 Calibrated device for measuring dimensions of the cut chevron after fracture, reading to an accu

34、racy of 0,002 mm or better. NOTE This may be achieved by use of an appropriate travelling microscope, or a conventional microscope with a calibrated stage micrometer, or a microscope with a micrometer eyepiece. 5.5 Humidity measuring device for measuring relative humidity to an accuracy of 2 %, e.g.

35、 those according to ISO 4677. 6 Test pieces 6.1 Material selection Select the material or components from which test pieces are to be machined with reference to the considerations given in EN 1006. 6.2 Test piece dimensions 6.2.1 The test pieces shall preferably be of dimensions as for determination

36、 of flexural strength and described in EN 843-1. Alternatively, if availability of material permits, the dimensions may be scaled larger for convenience of machining of the notch. NOTE It is usually advantageous to test coarse-grained or heterogeneous materials in larger test piece sizes because it

37、improves the chances of obtaining a valid test (see 7.9). 6.2.2 The standard size test pieces shall be (3,00 0,15) mm (4,00 0,15) mm in cross-section, and have a minimum length of 45 mm. The surfaces shall be machined to a flatness of better than 0,01 mm over the test piece length, and opposite pair

38、s of faces shall be parallel to better than 0,01 mm over the test piece length. The section should be visibly rectangular. NOTE Chamfering in accordance with EN 843-1 is unnecessary for this test. DIN EN 14425-3:2010-11 EN 14425-3:2010 (E) 6 6.2.3 The test piece surfaces shall be ground to a good qu

39、ality finish using final grinding with a peripheral wheel of grit size between 320 and 500 mesh grit, using a depth of cut of no more than 0,002 mm for the last 0,04 mm of material removed from each surface. No edge treatment is necessary. NOTE Although a large notch is placed in the test piece, the

40、 quality of grinding remains important for dimensional accuracy for registration in cutting the notch and for minimizing residual stresses. 6.3 Sawn notch 6.3.1 The notch is produced by two saw cuts at an appropriate angle to each other as shown in Figure 1. The notch width shall be less than 0,20 m

41、m at the surface, and the notch root radius should be less than 0,1 mm. The grit size of the saw or grinding wheel employed shall be 320 mesh or smaller. For standard test pieces, the test piece shall be orientated such that the notch tip is opposite the 3 mm width face. The notch geometry may be se

42、lected to suit requirements. However, it is recommended that: a) the angles of the two sides of the notch to the test piece faces are equal to within 1, and the notch tip is central within the test piece to within 0,05 B where B is the test piece width; b) the position of the notch tip, a0, below th

43、e test piece surface is about 20 % of the depth of the test piece, W; c) the positions of run-out of the notch through the test piece sides, a11, a12are closely similar, and are in the range 90 % to 100 % of the test piece depth, W. NOTE 1 The use of a surface grinder or precision slicing saw permit

44、s straight-tipped cuts to be made. The use of a non-traversing saw, or a wire saw, is not recommended because the line of the notch tip produced is not straight. This can introduce a considerable error in the use of the calibration equations. NOTE 2 The reproducibility and quality of machining of th

45、e notch can influence the reproducibility of the test result. In general, narrower and more precise cutting encourages more reproducible initial stable crack growth and reduces the scatter in results. 6.3.2 A simple method of obtaining the required precision of cutting is to prepare a V-block with a

46、n end stop against which the test piece can be registered. The test piece is clamped on one side to permit the first cut, and is then rotated and clamped on the other side to allow the second cut of equal depth to be coplanar with the first. The angle of the V-block is the same as that required for

47、the notch angle. 6.3.3 A minimum of five test pieces shall be prepared. 7 Procedure 7.1 Measure the external dimensions of the test piece at the notch to the nearest 0,002 mm using the micrometer (5.3). 7.2 Measure the notch lengths a11and a12(to the points where the roots of the notch meet the exte

48、rnal surfaces) to the nearest 0,002 mm using the calibrated device (5.4). The difference between the average value a1and the individual values shall not be greater than 0,05 W, where W is the test piece thickness. 7.3 Adjust the sensitivity of the load recording device to permit an accuracy of subse

49、quent measurement to better than 1 % of recorded values. Adjust the recording and plotting parameters of the recording device to permit clear identification of the load/time or load/displacement behaviour (see Figure 2). 7.4 Insert the test piece in the strength test apparatus with the tip of the chevron notch facing the outer support rollers, and align it carefully to ensure that the support and loading spans are centralised to within 0,2 mm in accordance with EN 843-1:20