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1、BRITISH STANDARD BS EN843-1:1995Advanced technical ceramics Monolithic ceramics Mechanical properties at room temperature Part 1: Determination of flexural strengthThe European Standard EN 843-1:1995 has the status of aBritish StandardBS EN 843-1:1995Cooperating organizationsThe European Committee f
2、or Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries:Austria Oesterreichisches Normungsinstitut BelgiumInstitut belge de normalisation DenmarkDansk StandardFinland Suomen Standardisoimisliito,
3、 r.y. FranceAssociation franaise de normalisation GermanyDeutsches Institut fr Normung e.V. GreeceHellenic Organization for Standardization IcelandTechnological Institute of IcelandIreland National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione LuxembourgInspection du T
4、ravail et des Mines NetherlandsNederlands Normalisatie-instituut NorwayNorges Standardiseringsforbund PortugalInstituto Portugus da QualidadeSpainAsociacin Espaola de Normalizacin y CertificacinSwedenStandardiseringskommissionen i SverigeSwitzerland Association suisse de normalisationUnited KingdomB
5、ritish Standards InstitutionThis British Standard, having been prepared under the direction of the Refractory Products Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on15 March 1995 BSI 12-1999The following BSI references relate to the work
6、 on this standard:Committee reference RPM/13Draft for comment 92/45075 DCISBN 0 580 23140 2Amd. No.DateCommentsAmendments issued since publicationBS EN 843-1:1995ContentsPage Cooperating organizationsInside front cover National forewordii Foreword 2Text of EN 843-13National annex NA (informative) Co
7、mmittees responsibleInside back cover BSI 12-1999iBS EN 843-1:1995National forewordThis British Standard has been prepared under the direction of the Refractory Products Standards Policy Committee and is the English language version of EN 843-1:1995 Advanced technical ceramics Monolithic ceramics Me
8、chanical properties at room temperature Part 1: Determination of flexural strength, published by the European Committee for Standardization (CEN). No current British Standard is superseded.EN 843-1 was produced as a result of international discussions in which the UKtook an active part.A British Sta
9、ndard 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 immunity from legal obligations.Summary of pagesThis document comprises a front cover, a
10、n inside front cover, pages i and ii, the EN title page, pages 2 to 12, an inside back cover and a back cover.This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. BSI 12-1999iiEUROPEAN S
11、TANDARD NORME EUROPENNEEUROPISCHE NORMEN 843-1January 1995ICS 81.060.10; 81.060.20Descriptors: Ceramics, environmental tests, mechanical properties, determination, flexural strengthEnglish versionAdvanced technical ceramics Monolithic ceramics Mechanical properties at room temperaturePart 1: Determi
12、nation of flexural strengthCramiques techniques avances Cramiques monolithiques Proprits mcaniques temprature ambiante Partie 1: Dtermination de la rsistance en flexionHochleistungskeramik Monolithische Keramik Mechanische Eigenschaft bei Raumtemperatur Teil 1: Bestimmung der BiegefestigkeitThis Eur
13、opean Standard was approved by CEN on 1995-01-04. 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-to-date lists and bibliographical references concer
14、ning such national standards may be obtained on application to the Central Secretariat or to any CEN member.The European Standards exist 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 lan
15、guage and notified to the Central Secretariat has the same status as the official versions.CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and
16、United Kingdom.CENEuropean Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr NormungCentral Secretariat: rue de Stassart 36, B-1050 Brussels 1995 Copyright reserved to CEN membersRef. No. EN 843-1:1995 EEN 843-1:199513 BSI 12-1999ForewordThis European Standard has b
17、een prepared by Technical Committee CEN/TC184, 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 July 1995, and conflicting natio
18、nal standards shall be withdrawn at the latest by July 1995.EN 843 consists of five Parts: Part 1: Determination of flexural strength; Part 2: Determination of elastic moduli; Part 3: Determination of sub-critical crack growth; Part 4: Determination of hardness; Part 5: Statistical analysis of fract
19、ure data. According to the CEN/CENELEC InternalRegulations, the following countries are bound toimplement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg,Netherlands, Norway, Portugal, Spain, Sweden,Switzerland and United Kingd
20、om.ContentsPageForeword21Scope32Normative references33Definitions 34Significance and use35Apparatus46Test pieces77Test procedure88Calculations99Test report10Annex A (informative) Bibliography12Figure 1 Schematic diagrams of function of a) three-point bend test jig and b) four-point bend test jig ind
21、icating the articulation androtation required for the rollers 5Figure 2 Test span dimensions andtolerances6Figure 3 Dimensions and tolerancesof machined test pieces111 ScopeThis Part of EN 843 describes methods for determining the nominal flexural strength of advanced monolithic technical ceramic ma
22、terials at ambient temperature. The available loading geometries are three- and four-point flexure, using rectangular section test pieces of two prescribed geometries: 20 mm support span (A) and 40 mm support span (B).The test prescribes four categories of surface finish applied to the test pieces:I
23、: as-fired or annealed after machining;II: machined using agreed grinding procedures and material removal rates;III: standard finishing procedures: III.1: finishing by grinding;III.2: finishing by lapping/polishing.NOTE The test may not give representative results if the mean linear intercept grain
24、size exceeds 5 % of the thickness of the test piece, with the exception of single crystals.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the p
25、ublications 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 the publication referred to applies.ENV 623-4
26、, Advanced technical ceramics Monolithic ceramics General and textural properties Part 4: Surface roughness.EN 10002-2, Tensile testing of metallic materials Part 2: Verification of the force measuring system of the tensile testing machine.ISO 3611, Micrometer callipers for external measurement.ISO
27、4677-1, Atmospheres for conditioning and testing Determination of relative humidity Part 1: Aspirated psychrometer method.ISO 4677-2, Atmospheres for conditioning and testing Determination of relative humidity Part 2: Whirling psychrometer method.3 DefinitionsFor the purposes of this Part of EN 843,
28、 the following definitions apply:3.1nominal flexural strengththe maximum nominal stress at the instant of failure supported by the material when loaded in elastic bending3.2three-point flexurea means of bending a beam test piece whereby the test piece is supported on bearings near its ends, and a ce
29、ntral load is applied3.3four-point flexurea means of bending a beam test piece whereby the test piece is supported on bearings near its ends, and is loaded equally at two positions symmetrically disposed about the centre of the supported spanNOTE The term “quarter-point flexure” is sometimes used fo
30、r the four-point flexure geometry wherein the load positions are each one-quarter of the support span from the support bearings, as is the case in this standard.4 Significance and useThis test is intended to be used for material development, quality control, characterization and design data acquisit
31、ion purposes. The strength level determined by the test is calculated on the basis of linear elastic bending of a thin beam on the assumption that the material being tested is elastically homogeneous and isotropic, and shows linear (Hookean) stress-strain behaviour.The result obtained from a strengt
32、h test is determined by a large number of factors associated with the microstructure of the material, the surface finishing procedure applied in preparation of the test pieces, the size and shape of the test piece, the mechanical function of the testing apparatus, the rate of load application and th
33、e relative humidity of the ambient atmosphere. As a consequence of the brittle nature of ceramics, there is usually a considerable range of results obtained from a number of nominally identical test pieces. These factors combined mean that caution in the interpretation of test results is required. F
34、or many purposes, and as described in this standard, the results of strength tests may be described in terms of a mean value and a standard deviation. Further statistical evaluation of results is required for design data acquisition, and may be desirable for other purposes.This method places closely
35、 defined restrictions on the size and shape of the test piece and on the function of the test apparatus in order to minimize the errors that can arise as a consequence of the test method.NOTE The basis for the choice of dimensions and tolerances of test pieces and of the requirements of the test jig
36、 may be found in A.1.All other test factors are required to be stated in the test report (see clause 9) in order to allow intercomparison of material behaviours. It is not possible rigorously to standardize particular surface finishes, since these are not absolutely controllable in mechanical terms.
37、 The inclusion of a standard preparation procedure (see 6.3) as one of the surface finish options in this method is intended to provide a means of obtaining a minimum amount of residual grinding damage in the test material.The extrapolation of flexure strength data to other geometries of stressing,
38、to multiaxial stressing, to other rates of stressing or to other environments should be viewed with caution.The origin of fracture in a flexure test can be a valuable guide to the nature and position of strength-limiting defects. Fractography of test pieces is highly recommended. In particular, the
39、test may identify fracture origins as being edge defects (caused by edge preparation), surface defects (caused by surface preparation), or internal defects (caused by manufacturing inhomogeneities such as pores, large grains, impurity concentrations). Not all advanced monolithic technical ceramics a
40、re amenable to clear fractography.5 Apparatus5.1 Test jig. The test jig shall function as specified below in order to minimize misalignments, twist and frictional forces applied to the test piece.NOTE 1 The precise test jig design is not specified, only the function.Schematic arrangements of the tes
41、t jig function are shown in Figure 1 a) for three-point flexure, and Figure 1 b) for four-point flexure.The test piece is supported on two bearing edges perpendicular to its length. The outer support bearing edges shall be parallel rollers ofdiameter 2,5 mm 0,2 mm (test pieces for span A;see 6.2) or
42、 5,0 mm 0,2 mm (test pieces for span B;see 5.2), and shall be capable of rolling outward onflat support surfaces (see Figure 2). One of the rollers shall additionally be capable of rotating about an axis parallel to the length of the test piece such that torsional loading is minimized. The two rolle
43、rs shall be positioned initially with theircentres 20 mm 0,5 mm apart (span A)or 40 mm 0,5 mm apart (span B) with their axes parallel to within 1. The separation of the centres of the rollers in their starting positions shall be measured to the nearest 0,1 mm with the travelling microscope (see 5.3.
44、2). The rollers shall be madefrom hardened steel or other hard material with ahardness greater than 40 HRC (Rockwell C scale). The rollers shall have a smooth burr-free surface finish with roughness less than 0.5 4m Ra, and shall have diameter uniform to 0,02 mm.NOTE 2 Particular care should be take
45、n when testing very high strength materials ( 1 GPa) that flattening of the rollers by the test piece or Hertzian indentation of the rollers into the supports does not restrict their rotation. High hardness rollers ( 60 HRC) are recommended for testing such ceramics.For three-point flexure, a third
46、roller is located at the mid-point between and parallel to the two support rollers. This roller has the same diameter as the support rollers, and is similarly free to rotate about an axis parallel to the length of the test piece. Its position relative to the midpoint between the support rollers shall be to better than 0,2 mm, measured t
