1、 ISO 2016 Fine ceramics (advanced ceramics, advanced technical ceramics) Test method for flexural strength of monolithic ceramics at room temperature Cramiques techniques Mthode dessai de rsistance en flexion des cramiques monolithiques temprature ambiante INTERNATIONAL STANDARD ISO 14704 Third edit
2、ion 2016-04-15 Reference number ISO 14704:2016(E) ISO 14704:2016(E)ii ISO 2016 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by an
3、y 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 ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 40
4、1 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO 14704:2016(E)Foreword iv 1 Scope . 1 2 Normative references 1 3 Terms and definitions . 1 4 Principle 3 5 Apparatus . 3 5.1 Testing machine . 3 5.2 Test fixture 3 5.2.1 General 3 5.2.2
5、Bearings . 4 5.2.3 Four-point fixture: semi-articulating . 4 5.2.4 Four-point fixture: fully articulating . 4 5.2.5 Three-point fixture: semi-articulating 4 5.2.6 Three-point fixture: fully articulating 5 5.2.7 Positioning of bearings . 5 5.2.8 Fixture material 6 5.3 Micrometer . 6 6 Test pieces . 6
6、 6.1 Test piece size 6 6.1.1 Machined test pieces 6 6.1.2 As-fired or heat-treated test pieces . 6 6.2 Test piece preparation 7 6.2.1 General 7 6.2.2 As-fired . 7 6.2.3 Customary machining procedure 7 6.2.4 Component-matched procedure 7 6.2.5 Basic machining procedure 7 6.2.6 Parallelism, orthogonal
7、ity and chamfer sizes . 8 6.2.7 Handling of test pieces 9 6.2.8 Number of test pieces 9 7 Procedure. 9 8 Calculation .11 9 Test report 12 10 Strength scaling factors 13 Annex A (informative) General information14 Annex B (normative) Test fixtures .15 Annex C (informative) Typical fracture patterns i
8、n ceramic test pieces 21 Annex D (informative) Chamfer correction factors 23 Annex E (informative) Weibull scaling factors 26 Bibliography .28 ISO 2016 All rights reserved iii Contents Page ISO 14704:2016(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation
9、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 in a subject for which a technical committee has been established has the right to be represented on that committee. I
10、nternational organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those
11、 intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (se
12、e www.iso.org/directives). 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. Details of any patent rights identified during the development of the docu
13、ment will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms an
14、d expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/TC 206, Fine ceramics. This third
15、edition cancels and replaces the second edition (ISO 14704:2008), which has been technically revised.iv ISO 2016 All rights reserved INTERNATIONAL ST ANDARD ISO 14704:2016(E) Fine ceramics (advanced ceramics, advanced technical ceramics) Test method for flexural strength of monolithic ceramics at ro
16、om temperature 1 Scope This International Standard specifies a test method for determining the flexural strength of monolithic fine ceramics, and whisker- or particulate-reinforced ceramic composites, at room temperature and applies to materials with grain size less than 200 m. This test method may
17、be used for materials development, quality control, characterization and design data-generation purposes. NOTE Since fracture is due to tensile stress, flexural strength data can be used to calculate a uniaxial tensile strength considering the effect of the tested volume and Weibull-statistics. So,
18、flexural strength is often used in substitute for uniaxial tensile strength. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated r
19、eferences, the latest edition of the referenced document (including any amendments) applies. ISO 3611, Geometrical product specifications (GPS) Dimensional measuring equipment: Micrometers for external measurements Design and metrological characteristics ISO 7500-1, Metallic materials Calibration an
20、d verification of static uniaxial testing machines Part 1: Tension/compression testing machines Calibration and verification of the force-measuring system 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 flexural strength maximum nominal stres
21、s at fracture of a specified elastic beam loaded in bending 3.2 four-point flexure configuration of flexural strength testing where a test piece is loaded equally by two bearings symmetrically located between two support bearings Note 1 to entry: See Figure 1, a) and b). Note 2 to entry: The bearing
22、s may be cylindrical rollers or cylindrical bearings. ISO 2016 All rights reserved 1 ISO 14704:2016(E) L = 40 mm 0,1 mm a) Four-point-1/4 point flexure L = 30 mm 0,1 mm b) Four-point-1/3 point flexure L = 30 mm 0,1 mm or 40 mm 0,1 mm c) Three-point flexure Key 1 loading bearings 2 support bearing 3
23、test piece Figure 1 Flexural test configurations 3.3 four-point-1/4 point flexure specific configuration of four-point flexural strength testing where the inner bearings are situated one- quarter of the support span away from the two outer bearings Note 1 to entry: See Figure 1 a).2 ISO 2016 All rig
24、hts reserved ISO 14704:2016(E) 3.4 four-point-1/3 point flexure specific configuration of four-point flexural strength testing where the inner bearings are situated one- third of the support span away from the two outer bearings Note 1 to entry: See Figure 1 b). 3.5 semi-articulating fixture test fi
25、xture designed to apply uniform and even loading to test pieces that have flat and parallel surfaces 3.6 fully articulating fixture test fixture designed to apply uniform and even loading to test pieces that may have uneven, non- parallel or twisted surfaces 3.7 three-point flexure configuration of
26、flexural strength testing where a test piece is loaded at a location midway between two support bearings Note 1 to entry: See Figure 1 c). Note 2 to entry: Four-point flexure (3.2) is usually preferred, since a large amount of material is exposed to the maximum stress (see Annex A for more informati
27、on). 4 Principle A beam test piece with a rectangular cross-section is loaded in flexure until fracture. The load at fracture, the test fixture and test piece dimensions are used to compute the flexural strength which is often used in substitute for uniaxial tensile strength of a ceramic. The materi
28、al is assumed to be isotropic and linearly elastic. 5 Apparatus 5.1 Testing machine The testing machine shall be capable of applying a force to the loading roller (three-point flexure) or equally to the loading rollers (four-point flexure) in order to stress the test piece. The machine shall be capa
29、ble of applying the force at a constant loading or displacement rate. The test machine shall be equipped for recording the peak load applied to the test piece. The accuracy of the test machine shall be in accordance with ISO 7500-1, Class 1, with an accuracy of 1 % of indicated load at fracture. 5.2
30、 Test fixture 5.2.1 General Three- or four-point flexure configurations shall be used, as illustrated in Figure 1. The four-point-1/4 point configuration is recommended. The fixture shall have bearings that are free to roll, as described in 5.2.2, in order to eliminate frictional constraints when th
31、e test piece surfaces expand or contract during loading. In addition, the fixture shall be designed so that parts “articulate” or tilt to ensure uniform loading to the test piece. The articulation is designed so that parts of the fixture can rotate, as shown in Figure B.1, to ensure even loading on
32、the left and right bearings. An articulation is also needed to ensure that all the bearings evenly contact the test piece surfaces and apply uniform load. Semi-articulated fixtures have some articulating or tilting capabilities and may be used with test pieces that have flat and parallel surfaces, s
33、uch as on as-machined test pieces. A semi-articulating fixture has pairs of upper and lower bearings that articulate to match the test piece surfaces, as shown in Figures B.2 and B.3. Fully articulated fixtures have more moving parts and are necessary for test pieces that do not have flat and ISO 20
34、16 All rights reserved 3 ISO 14704:2016(E) parallel surfaces. They allow independent articulation of the bearings. Fully articulated fixtures often are necessary for as-fired, heat-treated or oxidized test pieces, since uneven loading can cause twisting and severe errors. A fully articulating fixtur
35、e may also be used with machined test pieces. 5.2.2 Bearings Test pieces shall be loaded and supported by bearings. The bearings may be cylindrical rollers or cylindrical bearings. The bearings shall be made of a steel which has a hardness of no less than HRC 40 for test piece strengths up to 1 400
36、MPa, or no less than HRC 46 for test piece strengths up to 2 000 MPa. Alternatively, the bearing may be made of a ceramic or hardmetal with an elastic modulus between 200 GPa and 500 GPa and a flexural strength greater than 275 MPa. The bearing length shall be greater than or equal to 12 mm. The bea
37、ring diameter shall be approximately 1,5 times the test piece thickness (d). Diameters between 4,5 mm and 5 mm are recommended. The bearings shall have a smooth surface and shall have a diameter that is uniform to 0,015 mm. The bearings shall be free to roll in order to eliminate friction. In four-p
38、oint flexure, the two inner bearings shall be free to roll inwards, and the two outer bearings shall be free to roll outwards. In three-point flexure, the two outer bearings shall be free to roll outwards, and the inner (middle) bearing shall not roll. NOTE 1 Friction can cause errors in the stress
39、calculations. The rolling can be accomplished by several designs. The bearing can be mounted in roller bearing or cylindrical bearing assemblies. It is also acceptable, and simpler, for the bearings to be free to roll on the fixture surface, as shown in Figure 2. The bearing diameter is specified on
40、 the basis of competing requirements. The bearings should not be so large as to cause excessive change in the moment arm as a test piece deflects, as this can create errors from contact-point tangency shift. On the other hand, the bearings should not be so small as to create excessive wedging stress
41、es in the test piece or create contact stresses that damage the fixture. NOTE 2 The bearing hardness and stiffness requirements and guidelines are intended to ensure that test pieces with strengths up to 1 400 MPa (or 2 000 MPa), and elastic moduli as high as 500 GPa, can be tested without damaging
42、the fixture. Higher-strength or stiffer ceramic test pieces can require harder bearings. For example, if the bearing elastic modulus is greater than 500 GPa, then it is advisable to lengthen the bearings and the fixture support width to more than 12 mm to distribute the forces over a longer bearing
43、length. 5.2.3 Four-point fixture: semi-articulating Figure B.2 a) shows the actions of the bearings in this fixture. The two inner bearings shall be parallel to each other to within 0,015 mm over their length ( 12 mm in accordance with 5.2.2). The two outer bearings shall be parallel to each other t
44、o within 0,015 mm over their length. Either the two inner or the two outer bearings shall be capable of articulating (tilting) together as a pair to match the test piece surface. All four bearings shall rest uniformly and evenly across the test piece surface. The fixture shall apply equal load to al
45、l four bearings. All four bearings shall be free to roll. 5.2.4 Four-point fixture: fully articulating Figure B.2 b) shows the actions of the bearings in this fixture. One bearing need not articulate (tilt). The other three bearings shall articulate (tilt) independently to follow the test piece surf
46、ace. All four bearings shall rest uniformly and evenly across the test piece surface. The fixture shall apply equal load to all four bearings. All four bearings shall be free to roll. 5.2.5 Three-point fixture: semi-articulating Figure B.3 a) shows the actions of the bearings in this fixture. The tw
47、o outer bearings shall be parallel to each other to within 0,015 mm over their length ( 12 mm in accordance with 5.2.2). The two outer bearings shall articulate together to follow the test piece surface, or the middle bearing shall articulate to follow the test piece surface. All three bearings shal
48、l rest uniformly and evenly across the test piece surface. The fixture shall be designed to apply equal load to the two outer bearings. The two support (outer) bearings shall be free to roll outwards. The middle bearing shall be fixed and not free to roll.4 ISO 2016 All rights reserved ISO 14704:201
49、6(E) 5.2.6 Three-point fixture: fully articulating Figure B.3 b) and c) show the actions of the bearings in this fixture. Any two of the bearings shall be capable of articulating (tilting) independently to rest uniformly and evenly across the test piece surface. The fixture shall be designed to apply equal load to the two outer bearings. The two support (outer) bearings shall be free to roll outwards. The middle bearing shall not roll. 5.2.7 Positioning of bearings The bearings shall be positioned so that the spans are
