1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 14628:2012Fine ceramics (advancedceramics, advanced technicalceramics) Test method forrolling contact fatigue ofsilicon nitride ceramics at roomtemperature by balls-on-fla
2、tmethodBS ISO 14628:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 14628:2012.The UK participation in its preparation was entrusted to TechnicalCommittee RPI/13, Advanced technical ceramics.A list of organizations represented on this committee can beobtai
3、ned on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 70809 1ICS 81.060.30Compliance with a
4、 British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 July 2012.Amendments issued since publicationDate Text affectedBS ISO 14628:2012 ISO 2012Fine ceramics (advanced ceramics, advanc
5、ed technical ceramics) Test method for rolling contact fatigue of silicon nitride ceramics at room temperature by balls-on-flat methodCramiques techniques Mthode dessai de fatigue de contact de roulement des cramiques au nitrure de silicium temprature ambiante par la mthode des billes sur surface pl
6、aneINTERNATIONAL STANDARDISO14628First edition2012-07-15Reference numberISO 14628:2012(E)BS ISO 14628:2012ISO 14628:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in
7、 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 ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749
8、 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 14628:2012ISO 14628:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Normative references . 13 Terms and definitions . 14 Principle . 25 Testing machine . 25.1 Structure of testing mach
9、ine 25.2 Loading precision . 46 Test specimens 46.1 Test specimen geometry . 46.2 Fixation of test specimen 56.3 Specimen thickness . 56.4 Surface finish . 56.5 Number of test specimens 57 Test method 57.1 Balls 57.2 Loading method . 57.3 Lubrication 67.4 Detection of surface failure 68 Treatment of
10、 test result 78.1 Mean effective load . 78.2 Mean effective mechanical input . 78.3 Flaking of ball surface 89 Test report . 8Annex A (informative) General information .10Bibliography .12BS ISO 14628:2012ISO 14628:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide
11、 federation 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
12、committee. International 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.International Standards are drafted in acco
13、rdance with the rules given in the ISO/IEC 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 requir
14、es 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.ISO 14628 was prepared by Technical C
15、ommittee ISO/TC 206, Fine ceramics.iv ISO 2012 All rights reservedBS ISO 14628:2012ISO 14628:2012(E)IntroductionRolling contact fatigue (RCF) performance is essential for predicting the life of a rolling element. In general, RCF performance is evaluated from the life at a specific failure probabilit
16、y obtained by the Weibull analysis of test data under constant loading conditions. This International Standard specifies a fast and reliable method to compare RCF performance under stepwise loading as an alternative to accurate quantification by RCF tests under constant load. Ranking candidate mater
17、ials, in other words comparison of performance among them, would be of value for choosing materials of required performance for bearings. In addition, material suppliers would receive feedback from the test results, allowing them to achieve a higher level of RCF performance. ISO 2012 All rights rese
18、rved vBS ISO 14628:2012BS ISO 14628:2012Fine ceramics (advanced ceramics, advanced technical ceramics) Test method for rolling contact fatigue of silicon nitride ceramics at room temperature by balls-on-flat method1 ScopeThis International Standard specifies a test method for rolling contact fatigue
19、 of silicon nitride ceramics under stepwise loading that is carried out at room temperature. This test may be used as follows: relative comparison of the rolling contact fatigue performance, a pass/fail test for material qualification of rolling elements or choosing an appropriate load level for RCF
20、 testing under constant load.2 Normative referencesThe 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) applies
21、.ISO 3290-1:2008, Rolling bearings Balls Part 1: Steel ballsISO 3290-2:2008, Rolling bearings Balls Part 2: Ceramic ballsISO 3611:2010, Geometrical product specifications (GPS) Dimensional measuring equipment: Micrometers for external measurements Design and metrological characteristicsISO 4287:1997
22、, Geometrical Product Specification (GPS) Surface texture: Profile methodTerms, definitions and surface texture parametersISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories.3 Terms and definitionsFor the purposes of this document, the following terms
23、and definitions apply.3.1rolling contactcontact between rolling elementsNOTE Under pure rolling contact conditions, the relative velocity at the point of contact is zero. The relative velocity between real rolling elements is not, however, zero in most cases.3.2surface failureflaking of test specime
24、n surface3.3rolling contact fatigueformation of surface failure due to cyclic rolling contact stress well below the stress when surface failure occurs under monotonic loading3.4rolling contact fatigue testtest where repeated rolling contact stress is applied to a test specimen, and the number of cyc
25、les to surface failure is measuredINTERNATIONAL STANDARD ISO 14628:2012(E) ISO 2012 All rights reserved 1BS ISO 14628:2012ISO 14628:2012(E)3.5stepwise loadingloading method in which load is increased stepwise at regular intervals until the final failure of the test specimen3.6contact trackcircular t
26、rail formed on a test specimen by repeated rolling contact of balls3.7mean effective loadconstant load equivalent to stepwise loading3.8maximum Hertzian stressmaximum contact stress between two bodies using the elastic stress analyzing theory by Hertz3.9bearing-grade silicon nitridesilicon nitride c
27、eramics specially designed for rolling elements4 PrincipleThe life of flat plate under cyclic rolling contact stress, which is applied by balls rotating unidirectionally thereon, is determined by measuring the number of stress cycles to the final surface failure of the plate.5 Testing machine5.1 Str
28、ucture of testing machineA testing machine shall be so constructed that rolling contact stress can be applied to the surface of a flat plate test specimen by balls thereon equally spaced with a retainer (see Figure 1). The balls shall be rolling in a circle with the rotation of the shaft washer of a
29、 90 contact angle thrust ball bearing of a specified bore diameter. The shaft washer shall be rotated unidirectionally.The testing machine is shown schematically in Figure 2. Load is applied by dead weights at the end of loading arm.The testing machine shall be equipped with an automatic shutoff wit
30、h a device detecting the surface failure, an apparatus capable of obtaining the number of rotations until the stop of testing, and a mechanism where its automatic reactivation is prevented when the testing machine is stopped for reasons of power failure or others.NOTE 1 The shaft washer should be ch
31、osen on the basis of diameters of the ball and main shaft of the testing machine.NOTE 2 The dimensions of the retainer depend on those of the shaft washer, ball diameter and number of balls.2 ISO 2012 All rights reservedBS ISO 14628:2012ISO 14628:2012(E)AAOSection A-O-A1D2345Key1 ball of diameter D2
32、 test specimen3 main shaft of a testing machine4 shaft washer of a 90 contact angle thrust bearing5 retainerFigure 1 Balls-on-flat configurations ISO 2012 All rights reserved 3BS ISO 14628:2012ISO 14628:2012(E)51234Key1 oil bath (balls-on-flat configurations are inside)2 ball for pivot point to sust
33、ain oil bath3 loading lever4 dead weight5 motorFigure 2 Schematic of testing machine5.2 Loading precisionThe fluctuation of the test load shall be within 1 % of the chosen value.NOTE The test load can be applied with a dead weight with accuracy thereof. Usually the load by dead weight(s) is increase
34、d with a lever by a specific factor.6 Test specimens6.1 Test specimen geometryThe test specimen shall be a flat plate. The parallelism tolerance on opposite surfaces of the plate is 0,015 mm. The use of test specimens having twisting or warpage, which may lead to oscillation of the testing apparatus
35、, is not permitted. The test specimen shall have enough margin outside a contact track to be fixed, as well as to 4 ISO 2012 All rights reservedBS ISO 14628:2012ISO 14628:2012(E)prevent the effect of the edge of the test specimen on the stress distribution around the point of contact, which may caus
36、e chipping of material.6.2 Fixation of test specimenThe test specimen shall be fixed on the bottom of an oil bath to be immobilized and to prevent oscillation.Special care should be paid to the surface finish and flatness of the bottom of the oil bath to fix the test specimen firmly thereon.6.3 Spec
37、imen thicknessThe specimen shall have enough thickness to prevent flexural oscillation of a plate. The thickness should be measured with a micrometer such as that described in ISO 3611 or alternative-dimension measuring instruments with a resolution of 0,002 mm or finer. If the specimen is measured
38、before the test, measure the thickness at around the central part to avoid unnecessary contact to a prospective contact track.6.4 Surface finishThe test specimen shall have a ground and polished surface. The roughness shall be 0,1 m Ra or smaller, as defined in ISO 4287. Subsurface damage during gri
39、nding shall be removed by subsequent polishing to eliminate the effect thereof on the test result.The skewness Rsk, as defined in ISO 4287, of the test specimen should also be measured.NOTE When the Rsk exhibits a large positive value, it implies that the measured surface has more convex area than c
40、oncave. The Rsk of a large positive value is not recommended for RCF testing because the test result may be affected by the surface integrity of a test specimen6.5 Number of test specimensThe number of test specimens shall be based on the agreement between the tester and the requester. If a threshol
41、d value for a pass/fail test is set, at least five test specimens should be prepared.7 Test method7.1 BallsBalls made of bearing-grade silicon nitride should be used for testing materials for bearing applications. The ball grade of balls should be G5 or G3, as defined in ISO 3290-2. If the purpose o
42、f the test is a pass/fail test for material qualification of rolling elements, bearing balls made of steel as defined in ISO 3290-1 may also be used.Balls shall be in a retainer to keep a fixed spacing.The ball diameter and number of balls should be agreed between a tester and a requester.NOTE Three
43、 or six balls are commonly used in the balls-on-flat configuration.7.2 Loading methodThe test load shall be applied under the stepwise loading condition where the load is increased stepwise at regular intervals until a final failure as shown schematically in Figure 3. The starting load of the loadin
44、g step and the loading interval should be agreed between a tester and a requester.NOTE 1 Some sorts of silicon nitride ceramics may exhibit a sensitivity to loading history. An excessively low starting load may lead to overestimating of rolling contact fatigue performance.NOTE 2 If the objective of
45、the test is the relative comparison with existing data of tests under constant loading, the test may be conducted under constant load as an alternative. ISO 2012 All rights reserved 5BS ISO 14628:2012ISO 14628:2012(E)0YX123KeyX number of revolutionsY load (kN)1 starting load2 regular interval of loa
46、ding3 final failure of a test specimenFigure 3 Stepwise loading7.3 LubricationThe test specimen and balls shall be immersed in lubricating oil during a test.The kinematic viscosity of oil should be chosen to maintain the contact under partial or complete elastohydrodynamic lubrication.NOTE To mainta
47、in the contact under partial or complete elastohydrodynamic lubrication, a paraffinic oil of higher kinematic viscosity, such as 68 mm2/s, should be chosen.7.4 Detection of surface failureThe surface failure of a test specimen may be detected by the increase in vibrational acceleration of balls. An
48、accelerometer should be mounted on a component where the vibration is mechanically amplified, such as the loading end of a loading lever. (See Figure 2.) If the acceleration exceeds a set threshold, the testing machine shall be automatically stopped.NOTE To avoid automatic shutoff by noise, the set
49、threshold may range from 2 to 3 times of the signal level for vibrational acceleration immediately after the start of testing at each loading step.6 ISO 2012 All rights reservedBS ISO 14628:2012ISO 14628:2012(E)8 Treatment of test result8.1 Mean effective loadCalculate the mean effective load Pmaccording to the following equation from loading conditions and number of rotations at each loading step until the stop of testing.PPNNkpkkkkkkpm=111(1)wherePkis the load per ball at k th loading step (N
