1、BRITISH STANDARD BS ISO 6281:2007 Plain bearings Testing under conditions of hydrodynamic and mixed lubrication in test rigs ICS 21.100.10 BS ISO 6281:2007 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2007 BSI 2007 ISBN 978 0 5
2、80 54574 0 National foreword This British Standard is the UK implementation of ISO 6281:2007. The UK participation in its preparation was entrusted to Technical Committee MCE/12, Plain bearings. A list of organizations represented on this committee can be obtained on request to its secretary. This p
3、ublication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. Date Comments Reference number ISO 6281
4、:2007(E)INTERNATIONAL STANDARD ISO 6281 First edition 2007-06-15 Plain bearings Testing under conditions of hydrodynamic and mixed lubrication in test rigs Paliers lisses Essai des paliers lisses dans les conditions de lubrification hydrodynamique et mixte dans des machines dessai pour paliers BS IS
5、O 6281:2007ii iii Contents Page Foreword iv 1 Scope . 1 2 Symbols . 1 3 Test objectives for bearing properties . 2 4 Test rigs . 3 5 Test procedures 6 6 Testing and test report. 8 Bibliography . 15 BS ISO 6281:2007iv Foreword ISO (the International Organization for Standardization) is a worldwide fe
6、deration 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 com
7、mittee. 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 accord
8、ance 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 require
9、s 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 6281 was prepared by Technical C
10、ommittee ISO/TC 123, Plain bearings, Subcommittee SC 2, Materials and lubricants, their properties, characteristics, test methods and testing conditions. This first edition of ISO 6281 cancels and replaces ISO/TR 6281:1990, of which it constitutes a technical revision. BS ISO 6281:2007 1 Plain beari
11、ngs Testing under conditions of hydrodynamic and mixed lubrication in test rigs 1 Scope This International Standard establishes guidelines for the testing of lubricated plain journal bearings in test rigs, running under conditions of hydrodynamic or mixed lubrication, during bearing and/or material
12、development. It deals with both static and dynamic loading in solid and multi-layer journal bearings. It is not applicable to the testing of dynamic characteristics of lubricant film in journal bearings applied in calculation of vibration and stability of turbo-rotors. Further details of test proced
13、ures will need to be established when carrying out testing based on these guidelines. 2 Symbols See Table 1. Table 1 Symbols Symbol Description Unit a Length of period s B Bearing width mm F Bearing load N F* Bearing load per unit bearing width N/mm f Coefficient of friction of journal bearing t Tim
14、e s U Sliding velocity m/s Direction of bearing load Angular velocity rad/s Dynamic viscosity of lubricant N s/m 2BS ISO 6281:20072 3 Test objectives for bearing properties The test objectives for plain journal bearing test rigs operating under conditions of hydrodynamic or mixed lubrication are to
15、obtain information, among others, on the following bearing properties, which can serve as critical variables when designing and applying the bearing (see ISO 4378): a) running-in ability; b) wear resistance; c) compatibility between bearing and journal materials (resistance to adhesion); d) embeddab
16、ility (foreign particles absorption); e) resistance to journal scoring and abrasion; f) conformability; g) deformability (compressive strength); h) resistance to erosion (cavitation erosion, fluid erosion, particle erosion); i) static load carrying capacity; j) dynamic load carrying capacity (fatigu
17、e strength); k) friction characteristics; l) lubricant flow rate characteristics; m) temperature increase characteristics. Of these bearing properties, the first group, a) to h), depends primarily on the mechanical and tribological properties of sliding materials under specified conditions. The seco
18、nd group, i) to m), depends primarily on hydrodynamic variables, and therefore also on viscosity as a function of temperature, pressure and shear rate, energy dissipation in the lubricant film (shear heating and heat dissipation), and elastic and thermal deformation of the bearing and journal, and h
19、ence change of lubricant film thickness (thermo-elastohydrodynamic lubrication). The determination of these bearing properties, or test objectives, requires lubrication conditions that can involve boundary, mixed or hydrodynamic lubrication the three modes of lubrication regime. In certain cases, a
20、repeated, time-dependent change between mixed and hydrodynamic lubrication can be required. NOTE Specific test methods may not yet exist for all of the above-mentioned bearing properties. Figure 1 depicts the typical relation between the dimensionless number, U/F*, and the coefficient, f, of frictio
21、n of the journal bearing, where , U and F* denote dynamic viscosity of the lubricant, sliding velocity and bearing load per unit bearing width (F* = F/B), respectively. It shows the three regimes of boundary, mixed and hydrodynamic lubrication and qualitatively indicates the dependence between these
22、 important parameters. BS ISO 6281:2007 3Key 1 boundary lubrication 2 mixed lubrication 3 hydrodynamic lubrication Figure 1 Three modes of lubrication regime 4 Test rigs 4.1 General recommendations It is often more practical and efficient to investigate the bearing in a test rig than in an actual ap
23、plication. The design of the bearing test rig should be such as to simulate as far as possible all the relevant characteristic parameters (geometric, dynamic, hydrodynamic, thermal, thermodynamic, etc.) of the actual application. In addition, the following is recommended for the test rig. a) Simple
24、mechanical construction. b) Simple dismantling and assembly procedures for the test objects; with well-defined positioning of the bearing and housing; preferably it should be possible to inspect the test bearing in situ. In addition, the test rig should be equipped with an emergency stop mechanism,
25、both for safety reasons and to allow the inspection of the sliding surface before the onset of catastrophic damage. c) Well-defined dimensions for the test bearing. d) High dimensional stability with little shaft deflection. The test rig should be as rigid as possible, with a high natural frequency.
26、 In special cases, however, it may be necessary to vary the dimensional stability or the shaft deflection in order to simulate the operating condition of the actual application. e) Appropriate lubricant supply condition. When the lubricant flow within the bearing clearance has to be simulated exactl
27、y, the circumferential and axial position of the lubricant supply in the test rig should be the same as in the actual application. f) Well-defined and experimentally verifiable lubrication conditions. g) The regime of laminar or turbulent flow should be the same in the test rig and in the actual app
28、lication. h) The rig should replicate as far as possible the temperature and stress range that can occur in practice. i) Appropriate measuring techniques or equipment should be employed. BS ISO 6281:20074 4.2 Generic types of test rig Generic types of test rig for plain journal bearings are shown in
29、 Figures 2 and 3. Figure 2 a) and b) depict the rotational motion of the journal, where a combination of both is also possible. In practice, many more patterns of journal motion other than rotation may occur, such as inclination, bending, axial, conical and their combinations. In addition, the beari
30、ng itself can rotate or oscillate or even move in space instead of, or together with, the journal, as with a crank-pin bearing. In any case, the relative motion of the journal to the bearing has to be known (measurable) exactly. However, constant rotational speed of journal and the parallel movement
31、 of journal to bearing are the simplest and most preferable for testing. Figure 3 shows patterns of the bearing load. In the case of statically loaded journal bearing Figure 3 a), the magnitude, F, and the direction, , of the bearing load are constant. In a special case of dynamically loaded bearing
32、, F is constant, but increases or decreases with time Figure 3 b). In the general case of dynamically loaded bearing Figure 3 c), both or at least one of F and change periodically, while the remaining variable can be constant. The periodic form of F (also ) is then arbitrary, such as sinusoidal with
33、 or without constant offset, curving steeply up and downwards, as, for example, in engine bearing loading. With regard to the loading of the test bearing, it is often more practical to load the test bearing directly supported by the journal Figure 4 a), than to load the test bearing indirectly throu
34、gh the journal Figure 4 b). For static loading, a dead weight system, with or without lever, or hydraulic or pneumatic actuation can be used. For dynamic loading, a rotating or vibrating mass system, with or without lever, an electromagnetic exciter, hydraulic actuation, etc., can be applied. Dynami
35、c loading by means of a mass fixed to the journal seems to be simple, but the amplitude of the bearing load is then determined primarily by the rotational speed of the journal. Therefore, it is not easy to change the load amplitude independently of the rotational speed. Furthermore, the magnitude an
36、d direction of the bearing load have to be precisely measured, and it is important to let the journal move freely inside the bearing clearance without hindrance from the loading mechanism. Besides such bearing test rigs operating under hydrodynamic or mixed lubrication, as described above, many othe
37、r kinds of test apparatus and test methods may be used to investigate the tribological or mechanical properties of bearing materials, including coefficient of friction, mechanical strength, hardness, elasticity, plasticity and bond strength. The study of the tribological properties of boundary films
38、 has also led to the development of other test apparatus and methods; these are, however, outside the scope of this International Standard (see ISO 4384-1, ISO 4384-2, ISO 4385, ISO 7148-1, ISO 7148-2, ISO 7905-2, ISO 7905-3 and ISO 7905-4). NOTE The testing of the resistance to corrosion of bearing
39、 materials by the lubricant is the subject of ISO 10129. a) Rotation b) Oscillation Figure 2 Rotational motion of journal BS ISO 6281:2007 5a) Static load b) Dynamic load (rotating load) c) Dynamic load (arbitrary pattern) Key a length of period F bearing load direction of bearing load t time angula
40、r velocity Figure 3 Examples of bearing load patterns BS ISO 6281:20076 a) Load on bearing b) Load on journal Key F bearing load angular velocity 1 test bearing 2 journal Figure 4 Two modes of load application 5 Test procedures The actual test procedure depends on the property to be determined. It i
41、s important to establish the test conditions in order to ensure that test results obtained on test rigs are applicable in practice and that results obtained on different test rigs are mutually compatible. In the following, guidelines or examples of test procedures for obtaining the bearing propertie
42、s according to Clause 3, a) to m), are described together with the evaluation of the results. Bearing properties a) to h) depend primarily on mechanical and tribological characteristics of the bearing material itself, and in some cases, may be determined qualitatively by proper material testing. How
43、ever, they can be evaluated quantitatively only by testing in bearing test rig. When stepwise increase or decrease of bearing load or severity of operating condition is prescribed, thermal equilibrium must be achieved in the test object at each step to assure reproducibility of the results. During t
44、he test, it is important to be aware of the eventual change of the test object itself, even under seemingly constant operating conditions, through wear, foreign particles embedding, diffusion, chemical reaction, lubricant degradation, etc. This should be verified and documented in the test report. a
45、) Running-in ability The change of surface topography, roughness, friction torque, wear rate 1)or wear intensity 2)of the bearing, or the temperature of the lubricant and/or bearing should be measured from the initial state of the sliding surfaces under the specified operating condition. From the ch
46、aracteristic change of these variables with time, the completion of running-in process can be detected. The shorter the time until running-in is completed, the higher the running-in ability. 1) Ratio of wear extent to the time interval during which it has developed. 2) Ratio of wear extent to the sp
47、ecified distance on which wear developed or to the volume of the work done. BS ISO 6281:2007 7 b) Wear resistance The severity of the operating condition of the bearing should be increased until wear occurs. Wear can be mechanical or mechano-chemical in nature. The former can be adhesive wear, seizu
48、re, scoring or scratching, abrasion, fatigue wear, spalling, cavitation wear, erosive wear or fretting wear. The latter can be oxidative wear, fretting corrosion or electro-erosive wear. The more severe the operating condition under which wear begins to occur and the smaller the wear rate and/or the
49、 wear intensity, the higher the wear resistance. c) Compatibility between bearing and journal material (resistance to adhesion) The frictional torque and/or the temperature of the lubricant and bearing should be measured during the stepwise increase in the severity of the operating condition (i.e. increase in inlet lubricant temperature, specific bearing load, sliding velocity), and the occurrence of adhesion should be detected. The more sever
