1、December 2015 English price group 21No 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).ICS 21.100.10!%Jw?“2398428www.din.d
2、eDIN ISO 7146-1Plain bearings Appearance and characterization of damage to metallic hydrodynamic bearings Part 1: General (ISO 7146-1:2008),English translation of DIN ISO 7146-1:2015-12Gleitlager Erscheinungsbild und Charakterisierung von Schden an lgeschmierten metallischen Gleitlagern Teil 1: Allg
3、emeines (ISO 7146-1:2008),Englische bersetzung von DIN ISO 7146-1:2015-12Paliers lisses Aspect et caractrisation de lendommagement des paliers mtalliques couche lubrifiante fluide Partie 1: Gnralits (ISO 7146-1:2008),Traduction anglaise de DIN ISO 7146-1:2015-12www.beuth.deDocument comprises pagesDT
4、ranslation by DIN-Sprachendienst.In case of doubt, the German-language original shall be considered authoritative.5612.15A comma is used as the decimal marker. Contents Page National foreword .3 National Annex NA (informative) Bibliography 4 Introduction .5 1 Scope 6 2 Normative references 6 3 Terms
5、 and definitions .6 4 Descriptions, causes, and features of damage 7 4.1 Damage .7 4.2 Damage causes 7 4.3 Damage appearances 7 4.4 Damage characterization 8 4.5 Relationship between damage appearance and damage characterizations .8 5 Guidelines for damage analysis .10 5.1 General 11 5.2 Step 1 11 5
6、.3 Step 2 11 5.4 Step 3 11 5.5 Step 4 11 5.6 Step 5 11 6 Damage to the bearing surface damage characteristics, typical damage appearances and possible damage causes .12 6.1 General 12 6.2 Static overload .12 6.3 Dynamic overload 13 6.4 Wear by friction 20 6.5 Overheating 23 6.6 Insufficient lubricat
7、ion (starvation) 25 6.7 Contamination 30 6.8 Cavitation erosion 41 6.9 Electro-erosion .43 6.10 Hydrogen diffusion 44 6.11 Bond failure 46 7 Damage to the bearing back .47 7.1 General 47 7.2 Dynamic overload on the bearing back .47 7.3 Wear by friction on the bearing back .49 7.4 Contamination with
8、particles on the bearing back 51 8 Special position of damage appearances .52 Annex A (informative) Example of use of Table 1 55 2DIN ISO 7146-1:2015-12 National foreword This document (ISO 7146-1:2008) has been prepared by Technical Committee ISO/TC 123 “Plain bearings” (Secretariat: JISC, Japan),
9、Subcommittee SC 2 “Materials and lubricants, their properties, characteristics, test methods and testing conditions”. The responsible German body involved in its preparation was DIN-Normenausschuss Wlz- und Gleitlager (DIN Standards Committee Rolling Bearings and Plain Bearings), Working Committee N
10、A 118-02-02 AA Werkstoffe, Schmierung, Prfung. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. DIN shall not be held responsible for identifying any or all such patent rights. The DIN Standards corresponding to the International S
11、tandards referred to in this document are as follows: ISO 4378-1 DIN ISO 4378-1 ISO 4378-2 DIN ISO 4378-2 ISO 4378-3 DIN ISO 4378-3 ISO 4378-4 DIN ISO 4378-4 ISO 7146-2 DIN ISO 7146-2 3DIN ISO 7146-1:2015-12 National Annex NA (informative) Bibliography DIN ISO 4378-1, Plain bearings Terms, definitio
12、ns, classification and symbols Part 1: Design, bearing materials and their properties DIN ISO 4378-2, Plain bearings Terms, definitions, classification and symbols Part 2: Friction and wear DIN ISO 4378-3, Plain bearings Terms, definitions, classification and symbols Part 3: Lubrication DIN ISO 4378
13、-4, Plain bearings Terms, definitions, classification and symbols Part 4: Basic symbols DIN ISO 7146-2, Plain bearings Appearance and characterization of damage to metallic hydrodynamic bearings Part 2: Cavitation erosion and its countermeasures 4DIN ISO 7146-1:2015-12 Introduction In practice, dama
14、ge to a bearing may often be the result of several mechanisms operating simultaneously. It is the complex combination of design, manufacture, assembly, operation, maintenance, and possible reconditioning which often causes difficulty in establishing the primary cause of damage. In the event of exten
15、sive damage or destruction of the bearing, the evidence is likely to be lost, and it will then be impossible to identify how the damage came about. In all cases, knowledge of the actual operating conditions of the assembly and the maintenance history is of the utmost importance. The classification o
16、f bearing damage established in this part of ISO 7146 is based primarily upon the features visible on the running surfaces and elsewhere, and consideration of each aspect is required for reliable determination of the cause of bearing damage. Since more than one process may cause similar effects on t
17、he running surface, a description of appearance alone is occasionally inadequate in determining the cause of damage. Thus Clause 4 is subdivided into several subclauses including damage appearance and damage characteristics. For the procedure of damage analysis, Clause 5 may give a helpful guide. In
18、 Clauses 6 and 7, examples of all damage characteristics with typically associated damage appearance are given. 5DIN ISO 7146-1:2015-12 Plain bearings Appearance and characterization of damage to metallic hydrodynamic bearings Part 1: General 1 Scope This part of ISO 7146 defines, describes and clas
19、sifies the characteristics of damage occurring in service to hydrodynamically lubricated metallic plain bearings and journals. It assists in the understanding of the various characteristic forms of damage which may occur. Consideration is restricted to damage characteristics which have a well-define
20、d appearance and which can be attributed to particular damage causes with a high degree of certainty. Various appearances are illustrated with photographs and diagrams. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated referen
21、ces, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 4378-1, Plain bearings Terms, definitions, classification and symbols Part 1: Design, bearing materials and their properties ISO 4378-2, Plain bearings T
22、erms, definitions, classification and symbols Part 2: Friction and wear ISO 4378-3, Plain bearings Terms, definitions, classification and symbols Part 3: Lubrication ISO 4378-4, Plain bearings Terms, definitions, classification and symbols Part 4: Basic symbols ISO 7146-2, Plain bearings Appearance
23、and characterization of damage to metallic hydrodynamic bearings Part 2: Cavitation erosion and its countermeasures 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 4378-1, ISO 4378-2, ISO 4378-3, ISO 4378-4 and the following apply. 3.1 damage to plai
24、n bearings bearing damage all changes in appearance occurring on the bearing surface and/or on the bearing back during operation that adversely affect the performance of the bearing 6DIN ISO 7146-1:2015-12 4 Descriptions, causes, and features of damage 4.1 Damage 4.1.1 General Damage to plain bearin
25、gs is a phenomenon that adversely changes their tribological function, usually accompanied with a change in appearance. The damage is initiated by the damage cause and develops to the end of service life. As long as no abnormal conditions occur, service life of the plain bearing relates to the servi
26、ce life of the machine. 4.1.2 Indicators of damage Typical indicators observed during machine operation are: continuously increasing service temperature, decline of lubricant pressure, noise, vibration, and bad smell. 4.2 Damage causes The cause is the practical event that initiates and leads to dam
27、age. The majority of damage causes will be found outside the bearing. 4.3 Damage appearances Damage appearance is a defined visible picture of the bearing surface and/or of the bearing back. Damage appearances are clearly different from each other. A plain bearing failure can show various damage app
28、earances. Usually damage appearances are directly associated with damage characteristics, but not directly with the damage cause (for exceptions, see 6.8 and 6.9). List of damage appearances: a) depositions; b) creep deformation; c) deformation due to temperature cycles; d) thermal cracks; e) fatigu
29、e cracks; f) material relief (loss of bond); g) frictional corrosion; h) melting out, seizure; i) polishing, scoring; j) traces of mixed lubrication, worn material; k) blue, black colour; l) corrosion, fluid erosion; m) embedded particles, particle-migration tracks, formation of wire wool; n) electr
30、ic arc craters; o) cavitation erosion appearance: worn-out material. 7DIN ISO 7146-1:2015-12 4.4 Damage characterization 4.4.1 General. A damage characterization is a description of what has happened based on a detected typical combination of damage appearances. Defined characteristics provide the b
31、asis for establishing the cause of damage. Damage characterizations are clearly different from each other, as specified in 4.4.2 to 4.4.11. 4.4.2 Static overload: material is loaded above compressive yield strength corresponding to actual operation temperature. 4.4.3 Dynamic overload: material is lo
32、aded above fatigue strength corresponding to actual operation temperature. Intensive dynamic load also favours damage by weakening the fit. 4.4.4 Wear by friction: wear by friction is confined to changes in microgeometry and to the loss of material as a result of interaction between journal and bear
33、ing. Movement between backing and housing also favours wear by friction. 4.4.5 Overheating: the heat balance in the lubricant, the bearing, the environment, and the cooling system as required at design stage is not realized resulting in a higher temperature than anticipated. The viscosity and, there
34、fore, the load capacity decrease with increasing temperature. This results again in temperature increase. The bearing, therefore, cannot operate stably if cooling cannot stop further temperature increase. 4.4.6 Insufficient lubrication (starvation): affecting the tribological system. 4.4.7 Contamina
35、tion of lubricant with foreign particles or reaction products can result in damage to a bearing. Foreign particles embedded between bearing backing and housing also favour damage. 4.4.8 Cavitation erosion: decreased pressure in liquids leads to evaporation of liquids and formation of vapour bubbles,
36、 which, when liquid pressure increases, implode, generating locally very high pressure, and cause erosion on sliding surfaces. 4.4.9 Electroerosion: a potential difference between journal and bearing can lead to an electric arc with locally high current flow which damages journal and bearing surface
37、. 4.4.10 Hydrogen diffusion: hydrogen may be incorporated in the steel backing or in an electroplated layer of the bearing. If hydrogen diffusion is blocked by a layer, blisters will occur. 4.4.11 Bond failure: delamination between lining and backing or between layers. A metallographic examination i
38、s required to distinguish from other damage characterizations. 4.5 Relationship between damage appearance and damage characterizations Damage characterization and damage appearance alter with the progress of damage from a primary to a secondary characteristic (see Figure 1). Different damage charact
39、erizations can correspond to the same damage appearance. One damage characterization can correspond to various damage appearances. Multiple damage characteristics can be found in one failure event. The damage characteristics provide the basis for analysing the cause (see Figure 2). Typical relations
40、hips are shown in Table 1 for damage to sliding surface and to bearing back. In most cases, Table 1 is the guideline for diagnosis of the final damage cause from the damage appearances via the damage characteristics. ?DIN ISO 7146-1:2015-12 ?8Figure 1 Damage appearances alter with the progress from
41、primary to secondary characteristics aDamage cause. bDamage characteristics. cDamage appearances. Figure 2 Damage characteristics provide the basis for analysing the cause ?DIN ISO 7146-1:2015-12 95 Guidelines for damage analysis Table 1 Interaction of damage appearances and damage characterizations
42、 Damage appearance Damage characterizations SubclauseDepositionsCreep deformation Deformationsdue totemperature cyclesThermalcracksFatigue cracksMaterialrelief(lossofbond) Frictionalcorrosion Meltingout,scoring Polishing,scoring Trace ofmixedlubrication,worn materialBlue,blackcolour Corrosion Fluid
43、erosion Embedded particles,particle-migration tracks,formationofwire woolElectricarc cratersCavitation erosion appearance:materialworn out Static overload 6.2 Dynamic overload a6.3 Dynamic overload b7.2 Wear by friction a6.4 Wear by friction b7.3 Overheating 6.5 Insufficient lubrication (starvation)
44、 6.6 Contamination (particles, chemicals) a6.7 Contamination (particles, chemicals) b7.4 Cavitation erosion 6.8 and ISO 7146-2 Electro-erosion 6.9 Hydrogen diffusion 6.10 Bond failure 6.11 aDamage to the sliding surface. bDamage to the bearing back. 10DIN ISO 7146-1:2015-12 5.1 General Analysis shou
45、ld be undertaken only by experts experienced in bearing metallurgy, bearing technology and bearing damage. Damage analyses based on photos alone are mostly unsuccessful. The following steps are a guideline for damage analysis. 5.2 Step 1 Establish service life. There is significant difference betwee
46、n damage after a short service life and damage after a long service life. With both cases similar damage appearances occur, but the cause is usually different. Typical causes of damage after short service life: faults in geometry or assembling, dirt, effect from a previous damage, modified service c
47、onditions since last start up. Typical cause of damage after long service life: modified service conditions. Typical cause of damage after very long service life: reduced dynamic material capability due to fatigue. 5.3 Step 2 Strict differentiation between damage characterization and damage appearan
48、ce is important. For a thorough analysis, all visible damage appearances shall be evaluated and combined in one or more damage characterizations, based on Table 1. 5.4 Step 3 Take into consideration the total system: bearing shaft lubricant housing. It is helpful to make a chemical analysis of a sam
49、ple from the bearing layer and to check its microstructure. If necessary, lubricant and filter content should be analysed. 5.5 Step 4 All information in connection with the period before the detected damage and the period during the damage should be brought together. 5.6 Step 5 Reviewing the initial list of damage characteristics together with the information from steps 3 and 4 usually leads to a reduction o
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