Tiêu chuẩn iso 07905 1 1995 scan

INTERNATIONAL STANDARD IS0 7905 l First edition 1995 02 01 Plain bearings Bearing fatigue Part 1 Plain bearings in test rigs and in applications under conditions of hydrodynamic lubrication Paliers li[.]

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INTERNATIONAL STANDARD

IS0

7905-l

First edition 1995-02-01

Part 1:

Plain bearings in test rigs and in applications under conditions of hydrodynamic lubrication

Paliers lisses - Fatigue des paliers - Partie 1: Paliers dans /es machines d’essai et dans /es applications en lubrification hydrodynamique

Reference number IS0 7905-I :1995(E)

Copyright International Organization for Standardization

Provided by IHS under license with ISO

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Foreword

and non-governmental, in liaison with ISO, also take part in the work IS0

(IEC) on all matters of electrotechnical standardization

circulated to the member bodies for voting Publication as an International

Standard requires approval by at least 75 % of the member bodies casting

a vote

their properties, characteristics, test methods and testing conditions

bearings - Bearing fatigue:

- Part 1: Plain bearings in test rigs and in applications under conditions

of hydrodynamic lubrication

- Part 2: Test with a cylindrical specimen of a metallic bearing material

- Part 3: Test on plain strips of a metallic multilayer bearing material

terial

Annex A forms an integral part of this part of IS0 7905 Annex B is for

information only

0 IS0 1995

or utilized in any form or by any means, electronic or mechanical, including photocopying and

microfilm, without permission in writing from the publisher

International Organization for Standardization

Case Postale 56 l CH-1211 Geneve 20 l Switzerland

Printed in Switzerland

ii

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`,`,`,,,,`,,,`,,``,``,```,-`-`,,`,,`,`,,` -INTERNATIONAL STANDARD CJ IS0 IS0 7905-1:1995(E)

Plain bearings - Bearing fatigue -

Part 1:

Plain bearings in test rigs and in applications under

conditions of hydrodynamic lubrication

1 Scope

This part of IS0 7905 describes a method of improv-

ing test result comparability by evaluating the stresses

annex A) A similar evaluation is required in practical

pressure build-up in the hydrodynamic film, it is es-

sential to fully state the conditions of operation and

sional and running characteristics, the inclusion of the

following adequately defines the fatigue system:

a)

b)

cl

bearing oil film thickness as a function of time and

location to ensure no excessive local overheating

or shearing as a result of mixed lubrication when

running in;

axially with time under dynamic loading;

pecially the maximum alternating stress

mixed lubrication, wear, dirt, tribochemical reactions

cating the fatigue problem This part of IS0 7905 is

therefore restricted to fatigue under full hydrodynamic

separation of the bearing surfaces by a lubricant film

This part of IS0 7905 applies to oil-lubricated plain

cylindrical bearings, in test rigs and application running

in conditions of full hydrodynamic lubrication It com-

bearings

NOTE 1 The number of practical applicatrons with differ-

bearing test rigs If the conditions of lubrication employed

on these test rigs are not defined in detail, test results from different rigs are generally neither comparable nor applicable

in practice Different test rigs may yield inconsistent ranking between equal materials

through reference in this text, constitute provisions

of this part of IS0 7905 At the time of publication, the editions indicated were valid All standards are subject

to revision, and parties to agreements based on this

possibility of applying the most recent editions of the

Standards

their values and general rules for specifying require- men ts

bearings - Part 1: Calculation procedure

1) To be published

1

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bearings - Part 2: Functions used in the calculation

procedure

ameters

In this part of IS0 7905 the objective of testing with

plain bearing test rigs, operating in conditions of full

load-carrying capacity e.g the fatigue indurance limit

of the bearing layer material in terms of amplitude of

stress and number of cycles This may be presented

as a a,,-N curve (endurance limit stress plotted against

number of cycles), or as the endurance limit stress for

reached when cracks appear in the bearing surface

full hydrodynamic lubrication is a necessary simplifi-

cation of the fatigue problem This implies that the

essential running-in of the bearing under test shall be

stress which may cause surface microcracks

NOTE 2 It should be noted that fatigue testing of bearing

materials may be conducted also by utilizing the more clas-

sic methods of testing See parts 2 to 4 of IS0 7905

4.1 Test rigs

In order to define the operating and lubricating con-

ditions, the test rig shall have the following charac-

teristics:

b) easy dismantling, preferably with an in situ bear-

ing inspection capability;

shaft deflection;

film pressure development;

tice

4.2 Test methods

The test methods shall have the following characteristics:

a)

b)

cl

d)

e)

5

niques for oil film thickness, lubricant temperature, pressure distribution and crack disintegration debris; such techniques for the latter aspect in-

wear or X-ray fluorescent analysis of intermittently

dynamic conditions (e.g the verification of effec-

behaviour);

clear distinction between mixed lubrication during running-in and full hydrodynamic lubrication during fatigue testing;

the stress can traverse the bearing as uniformly

as possible (rotating load) in order to detect irregularities in the bearing material;

ible hydrodynamic conditions (i.e a rotating load

tribution equal to a static load)

Test methods

In order to assure the compatibility of test results from different test rigs and their putting into practice,

shall be detailed, starting with test conditions, bearing

fatigue testing

5.1 Characteristic conditions

This is designed in order to avoid excessive temperature and frictional shear stress due to heavy asperity contact The progress of running in may be monitored

greater than (& +I&), where h, equals the mini-

IS0 7902, and Rz,b and R,,, are the height of the profile irregularities in ten points of the bearing and counter-

2

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`,`,`,,,,`,,,`,,``,``,```,-`-`,,`,,`,`,,` -0 IS `,`,`,,,,`,,,`,,``,``,```,-`-`,,`,,`,`,,` -0 IS0 7905-1:1995(E)

ishing during running-in will allow the value of kc to

be reduced but during fatigue testing it should not be

less than the initial value of R,,, The running-in pro-

duration of zero electrical contact resistance

bearing is electrically isolated from the test rig The elec-

trical scheme should provide for monitoring a 10 mV differ-

ence of potential between the shaft and bearing at a supply

point with 100 R internal resistance, which drops to

0.01 mV during asperity contact Load increments should

be adjusted so as to minimise the duration of asperity con-

tact

assembly

ancies may include housing distortion, shaft deflection

plain bearing surface

as a function of time

These form the basis of evaluation of peripheral/axial

namic stresses in the individual bearing layers in order

durance limit

dynamic film development and stress by gauges may be

carried out by evaporated thin metal film techniques The

measurement should be conducted beforehand under the

same conditions, but not during the fatigue testing pro-

cedure

effect the first fatigue damage

cracks (greater than 5 mm in length) or breakout of bearing lining material Normally u&V curve testing is

quoted at a specified number of cycles; e.g 3 x 106,

10 x lo”, 25 x 1 O6 or 50 x 1 06 A specimen without failure during fatigue testing to a specified endurance should be identified in the report Due to the scatter

of test results normally experienced and the statistical nature of the fatigue limit, it is recommended that the results are evaluated on the basis of statistical methods

5.2 Characteristic information

If the evaluation of the test results up to the endurance limit stress at fixed temperatures, controlled to

f 2 “C, is not carried out by the investigator himself then it will be necessary to fully report the information

ing test (e.g diffusion or a similar process) this should

allurgical report) The information is subdivided in such

depending on the degree of detailed evaluation of the end result - the endurance limit stresses

5.2.1 Test rig description

load principles, design limits, lubricant supply includ-

and arrangements

bearing, including different layer thicknesses; housing

and Poisson’s ratio

3

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5.2.4 Specific details of test load

during running-in and fatigue testing; the duration of

the test

supply holes (or grooves); flowrate

This should comprise the film temperature in bulk and

perature near the damage zone as close as possible

development

All of the above descriptions are necessary for evalu-

test If the hydrodynamic status is evaluated, then the

together with data on bearing material temperature

thickness related to roughness data during running-in

and fatigue testing

This should contain lubricant film pressure distribution

and variation with time and location relative to the

bearing surface, in such detail that pressure gradients

are indicated with sufficient precision

test

This should include the distribution with time and lo-

cation relative to the bearing surface in order to de-

mean and alternating stress at the endurance limit

IS0 7905) by means of the Haigh diagram in which stress amplitude is plotted against mean stress

position and extent of cracking; absence or presence

of wear or scoring; together with any findings result-

shall be concluded that the oil film thickness is inad- equate and the conditions of the test shall be changed

in order to avoid wear

materials Evaluation of the stress relevant to fatigue is simpler

if the hydrodynamic conditions are easily reproduced

which is most exactly defined by calculation If some

and bearing width ratios is possible (see annex A)

In order to cause failure by fatigue in high strength material without wear or seizure it will be necessary

lubricant viscosity and very low surface roughness) to

vent metallic contact It may also be possible to per-

unidirectional pure sinusoidal load

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Annex A

(normative)

Evaluation of stress

From practical experience and research it is evident

that fatigue starts with axial cracks in cylindrical

bearings due to alternating tangential stresses Whilst

it is probable that the stresses will vary in the axial as

well as the circumferential plane, in the absence of a

of the bearing, i.e a two-dimensional solution

Under dynamic load which varies not only with time,

but also with position on the surface, the different

tangential stresses within the bearing layers In order

to evaluate the stress distribution resulting from mo-

cluding the bearing housing Loading is by momentary

by outer diameter reaction pressures

The ring model may be treated as different material

stresses can be evaluated by several solutions These

are Airy’s stress function [equations (1) or (21-J and

analytical methods [equations (31, (41, (51, (6) and (7)]

analysis methods such as finite and boundary element

an adequate subdivision of the bearing circumference

and load cycle to evaluate the mean and alternating

stresses in sufficient circumferential locations Their

It therefore becomes apparent that fatigue stress cal-

an invariable film pressure distribution rotates round

location to obtain mean and alternating stress ampli-

tudes

1 Peak oil film pressure

2 Direction of load

3 Ring 1 (housing and steel back) E,, Y,

4 Ring 2 (liningjinterlayer) E2, v2

5 Ring 3 (overlay) ES, v3

Symbol Definition Unit

d = 23

housing, d;l = d,/d

valid for figureA.3, d;,, = d,/d = I,45

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Symbol Definition Unil

E’ = W%so

steel back

thickness

ing dimension, d,jd not equal to 1,45 1) (see figure AS)

thickness, $ = s-Jd not equal to 0,004 7 1) (see figureA.6)

profile irregularities in ten points)

steel back)

ing back and lining

thickness negligible)

s; = s2/d

valid for figureA.3, s;,~ = s,/d = 0,004 7

back Poisson’s ratio, valid for figure A.3 - (all linings, v2 = 0,341

Poisson’s ratio, valid for figure A.4 - (all overlays, v3 = 0,331

Symbol Definition Unit

1) There are different factors for lining and overlay for both DA and R’

Subscripts:

R’ stress ratio

s2 liningjinterlayer

s3 overlay

be calculated for rotating load in dimensionless terms

of stress cr* = o/p, i.e related to specific load p as a

so = p x *2

%f x 63

bearing diameter/width ratio d/b for the bearing lining

the lining thickness parameters; and for bearin

Q lining

Poisson’s ratios for both layers are fixed as given in the list of symbols (see A.2)

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For bearing lining material with Young’s modulus E2

not equal to I!& the values of stress amplitude CT;\ are

obtained by:

For lining:

a;\,2 =

c&c(O,852 + 0,143 8 x E’)

( 5 )

(A.11 For overlay:

IT;;\.3 = ui,3,0 (1,004 x E’) - oro88 8 5 04.2)

Figures A.3 and A.4 include equations for calculating

the stress ratio R’ = Umin/a,,, (see figureA.2) From

this ratio, the mean stress a can be obtained from the

following equation:

1 +R’

a=u*x-

stress) The stress ratio R’ is nearly independent from

ever, it has to be corrected for other lining material

with modulus not equal to E2,0 = 63 x lo3 MPa:

For lining:

R; = - 4,410 x E’(- ‘*“‘) + 0,023 9 x

For overlay:

R; = - 3,200 x E’( - Om4 ‘1 + 0,020 2 x

(A.51

KH and K2 in order to transfer the results from figures

lining and Overlay for both “A and R’

started after 1,8 x lo6 load cycles The bearing data were:

Relative clearance (averaged value) Housing outer diameter 0& = 170 mm Lining thickness s2 = 0,5 mm Effective dynamic viscosity at 100 “C Young’s modulus of lining

Rotating speed

(I- = l/l 000 d;, = 2,77 s; = 0,008 1

E2 = 29,5 x lo3 MPa

o = 314.16 s-’

From figure A.3 for So = 4.68 and d/b = 2,5 find the dimensionless alternating stress in the lining:

&,o = or95

equation (A.11 with E’ = 29,5/63 = 0,468:

ai, = 0,95 x (0,852 + 0,143 8 x 0,468) x

x 2 5( - 0,103 4 + 0,101 0 x 0,468)

= 0,95 x (0,852 + 0,067 3) x 2,5-“,056

= 0.95 x 0,919 3 x 0,949 9 = 0.83

7

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For stress ratio R', calculate from equation (A.41 cor-

rection for Young’s modulus:

R’ = - 4,410 x 0,468- ‘*“’ + 0,023 9 x 4,68 x

x 0,468- 28542

=- 4,410 x 2,323 + 0,023 9 x 4,68 x 6,881

=- lo,24 + 0,77 = - 9,47

di/di c = 2,77/l ,45 = 1,91 and extrapolating figureA

for lining gives:

K H.A.2 = 1 t3’

and

K ,.,R*,2 = o,go

.$/s;,~ = 0,008 l/O,004 7 = 1,72 from figureA gives:

0 N’

* d

b

3

5

K 2,A,2 = o,gg and

K 2,R*,2 = 0%

With specific load 14,7 MPa and the above calculated corrections the actual alternating stress amplitude is:

‘T A = 0; X P X KH,,,, X K~,A,P = 0,83 x 14,7 x

x 1,30 x 0.99 = 15,7 MPa

The stress ratio is:

= - 9,47 x 0,90 x 0,96 = - 8,2

Finally the actual mean stress from equation (A.31 is:

cr= 15.7 x -L -72 = - 12,3 MPa

92

4 3.8 3,6 3,4

32

3 2,8 2.6 2.4

2.2

2

1.8

1.6 1.4 1.2

1

03

086

OA

02

n

0,’

, 0,

n

” 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Figure A.3 - Lininglinterlayer (&, = 63 x 1 O3 MPa; v2 = 0,34; s2,0 = 0,004 7; di,, = 4,451

Tiêu đề	Bearing fatigue - Part 1: Plain bearings in test rigs and in applications under conditions of hydrodynamic lubrication
Trường học	International Organization for Standardization
Chuyên ngành	Plain bearings
Thể loại	International standard
Năm xuất bản	1995
Thành phố	Geneve

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