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UDC 669.14 - 423 : 620.178.3
IS0
FOR STA N DARD IZ AT1 ON
I NT ERN AT I ON A L O RG A N I2 AT1 ON
IS0 RECO M M EN DATI ON
R 1143
ROTATING BAR BENDING FATIGUE TESTING
1st EDITION
November 1969
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 1143, Rotating bar bending fatigue testing, was drawn up by Technical Committee
ISO/TC 17, Steel, the Secretariat of which is held by the British Standards Institution (BSI).
Work on this question led to the adoption of a Draft IS0 Recommendation.
In June 1968, this Draft IS0 Recommendation (No. 1350) was circulated to all the IS0 Member Bodies for
enquiry. It was approved, subject to a few modifications of an editorial nature, by the following Member Bodies :
Australia Italy Spain
Brazil Japan Sweden
Canada Korea, Rep. of Switzerland
Czechoslovakia Netherlands Thailand
Denmark
Norway Turkey
Finland Peru U.A.R.
Germany Poland United Kingdom
Hungary Portugal U.S.A.
India Romania U.S.S.R.
Israel South Africa, Rep. of
Two Member Bodies opposed the approval of the Draft :
Belgium
France
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council, which decided,
in November 1969, to accept it as an IS0 RECOMMENDATION.
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-3- ISO/R 1143-1969 (E)
IS0 Recommendation Fi 1143 November 1969
ROTATING BAR BENDING FATIGUE TESTING
1. SCOPE
This IS0 Recommendation gives the conditions for carrying out rotating bar bending fatigue tests on test
pieces having a nominal diameter between 5 mm (0.2 in) and 12.5 mm (0.5 in) without deliberately introduced
stress concentrations. The tests are carried out at room temperature, in air, the test piece being rotated.
Results of fatigue tests may be affected by atmospheric conditions and where controlled conditions are required,
clause 2.1 of IS0 Recommendation R 554, Standard atmospheres for conditioning andior testing - Standard
reference atmosphere - Specifications, applies.
2. OBJECT OF TEST
Tests are made to determine fatigue properties such as the S/N curve described in IS0 Recommendation R 373,
General principles of fatigue testing of metals.
3. PRINCIPLE OF TEST
Nominally identical test pieces are used, each being rotated and subjected to a bending moment. The forces
giving rise to the bending moment do not rotate. The test piece may be mounted as a cantilever, with single-
point or two-point loading, or as a beam, with four-point loading. The test is continued until the test piece
fails or until a pre-determined number of stress cycles has been exceeded. (See section 10.)
NOTE. - For definitions of failure see IS0 Recommendation R 373.
4. SYMBOLS AND DEFINITIONS
In this IS0 Recommendation the following symbols are used :
Symbols Definitions
The diameter of the gripped or loaded end of the test
piece.
The diameter of the test piece where the stress is a maximum
Radius* at the ends of the test section which starts the
transition from the test diameter d.
Further symbols and definitions relating to fatigue testing are given in IS0 Recommendation R3
*
This radius need not be a true arc of a circle over the whole of the length between the end of the test section and the start of
the enlarged ends for the test pieces shown in Figures 1, 4 and 5.
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ISO/R 1143-1969 (E)
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5. SHAPE AND SIZE OF TEST PIECE
5.1 Forms of test section
The test section may be
cylindrical, with tangentially blending fillets at one or both ends (see Figures 1,4 and 5);
(a)
(b) tapered (see Figure 2);
toroidal (see Figures 3,6 and 7).
(c)
In each case the test section should be of circular cross-section.
The form of test section may be dependent on the type of loading to be employed. While cylindrical or
toroidal test pieces may be loaded as beams, or as cantilevers with either single-point or two-point loading,
the tapered form of test piece is used only as a cantilever with single-point loading. Figures 1 to 7 show,
in schematic form, the bending moment and nominal stress diagrams for the various practical cases.
The volumes of material subjected to high stresses are not the same for different forms of test piece,
and they may not necessarily give identical results. The test in which the largest volume of material is
highly stressed is preferred.
Experience shows that, for threaded test pieces of certain material, a ratio of at least 3 : 1 between the
cross-sectional areas of the test portion and the threaded section is desirable.
NOTE. - In tests on certain materials a combination of high stress and high speed may cause excessive heating of the
test piece. This effect may be reduced by subjecting a smaller volume of the material to the specified stress. If the
test piece is cooled, the medium should be such that it does not react with the material of the test piece.
5.2 Diameter of test pieces
All the test pieces employed for a fatigue determination should have the same nominal diameter,
d 10.05 mm (0.002 in).
The nominai value of the diameter, d, should be between 5 mm (0.2 and 12.5 mm (0.5 in). The
recommended values of dare 6 mm (0.25 in), 7.5 mm (0.3 in), and
For the purpose of calculating the load to be applied to obtain the required stress, the actual minimum
diameter of each test piece should be measured to an accuracy of 0.01 mm (0.0005 in). Care should be
taken during the measurement of the test piece prior to testing to ensure that the surface is not damaged.
On cylindrical test pieces subject to constant bending moment (see Figures 4 and 5) the parallel test
section should be parallel within 0.025 mm (0.001 in). For other forms of Cylindrical test pieces (see
Figure 1) the parallel test section should be parallel within 0.05 mm (0.002 in). The transition fillets at
the ends of the test section should have a radius not less than 3d. For toroidal test pieces, the section
formed by the continuous radius should have a radius not less than 5d.
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ISO/R 1143-1969 (E)
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6. PREPARATION OF TEST PIECE
6.1 Method of machining
It is necessary to ensure than any cutting or machining operation required, either to rough the test
piece out from a blank or to machine it to size, does not alter the metallurgical structure or properties
of the test piece. All cuts taken in machining should be such as to minimize work-hardening of the
surface of the test piece. Grinding may be used particularly in finishing to size test pieces of the harder
steels, but an adequate supply of coolant should be ensured so as to avoid undue heating of the surface.
(See clause 4.2 of IS0 Recommendation R 373.)
Throughout any machining or grinding procedures, the tool or cutter sharpness and setting, the conditions
of the wheel and the grinding machine and speeds and feeds, should conform with good workshop
practice for the material commensurate with the requirements of clauses 6.2, 6.3 and 6.4.
6.2 Turning
It is recommended that the following procedures should be adopted :
6.2.1 In rough turning the test piece from a diameter x + 5 mm (x + 0.2 in) (x will generally be the
diameter, d, plus a suitable allowance for surface finishing) to x + 0.5 mm (X + 0.02 in), a succession
of cuts of decreasing depth should be made, the recommended depths of cuts being as follows :
1.25 mm (0.05 in)
0.75 mm (0.03 in)
0.25 mm (0.01 in)
6.2.2 From a diameter of x + 0.5 mm (x + 0.02 in) to x, a further succession of cuts of decreasing depth
should be made, the recommended depths of these cuts being as follows :
0.1 25 mm (0.005 in)
0.075 mm (0.003 in)
0.05 mm (0.002 in)
For these finishing cuts, a feed not exceeding 0.06 mm (0.0025 in) per revolution should be used.
6.3 Grinding
For test pieces in
...