ASTM D7107-04

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Designation: D7107 – 04
Standard Test Method for
Creep Measurement of Self-Lubricating Bushings
This standard is issued under the fixed designation D7107; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
1.1 This test method determines the amount of creep exhib- 4.1 Self-lubricating bushings with low creep rates are used
ited by self-lubricating bushings exposed to a high load for an in hydropower turbines and other applications in which bush-
extended period of time. ing distortion could cause misalignment of shafts and linkages.
1.2 This test method is designed to reproduce conditions 4.2 An assumption is made that if the creep is satisfactory at
typical of those encountered by trunnion bushings in hydro- 55 160 kPa (8000 psi), it will also be satisfactory at lower
power applications and any other bushings subjected to high pressures.
continuous loading and low-speed oscillating applications.
5. Apparatus
1.3 This test method is conducted on cut segments of the
bushings. 5.1 The loading frame shall be capable of applying and
maintaining the required load on the specimens, despite any
1.4 The values given in SI units are to be regarded as the
standard in all property and dimensional tables. change in the dimensions of the specimens.
5.2 Bushing specimens are mounted in-line on the test
NOTE 1—There is no known ISO equivalent to this standard.
apparatus such that when load is applied at one end of the
1.5 This standard does not purport to address all of the
apparatus (by means of a hydraulic cylinder) all specimens
safety concerns, if any, associated with its use. It is the
receive the same load.
responsibility of the user of this standard to establish appro-
5.3 Bearing test pressure is maintained at 55 160 kPa (8000
priate safety and health practices and to determine the
psi) on the projected area of the bushing specimen.
applicability of regulatory limitations prior to use.
5.4 Pressure is held (nearly) constant by means of an
automatic pumping system and an accumulator.
2. Terminology
5.5 A suitable test frame configuration is shown in Annex
2.1 Definitions:
A1.
2.1.1 creep strain, n—total strain, at any given time, pro-
5.6 The creep-measuring device consists of an eddy-current
duced by the applied stress during a creep test.
sensor anchored to one end of a specimen group (four test
samples) directed at a target attached to the other end of the
3. Summary of Test Method
group.
3.1 Segments of the bushing are mounted in-line on the test
5.7 The overall change in lengths of the four specimens is
apparatus such that when load is applied at one end of the
monitored to an accuracy of 2.54 µm (0.0001 in.).
apparatus, by means of a hydraulic cylinder, all specimens are
simultaneously loaded exactly the same. 6. Test Specimens and Test Units
3.2 Bearing test pressure is maintained at 55 160 kPa (8000
6.1 Paragraph 6.2 and Fig. 1 define the test sample configu-
psi) on the projected area of the bushing specimen.
ration. The samples are clamped into sample supports as
3.3 Pressure is held constant by means of an automatic
described in Section 7.
pumping system and an accumulator.
6.2 Each test shall use four identical bushing material
3.4 The actual amount of creep is measured over an ex-
specimens meeting the following requirements (reference Fig.
tended period of time.
1):
6.2.1 Inside Radius of Tubular Form—6.350 6 0.013 cm
(2.500 6 0.005 in.),
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
6.2.2 Thickness—0.952 6 0.005 cm (0.375 6 0.002 in.),
and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.
6.2.3 Length—6.98 + 0.000/-0.013 cm (2.75 + 0.000/-0.005
Current edition approved Dec. 1, 2004. Published December 2004. DOI:
10.1520/D7107-04. in.),
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7107 – 04
FIG. 1 Test Sample Configuration
6.2.4 Angle of Arc (Each Finished Specimen)—120 6 1.0°, 7.1.3 Length—6.985 + 0.000/-0.025 cm (2.75 + 0.000/-
and 0.010 in.),
6.2.5 Surface Finish—R 3.2 µm (125 µin.) minimum. 7.1.4 Perpendicularity—Ends perpendicular with cylinder
a
axis within 50 µm (0.002 in.), and
7. Preparation of Apparatus
7.1.5 Surface Finish—R 0.4 µm (16 µin.) minimum.
a
7.2 Sample Supports:
7.1 Sample Spacer:
7.2.1 Material and Temper—AL 6061 T6 or T6511,
7.1.1 Material and Temper—AL 6061 T6 or T6511,
7.1.2 Diameter—2.700 6 0.005 cm (5.000 6 0.002 in.), 7.2.2 Radii—7.302 6 0.025 cm (2.875 6 0.010 in.),
D7107 – 04
7.2.3 Length—6.985 + 0.000/-0.025 cm (2.75 + 0.000/-
...