ASTM_D_7107_-_04_2010.pdf

Designation:D710704(Reapproved 2010)Standard Test Method forCreep Measurement of Self-Lubricating Bushings1This standard is issued under the fixed designation D7107;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method determines the amount of creep exhib-ited by self-lubricating bushings exposed to a high load for anextended period of time.1.2 This test method is designed to reproduce conditionstypical of those encountered by trunnion bushings in hydro-power applications and any other bushings subjected to highcontinuous loading and low-speed oscillating applications.1.3 This test method is conducted on cut segments of thebushings.1.4 The values given in SI units are to be regarded as thestandard in all property and dimensional tables.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.NOTE1There is no known ISO equivalent to this standard.2.Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 creep strain,ntotal strain,at any given time,pro-duced by the applied stress during a creep test.3.Summary of Test Method3.1 Segments of the bushing are mounted in-line on the testapparatus such that when load is applied at one end of theapparatus,by means of a hydraulic cylinder,all specimens aresimultaneously loaded exactly the same.3.2 Bearing test pressure is maintained at 55 160 kPa(8000psi)on the projected area of the bushing specimen.3.3 Pressure is held constant by means of an automaticpumping system and an accumulator.3.4 The actual amount of creep is measured over an ex-tended period of time.4.Significance and Use4.1 Self-lubricating bushings with low creep rates are usedin hydropower turbines and other applications in which bush-ing distortion could cause misalignment of shafts and linkages.4.2 An assumption is made that if the creep is satisfactory at55 160 kPa(8000 psi),it will also be satisfactory at lowerpressures.5.Apparatus5.1 The loading frame shall be capable of applying andmaintaining the required load on the specimens,despite anychange in the dimensions of the specimens.5.2 Bushing specimens are mounted in-line on the testapparatus such that when load is applied at one end of theapparatus(by means of a hydraulic cylinder)all specimensreceive the same load.5.3 Bearing test pressure is maintained at 55 160 kPa(8000psi)on the projected area of the bushing specimen.5.4 Pressure is held(nearly)constant by means of anautomatic pumping system and an accumulator.5.5 A suitable test frame configuration is shown in AnnexA1.5.6 The creep-measuring device consists of an eddy-currentsensor anchored to one end of a specimen group(four testsamples)directed at a target attached to the other end of thegroup.5.7 The overall change in lengths of the four specimens ismonitored to an accuracy of 2.54 m(0.0001 in.).6.Test Specimens and Test Units6.1 Paragraph 6.2 and Fig.1 define the test sample configu-ration.The samples are clamped into sample supports asdescribed in Section 7.6.2 Each test shall use four identical bushing materialspecimens meeting the following requirements(reference Fig.1):6.2.1 Inside Radius of Tubular Form6.350 6 0.013 cm(2.500 6 0.005 in.),6.2.2 Thickness0.952 6 0.005 cm(0.375 6 0.002 in.),6.2.3 Length6.98+0.000/-0.013 cm(2.75+0.000/-0.005in.),1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved Nov.1,2010.Published March 2011.Originallyapproved in 2004.Last previous edition approved in 2004 as D7107-04.DOI:10.1520/D7107-04R10.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.2.4 Angle of Arc(Each Finished Specimen)120 6 1.0,and6.2.5 Surface FinishRa3.2 m(125 in.)minimum.7.Preparation of Apparatus7.1 Sample Spacer:7.1.1 Material and TemperAL 6061 T6 or T6511,7.1.2 Diameter2.700 6 0.005 cm(5.000 6 0.002 in.),7.1.3 Length6.985+0.000/-0.025 cm(2.75+0.000/-0.010 in.),7.1.4 PerpendicularityEnds perpendicular with cylinderaxis within 50 m(0.002 in.),and7.1.5 Surface FinishRa0.4 m(16 in.)minimum.7.2 Sample Supports:7.2.1 Material and TemperAL 6061 T6 or T6511,7.2.2 Radii7.302 6 0.025 cm(2.875 6 0.010 in.),FIG.1 Test Sample ConfigurationD7107 04(2010)2 7.2.3 Length6.985+0.000/-0.025 cm(2.75+0.000/-0.010 in.),and7.2.4 Radii Surface FinishesRa0.8 m(32 in.)mini-mum.7.3 Other Machined Parts and Sample Clamps:7.3.1 Material and TemperAL 6061 T6 or T6511 and7.3.2 FinishRa3.2 m(125 in.).7.4 Assembly7.4.1 The test spec