ISO 7905-3:1995 pdf download – Plain bearings – Bearing fatigue 一Part 3: Test on plain strips of a metallic multi layer bearing material.
This part of lSO 7905 specifies a method for the de-termination of the endurance limit in fatigue of plainstrips of multilayer bearing materials. Additionally itprovides the opportunity of studying the influence onthe strips of hydraulic pressure and variable tempera-ture,
Test specimens
The test specimens shall be flat thin strips of rec-tangular cross-section to the dimensions shown in figure 1. To avoid fracture starting at the clampedportion,the edges shall be carefully chamfered bygrinding and the test section shall be contured asshown in figure 1.
For a multilayer bearing material, the layer dimensionsof the test specimen shall be representative of themanufacturing sequence and the test specimen shallbe finished to the same surface texture.Care shouldbe taken before and during the test not to damage thesurface mechanically or .by corrosion. The deficiencyof this test method lies in the absence of possilblleresidual stress associated with the bearing manufac-turing process.
3Test method
The test principle is illustrated in figure 2.The speci-mens shall be clamped at one end and loaded at theother end by force or displacement.The load shallfluctuate from tension to compression over the run-ning surface. Additionally a tensile or compressiveprestress may be applied in order to evaluate de-pendency upon mean stress. The test equipment ispreferably located in a chamber containing a lubricantat fixed levels of temperature to+ 2C.Alternativelytests may be conducted in air at fixed levels of tem-perature + 2″C.
Bending stress shall be measured by a strain gaugenear the clamping point on the back of the bearing-The required bending stress at the damaged sectionmay be evaluated by calculation, knowing the relativelocation of the strain gauge and first crack, and thethickness and Young”s modulus of the lining and steelbacking.
NOTE 1 The stresses in plain layered strips under con-dition of bending may be evaluated theoreticalty.
The test frequency shali have a range of 50 to80 Hertz.Crack detection shall be performed by dyepenetrant method or by microscope.The amplitudeshall be controlled by force (F) or displacement ls).
4Evaluation and presentation of testresults
The endurance limit stresses should be presented inthe form of o-N curves at predetermined tempera-ture 王 2“C]against a detailed description of thebearing material.Normaly oe-N curve testing is ter-minated for practical considerations at 50 x 10stresscycles. The endurance limit stress may be quoted ata specified number of cycles e.g. 3x 10.10× 108.25 × 10or 50 × 10°.A specimen without failure during fatigue testing to a specified endurance should beidentified in the report. Due to the scatter of test re-sults normally experienced and the statistical natureof the fatigue limit, it is recommended that the resultsbe evaluated on the basis of a statistical method.Another presentation of the endurance limit stressmay be effected by means of the Haigh diagramwhich plots stress amplitude against mean stress.Metallographic examination will provide detailed evi-dence of the damage mechanism.corrosive attackand diffusion resulting from thermal effects.