A study of the investigation for the limit condition of fluid lubrication

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(1)Under the severe condition, in which the hydrodynamic lubrication changes to mixed one, the sliding surface roughness plays a important role. Therefore, oil-film pressure has to be measured on different small roughness. Using bias sputtering, a thin-film sensor could be fabricated even for the roughness under Ry=0.4μm.(2)Aluminum alloy used as lead film for pressure sensor adhered only weakly to the insulating film, so that it caused problem of sensor durability. Adding O_2 to Argon in the early stage of sputtering, adhesion strength of the aluminum alloy could be increased remarkably.(3)When the thin-film sensor was exposed to high temperature over 200℃, the initial resistance changed considerably and the temperature coefficient of resistance (T.C.R) increased. As a countermeasure, a Si3N4-film, instead of oxide-film, was applied successfully as a insulating and a protection film. But the strength of adhesion decreased and has to be improved in the future.(4)In order to investigate … More the influence of temperature on T.C.R. mentioned above, two test pieces of different thermal history were analyzed by ESCA. The results have shown that manganese was possibly segregated out of the sensor alloy, Cu-Mn-Ni and has combined with the neighboring oxide-film.(5)In order to get the strong protection film, it was tried to fabricate a diamond-like carbon film(DLC). The study has revealed that the isolation film could be secured by 40% addition of hydrogen to Ar as sputtering gas. However, the shear strength of the film is still low and has to be improved further to be used under severe mixed lubrication condition.(6)In order to measure the oil film pressure even under the severe mixed lubrication, the protection film of the thin-film sensor was fabricated successfully using a special RF magnetron sputtering apparatus with coil coil-power assistance. The strength of the sensor was increased more than ten times.(7)Oil-film pressure was measured using a test rig with a ball and a reciprocating flat bed to which a test piece with a thin-film pressure sensor was mounted. The test results have, however, shown that the measured pressure was only 2% of the calculated Hertzian contact pressure in the range of 68-118MPa. As the reason for this discrepancy, it was found that the area of contact between the ball and the sensor is much smaller than the pressure feeling area of the sensor.(8)Using the same test rig and load as above, oil film temperature was measured with a thin-film thermo-couple sputtered on to the test piece. The temperature level of the test piece was changed from 20℃ to 80℃. As a result, instantaneous temperature increase and that of contact were found to be different, requiring further investigation. Less