A Basic Study on Thermo-Elasto-Plastic Mixed Hydrodynamic Lubrication Problems

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The lubrication condition between an elastic socket and a glas sphere subjected to a sinusoidal load was observed by a miniature ITV camera through the glass sphere. Generation of a cavitation zone around the contact area were observed in the load reducing phase. A high subambient pressure was measured in the cavity and it was reduced when the area of cavity increased with the progress of the time. The difference of the curvature between the surfaces plays an important roll in deciding the mode of lubrication. If the conformity is low, highly concentrated contact occurs over a short period of time. On the other hand, if the both surfaces are highly conformed, the fluid is kept between two surfaces and considerably high fluid pressure is generated over a wide area and then, the contact pressure is kept low at the center. However, the maximum contact pressure occurs not in the center but near the outside edge. Judging from the above results, the conformity must be selected carefully to reduce wear and it is important to chose the shape of two surfaces near the edge to reduce contact pressure and their wear. A new elasto-sixed lubrication theory was developed and the results were compared with those from the experiments and both agreed well.Mixed lubrication between two parallel surfaces were also investigated using a pin and disc. When the bearing number increased, transition from mixed lubrication to fluid lubrication occurred and the friction coefficient was reduced significantly to 0.01. A theoretical model was developed for the contact between two rough surfaces and also the thermal distortion of the shape of the pin was also considered. The reason to show such a small friction between two parallel surfaces was found to be the change of the shape of the pin due to heating.