| Lubricant is very important for machine. Friction and wear, caused by relative movement of two contacting parts, can be reduced by lubricant oil-film. This oil-film is very thin. If it collapses, heating and wear of the contacting components accelerate dramatically and machines can not work at last. So it is important to monitor on-line the oil-film thickness and give an early warning before machine elements damage occurs. In comparison with electrical methods and optical methods, the ultrasound method removes the requirement of electrical isolation and transparency and so it has a good prospect. However, these previous measurements used a bulky transducer. This necessitated a hole to be drilled in the workpiece to locate the transducer. This paper focuses on the ultrasonic measurement method. And a piezoelectric aluminum nitride film is deposited in the form of a very thin layer onto the surface of workpiece. In this way the oil-film can be measured noninvasively.According to the correlation theory of the propagation of incidence ultrasound in three mediums, the resonant model and spring model are established for the different oil-film thickness measurement. Compared the two models, the reflection-coefficient spectrum is simulated by MATLAB. This spectrum can be used to help select an appropriate model to measure a given oil-film thickness.In this paper, Al N thin films were deposited on stainless steel by a reactive magnetron sputtering technology. Fabrication process of Al N thin films was designed. Effect of sputtering power, substrate temperature, gas flow and N2 concentration on the growth of Al N thin films was studied. The films were characterized by X-ray Diffraction(XRD) experiment technology. The surface morphology of the films was observed by using Atomic Force Microscope(AFM). The results revealed that the oriented Al N thin films can be deposited with higher sputtering power, lower roughness and a ratio for the nitrogen flow rate of 30 to 70 percent. |
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