Research On Measurement Of Ultrasonic Oil Film Thickness And AlN Piezoelectric Transducer

The rapid development of science and technology has increasingly demanded equipment performance and extreme working conditions have become more and more common.Under such extreme conditions,the thickness of the lubricating oil film in the equipment is reduced.If the oil film is too thin,the key parts of the equipment will fail to lubricate.If the oil film is thick,the equipment will be unstable.The thickness of the oil film has become a key parameter for judging whether the equipment can run safely,so the measurement of the lubricant film is important to engineering practice.In this paper,a resonance model and a spring model based on the reflection coefficient method are established.The reflection coefficients of the two models are simulated and analyzed,which is consistent with the theoretical analysis.The reflection coefficient method was applied to the measurement of the thickness of the curved oil film.The influence of the curvature and the accuracy of the transducer installation on the measurement results was analyzed.The sliding bearing and rolling bearing models were used to study the measurement results.A finite element model of the composite structure of the AlN piezoelectric transducer was established.The mode shape,resonance frequency,admittance and effective electromechanical coupling coefficient were studied.The oil and air domains were added to the original model to establish electrical-Solid-acoustic multi-physics field coupling model.The sound field is studied,including time domain analysis(transmission of ultrasound in lubricating oil)and frequency domain analysis(sound pressure,sound pressure level,directivity).The influencing factors of magnetron sputtering coatings were analyzed.Coating experiments were performed on stainless steel and silicon.The effects of nitrogen flow rate,sputtering power and transition layer materials on the crystallization properties of AlN piezoelectric thin films were studied.XRD and SEM technology were used to characterize the results.The high-quality AlN thin film on the silicon substrate was patterned and a composite AlN piezoelectric transducer was fabricated.In order to verify the correctness of the measurement theory and simulation results,a static oil film measurement platform was designed and built.Oil films with a thickness of 130μm,140μm,150μm,160μm under the resonance model and 9μm under the spring model are measured with good results.