The Research On The Mechanism For Aluminum Nitride Piezoelectric Thin Film Ultrasonic Oil Film Measurement

In order to reduce friction and wear in the mechanical equipment key parts(mechanical seals,bearings,etc.),therefore lubricant oil is often added between the relative movement of two contacting parts,which can reduce friction and wear caused by relative movement of two contacting parts.When the film thickness is appropriate,the machine can work successfully.So it is very important to monitor on-line the oil-film thickness and give an early warning before machine elements damage occurs.There are many the film thickness measurement methods,such as electrical method,optical method,the ultrasonic measurement method has been widely used.The ultrasound has a good direction,a strong penetrative skill,and it can be used for the purpose of nondestructive testing and adapt to the actual work environment.The paper focuses on the research on the mechanism for aluminum nitride piezoelectric thin film ultrasonic oil film measurement.According to the correlation theory of the propagation of incidence ultrasound,in view of the need of measuring oil film with different thickness,the paper study the wave theory and the resonant model and spring model are established for the different oil-film thickness measurement.The paper discussed the influence of roughness on the reflection coefficient of acoustic wave and established the acoustic wave reflection coefficient model under different rough surfaces.The paper studied the piezoelectric MEMS ultrasonic transducer.It’s key part is piezoelectric vibrator,and the working characteristics and principle of piezoelectric vibrator are discussed.And the finite element analysis software COMSOL Multiphysics was used to simulate and study the vibration characteristics of the piezoelectric vibrator in the thickness direction.The paper designed a new structure of piezoelectric transducer,which can reduce the volume and save the cost.In this paper,AlN thin films were deposited on stainless steel by a reactive magnetron sputtering technology.Fabrication process of AlN thin films was discussed in this paper.And the paper research the effect of N2 concentration,sputtering power on the growth of AlN thin films.AlN thin film structure was characterized by X-ray diffraction(XRD)and atomic force microscope(AFM),and the meaning of the result is discussed.