Research On Measuring Method Of Liquid Layer Thickness Based On Ultrasonic

Various mechanical transmission structures such as mechanical seals,bearings,and guide rails often produce friction and wear due to contact.In order to protect the mechanical equipment from damage,a layer of liquid is usually introduced in the mechanical transmission parts to play the role of lubrication,cooling,sealing and antirust.Once the liquid layer fails,the mechanical transmission structure in operation loses protection and irreversible damage occurs.In severe cases,it will cause mechanical equipment failure,bring property damage,and even bring hidden safety hazards and affect personal safety.In order to ensure the safe operation of mechanical equipment,it is particularly important to monitor the working state of the liquid layer and ensure its normal operation.In view of this,it is not only scientifically significant to carry out research on the measurement of the thickness of the liquid layer by ultrasound,but also has practical engineering value.With the purpose of solving the problem of measuring the thickness of the liquid layer in the mechanical transmission structure,this paper has carried out research on the method of ultrasonically measuring the thickness of the liquid layer of the mechanical structure after setting up an experimental platform for measuring the thickness of the liquid layer in the laboratory.The specific research content is as follows.According to the acoustic properties of the three-layer medium,by analyzing the reflection coefficient of the intermediate liquid layer,the resonance model is derived from the resonance frequency in the reflection coefficient,and the spring model is derived from the stiffness coefficient in the reflection coefficient.According to the frequency range of the ultrasonic transducer,the thickness ranges of the liquid layer that can be measured by the spring model method and the resonance model method are determined respectively.Based on the propagation characteristics of ultrasound,the correlation coefficient model is derived.The phase change law of the ultrasonic pulse signal will change with the change of the thickness of the measured liquid layer.According to this law,the phase model is derived.After the establishment of four ultrasonic measurement models,the measurement accuracy of these four models and the influencing factors of ultrasonic measurement errors were analyzed.In the laboratory,an ultrasonic measurement liquid layer thickness test platform was built,and the ultrasonic measurement of liquid layer thickness was carried out.For liquid layers of different thicknesses,spring models,resonance models,correlation coefficient models,and phase models were used for measurement and calculation.The experimental results show that the calculated values of the four measurement models are basically consistent with the actual values,and the advantages and disadvantages of the four models are analyzed and compared.The derivation of the phase model provides a new idea and method for ultrasonic measurement of the thickness of the liquid layer of the mechanical structure.