| During machines operation, friction and wear will occur between two contacting surfaces. If thefriction is serious, it would cause serious failure. Therefore lubricant oil is often added between them.The film thickness influences the mechanical equipment operating. When the film thickness isappropriate, the machine can work successfully. So it is significant to measure the oil film thickness inactual production. Among the film thickness measurement methods, the ultrasonic measurementmethod can adapt to the actual work environment better and it has a good prospect. This paper focuseson the ultrasonic measurement method and the measuring system.A resonance model and a spring model are established on the basis of wave theory. The formeruses the minimum value of the reflection coefficient in its frequency spectrum. And the latter uses themonotonic relationship between the reflection coefficient and the film thickness. When the thicknessis greater than or close to the ultrasonic wavelength, the resonance model is used; otherwise the springmodel is chosen.The ultrasonic transducer is an important component in the measurement system. Thus itsacoustic characteristics need to be studied. According to the measurement requirements, theappropriate transducer is selected. Besides, the acoustic field of transducer array and the influenceparameters are also studied.This paper has designed and made the measurement circuits based on the models. The programof hardware drivers and data processing program have been compiled. And different film thickness isconstructed as the standard thickness in the measurement experiments.Film thickness measurement experiments have been done by use of the designed system. Theresonant model or the spring model is chosen to calculate different thickness. Then by comparing theexperimental results with the actual thickness, we find that the relative error of the measurementvalues is small. This verifies the availability of the designed system and the measurement models. |
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