New testing method for viscosity of packaged liquids with ultrasonic pulse

Viscosity of liquids involves various functions and quality of liquid products such as machine oils, adhesives, cosmetics and certain types of foods. Based on the viscosity, the quality of the liquids can be inspected. This application needs a testing method for the viscosity when the liquids are in sealed packages and pipes of industrial plants. However, the conventional methods, which are the capillary type viscometer, the rotational viscometer and the oscillation viscometry, cannot test the viscosity of the inner liquids isolated by the package walls. This study aims to develop a new viscosity testing method for the inner liquids. We use ultrasonic pulse that propagates through the wall and the liquid. The viscosity is estimated from the attenuation of the ultrasonic pulse that propagated in the liquid. This method consists of an experimental approach to measure the attenuation and a theoretical approach to correlate the attenuation to the viscosity. The theoretical approach is a numerical simulation with lumped mass model. In this paper, we demonstrated the numerical simulation and a simple experiment as the experimental approach to test the viscosity of several kinds of liquids whose viscosities were already known. The viscosities were estimated as an index of viscosity that were proportional to the known viscosity in more than 100 mPas.