Magnetorheological fluid sedimentation characterization via laser transmittance intensity method

Abstract

The sedimentation measurement is of significant importance when designing and synthesizing magnetorheological (MR) fluid for engineering applications. Generally, visual observation is always used to discern the mud line position but knows nothing about the concentration distribution under the mud line. The method using electromagnetic scanning is limited by the position resolution because of the height of the inductor, and the method based on thermal conductivity is time-consuming and determines the sedimentation status at a specific location. In this paper, the sedimentation behavior is revealed by the laser transmittance intensity (LTI) method which is based on scattering when the light passes through the MR fluid, the higher the concentration and the stronger the scattering, the weaker the received light intensity. Specifically, the laser diode and the photodiode were utilized as the light source and receiver, respectively. MR fluid samples in a series of concentrations are used to obtain the correlation between volume fraction and photodiode output voltage, and that is taken as the calibration of the sensing method. In the experiments, the scanning with height and the sensing with time are jointly employed to characterize the settling process of a specific MR fluid.