DETERMINATION OF THE RESISTANCE FORCE ACTING ON BODIES MOVING IN DILATANT SILICONE-BASED COMPOSITE FLUIDS

Abstract

The aim of this work is to quantitatively investigate the resistance forces acting on specimens moving in composite dilatant mixtures (CDMs) based on silicone oil with different volume fractions of solid corundum particles (10%, 20%, 30%, 40%, 50%).

To conduct the experimental study, an original device was developed that enables measurement of the force acting on a specimen during its free immersion into the tested mixture. The device is based on an Arduino Uno microcontroller and includes a load cell with an HX711 module as well as an electromagnetic unit that ensures identical starting conditions for each run.

The repeatability of the experiments was achieved by standardizing the geometry and mass of the specimen and by performing multiple measurement series. The results were statistically summarized; the generalized force curve was formed using the 95th percentile, which reduces the influence of random noise while correctly representing peak loads.

In addition, an analysis of the distribution of the solid-phase particles by diameter and roundness coefficient was performed. The analysis showed that most particles have an equivalent diameter of approximately 3–5 μm; it was also established that the particles are heterogeneous in shape and have irregular outlines with pronounced angular contours, as confirmed by low values of the roundness coefficient.

During experiments with CDMs containing 10% and 20% corundum, the recorded resistance forces did not reach the maximum possible values because these mixtures were not able to effectively decelerate the specimen before it reached the structural limitations of the device. For CDMs with 30%, 40%, and 50% corundum, the results demonstrated a fundamentally different response to the applied load: the resistance force increased sufficiently for the specimen to come to a complete stop within the CDM. For 50% corundum, the mixture exhibited an almost paste-like consistency.

A series of experiments with controlled variation of the specimen immersion speed was also performed. The speed was changed by increasing the mass of the moving unit. For CDMs containing 30% and 40% corundum, an increase in the interaction force with increasing speed and higher peak resistance-force values were observed.

As a result of this work, it was established that the characteristics of resistance forces during the interaction of the specimen with composite dilatant mixtures are determined by the volume fraction of corundum and the loading conditions. It was shown that CDMs with concentrations of 30% and 40% are the most suitable for capturing dilatant behavior, whereas mixtures with 10% and 20% do not provide conditions for the correct manifestation and registration of maximum resistance-force values. Increasing the concentration to 50% shifts the mixture toward an almost paste-like state and limits the validity of the measurements.