The problem of standardising the static friction force measurement in plant granular materials

The article presents the problems of measuring the static friction force of granular materials of plant origin. Measurements as such do not have clearly defined procedures. This leads to a situation in which it is very difficult to compare the results obtained by different researchers. The tests were performed on a linear tribometer. The authors demonstrated the effect of sample slip velocity on the maximum value of the measured friction force and observed the effect of inertia force on the friction force oscillations in the initial phase of sample slip. The difference between the maximum force T-1max and the minimum force T-1min recorded in the first friction ripple cycle can be considered as the basic parameter for evaluating the effect of inertia on the measurement results on a given measuring device. To omit the force of inertia, the authors propose conducting tests under quasi-static conditions, at a slip velocity of 0.5 mm/min. (C) 2022 Elsevier B.V. All rights reserved.