Static and dynamic friction coefficients of grain crops and mineral materials

There are many devices for determining the coefficients of external friction, but there are almost no devices for determining the coefficients of internal friction of bulk products. The paper considers the question of physical and mechanical characteristics of bulk materials - the coefficients of external and internal friction. The purpose of this study was to create a device for determining the friction characteristics of bulk materials and its approbation by determining the coefficients of static and dynamic friction of grain materials. The basic parameters of the installation to determine the friction characteristics of bulk materials were defined - static and dynamic, internal and external friction coefficients. The developed installation allows measurements of shear forces inside the bulk material. The relationship between the coefficient of static and dynamic friction in organic and inorganic bulk materials is revealed. Grain crops have a higher value of the dynamic coefficient of friction at a speed up to 0.215 m/s. The difference between the values of static and dynamic friction coefficients was not revealed in the specified speed range of legumes. Dynamics of change in the coefficient of friction for grain crops depending on speed is studied using the example of wheat, and for mineral materials - using the example of table salt. For a speed range of 0-0.215 m/s, the relative change in the coefficient of friction for grain crops has a polynomial regression model, for mineral materials it has a logarithmic.