In general, the kinetic friction coefficient can, under any contact loading condition, be determined using methods completely different from the existing methods based on the measurements of contact load and friction force. The proposed method refers to the determination of kinetic friction coefficient using the dynamic equation of motion for a rotating body, where the active force acts on the rotating body only at the initial moment of motion, while body masses, which are concentrically and eccentrically distributed in relation to the axis of rotation, provide a static and dynamic component of a desired 'sleeve-bearing' contact load. If the body angle of rotation change is experimentally determined as a function of time, then, based on the dynamic equation of motion, it is possible to determine the current friction coefficient values for the entire time period from the start of the motion to the rotation stop. It can be said that acceleration is a physical and energy indicator for friction and energy dissipation in tribomechanical systems, and that it defines the complete dynamics of the friction process itself.
The paper investigates the effects of roller pressing on the hardness, roughness, and elastic modulus of wooden workpieces. For research purposes, a roller pressing device based on purely mechanical processing was designed and developed. Four different levels of pressing force have been applied to eight different types of wood: cherry, fir, alder, linden, beech, walnut, oak, and ash. The obtained results indicate that the proposed processing method can significantly improve the hardness, elastic modulus, and surface quality of wooden workpieces. The ash sample exhibited the largest relative increase in hardness (175.9%), while the most significant relative increase in the elastic modulus (66.73%) was measured on the linden sample. The largest relative decrease in surface roughness (54.75%) was achieved on the alder sample. For all types of wood except for fir, in which case an increase in pressing force did not produce the desired reduction of roughness, correlation coefficients indicate a strong relationship between the pressing force as an input variable and the elastic modulus, hardness, and roughness as output variables.
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