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The article devotes to development of mathematical model of sawdust briquetting process, establishing relationship between the briquettes density, the moulding speed and pressing effort. The study uses elastic-viscous-plastic Bingham body stress-strain equation as a rheological model of the sawdust being briquetted, the model parameters are non-linear functions of the sawdust density; classical Runge-Kutta method was used for solving the nonlinear differential stress-strain equation. The calculations results show that at a constant moulding pressure, the briquette density varies non-linearly over the processing time. At constant moulding pressure of 50 MPa, the calculated briquettes density reaches 1 g/cm3, at the pressure of 100 MPa the density approaches 1.2 g/cm3, and at the pressure of 150 MPa the density reaches 1.25 g/cm3. Basing on the calculation results, the study obtains approximate equation for estimating the briquette density depending on initial density of the briquette raw material, the moulding pressure and the working body speed, and approximate equation for estimating the required moulding pressure depending on initial and required briquette density, processing time or the moulding speed. [ABSTRACT FROM AUTHOR]

The aim of the study is verification of theoretical models, previously suggested by the authors for calculating rut depth and snow compaction under influence of forestry vehicles. The study bases on methods of field experiment design and methods of statistical data processing and uses wheeled forwarder John Deere 1210G as experimental set. Field tests were conducted on experimental skidding roads with loose snow, where the snow cover depth was approximately 50 cm, and on skidding roads with slightly compacted snow with a cover of approximately 30-35 cm. Experiments were carried out when equipping the forwarder with EcoTrack bogie-tracks, as well as without them. Travel load of the forwarder was 0, 50% and 100% of its capacity (contact pressure in the range of 0.026-0.071 MPa). Analysis of the data shows that the maximum difference between theoretical values of loose snow density after the vehicle passage from the experimental ones does not exceed 6.5%, for slightly compacted snow the difference does not exceed 7%. The maximum difference between theoretical values of the rut depth and the experimental ones on loose snow is 12.5%, on slightly compacted snow the difference is 14%. [ABSTRACT FROM AUTHOR]