| Abstract [eng] |
The research object of this paper is a Scania tractor unit (hereinafter – the tractor) with a semi-trailer and Volvo tractor (hereinafter – log truck) with a trailer. The issues under consideration are the longitudinal motion dynamics of these heavy-duty vehicles and its dependence on the heavy-duty vehicle mass. The acting loads, technical characteristics of the heavy-duty vehicles have been analysed, and center of gravity coordinates for loaded and empty vehicles that are necessary for further calculations have been found. The longitudinal dynamics parameters determined during the experimental trial have provided the extreme acceleration values of empty and loaded trucks. During speed pickup, the loaded log truck is subject to 1.761 m/s2 lower acceleration than an empty log truck, and the acceleration distance and time are higher, respectively, by 27.15 s and 363 m. During speed pickup, the loaded tractor is subject to 1.252 m/s2 lower acceleration than an empty tractor, and the acceleration distance and time are higher, respectively, by 41.9 s and 588 m. During braking, the loaded log truck is subject to -1.514 m/s2 lower acceleration than the empty log truck, and its braking distance and time are, respectively, higher by 3.6 s and 36.2 m. During braking, the loaded tractor is subject to -1.048 m/s2 lower acceleration than the empty tractor, and its braking distance and time are higher, respectively, by 1.25 s and 8 m. Extreme acceleration and braking results for tractors of different masses (13795 kg; 28435 kg; 43120 kg; 72455 kg) has been assessed by numerical modeling. Results of the longitudinal motion dynamics of the tractor have demonstrated that the loaded tractor is subject to 2.85m/s2 lower acceleration during braking than the empty tractor, and the braking distance and time are higher by, respectively, 1.725 s and 18 m. During speed pickup, the loaded tractor is subject to 2.036m/s2 lower acceleration than the empty tractor, and its acceleration distance and time are higher by, respectively, 31.475 s and 425.4 m. With the masses of empty and loaded trucks and the maximum acceleration acting in the center of gravity available, the maximum acting inertia force has been determined. During speed pickup, the log truck has been found to demonstrate greater inertia forces than the tractor – despite greater mass, the log truck tends to develop greater acceleration. On the other hand, during braking, the tractor shows greater braking inertia forces compared to the log truck. |
