ExpErimEntal and modEl studiEs on thE influEncE of thE run flat tirE damagE on braking dynamics of thE multi-axial spEcial purposE vEhiclE EkspErymEntalnE i modElowE badania wpływu uszkodzEnia opon run flat na dynamikę hamowania wiEloosiowEgo pojazdu spEcjalnEgo*

Tire damage, that occurs quite often during operation of special purpose vehicles (building, forest, military, agricultural heavyduty vehicles), affects a vehicle motion also during sudden braking. Motion of a four-axial vehicle has been analysed in order to evaluate the influence of tire damage (cracking, tearing) on its behaviour during sudden braking and based on that to evaluate the possibilities of driver’s reactions to motion disorders resulting from that emergency condition. Using the PC-Crash software, a vehicle model was designed allowing for simulation of special-purpose vehicle motion. The vehicle model includes a possibility of occurring of sudden tire damage when in motion. In such situation a model of cooperation of a tire and a surface is of crucial significance. A semi-empirical, non-linear TMeasy tire model was used. Its parameters were obtained on the basis of the results of the tests performed on 14.00R20 tires with run flat inserts. A vehicle model parameterization was based on the results of the vehicle measurements, however the validation was based on the results of experimental road tests of braking with damaged tires. Performed calculations and simulations indicated that when braking is started a process of vehicle deviation and related motion track modification is initialized. The motion track deviation increases as the initial braking speed is increased.