DEVELOPMENT AND ANALYSIS OF INTERMEDIATE TRIPPED VEHICLE ROLLOVER MODEL (ITRS). FINAL REPORT

This report describes the development of the Intermediate Tripped Rollover Simulation (ITRS) which can be used to investigate the rollover behavior of vehicles impacting a roadside curb. The eight degree-of-freedom ITRS model consists of sprung and unsprung masses interconnected through suspension elements. The ITRS model accounts for complete forward, lateral and directional dynamics and is capable of simulating vehicle skidding motion, simultaneous and oblique impact of the front and rear wheels with a curb, and subsequent tripped rollover under a variety of initial conditions. The ITRS vehicle model has been thoroughly examined for the energy exchanged between the vehicle components. Two energy based rollover functions were developed and examined to assess their ability to predict rollover. It has been shown that, if tripped rollover is to occur at critical speed, the dynamic criteria for rollover become satisfied when vehicle roll angles equal 9.5 and 11.5 degrees for impact angles of 0 and 25 degrees, respectively. The influence of all design parameters on vehicle rollover stability during both side and oblique impacts has been determined using the percentage sensitivity functions. The sensitivity results demonstrate that geometrical, mass and impact deformation characteristics have the largest influence on vehicle rollover propensity in tripped rollover situations.