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A coordinated test and analysis program was conducted to determine whether a previously proposed, linear, analytical model could be adapted to simulate low speed impacts for vehicles with various combinations of energy absorbing bumpers (EAB). The types of bumper systems impacting one another in our program included, in various combinations; foam, piston and honeycomb systems. Impact speeds varied between 4.2 and 14.4 km/h (2.6 and 9.0 mph) and a total of 16 tests in 6 different combinations were conducted. The results of this study reveal that vehicle accelerations vary approximately linearly with impact velocity for a wide variety of bumper systems and that a linear mass-spring-damping model may be used to efficiently model each vehicle/bumper-system for low speed impacts.

An efficient model for simulating articulated vehicle dynamics for yaw stability during heavy braking is developed. The system’s governing equations are derived using Lagrange’s Equations, eliminating the need for any assumptions concerning forces at the tractor-trailer hitch. Detailed parametric results are presented. Six important dimensionless parameter groups affecting yaw stability are identified. Parametric plots based upon numerical simulations, are presented and a yaw stability limit criterion is defined to evaluate the simulation results. The graphical results show that increasing trailer braking consistently increases stability, while increasing the trailer to tractor weight-ratio decreases stability assuming balanced tractor braking. The most influential parameter affecting vehicle stability is the trailer fore/aft C.G. position.