Abstract

A systematic study is performed to understand the dynamics of collisions involving a modern light weight passenger car and a heavy freight vehicle and to design an improved crash energy management system to reduce the severity of collisions. A concept of an energy dissipating under-ride guard is analytically modeled and the performance potentials are investigated under direct and oblique impacts to enhance the crashworthiness of automobiles involved in collisions with heavy freight vehicles. The under-ride guard is analytically modeled incorporating non-linearities due to asymmetric damping, stiffness, clearance spring and kinematics of linkages, using the principle of conservation of momentum and Lagrangian dynamics. Hardware-in-the-loop tests are performed to evaluate the impact energy dissipated by the damper and to verify the proposed model. The performance benefits of the proposed guard are investigated using a performance criterion based upon the magnitude of intrusion of the car mass, peak car mass acceleration, and dissipated energy. A multi-variable design optimization is performed to minimize the magnitude of intrusion and peak acceleration, and maximize the energy dissipated by the damper. A lumped parameter model of a lightweight vehicle is further formulated to study the car-to-truck collision and is analyzed under impacts with conventional and damped under ride guards. The dynamic response characteristics of different lumped masses subject to direct impacts at different velocities are analyzed and the guard parameters are optimized to achieve minimum peak acceleration level. A detailed finite element model of the car structure is further developed using DYNA3D and an elastic-plastic analysis of the car-to-under-ride guard is performed. The results obtained using the rigid body, lumped parameter model and the finite element analysis are discussed to illustrate the relative merits of the methods. The crashworthiness of the automobile impacting heavy freight vehicles is further enhanced by incorporating crush elements to absorb the impact energy. Experimental studies are conducted to enhance an understanding of the crash behavior, energy absorption capacity and the strain rate effect on the energy absorption capacity of crush elements made of different composite materials. The advantages of using crash elements made of composite materials to reduce passenger casualty are investigated through analysis of lumped parameter and finite element models. The results of the study show that the severity of a crash involving an automobile and a heavy vehicle can be significantly reduced by the proposed guard