Citation

Yoganandan NA, Almusallam A, Myklebust J, Jr AS. Math. Comput. Model. 1988; 11: 440-444.

Copyright

(Copyright © 1988, Elsevier Publishing)

DOI

10.1016/0895-7177(88)90530-4

PMID

unavailable

Abstract

An automobile can be conceived as a structure that houses living occupants within. During a crash environment interactions exist between the occupant and the vehicle interior. Deformations of the root of the vehicle play an important part in the mechanics of rollover accidents. An understanding of the interaction between the roof deformations and occupant kinematics leads to a better structural design of the vehicle and hence, an improved occupant protection against trauma. In this study, a multi-degree-of-freedom system lumped parameter model simulated a rollover accident during the initial phase wherein the airborne automobile is contacting the ground surface with a certain initial drop velocity. The vehicle is simulated by a mass-spring system, the mass representing the vehicle weight, the spring simulating the superstructure crushability characteristics of the roof and the pillars. The occupant torso, head and neck are simulated by a combination of mass and 2 springs. The effect of occupant restraint and the compressibility of the seat is incorporated by suitable tensile and compressive stiffnesses for the corresponding springs. The resulting coupled differential equation of motion can be solved numerically with suitable end conditions. The occupant survival space, defined as the net available clearance between the head of the occupant and the bottom of the vehicle roof interior, an important parameter that influences the forces in the occupant, is also included in the analysis. Parametric studies were conducted to study the effect of geometric and material variables on the forces imparted to the occupant. A direct relation was found to exist between the forces in the occupant and initial roll velocity. A reduction in the occupant force occurred due to an increase in the superstructure rigidity, increased survival space and decreased compressibility of the seat. These parameters had, on the contrary, only marginal effects on the vehicle dynamic forces. Decrease in vehicle mass resulted in a decrease of the forces both on the occupant and the vehicle. In addition, the restraining force on the occupant was small up until the time it comes in contact with the superstructure. This time it was found to be insensitive to changes in the structural stiffness of the vehicle. Lower vehicle stiffness delayed the time at which the peak force in the vehicle and occupant occurred. Whilst a detailed non-linear analysis is recommended to completely describe the mechanics of rollover, this simple linear multi-degree-of-freedom lumped parameter technique provides an insight into the modeling of the occupant-vehicle interaction.