Impact Reduction of an Automotive Occupant by “Ride Down” Effect in Head-on Collision

Abstract

During a car frontal collision, some part of the occupant's kinetic energy is transferred to the vehicle through the restraint system. The high ratio of the transferred energy has the advantage of protecting the occupant. This phenomenon is called “ride down effect”. It is known from experience that if the deceleration of the automotive body is large in the early stages of a collision, the effect becomes large, provided that the vehicle kinetic energy and the maximum value of the automotive body deformation are same. In order to design an automotive body structure taking into consideration the ride down effect, the dynamic relation between the occupant deceleration, which is one of important injury criteria, and the automotive body structure must be studied. However, there have been few researches to analyze the theoretical mechanism of the ridedown effect in detail. In this paper, we formulated ridedown effect focusing on the protection devices using a two-degree-of-freedom model for a vehicle and an occupant. The relationship between the index of the ride down effect and the occupant deceleration caused by crashing the automotive body structure was theoretically analyzed, and an optimum automotive crash design was examined.