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Theoretical Study on Ridedown Effect in Frontal Collision
Published October 22, 2006 by Society of Automotive Engineers of Japan in Japan
During a car frontal collision, some part of the occupant's kinetic energy is transferred to the car through the restraint system such as a seat belt. The high ratio of the transferred energy in the early stage of collision has the advantage of protecting the occupant. This phenomenon is called "ridedown effect." It is known from experience that if the deceleration of the car body is large in the early stages of a collision, the ridedown effect increases. If the car's body structure and a restraint system are designed in consideration with the ridedown effect, good performance can be expected. The relationship between the ridedown effect and injury criteria should be studied prior to designing a car body. Knowledge obtained from this study would provide useful information for the initial design stage. There have been a few studies that analyze the theoretical mechanism of the ridedown effect in detail.
In this paper, we formulate the ridedown effect, focusing on the work done by restraint systems using a small-degree-of-freedom model for a car and an occupant. The relationship between the index of the ridedown effect and the occupant's deceleration caused by crashing the car body was analyzed theoretically. As a result, we obtained a new insight, and it was possible to develop optimum design guidelines for the initial design stage.