Car Automotive

Posts Tagged ‘Occupant’

In the development of a new vehicle platform, its crashworthiness is an important concern, and it is imperative to compare the impact severity of the vehicle and occupants under various test and design conditions. Since an impact is a physical event that involves analyses of impulses and energy components, such as kinetic energy, energy absorption, and energy dissipation, the analyses require both the principle of work and energy and that of impulse and momentum. Although both principles are derived from Newton’s Second Law, they are not mutually exclusive when it comes to solving problems involving impact and excitation.

It will be shown that any crash event, modeled by either a single-mass or a multi-mass system, involves impact and/or excitation. Recognizing the existence of the impact and/or excitation, the closed-form formulas derived in Section can be utilized to solve problems. Case studies, such as the dynamic principles of pyrotechnic pretensioner on the occupant responses, are investigated. The preloading effect of a restraint system on the occupant response and ridedown  efficiency are discussed. Many crashworthiness topics related to single and multi-vehicle collisions are analyzed by the engineering principles presented so far for determining the degree of crash severity. Applications of these principles to vehicle-to-vehicle compatibility, shear loading of truck body mounts due to eccentric loading, and the methodology of accident reconstruction methodology are also presented.

In the simple vehicle and occupant model shown in , once the free travel space or restraint slack is expended, the occupant contacts the vehicle interior surface or restraint system. To ensure that the occupant relative contact velocity is less than the initial barrier impact speed, it will be shown the free travel space should be less than the dynamic crush.  shows the relationships between the ratio of contact velocity to impact speed and the ratio of free travel to dynamic crush. Note that the same relationship exists for the ratio of contact time to time of dynamic crush.

The equations of motion for a simple vehicle!occupant model are reviewed. In a study by Huang [1] on vehicle and occupant crash dynamics, a simple model with a constant force level structure and a restraint system was used. The equations of motion for the vehicle and occupant are derived based on the vehicle equivalent square wave (ESW). These are shown as follows.