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. | CHAPTER 7 CRASH SEVERITY AND RECONSTRUCTION INTRODUCTION 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 of Chapter 4 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. OCCUPANT MOTION UNDER IMPACT AND EXCITATION Occupant motion in the vehicle compartment is controlled by both the vehicle and restraint impact factors. Both factors complement each other in producing the occupant responses in a particular test condition. Since any vehicle produced needs to be certified to meet the federal vehicle safety standard it is not unusual to see a truck equipped with a pyrotechnic device
