Any crash dynamic event involves impact and/or excitation. The mechanisms of impact and excitation for full vehicle crash testing and laboratory Hyge sled testing are covered in this chapter. A simple occupant ridedown criterion using kinematic relationships is formulated. This criterion specifies the minimum vehicle crush space needed when a given occupant free travel space in the compartment is specified. During the ridedown, the vehicle undergoes a deformation process which is the first collision of the event, followed by the second collision where the occupant travels and contacts the vehicle interior surface or restraint. It will be shown that. | CHAPTER 4 BASICS OF IMPACT AND EXCITATION MODELING INTRODUCTION Any crash dynamic event involves impact and or excitation. The mechanisms of impact and excitation for full vehicle crash testing and laboratory Hyge sled testing are covered in this chapter. A simple occupant ridedown criterion using kinematic relationships is formulated. This criterion specifies the minimum vehicle crush space needed when a given occupant free travel space in the compartment is specified. During the ridedown the vehicle undergoes a deformation process which is the first collision of the event followed by the second collision where the occupant travels and contacts the vehicle interior surface or restraint. It will be shown that for a satisfactory ridedown the relative contact speed is always less than the initial vehicle to rigid barrier impact speed. Using a simple occupant vehicle model the ridedown mechanism is described mathematically and the computation of the ridedown efficiency is shown in closed-form solutions. Consequently the sensitivity of the occupant response to the vehicle structure and restraint parameters can be examined. Regression analysis of the test data confirms the analytical trend prediction. Taking advantage of closed-form solutions the effects of physical parameters on model output responses can be evaluated. To illustrate the application of the various mathematical models in analyzing the vehicle impact and sled excitation dynamics the basic concepts and solution techniques used in deriving solutions of the models are presented. To the extent possible closed-form solution techniques are utilized. The use of interior space or restraint slack in the modeling requires a time shift which makes the closed-form approach more complex. However once the slack is taken out during impact the analysis of the occupant response in the restraint coupling phase is the same as the model without slack. The mathematical dynamic models consisting of springs and dampers in .
