and , respectively. Shown in Fig. , the impulses of the two vehicles between 0 to 20 ms are mainly due to the stiff front rail design and damping of the body mount. They are not considered the decelerations of the main body of the truck. It will be shown in Chapter 5 that the impulsive transient responses at the beginning of the crush are mainly controlled by the damping characteristics of the body mounts, positioned between the compartment (or cab) and frame. The steady state compartment responses, where the peak body deceleration occurs, are attributed mainly to and. | and respectively. Shown in Fig. the impulses of the two vehicles between 0 to 20 ms are mainly due to the stiff front rail design and damping of the body mount. They are not considered the decelerations of the main body of the truck. It will be shown in Chapter 5 that the impulsive transient responses at the beginning of the crush are mainly controlled by the damping characteristics of the body mounts positioned between the compartment or cab and frame. The steady state compartment responses where the peak body deceleration occurs are attributed mainly to and controlled by the spring stiffness of the system. Table Weight Effects on Major Vehicle Responses in 35 mph Rigid Barrier Tests Truck Weight lb Transient State At g peak acceleration Steady State AP g peak acceleration C in dynamic crush Tm ms time at C 6200 heavier 40 @ 53 ms 65 5600 lighter 37 40 @ 43 56 Case Study 2 Compute the truck stiffness in a low speed impact A truck was tested in a perpendicular barrier condition with the following data V 14 mph A 19 g rocker panel at B-post and w 5800 lb Determine the structural stiffness and the dynamic crush and show the transient dynamic responses. Define . characteristic deceleration V 14 mph mph Compute . specific stiffness therefore K - Wx 13410 Ib in Define . .9. .9. .592 V A K M mph therefore C Ex. 592 14 in The computed dynamic crush C compares fairly well with the inches obtained in the test film analysis. Case Study 3 Compute the car stiffness in a low speed impact. Two tests were conducted using a full-size sedan with a test weight of4200 lbs. They were tested in 8 and 14 mph fixed barrier conditions with dynamic crushes of and inches respectively. Determine the structural stiffness and the transient response of the car in the two test conditions. Using the formulas for the spring-mass impact model the transient responses and model parameters were .
