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This paper discusses the modeling of vehicle rollover collisions and resulting occupant motions. MADYMO is used to model a completely instrumented NHTSA dolly rollover collision of a Bronco II. Animated modeled motions are compared to actual video footage of the rollover. Measured acceleration pulses from the test are compared with the computed accelerations of the vehicle center of gravity, and driver head and chest accelerations. Also the vehicle roll velocity test data are compared to the computed values. It was found that there was good agreement between the modeled and test results. From the results, we discuss the capability to determine the injury of the occupant from the computed results.

A technique has been devised whereby brake thermal characteristics may be determined by measuring brake temperature, vehicle velocity, and braking torque over a wide range of operating conditions. The relationships between these experimental parameters are then determined using statistical methods of regression analysis. With the use of computer data acquisition systems, and the relative ease with which massive amounts of data may be accumulated, mathematical relationships may be developed. These rather simple mathematical relations then can be used to indicate such complex phenomena such as heat transfer coefficients from the brake surface.

With the advent of the Emergency Locking Retractors (ELRs) in the seventies, the mechanism of the seat belt safety system started becoming increasingly complex. The ELRs were made either webbing sensitive or vehicle sensitive. The former type contained an inertial device that activated after sensing webbing acceleration. The latter contained an inertia responsive pendulum mass and had the ability to lock-up whenever the vehicle experienced a sudden change in velocity or a sudden tilt or rotation. In this paper, the ELR mechanisms that employ the pendulum-pawl system are discussed and their susceptibility to fail under certain conditions investigated. The present research was conducted to evaluate the effectiveness of the ELR mechanisms and identify those conditions where the ELR was least effective.

Using the validated computer model described in reference (1), general design rules of thumb are developed for the design of single passenger off-road vehicles (ATV). The question of spring stiffness balance from front to rear is discussed along with the effects of damping ratios in jounce and rebound, and tire/suspension stiffness ratio, and suspension travel. The design objective is to minimize vehicle bounce and pitch accelerations transmitted to the rider and to maintain as flat of a riding position as possible.

In modeling the mechanics of an ATV in acceleration, stopping, hill climbing or descending maneuvers, it is necessary to understand the nature of the frictional forces on the tires of the vehicle. The tire's force characteristics in the longitudinal direction are not as simple as for automotive tires acting on paved surfaces. The interaction of the lugs of the tires with the soil, grass, rocks, roots, and surface anomalies all affect the longitudinal forces transmitted to the vehicle. The typical modeling of the tire's interaction as a force being equal to the normal force times some constant friction coefficient is totally inadequate. Unlike normal tires, the ATV tire has a pulsing effect while at limit conditions. Even on level pavement the pulsing persists which indicates that is not necessarily a surface interaction phenomenon. The frictional spikes are significantly above 1.0 rising as high as 1.89 and will affect one's prediction of the motion of the vehicle.

Occupants of off-road vehicles are very susceptible to the effects of vertical accelerations. Root mean square values normally accepted are 0.25 g's for longer duration and 0.4 g's for a shorter duration (up to two hours per day) (ref. 1). Typical off-road vehicles stiffen the suspension in order to prevent bottoming of the vehicle. This causes the ride to be extremely rough, meaning the vertical accelerations are at the limit of the human endurance. The speed of the vehicle is then limited by the endurance of the individual. By lengthening the suspension travel and tuning the spring stiffness and damping coefficients, a smooth and controllable ride is achieved thus increasing the natural limit speed. “Whoop-de-doos” are referred to by off-road drivers as a set of evenly spaced waves in the path of travel. These are often caused by repeated traffic over a soft surface. These bumps are sinusoidal in nature and are usually spaced 6 meters apart and 0.2 meters high.

Can a buckle designed with a lock for the latch when struck on the face, back, or side, also have this same feature when accelerated along the longitudinal axis? Six seatbelt buckles from various manufacturers were tested to determine their dynamic characteristics in the longitudinal direction along the mounting stalk. Patented designs of the buckles were intended to prevent inertial unlatching of the buckle. Although they may perform well in lateral and vertical directions, when force is applied along the direction parallel to the mounting stalk the buckles could be made to release. If the buckle is mounted in the vehicle with a rigid stalk, could impact pulses be transmitted to the buckle to cause release? A test apparatus was constructed where the buckle could be mounted with the stalk and webbing. The webbing could be preloaded and the buckle was accelerated by impacting the mounting point at the base of the stalk.