Search Results

Full-scale vehicle crash testing is often used as an engineering tool to reproduce the dynamic conditions of real-world accidents. The complex and destructive nature of conducting these crash tests makes them very expensive. Often times engineering analysis requires multiple tests wherein occupant motion or vehicle component performance comparisons are made when subject to specific dynamic conditions. For these situations, sled testing becomes the preferred evaluation method. Sled testing allows engineers to reproduce the dynamic conditions of a full-scale crash test in a controlled environment at a fraction of the cost. A particular advantage of sled testing is that only a single vehicle is consumed. Typically the occupant compartment of the vehicle, referred to as a vehicle buck, is mounted to the test sled. The sled and buck can then be subjected to accelerations representative of a particular crash environment.

In testing to determine the yaw oscillation response of a vehicle-trailer combination, the vehicle combination is driven in a straight line, at a specified speed; then a rapid, fixed-amplitude, short-duration pulse is applied to the steering wheel, while maintaining a constant speed. These requirements often result in multiple test runs to ensure an acceptable minimum variability in the damping ratio estimate for the vehicle-trailer combination. This paper investigates techniques for relieving the demands placed on the driver and for acquiring and processing the data required for analysis from this test. The testing used two different vehicle-trailer combinations, two different drivers, and an Automated Steering Controller (ASC). Damping ratio estimate comparisons were made between drivers, drivers and the ASC, transducers, data filtering, and calculation methods.

The mechanics of on-road, friction-induced rollovers were studied with the aid of a three-dimensional computer code specifically derived for this purpose. Motions of the wheels, vehicle body, occupant torso, and head were computed. Kane's method was utilized to develop the dynamic equations of motion in closed form. On-road rollover kinematics were compared to a dolly-type rollover at lesser initial speed, but generating a similar roll rotation rate. The simulated on-road rollover created a roof impact on the leading (driver's) side, while the dolly rollover simulation created a trailing-side roof impact. No head-to-roof contacts were predicted in either simulation. The first roof contact during the dolly-type roll generated greater neck loads in lateral bending than the on-road rollover. This work is considered to be the first step in developing a combined vehicle and occupant computational model for studying injury potential during rollovers.

This paper describes an investigation that seeks to understand how rollovers occur in real-world crashes, both by studying real world crashes and by analyzing vehicle handling tests to gain insights into potential mechanisms of pre-crash loss of control. In particular, this study focuses on one type of rollover, namely single-vehicle rollovers that follow a pattern of the vehicle first leaving the roadway and then returning to the roadway typically out-of-control. Aims of this study included the following: To describe the frequency and characteristics of single-vehicle rollovers involving an off-roadway excursion followed by a complete, if only temporary return to the roadway. To the extent possible, given available data, to assess the nature and consequences of driver inputs during the crash sequence. To define characteristics of crash scenarios which include a substantial proportion of this subset of single-vehicle rollovers.

Testing techniques for creating rollovers have been a subject of much study and discussion, although previous work has concentrated on creating a repeatable laboratory test for evaluating and comparing vehicle designs. The two testing methodologies presented here address creating rollover tests that closely mimic a specific accident scenario, and are useful in accident reconstruction and evaluation of vehicle performance in specific situations. In order to be able to recreate accidents on off-road terrain, a test fixture called the Roller Coaster Dolly (RCD) was developed. With the RCD a vehicle can be released at speed onto flat or sloping terrain with any desired initial roll, pitch and yaw angle. This can be used to create rollover collisions from the trip stage on, including scenarios such as furrow trip on an inclined road edge.

Vehicle aspect ratio has been reported as a significant factor influencing the likelihood of fatality or severe injury/fatality during single-vehicle rollover crashes. To investigate this, dynamic simulations of friction-induced rollover accidents were performed using different roof heights, but otherwise identical vehicle parameters and initial conditions. Higher aspect ratios tended to cause the leading side roof to impact first, with significant impact force. The roof impact forces during the first roll of higher-roofed vehicles were primarily laterally directed with respect to the vehicle. Impact locations during subsequent rolls were less predictable. Lower aspect ratios produced higher impact forces on the trailing side roof that were more vertically oriented with respect to the vehicle. The vertically oriented forces potentially create greater risk for severe neck or head injuries.