Search Results

This paper reports on seventy additional tests conducted using a mechanical device described by Bonugli et al. [4]. The method utilized quasi-static loading of bumper systems and other vehicle components to measure their force-deflection properties. Corridors on the force-deflection plots, for various vehicle combinations, were determined in order to define the system stiffness of the combined vehicle components. Loading path and peak force measurements can then be used to evaluate the impact severity for low speed collisions in terms of delta-v and acceleration. The additional tests refine the stiffness corridors, previously published, which cover a wide range of vehicle types and impact configurations. The compression phase of a low speed collision can be modeled as a spring that is defined by the force-deflection corridors. This is followed by a linear rebound phase based on published restitution values [1,5].

Google Earth is a map and geographical information application created and maintained by Google Corporation. The program displays maps of the Earth using images obtained from available satellite imagery, aerial photography and geographic information systems (GIS) 3D globe. Google Earth has become a tool often used by accident reconstructionists to create site drawings and obtain dimensional information. In some cases, a reconstructionist will not be able to inspect the site of the crash due to various circumstances. For example, a reconstruction may commence after the roadway on which the accident occurred has been modified. In other cases, the time and expense required to physically inspect the incident site is not justifiable. In these instances, a reconstructionist may have to rely on Google Earth imagery for dimensional information about the site. The accuracy of Google Earth is not officially documented.

This is the complete manuscript and replacement for SAE paper 2014-01-0482, which has been retracted due to incomplete content. This paper reports on 76 quasi-static tests conducted to investigate the behavior of road vehicle bumper systems. The tests are a quasi-static replication of real world low speed collisions. The tests represented front to rear impacts between various vehicles. Force and deflection were captured in order to quantify the stiffness characteristics of the bumper-to-bumper system. A specialized test apparatus was constructed to position and load bumper systems into each other. The purpose was to replicate or exceed damage that occurred in actual collisions. The fixture is capable of positioning the bumpers in various orientations and generates forces up to 50 kips. Various bumper-to-bumper alignments were tested including full overlap, lateral offset, and override/underride configurations.

Rollover crashes are often difficult to reconstruct in detail because of their chaotic nature. Historically, vehicle speeds in rollover crashes have been calculated using a simple slide-to-stop formula with empirically derived drag factors. Roll rates are typically calculated in an average sense over the entire rollover or a segment of it in which vehicle roll angles are known at various positions. A unified model to describe the translational and rotational vehicle dynamics throughout the rollover sequence is lacking. We propose a pseudo-cylindrical model of a rolling vehicle in which the rotational and translational dynamics are coupled to each other based on the average frictional forces developed during ground contacts. We describe the model as pseudo-cylindrical because vertical motion is ignored but the ground reaction force is not constrained to act directly underneath the center of gravity of the vehicle.

The increasing prominence of end-release buckles in automotive restraint systems has been accompanied by criticisms that they are susceptible to inertial unlatching in collisions due to transfer of vertical impulses from the vehicle body or chassis through the buckle stalk to the buckle. It has been asserted that the accelerations imparted to the buckle are significantly amplified relative to the initial input to the vehicle body or chassis. In this study, a test procedure was developed to measure the in-situ dynamic response of restraint system buckles to vertical impulse. The procedure was used to evaluate buckle assembly response to impulses input at, or near, the buckle stalk floor anchors in several vehicles. The advantage of this technique over full-scale drop testing and component-level shock table impacts is that the desired response information may be acquired in-situ without damage to the vehicle.

Results from a series of repeated-impact crash tests of a 1990 Ford Taurus sedan into a rigid, vertically offset barrier are presented in this paper. The purpose in conducting these crash tests was to further investigate override/underride crush energy behavior. The testing set-up and conduct are described and the test results, including impact speed, rebound speed and residual crush profiles are presented. The results of these tests are discussed and compared to the existing crash test data for this vehicle model. Previously suggested override/underride crush energy methodologies are also applied to the new data.

In automobile accident reconstruction it is often necessary to quantify the energy dissipated through plastic deformation of vehicle structures. For collisions involving the front structures of accident vehicles, data from Federal Motor Vehicle Safety Standard (FMVSS) 208 and New Car Assessment Program (NCAP) frontal barrier impact tests have been used to derive stiffness coefficients for use in crush energy calculations. These coefficients are commonly applied to the residual crush profile of the front bumper in real-world traffic accidents. This has been accepted as a reasonable approach, especially if there has been significant involvement of the front bumper and its supporting structures. For impacts where the structures above the bumper level are deformed more than the bumper itself, this approach may not be so readily applied.

In this paper a detailed analysis of a staged two-vehicle impact is conducted. The staged impact consisted of two moving vehicles impacting in a left front corner-to-right front corner configuration. Both vehicles were outfitted with an array of triaxial accelerometers. An Anthropomorphic Test Device (ATD) was located in the driver position in one of the test vehicles. High-speed film cameras were installed on the vehicle, documenting the test dummy motion during the impact. The impact and subsequent vehicle motions were documented with offboard real-time video and high-speed film cameras. The accelerometer data from both vehicles are analyzed. This analysis demonstrates the effects of yaw motion on the determination of Delta-V and on occupant kinematics. The notion of a Principal Direction of Force (PDOF) in a yawing vehicle is also discussed.

In this paper the characteristics of on-road rollover accidents are discussed. Typical rollover scenarios are presented and the phases of rollover leading up to and including vehicle trip are reviewed. Test data from various vehicle handling test programs are reviewed. The data from a test program that included maneuvers through an obstacle avoidance course are reviewed in detail. This program included tests in which the vehicle successfully traversed the course as well as tests where intentional vehicle tip-ups occurred. Comparisons of the driver input data (steering wheel angle amplitude and steering wheel rate) and vehicle response data (lateral acceleration, yaw rate, body roll angle and roll rate) from this program are presented. A review of previous analytical models of the rollover trip phase is also included. The applicability of these models in estimating the energy dissipation/transfer and lateral impulse leading to vehicle tip-up in an on road rollover is discussed.

Concrete Median Barriers (CMB’s) are used extensively on the roadways of North America. They are most often used as permanent barriers on major freeways and highways and as temporary barriers in roadway construction zones. A drive along most stretches of roadway where CMB’s are in use will reveal multiple instances of automobile impact evidence. In this paper the characteristics of automobile impacts with CMB’s are analyzed. Specifically, the case of a yawing, side-slipping vehicle impact, where significant frontal engagement may occur, is considered. Typical damage patterns and residual crush profiles are reviewed as well as vehicle Delta-V, and Barrier Equivalent Velocity (BEV). Frictional energy losses, due to vehicle and CMB interaction, and their significance in the reconstruction of this type of collision are discussed. The vertical velocity component induced by the CMB in this type of impact is also examined.