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Wheels and tires on vehicles, are often directly (or indirectly) involved in collisions with other vehicles or fixed objects. In this study, the effects of the pneumatic tire and rim, as it contributes to a dynamic collision, was isolated and studied. A total of 15 mounted tires of various common sizes were selected to conduct 35 dynamic impact tests into the flat face of an instrumented concrete barrier. The tires and rims used in the tests ranged from heavy truck, light truck, down to common passenger vehicle tires. Each of the 15 tires and rims were impact tested individually to failure in order to explore the dynamic response and performance of pneumatic tires in collisions. Of the 35 tests, 28 were conducted with a single tire and rim configuration and 7 tests were conducted simulating a dual truck tire configuration. It was determined that the coefficient of restitution for 22 of the tire impacts into the rigid flat faced barrier were remarkably similar, around 0.9 ± 0.1.

A follow-up study on rollover testing was conducted along a section of a remote rural highway using six full-size sport utility vehicles (SUVs) of differing makes and models. The vehicles were instrumented and towed to highway speeds before being released, at which point an automated steering controller steered the vehicles through a series of maneuvers intended to result in rollover. A total of eight tests were conducted and documented, six rollovers and two non-rollover events. The six rollover events provide trip and tumbling conditions for each vehicle. The two non-rollover attempts produced cornering tire marks and allowed for the documentation of near roll conditions for the two out-of-control vehicles. All eight tests presented are instrumented real-world type tests that were later correlated based upon the data obtained.

Three full-size sedans were towed to highway speeds along a section of a remote rural highway. Upon release, an automated steering controller steered the vehicles through a series of maneuvers intended to result in rollover. Repeated attempts to roll each vehicle were made until rollover resulted. Non-rollover attempts produced cornering tire marks by the out-of-control vehicle. Out of numerous runs, 3 rollover and 2 non-rollover tests were selected for documentation and analysis. One additional steer-induced rollover test is presented that was conducted along a simulated road section at a closed test-track facility. All six tests presented are instrumented real-world type tests that were later reconstructed based upon the data obtained from on-board instrumentation, videotape, survey measurements, and still photographs obtained of each respective test.

A crash pulse representative of the accident event is often requested in addition to the reconstructed speed, deltaV, and PDOF. One approach to crash pulse generation is to scale available test data to the accident condition. Scaling formulas for time and acceleration are derived based upon commonly available accident reconstruction information from the crush profiles, closing speed, and vehicle deltaV. Scaling is based upon the compression phase of the crash pulse. A crash test similar to the accident may not be readily available unless a crash test is performed that is designed to represent a specific accident. Available test results may not reproduce the accident but may approximate it in several important aspects. In such situations it is necessary to scale a reconstructed crash pulse from the most representative test available based upon the test parameters and the reconstruction estimates.

Equations of motion for constant stiffness and constant force structural behavior are merged and extended to model the crash pulse of a structure that transitions from constant stiffness behavior at low crush to approach force saturation at higher crush. The crash pulse is divided into two regimes for modeling, dynamic compression and rebound. This merged ordinary differential equation produces a series of trigonometric-like functions that have adjustable characteristics such that they behave as the sine, cosine, and tangent functions at one extreme (constant stiffness structural behavior) and behave as polynomial functions at the other extreme (constant force structural behavior). Of particular interest is the modeling of structural behavior between these two limit behaviors.

Nine crash tests were conducted at various speeds on three vehicles in three locations under conditions that resulted in similar damage. The objective was to study the differences in crash pulse, deltaV, crush depth, and impact location with change in closing velocity from 20 to 55 mph. Three equal-weight Nissan Sentra vehicles were impacted in the front, rear, and side by an associated narrow object impact device. The three impactors were identically shaped, flat-faced, one-foot wide, and rigid; but each was designed to have a different weight (light, moderate, and heavy weight). The heavy, moderate, and light weight impactors collided with their associated test vehicle at low, medium, and high impacting speeds, respectively, in order to produce damage corresponding to a 20 mph BEV (Barrier Equivalent Velocity) in all nine tests. Impacts at the same location on the three vehicles produced nearly identical damage yet substantially differed in deltaV.

Crash behavior in narrow object impacts was examined for the perimeter of a 4-door full size sedan. Additional test data was obtained for this vehicle by impacting four sedans with a rigid pole mounted to a massive moving barrier (MMB) in the front, right front oblique, right side, and rear. The vehicles were stationary when impacted by the MMB. Two of the four cars were repeatedly impacted with increasing closing speeds in the front and side, respectively. Each test was documented and the resulting deformation accurately measured. The stiffness characteristics were calculated for the perimeter of car and were presented using the power law damage analysis model. The vehicle's crash performance in these pole tests was compared to that of NHTSA's flat fixed barrier tests (deformable and non-deformable) for the front, side, and rear of this vehicle.

Frontal, side, rear, pole and offset car to car data sets are examined using familiar damage analysis models: constant stiffness, bilinear stiffness, and force saturation. In addition to these, a non-linear power-law formulation is introduced and compared to the others. The power-law provides a nonlinear stiffness coefficient that transitions between a constant force model and constant stiffness model as the power goes from 0 to 1. It also provides a continuous, single valued function that is easily integrated and used in the analysis. Power-law nonlinearity can be used to smoothly fit low through high crush data. Geometric integral parameters are developed which represent irregular crush profiles. These permit graphical comparison of tests with non-uniform crush data (such as offset, side, and narrow object) with uniform crush test data. They also provide a means for comparison of accident damage with the test data set.

Damage analysis methods in accident reconstruction use an estimate of vehicle stiffness together with measured crush to calculate crush energy, closing speed, and vehicle delta-V. Stiffness is generally derived from barrier crash test data. The accident being reconstructed often involves one or more conditions for which vehicle stiffness is not well defined by existing crash tests. Massive moving barrier (MMB) testing is introduced as a tool to obtain additional and accident specific stiffness coefficients applicable for reconstruction. The MMB impacts a stationary vehicle of similar structure as the accident vehicle under accident-specific conditions like impact location, angle, over-ride / under-ride, offset and damage energy. A rigid or deformable structure is mounted to the front of the MMB, representative of the impacting structure in the accident. Four illustrative tests are presented.