Side impact crashes are the second most severe motor vehicle accidents resulting in serious and fatal injuries. One of the occupant restraint systems in the vehicle is the three point lap/shoulder harness. However, the lap/shoulder restraint is not effective in a far-side crash (impact is opposite to the occupant location) since the occupant may slip out of the shoulder harness. The present comprehensive study was designed to delineate the biomechanics of far-side planar crashes. The first part of the study involves a car-to-car crash to study the crash dynamics and occupant kinematics; the second part involves an epidemiological analysis of NASS/CDS 1988-2003 database to study the distribution of serious injury; the third part includes the mathematical MADYMO analysis to study the occupant kinematics in detail; and the fourth part includes an in-depth analysis of a real world far-side accident to delineate the injury mechanism and occupant kinematics. Results indicate that the shoulder harness is ineffective in far-side crashes. The upper torso of the belted driver dummy slips out of the shoulder harness and interacted with the opposite vehicle interior such as the door panel. The unbelted occupants had a similar head injury severity pattern compared to belted occupants. The present study is another step to advance towards better understanding of the prevention, treatment and rehabilitation of side impact injuries.

EI Consultants (formerly The Engineering Institute) has been studying solid rear axle tramp for well over a decade, and contributed several publications to the literature outlining recommended test methods and their results. Throughout the history of EI’s research, sustained tramp inputs have been achieved by use of a tire featuring affixed lumps of rubber to induce wheel hop at one end of the axle. The principal methodological guide for studying the vehicle response to this input has been the test methods and data analysis recommendations of test standard SAE J266: Steady-State Directional Control Characteristics for Passenger Cars and Light Trucks. More specifically, past testing has been patterned almost exclusively on the circle test (constant-radius/slowly-increasing-speed) method discussed in J266. Historically, the J266 recommendation for data analysis and presentation, i.e. understeer/oversteer gradients derived from a wheel angle versus lateral acceleration plot, were principally used. Recent research, along with fresh analysis of previous testing results, revealed limitations of the circle test and the J266 recommended manner of data analysis in the context of tramp resonance testing. During a constant-radius/slowly-increasing-speed test, a single control variable (speed) has the effect of changing both the lateral acceleration and the tramp input frequency simultaneously. This effect results in a non-steady-state test event where only a narrow portion of each test run expresses the resonant axle tramp phenomenon that is the intended object of the observation. To provide a wider view of vehicle response characteristics during sustained axle tramp, EI Consultants selected and evaluated expanded test methods in a recent testing project. These methods included performing circle tests at multiple radii, performing continuous tests modeled after the J266 constant-speed/variable-radius method, and performing path-following tests modeled after the slowly increasing steer method. Expanded data analysis and presentation methods were developed to quantify and understand the vehicle oversteer response in more effective ways than those recommended by J266. Due to the abrupt discontinuity in the vehicle’s response upon reaching the resonant tramp frequency, novel methods of data presentation were shown to be more useful in assessing vehicle characteristics during resonant tramp. Of particular value was examining the steering input delta in the vehicle speed and tramp input frequency domains during the phase of resonant axle response; and examining the difference between the actual yaw rate and the theoretical Ackerman yaw rate derived from the measured steer angle. This paper will detail the data analysis techniques that were developed to overcome the limitations of the J266 standard’s steer gradient methodology, and thus introduce a more useful approach to evaluating understeer/oversteer characteristics during non-steady-state test events. This paper is the first of two companion papers presenting theory and results from EI Consultants’ most recent axle tramp testing. This paper focuses on new understandings of test data analysis theory, while the second paper will summarize the results of numerous tests and their application to various suspension design strategies for improving solid rear axle tramp control, with a motivation for enhancing vehicle controllability and highway safety.

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