RESEARCH - Dynamics / Rollovers

Analyzing The Trip-Phase of Soft-Soil Rollovers
SAE Paper No. 2006-01-1558 Authors: Wesley D. Grimes, Jonathan A. Balasa, Eric J. Hunter, and Don Stevens

Rollover collisions sometimes involve a vehicle sliding and plowing on a soft-soil surface. There is little work published on the deceleration rates for a vehicle sliding and plowing in soft soil. Previous tests involving a 4-door sedan sliding sideways and plowing on a soft-soil surface were modeled using the HVE and SIMON 3-dimensional computer simulation program. The plowing forces were modeled using a series of friction multipliers. In addition, an SUV was simulated crossing the same surface in a similar fashion. Results based on these analyzed tests indicate that the average deceleration rate for either vehicle sliding sideways on this soft-soil surface may be approximated by using the vehicle's static stability factor, or T/2H. This paper presents computer modeling techniques used to analyze overturn crashes. Specifically the SIMON 3-dimensional computer simulation model is used in this work.

Properties of Passenger Car Tires With Tread Detachment
SAE Paper No. 2000-01-0697 Authors: Mark W. Arndt, Michael Thorne, and Charles P. Dickerson

A series of tire property tests have been performed at CALSPAN on the flat bed tire test machine. The tires used in the testing were inflated tires with the tread removed. Identical make/model/size tires in normal (tread not removed) condition were also tested. Three passenger car tires and one truck tire were tested. The purpose of this paper is to present comparative results of the testing and data analysis. The test results objectively demonstrate substantial differences in cornering properties. Grouping all tires together, the measured cornering stiffness of a modified tire was reduced on average to 36.1 percent of the normal tire measured properties (ranging from 24.1 to 49.4 percent; standard deviation was 7.7 percent). Overall the character of the modified tire cornering stiffness plots and other modified tire properties were demonstrated to be markedly changed.

Influence of Passenger and Cargo Load on the At Limit Handling of a Mini Van
SAE Paper No. 1999-01-0449 Authors: Mark W. Arndt, Charles P. Dickerson, and Stephen M. Arndt

Using analysis of a mini-van test vehicle's static load conditions as a guide, four different vehicle loading situations were constructed. The loading situations represent the corners of the vehicle''s center of gravity position envelope. For the testing described in this paper, a single vehicle under conditions of varied load was subjected to a series of test maneuvers designed to elicit objective measure and comparison of vehicle steady-state and transient response. The purpose of this paper is to describe the test method and present the results of handling testing and limit stability testing of a 1991 Ford Aerostar mini-van/extended van under four different loading conditions. Differences observed in the plotted results of vehicle steady-state response for different load conditions are detectable, but small. The test results demonstrate differences in vehicle transient response for different loading configurations. Test results indicate increase propensity for wheel lift during step steer maneuvers for increase loading of the vehicle. Test results demonstrate increased occupant and/or increased cargo changes the vehicle's steer behavior. Overall, vehicle limit handling performance and required driver performance for varying passenger and cargo loading was objectively documented and shown measurably changed.

Vehicle Handling with Tire Tread Separation
SAE Paper No. 1999-01-0120 and 1999-01-0450 Authors: Charles P. Dickerson, Mark W. Arndt, and Stephen M. Arndt

Catastrophic and sudden tire tread separation is an event that drivers of motor vehicles may encounter and, in some instances, is implicated as the cause of motor vehicle crashes and related injury or property damage. In an effort to understand how tire tread separation affects vehicle handling, a series of tread separation handling test programs were conducted. In each tread separation test program a sport utility vehicle was instrumented and equipped with steel belted radial tires that were modified to emulate tread separation between the inner and outer steel belts. The test vehicle was then subjected to a variety of open and closed loop handling test maneuvers. This paper presents the data and analysis from these tests. The research demonstrates through controlled experiments that a tire tread separation has an effect on the vehicle's fundamental handling characteristics. It also demonstrates that the effect depends on the position of the compromised tire on the vehicle.

Effects of Passenger and Cargo Loading on a Motor Vehicle's Mass Properties
SAE Paper No. 952676 Authors: Mark W. Arndt, Charles P. Dickerson, Stephen M. Arndt, Gregory A. Mowry, and Steven C. Shapiro

Vehicles may be loaded with passengers and cargo in varying configurations that affect its mass properties during normal use. Mass properties include CG location, weight, and mass moments of inertia. The objective of this paper is to develop an approach identifying possible passenger and cargo load configurations and accurately calculate and display their effect on a motor vehicle's mass properties. An approach is presented and discussed. The calculation method accounts for suspension compliance due to passenger and cargo loading. Overall, the approach provides more accurate and useful estimates of a motor vehicle's CG location and other mass properties. The approach may be of use to vehicle designers, operators, and regulators, providing enhanced access to vehicle parameters which are relevant to motor vehicle safety.

Evaluation of Experimental Restraints in Rollover Conditions
SAE Paper No. 952712 Authors: Mark W. Arndt, Gergory A. Mowry, Charles P. Dickerson, and Stephen M. Arndt

A controlled experimental program was conducted to determine the response of humans and a human surrogate with experimental lap belt restraints in -Gz acceleration environments. In the program, lap belt anchorage position (belt angle) and belt tension/slack were varied. Human volunteers were subjected to a static -1.0 Gz acceleration for each restraint configuration. A 95th percentile male Hybrid III dummy was subjected to a nominal 4.25 m/s (9.5 mph), -5 Gz impact while restrained by each restraint configuration. For the -Gz acceleration, significant changes in occupant head excursion were observed with varied lap belt configurations. In general, less pre-crash belt slack and higher lap belt angles produced significant reductions in occupant vertical excursions. This research provides data for use in evaluating or developing occupant survivability systems for rollover crash environments.

Error Analysis of Center-Of-Gravity Measurement Techniques
SAE Paper No. 950027 Authors: Steven C. Shapiro, Stephen M. Arndt, Gregory A. Mowry, Charles P. Dickerson, and Mark W. Arndt

The height of a vehicle's center-of-gravity (CG) is one factor that influences its handling characteristics. A number of height methods are used to measure CG within the automotive industry. This research determined which method has the greatest potential to produce accurate CG height measurements, given anticipated measurement tolerances. Several techniques for measuring vehicle CG height were analyzed mathematically. The contributions of various parameters to total error were determined and the total error inherent in each method was then compared.

Effects of Outrigger Design on Vehicle Dynamics
SAE Paper No. 940226 Authors: Charles P. Dickerson, Stephen M. Arndt, Gregory A. Mowry, and Mark W. Arndt

Outriggers are devices that arrest vehicle rollover during handling test maneuvers to protect the test vehicle and/or test driver. Validity of data in these tests has been questioned because the effect outriggers have on vehicle dynamics is not well understood. This research quantifies changes in handling characteristics with outriggers attached to a test vehicle. Three outrigger systems of different masses were developed and tested through various limit and sub-limit handling maneuvers. Analysis of the data generated during testing indicates improvements necessary for future outrigger designs leading to better understanding of vehicle dynamics and potentially reduced injuries from rollovers.