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EDC

Using SIMON To Drive Into Deep Potholes

The HVE White Paper section of the EDC website Library contains numerous examples of real-world crash reconstructions and research studies performed by HVE users from around the world. The HVE White Paper below, presented at the 2011 HVE Forum, is yet another excellent example of how HVE simulations, and the extensive capabilities of SIMON in particular, may be used to study the dynamics of a vehicle driving over an irregular terrain. In this example, the tires impact a deep pothole, resulting in unanticipated vehicle motion and accelerations that lead to the ejection and extensive injury of the vehicle operator.


HVE-WP-2011-1
Modeling a Pothole Impact of an Agricultural Tractor Using HVE and SIMON

Ciro Ramirez, PhD, PE, CSHO and R. Joe Thornhill, PhD, PE, CSHO
Thornhill, Ramirez & Associates, Inc.

ABSTRACT:

This paper presents an HVE study of the dynamics of a cabbed agricultural tractor pulling a large rotary shredder when impacting a deep pothole. The study was conducted using the SIMON physics module as part of an effort to quantify the way in which a tractor operator could be ejected from the tractor cab, possibly resulting in serious injuries from the shredder. The HVE radial spring tire model was used to predict tractor bounce as it encountered the hole at a variety of attack offsets and two different speeds. Unique vehicle features modeled for this study included agricultural tires and a rigid, unsprung front axle mounted on a pivot and angle limiting stops. A follow-up study was conducted by combining the SIMON soft soil model and field measurements to estimate the coasting distance of the tractor and shredder at the incident site if engine fuel flow is stopped.

INTRODUCTION:

Agricultural tractors are designed to provide high tractive force at low speeds over unpaved surfaces, with a secondary design feature being auxiliary power take-off (PTO) capability to drive implements such as rotary shredders/mowers and augers. Tractor designs do not typically include sprung suspensions, with operator comfort provided by seat suspensions instead. Agricultural tractors are intended for off-road use and are susceptible to overturning due to their high center of gravity. The lack of a sprung suspension can also cause violent tractor motions when encountering large bumps or potholes. The tractor dynamics study described in this paper was conducted to predict the motions caused by striking a large pothole while towing a rotary shredder.

The resulting displacement and acceleration at the operator's position were also studied in order to evaluate the likelihood of an unrestrained operator being ejected from the cab in such an event. These results were used in the analysis of an accident in which the operator was ejected through the rear window of the cab and severely injured when he was struck by the shredder.


To download this publication, visit the HVE White Paper section of the EDC website Library, click on the images above, or just click here. For more information about using HVE and SIMON for your crash reconstructions, please contact EDC Sales or call 503.644.4500.

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