RESEARCH - Simulations/Vizualizations

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.

Extracting Tire Model Parameters from Test Data

SAE Paper No. 2006-01-1399 Authors: Wesley D. Grimes, Jonathan A. Balasa, Eric J. Hunter, and Thomas Vadnais

Computer models used to study crashes require information to describe the vehicles. Information such as weight, length, wheelbase, tire locations, crush stiffness, tire parameters, etc. all require a reliable source. Usually the tire parameters are difficult to obtain. Analysts will routinely use default or "typical" values. In 1999, Engineering Dynamics Corp. (EDC) attempted to address this issue, with support from many in the field of crash reconstruction, by conducting tire tests. The resulting tire test data will be used to study motor vehicle performance. The computer simulations in use today require information about tire properties or lookup tables that must be extracted from raw collected data. This paper presents a basic overview of the tire test data and a technique for extracting the required tire parameters for use in computer simulation modeling.

Heavy Truck Brake Designer Validation Testing

EDC WP #2005-2 Authors: Thomas H. Vadnais, P.E. and Wesley D. Grimes, P.E.

In late August 2004, a week-long series of well-documented heavy truck braking tests was conducted at Transportation Research Center (TRC) in East Liberty, OH. Using the same tractor and flatbed semi-trailer, tests were performed with and without ABS, on wet and dry surfaces, loaded and unloaded, and at both 30 and 60 mph. Additional tests were done with the semi-trailer's ABS disabled, with only the tractor's ABS system cross-wired, with some of the tractor and trailer brakes out of adjustment, and with the bobtail tractor alone. Both the tractor and semi-trailer were documented to allow creation of an accurate HVE vehicle model, including all brake components. For this initial paper, SIMON runs, using the Brake Designer, were made of several actual test runs to validate the software against the actual test data. These were compared to similar simulations using generic vehicles. For this paper, only loaded, non-ABS, 60 mph tests were modeled, with all brakes in adjustment, and some out of adjustment.

Extracting Tire Model Parameters From Test Data

EDC WP# 2001-4 Authors: Wesley D. Grimes, P.E. and Eric Hunter

Computer models used to study crashes require data describing the vehicles. Data such as weight, length, wheelbase, tire locations, crush stiffness, tire parameters, etc. all require some source of information. Usually the tire parameters are difficult to obtain and analysts will routinely use default or "typical" values. Engineering Dynamics Corp. (EDC), with support from many in the field of crash reconstruction, conducted a tire test series in 1999 to obtain tire data that will be used in studying motor vehicle performance. The computer simulations in use today require some type of tire data coefficients or lookup tables that must be extracted from the raw collected data. This paper presents a basic overview of the tire test data and presents a technique for extracting the required tire parameters for use in computer simulation modeling.

The Importance of Crash Pulse Data When Analyzing Occupant Kinematics Using Simulations

EDC WP# 2000-2 Authors: Wesley D. Grimes, P.E., F. Denny Lee, Ph. D.

Computer simulations are frequently used to analyze occupant kinematics in motor vehicle crashes, including what they collide with during the crash and the severity of these internal collisions. From study of such occupant simulations, it is then possible to infer how the actual human occupants may have been injured in a crash. When using a simulation to study how occupants react in a vehicle crash, a crash-pulse is usually required as input to the occupant simulation model. This crash-pulse is typically generated from a study of the vehicle motion and acceleration during the crash. There are several different methods for obtaining such a crash-pulse which are in common use. Each of these methods produces a different shape for the crash-pulse, even with identical velocity changes for the vehicle. The time duration, maximum acceleration, and general shape of the crash-pulse may influence the predicted motion of the occupants. In this research, the GATB (Graphical Articulated Total Body) computer simulation model is used to study basic occupant kinematics using a variety of shapes for the crash-pulse, in order to determine how the specific shape of the crash- pulse affects the predicted occupant kinematics.

The Effect of Crash Pulse Shape on Occupant Simulations

SAE Paper No. 2000-01-0460 Authors: Wesley D. Grimes and F. Denny Lee

Computer simulations are frequently used to analyze occupant kinematics in motor vehicle crashes, including what they collide with during the crash and the severity of these internal collisions. From study of such occupant simulations, it is then possible to infer how the actual human occupants may have been injured in a crash. When using a simulation to study how occupants react in a vehicle crash, a crash-pulse is usually required as input to the occupant simulation model. This crash-pulse is typically generated from a study of the vehicle motion and acceleration during the crash. There are several different methods for obtaining such a crash-pulse which are in common use. Each of these methods produces a different shape for the crash-pulse, even with identical velocity changes for the vehicle. The time duration, maximum acceleration, and general shape of the crash-pulse may influence the predicted motion of the occupants. In this research, the GATB (Graphical Articulated Total Body) computer simulation model is used to study basic occupant kinematics using a variety of shapes for the crash- pulse, in order to determine how the specific shape of the crash-pulse affects the predicted occupant kinematics.

3-Dimensional Simulation of Vehicle Response to Tire Blow-outs

SAE Paper No. 980221 Authors: William Blythe, Terry D. Day, and Wesley D. Grimes

Sudden tire deflation, or blow-out, is sometimes cited as the cause of a crash. Safety researchers have previously attempted to study the loss of vehicle control resulting from a blow-out with some success using computer simulation. However, the simplified models used in these studies did little to expose the true transient nature of the handling problem created by a blown tire. New developments in vehicle simulation technology have made possible the detailed analysis of transient vehicle behavior during and after a blow-out. This paper presents the results of an experimental blow-out study with a comparison to computer simulations. In the experiments, a vehicle was driven under steady state conditions and a blowout was induced at the right rear tire. Various driver steering and braking inputs were attempted, and the vehicle response was recorded. These events were then simulated using EDVSM. A comparison between experimental and simulated results is presented. The research was extended by simulating blow-outs at other wheel locations and observing how various driver inputs affect the vehicle's response.

Documenting Scientific Visualizations and Computer Animations Used in Collision Reconstruction Presentations

SAE Paper No. 980018 Authors: Wesley D. Grimes, Charles P. Dickerson and Corbett D. Smith

Scientific visualizations and computer animations are frequently presented to show the results of simulation models or the opinions of a reconstructionist. In these cases it is important to properly document the graphical images being presented. Proper documentation depends somewhat on the methodologies used to produce the images, but every scientific visualization, computer animation, and computer generated image should be documented sufficiently to allow others to duplicate the images. There are also some basic data that should accompany any computer generated images that will reveal the basis of the motion for all primary objects being depicted. This paper presents some basic definitions and outlines the data that is required to document scientific visualizations and computer animations.

Using ATB Under the HVE Environment

SAE Paper No. 970967 Author: Wesley D. Grimes

The Articulated Total Body (ATB) program has been used to study occupant kinematics in motor vehicle collisions for several years. The ATB model is a complex 3-dimensional lumped-mass model available for many different computer systems, including the personal computer, and requires formatted data files for the data input. A new version of this model, Graphical Articulated Total Body (GATB), has been developed to be operated under the HVE (Human, Vehicle, Environment) computer environment. The GATB program uses the graphical system built into HVE. This aids in set up and execution of the model to study human occupants in motor vehicle collisions. This paper addresses the integration of the ATB model with the HVE environment and includes a validation study comparing the GATB results to those of the ATB program.

Programming Fortran Applications for HVE

SAE Paper No. 960889 Author: Wesley D. Grimes

The Human Vehicle Environment (HVE) program, developed by Engineering Dynamics Corporation, combines the vehicle parameters, physics and graphics into a single computer system for use in analyzing motor vehicle collisions, handling issues, studying occupant motion, etc. One of the most valuable assets of the HVE program is the open architecture that allows easy access to the data and graphics capabilities from an independent computer program. Thus, virtually any program that can be recompiled on the Silicon Graphics system can be set up to utilize the HVE tools. HVE is written in two computer languages known as C and C++ (pronounced "C plus plus"), this aids in the graphics processing. Unfortunately, FORTRAN programs do not automatically interface with C or C++ programs. These programs must be modified to allow a two-way data path to and from HVE. This paper will briefly review the concepts of interfacing programs and then give specific examples of combining FORTRAN programs with the HVE environment.

Using ATB in Collision Reconstruction

SAE Paper No. 950131 Author: Wesley D. Grimes

The Articulated Total Body (ATB) computer program, sometimes referred to as the Crash Victim Simulator (CVS), is a powerful tool to aid in studying occupant kinematics in motor vehicle collisions. There are many options available within the ATB/CVS model and associated utility programs, such as GEBOD, which allow an analyst to model specific collisions and occupants. This paper discusses ATB/CVS as a tool for use in collision reconstruction. Specific examples are presented in developing a crash pulse from vehicle simulation programs such as EDSMAC, SMAC, HVOSM, etc. Techniques are also presented for modelling other moveable objects within the occupant environment, such as a seat back, steering column, or intrusion into the occupant compartment. A series of programs to aid in setting up an ATB data file, the CAL-3D Users Convenience Package, is also discussed.

Classifying the Elements in a Scientific Animation

SAE Paper No. 940919 Author: Wesley D. Grimes

Computer animation and its use in the engineering/scientific community are in their infancy. As this visualization tool becomes more widely used and accepted, individual expectations may differ greatly regarding appropriate usage and documentation of an animation. This paper lays the foundation for establishing guidelines for documenting the data and techniques used in producing an animation. The many elements that make up an animation are discussed, along with their importance to the presentation. The ultimate goal, for using the proposed guideline, is to achieve consistency within the engineering / scientific community when evaluating an animation.

Computer Animation Techniques for Use in Collision Reconstruction

SAE Paper No. 920755 Author: Wesley D. Grimes

The use of computer animation in the analysis of automobile collisions provides a reconstructionist the ability to 'see' an object from any perspective and visually depict its movement in three-dimensional space. Although many computer animation programs are currently available, none of these off-the-shelf software and hardware combinations are directed specifically at animating vehicle or occupant motion in conjunction with a collision. Many computer programs, specifically created for modeling vehicle or occupant motion, are available, but these typically do not create visual images with the detail offered in computer animation programs. Analysts can generate the data for computer animation by using collision simulation programs along with computer spreadsheets. Techniques for calculating the data required for computer animation are discussed in this paper.