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In order to test and design vehicle systems it is often necessary to develop prototypes. A vehicle's steering system requires a qualitative analysis since it is difficult to quantify and measure subjective quantities such as the “feel” of a steering system. The virtual prototype system (VPS) provides an effective and flexible way of developing and testing the prototypes for qualitative testing. By creating a computer model of a vehicle's steering system using a dynamic simulation package and linking it to a virtual reality vehicle, a designer can drive the virtual prototype vehicle as if he or she were operating an actual vehicle.

Virtual reality technology permits engineers to assess visibility of virtual machines interactively in a virtual environment. Use of a virtual prototyping system allows one to investigate, in three dimensions, the effect of design changes on the visibility of critical machine components, such as the working tool. Although there have been successful applications of virtual prototyping systems to visibility assessment, there still exist system limitations that need to be overcome.

Virtual reality is an emerging technology with the potential for many engineering applications including machinery simulation. In this paper the writers describe the hardware and software components of a virtual reality system that simulates machinery. They detail the flow of information that occurs in this system and discuss the functioning of an existing system at the National Center for Supercomputing Applications (NCSA) located at the University of Illinois at Urbana-Champaign. Finally, they describe potential uses of virtual reality in product design, manufacturing, training and marketing.

Roll bars are currently a primary source of operator protection for recreational vehicles, for certain lawn and garden tractors and for small agricultural tractors. In this paper we describe a family of nonlinear models to predict the large deflection response of a roll bar due to yielding of the material. This yielding permits the structure to absorb energy. The stress-strain relationship employs a power law model. Subsequent calculation of the complementary energy stored in the structure and application of Castigliano's second theorem yield the deflection at the point of loading. To demonstrate the feasibility of this energy method in the simulation of testing of roll bars, we present numerical results for the side, vertical, and fore-aft loading cases. Results include the load-deflection response for each load case as well as the strain energy stored in the roll bar as it deforms.

ROPS-TEST is a newly developed, interactive, graphics program that may be used to simulate testing of roll bars. Cross-sections that it currently supports include solid rectangular, rectangular tubing, and circular tubing. ROPS-TEST can be used to simulate testing for crush, rear and side loading. Output from ROPS-TEST includes load-deflection and strain energy-deflection plots. ROPS-TEST does not replace actual testing of prototype roll bars. Rather it serves as a design tool to select the best design options for a particular application prior to actual testing of the prototype roll bars.

Basket motion of a cotton picker during the unloading cycle can produce unstable conditions that result in overturning the machine. The potential for overturning increases while operating the machine on a side slope with the basket dumping on the down-hill side. In this paper the writers investigate the influence of tire ballast, wheel weights and operator control of the hydraulic cylinder on the dynamic stability of the machine during the unloading cycle while operating on a side slope. Operator control at the beginning of the unloading cycle and near the end of the cylinder stroke promotes stable operation of the machine on a side slope.

Commercial software is now available for the dynamic simulation of industrial equipment using microcomputers. Applications in this paper include simulation of a backhoe work cycle, backhoe trench leveling and machine rollover. Key features of the software include interactive plots of response in color graphics, multiple frame displays of machine motion and on-the-fly changes of design parameters. In addition animation gives an added dimension of understanding to the machine motion under study.

Engineers from design, test and analysis teamed together to develop a suspension for the John Deere 862 Scraper. The design engineer coordinated developmental activities of the team. The engineering analyst helped evaluate initial design alternatives using an interactive program to predict ride performance. The test engineers instrumented a scraper to measure ride performance under a variety of conditions and suggested practical changes to the mechanical and hydraulic components of the suspension to improve its performance. The team approach proved to be a cost effective, timely approach to the design of off-highway vehicle suspensions.

Industry sponsored research and development benefits both industry and engineering institutions. The focus of this paper is on these benefits, the keys to a successful relationship and on suggestions for improved performance for future projects. Two recent cases illustrate the benefits of this relationship.

Three nonlinear finite element models were developed for prediction of the large deflection response of cab windows made from polycarbonate thermoplastic. Excellent correlation existed between deflections measured in the laboratory and those predicted for two of the models developed. As a result, use of these models provides the design engineer the opportunity to select the best design alternative prior to laboratory testing per SAE J1084.

A systems approach was used to reduce development time for product evaluation. The approach combines field measured load-time data with finite element modeling and strain-life prediction techniques. This allows the design engineer to estimate component life of design alternatives prior to construction and testing. The approach is illustrated with examples from the design evaluation of a motor grader main frame.