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This paper describes the simulation model of a backhoe excavator. The model uses a prescribed motion cycle and the objective of the program is to determine the power requirements for each of the cylinders as well as the total engine power requirement. Most computer simulations are developed by expressing the differential equations of motion for the system being studied. The known force inputs to the system are applied and the time response of the system is then obtained by numerically integrating the governing differential equations. This paper on the other hand develops the reverse of this. Utilizing a prescribed geometry and trajectory cycle for a linkage system as the input, the program solves for the types of force inputs that are required to achieve that trajectory. With the time dependence of the trajectory known, the total power required and the power required of each cylinder is also evaluated. A typical excavator linkage is shown in Fig. 1.

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.

Low aspect ratio wings are used extensively on open-wheeled race cars to generate aerodynamic downforce. Consequently, a great deal of effort is invested in obtaining wing profiles that provide high values of lift coefficient. If the wings are designed using 2-D methods, then it is necessary to take into account the change in operating angle of a typical airfoil section that occurs when it operates in the downwash generated by the wing. Accounting for this change during the design phase will ensure that the airfoil sections are optimized for their intended operating conditions. The addition of endplates to the wing serves to counteract the magnitude of the change in operating angle by effectively producing an increase in wing aspect ratio. During the design process at UIUC, an empirical method was used to provide an estimate of the effective aspect ratio of the wing and endplate combination.

In this work, an efficient and unified combustion model is introduced to simulate the flame propagation, diffusion-controlled combustion, and chemically-driven ignition in both SI and CI engine operation. The unified model is constructed upon a G-equation model which addresses the premixed flame propagation. The concept of the Livengood-Wu integral is used with tabulated ignition delay data to account for the chemical kinetics which is responsible for the spontaneous ignition of fuel-air mixture. A set of rigorously defined operations are used to couple the evolution of the G scalar field and the Livengood-Wu integral. The diffusion-controlled combustion is simulated equivalent to applying the Burke-Schumann limit. The combined model is tested in the simulation of the premixed SI combustion in a constant volume chamber, as well as the CI combustion in a conventional small bore diesel engine.

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.

Induction hardening of mild steel components often results in significant improvements in the static and cyclic load capability, with comparatively small increases in cost. Members subjected primarily to torsional loading are a relevant subset of the broad range of induction hardened components. Due to the variation of material properties and residual stresses, failures are “initiated” at the traditional geometric locations predicted for homogeneous materials and also at subsurface sites. The introduction of shear based fatigue parameters has necessitated the consideration of the residual stress as a three dimensional quantity, especially when analyzing subsurface failures. Not considering the tensoral nature of the residual stress can lead to serious errors when estimating fatigue life, and for larger magnitude loadings, the residual stress field may relax.

A numerical study of micro-explosion in multi-component droplets is presented. The homogeneous nucleation theory is used in describing the bubble generation process. A modified Rayleigh equation is then used to calculate the bubble growth rate. The breakup criterion is then determined by applying a linear stability analysis on the bubble-droplet system. After the explosion/breakup, the atomization characteristics, including Sauter mean radius and averaged velocity of the secondary droplets, are calculated from conservation equations. Micro-explosion can be enhanced by introducing biodiesel into the fuel blends of ethanol and tetradecane. Micro-explosion is more likely to occur at high ambient pressure. However, increasing the ambient temperature does not have a significant effect on micro-explosion. There exists an optimal composition in the liquid mixture for micro-explosion.

The purpose this paper is to delineate why there exists a trade-off between biomechanical realism and algorithmic efficiency for human motion simulation models, and to illustrate how empirical human movement data and findings can be integrated with novel modeling techniques to overcome such a realism-efficiency tradeoff. We first review three major classes of biomechanical models for human motion simulation. The review of these models is woven together by a common fundamental problem of redundancy—kinematic and/or muscle redundancy. We describe how this problem is resolved in each class of models, and unveil how the trade-off arises, that is, how the computational demand associated with solving the problem is amplified as a model evolves from small scale to large scale, or from less realism to more realism.

The ability to categorize, compare and segregate the roll dynamical behavior of various vehicles from one another is a subject of considerable research interest. A number of comparison paradigms have been developed (static stability index, roll couple methods, etc.), but all suffer from lack of robustness: results developed on the basis of a particular comparison metric are often not able to be generalized across vehicle lines and types, etc., or they simply do not segregate vehicles at all. In addition, most models do not describe vehicle dynamics in sufficient detail, and some contain no dynamics at all (e.g., static stability index = t/2h). In the present work, static stability index, a two-degree-of-freedom roll model and a three-degree-of-freedom roll and handling model were used to locate eigenvalues for a sample of 43 vehicles consisting of (1) passenger cars, (2) light trucks, (3) sport/utility vehicles and (4) minivans.

As engine researchers are facing the task of designing more powerful, more fuel efficient and less polluting engines, a large amount of research has been focused towards homogeneous charge compression ignition (HCCI) operation for diesel engines. Ignition timing of HCCI operation is controlled by a number of factors including intake temperatures, exhaust gas recirculation (EGR) and injection timing to name a few. This study focuses on the computational modeling of an optically accessible high-speed direct-injection (HSDI) small bore diesel engine. In order to capture the phenomena of HCCI operation, the KIVA computational code package has been outfitted with an improved and optimized Shell autoignition model, the extended Zeldovich thermal NOx model, and soot formation and oxidation models. With the above named models in place, several cases were computed and compared to experimentally measured data and captured images of the DIATA test engine.

A multicomponent fuel film vaporization model using continuous thermodynamics is developed for multidimensional spray and wall film modeling. The vaporization rate is evaluated using the turbulent boundary-layer assumption and a quasi-steady approximation. Third-order polynomials are used to model the fuel composition profiles and the temperature within the liquid phase in order to predict accurate surface properties that are important for evaluating the mass and moment vaporization rates and heat flux. By this approach, the governing equations for the film are reduced to a set of ordinary differential equations and thus offer a significant reduction in computational cost while maintaining adequate accuracy compared to solving the governing equations for the film directly.

A prediction model for hand prehensile movements was developed and validated. The model is based on a new approach that blends forward dynamics and a simple parametric control scheme. In the development phase, model parameters were first estimated using a set of hand grasping movement data, and then statistically analyzed. In the validation phase, the model was applied to novel conditions created by varying the subject group and size of the object grasped. The model performance was evaluated by the prediction errors under various novel conditions as compared to the benchmark values with no extrapolation. Analyses of the model parameters led to insights into human movement production and control. The resulting model also offers computational simplicity and efficiency, a much desired attribute for digital applications.

This paper presents a programmable E/H control valve consisting of five individually proportional flow control valves. With a hybrid control algorithm, this valve has programmable valve characteristics, such as adjustable valve deadband and flow control gain, and programmable valve functions, such as different center functions. System analyses and experimental evaluations indicate that this programmable valve is capable of replacing conventional E/H control valves in practical applications.

A dynamic model for the springless electrohydraulic valvetrain has been developed. The model speeds up the valvetrain development process by simulating effects of parameter changes, thus minimizing the number of hardware variations. It includes dynamic characteristics of check valves that enable energy recovery, hydraulic snubbers that limit seating velocity of the engine valves, and leakage in the control solenoids. A good match of the experimental data has been obtained for a single valve system, and the model calibration and validation have been completed. The known parameters are used together with some unknown calibration constants which have been tuned to match the experimental data. The simulation results for a twin valve system are also presented. The model applications for system performance analysis and for the closed-loop control of the engine valve lift are described. The cyclic variability of the experimental data is also discussed.

The transporting of live cattle involves the use of Class 8 tractors and livestock semi-trailers for transportation from farms and feedlots to processing plants. This travel may include unimproved roads, local streets, two lane highways, as well as interstate highways. Typically, cattle are compartmentalized in a “double deck” fashion as it provides utility and comports with size and weight limits for commercial Class 8 vehicles. Concern has been expressed for the effect of cattle movement upon the dynamic performance of the loaded Class 8 tractor-livestock trailer assembly. Loading guidelines exist for cattle that attempt to prevent injury or debilitation during transit, and literature exists on the orientation and some kinematics of loaded cattle. Considerable literature exists on the effect of liquid slosh in tankers and swinging beef carcasses suspended from hooks in refrigerated van trailers on the dynamic response and roll stability of those vehicles.

Constant Velocity (CV) joints are an integral part of modern vehicles, significantly affecting steering, suspension, and vehicle vibration comfort levels. Each driveshaft comprises of two types of CV joints, namely fixed and plunging types connected via a shaft. The main friction challenges in such CV joints are concerned with plunging CV joints as their function is to compensate for the length changes due to steering motion, wheel bouncing and engine movement. Although CV joints are common in vehicles, there are aspects of their internal friction and contact dynamics that are not fully understood or modeled. Current research works on modeling CV joint effects on vehicle performance assume constant empirical friction coefficient values. Such models, however are not always accurate, especially under dynamic conditions which is the case for CV tripod joints.

Environmental concerns have obstructed development of new landfill sites making it essential to efficiently use currently available space. Finite element methods are evaluated for predicting densification by compactors with the intent of eventually optimizing vehicle design with respect to compaction. A geometrically non-linear, plane strain, quasistatic analysis is used to capture the effects of a single rigid wheel. Future work will include multiple wheels and successive passes, three-dimensional simulations, and realistic material characterization.

Cyclic loading is not as damaging as static loading of ceramics at high temperatures. Microcrack growth retardation has been established as a mechanism for increasing the durability of ceramics at high temperatures. A combined experimental and theoretical approach provides a mechanistic understanding of the deformation and failure processes in ceramic materials at high temperatures. Results demonstrate that the high temperature behavior of some ceramic material systems are controlled by the behavior of the grain boundary phase whose response is considerably different under static and cyclic loading.

This paper describes and discusses a computer model that can be used to predict the hydraulic pump requirements of an excavator necessary to meet the specified productivity levels for a given set of design conditions. The model predicts the hydraulic cylinder flow rates, pressures, and power necessary to sustain a given work cycle. The study compares the results from a simulation of the excavator with actual test data obtained from a test vehicle taken during a typical work cycle.