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Technical Paper

Using R744 (CO2) to Cool an Up-Armored M1114 HMMWV

2005-05-10
2005-01-2024
The US Army uses a light tactical High-Mobility Multi-Purpose Wheeled Vehicle (HMMWV) which, due to the amount of armor added, requires air conditioning to keep its occupants comfortable. The current system uses R134a in a dual evaporator, remote-mounted condenser, engine-driven compressor system. This vehicle has been adapted to use an environmentally friendly refrigerant (carbon dioxide) to provide performance, efficiency, comfort and logistical benefits to the Army. The unusual thermal heat management issues and the fact that the vehicle is required to operate under extreme ambient conditions have made the project extremely challenging. This paper is a continuation of work presented at the SAE Alternate Refrigerants Symposium held in Phoenix last June [1].
Technical Paper

Transient and Steady State Performance Characteristics of a Two-Wheel-Steer and Four-Wheel-Steer Vehicle Model

1991-09-01
911926
Using a three-degree-of-freedom vehicle model (side-slip, yaw and roll degrees of freedom) and a nonlinear, saturating rire model, the behavior of a typical exemplar vehicle (1986 Dodge Lancer Turbo) was simulated. Steady state performance was examined through simulating a skidpad lateral accelerarion maneuver. A lane change maneuver was used to reprcsenr transient performance characteristics. A few simple experiments were conducted wirh rhe exemplar vehicle to establish parameters and verify some performance properties. Results of both steady srare and rransienr simulations showed that four -wheel steer offers lirrle or no demonstrated performance advanrages over two-wheel steer.
Technical Paper

Smart Icing Systems for Aircraft Icing Safety

2003-06-16
2003-01-2100
Aircraft incidents and accidents in icing are often the result of degradation in performance and control. However, current ice sensors measure the amount of ice and not the effect on performance and control. No processed aircraft performance degradation information is available to the pilot. In this paper research is reported on a system to estimate aircraft performance and control changes due to ice, then use this information to automatically operate ice protection systems, provide aircraft envelope protection and, if icing is severe, adapt the flight controls. Key to such a safety system would be he proper communication to, and coordination with, the flight crew. This paper reviews the basic system concept, as well as the research conducted in three critical areas; aerodynamics and flight mechanics, aircraft control and identification, and human factors.
Technical Paper

Reconfigurable Control System Design for Future Life Support Systems

2008-06-29
2008-01-1976
A reconfigurable control system is an intelligent control system that detects faults within the system and adjusts its performance automatically to avoid mission failure, save lives, and reduce system maintenance costs. The concept was first successfully demonstrated by NASA between December 1989 and March 1990 on the F-15 flight control system (SRFCS), where software was integrated into the aircraft's digital flight control system to compensate for component loss by reconfiguring the remaining control loop. This was later adopted in the Boeing X-33. Other applications include modular robotics, reconfigurable computing structure, and reconfigurable helicopters. The motivation of this work is to test such control system designs for future long term space missions, more explicitly, the automation of life support systems.
Technical Paper

Oversteer/Understeer Characteristics of a Locked Differential

1994-12-01
942485
The type of differential used in a vehicle has an important and often-neglected effect on handling performance. This is particularly important in racing applications, such as in IndyCar racing, in which the type of differential chosen depends on the course being raced (superspeedway ovals, short ovals, temporary street courses and permanent road courses). In the present work, we examine the effect of a locked rear differential on oversteer/understeer behavior. Using a linear tire model, it is shown that employing a locked differential adds a constant understeer offset to the steering wheel angle (SWA) -v- lateral acceleration vehicle signature. A computer simulation of steady-state cornering behavior showed that the actual effect is much more complicated, and is strongly influenced by static weight distribution, front/rear roll couple distribution, available traction and the radius of the turn being negotiated.
Technical Paper

Neural Networks in Engineering Diagnostics

1994-04-01
941116
Neural networks are massively parallel computational models for knowledge representation and information processing. The capabilities of neural networks, namely learning, noise tolerance, adaptivity, and parallel structure make them good candidates for application to a wide range of engineering problems including diagnostics problems. The general approach in developing neural network based diagnostic methods is described through a case study. The development of an acoustic wayside train inspection system using neural networks is described. The study is aimed at developing a neural network based method for detection defective wheels from acoustic measurements. The actual signals recorded when a train passes a wayside station are used to develop a neural network based wheel defect detector and to study its performance. Signal averaging and scoring techniques are developed to improve the performance of the constructed neural inspection system.
Technical Paper

Methods for Detection of Lubrication Failure Applied to a Swashplate Compressor

2000-03-06
2000-01-0974
Understanding lubrication failures at the shoe/swashplate contact of automotive swashplate compressors will greatly enhance the reliability of the air conditioning system. Maintaining proper lubrication is not always possible during transient conditions. Therefore, a method for detection of lubricant loss is of great interest to the automotive industry. Three methods for detecting lubrication loss were examined: contact resistance, acoustic emission, and dynamic pressure oscillations. A mobile air conditioning test stand capable of recording many system parameters was used. Oil return to the compressor was monitored using an oil separator and a refrigerant/oil concentration sensor. Data were taken during steady oil return rates and after oil shut off. The electrical contact resistance between the shoe and swashplate was used to indicate changes in the lubrication conditions at this critical interface. Measurements were taken at two oil return rates during steady oil return tests.
Technical Paper

Experimental Study of Open-Wheel Race-Car Front Wings

1998-11-16
983042
An experimental study was performed at the University of Illinois at Urbana-Champaign Low-Speed Wind Tunnel to quantify the performance and flowfield effects of two-element open-wheel-race-car front wing configurations. Four distinct configurations were tested in- and out-of-ground effect and at various speeds (Reynolds numbers), angles of attack, and flap positions. A splitter plate was installed in the wind tunnel to act as the ground plane. Data presented include balance force measurements, surface pressure data, and downstream flow measurements using a seven-hole probe. Results show that these elementary factors in the design of race-car front wings have a significant effect on wing performance and behavior of the downstream flowfield.
Technical Paper

Dynamics and Roll Stability of a Loaded Class 8 Tractor-Livestock Semi-Trailer

1999-11-15
1999-01-3732
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.
Technical Paper

Cylinder Pressure Data Acquisition and Heat Release Analysis on a Personal Computer

1986-02-01
860029
The availability and low price of personal computers with suitable interface equipment has made it practical to use such a system for cylinder pressure data acquisition. With this objective, procedures have been developed to measure and record cylinder pressure on an individual crank angle basis and obtain an average cylinder pressure trace using an Apple II Plus personal computer. These procedures as well as methods for checking the quality of cylinder pressure data are described. A simplified heat release analysis technique for an approximate first look at the data quality is presented. Comparisons are made between the result of this analysis, the Krieger-Borman heat release analysis which uses complete chemical equilibrium. The comparison is made to show the suitability of the simplified analysis in judging the quality of the pressure data.
Technical Paper

Comparison of Linear Roll Dynamics Properties for Various Vehicle Configurations

1992-02-01
920053
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.
Technical Paper

Cavitating Flow within an Injector-Like Geometry and the Subsequent Spray

2019-04-02
2019-01-0284
Cavitation plays a significant role in the spray characteristics and the subsequent mixing and combustion process in engines. Cavitation has beneficial effects on the development of the fuel sprays by improving injection velocity and promoting primary break-up. On the other hand, intense pressure peaks induced by the vapor collapse may lead to erosion damage and severe degradation of the injector performance. In the present paper, the transient cavitating flow in the injector-like geometry was investigated using the modified turbulence model and cavitation criterion. A local density correction was used in the Reynolds-averaged Navier-Stokes turbulence model to reduce the turbulent viscosity, which facilitates the cavitation development. The turbulent stress was also considered in the cavitation inception stage. The modified model is capable of reproducing the cavitating flow with an affordable computational cost.
Technical Paper

An Interactive Program for the Simulation of Roll Bar Testing

1993-09-01
932378
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.
Technical Paper

An Energy Approach to Nonlinear Analysis of Roll Bars

1993-09-01
932377
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.
Technical Paper

An Empirical Method for Estimating the Fatigue Resistance of Tensile-Shear Spot Welds

1983-02-01
830035
An empirical method which is based principally on estimates of the fatigue crack initiation life (NI) has been developed which predicts the fatigue resistance of tensile-shear spot welds in the long life regime. The method uses Basquin’s law and Peterson’s equation to estimate NI and thus is founded on the fatigue behavior of smooth specimens and modelling of the fatigue notch size effect. The fatigue notch factor (Kf) required in this analysis was obtained from Pook’s relationships for the stress intensity factors of tensile-shear spot welds. Estimates of NI are added to estimates of the fatigue crack propagation life NP to obtain the total fatigue life (NT) but in the long life regime NP can usually be neglected. The improvement of tensile-shear spot weld fatigue resistance through manipulation of geometry and material property variables are discussed with the aid of the model.
Technical Paper

A System for Virtual Reality Simulation of Machinery

1993-09-01
932376
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.
Technical Paper

A Prototype Computer Based Test System to Test Commercial Vehicle Air Brake Systems: Application and Test Results

1999-11-15
1999-01-3782
This paper describes a practical and efficient approach for determining complete transient, as well as steady state response of tractor-trailer air brake systems by recording pushrod displacement and air brake service line pressure as a function to time. The test hardware utilizes easy to fabricate “clip on” transducers to measure pushrod stroke length. Data acquisition is via LABVIEW‚. All transducers are easy to temporarily affix to any tractor- trailer and require no alteration to the vehicle. A complete system check takes less time than manually measuring pushrod stroke as required under FMCSA. This system with one treadle application and release gives digital timing and displacement history of all brakes. Useful information includes: application and release profiles (pushrod velocity), shoe compliance upon seating and crack pressure release points for both tractor and trailer relay valves.
Technical Paper

A Fatigue Life Prediction Method for Tensile-Shear Spot Welds

1985-02-01
850370
An empirical Three Stage Initiation-Propagation (TSIP) model has been developed which predicts the fatigue resistance of tensile-shear spot welds under constant amplitude loading. The improvements of tensile-shear spot weld fatigue resistance caused by changes in weld geometry, residual stresses and material properties variables are discussed with the aid of the model. The TSIP model suggests that, in addition to the influence of geometry, residual stresses at the site of crack initiation greatly influence the fatigue resistance of tensile-shear spot welds. The TSIP model predicts that material properties play a subtle role in determining the fatigue resistance of tensile-shear spot welds.
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