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Technical Paper


THIS paper reports work begun in 1935 at the instigation of the Murray Corp. of America. Methods used in studying the relations between the automobile seat cushion and its function in transporting passengers with greater comfort and less fatigue are described. Constructed for this purpose was a piece of apparatus called the Universal Test Seat, whose dimensions were completely adjustable with arrangements to vary the distribution of the supporting pressure in any manner which seemed most comfortable to the passenger. The authors describe tests made by use of this apparatus, present summaries of some of the results recorded and conclude that, to give the passenger the maximum comfort and least fatigue, the following mechanical objectives should be attained by the cushion: 1. To support the passenger over a large area to get the smallest unit pressure on the flesh; 2.
Technical Paper

Refinement and Validation of the Thermal Stratification Analysis: A post-processing methodology for determining temperature distributions in an experimental HCCI engine

Refinements were made to a post-processing technique, termed the Thermal Stratification Analysis (TSA), that couples the mass fraction burned data to ignition timing predictions from the autoignition integral to calculate an apparent temperature distribution from an experimental HCCI data point. Specifically, the analysis is expanded to include all of the mass in the cylinder by fitting the unburned mass with an exponential function, characteristic of the wall-affected region. The analysis-derived temperature distributions are then validated in two ways. First, the output data from CFD simulations are processed with the Thermal Stratification Analysis and the calculated temperature distributions are compared to the known CFD distributions.
Journal Article

A Copula-Based Approach for Model Bias Characterization

Available methodologies for model bias identification are mainly regression-based approaches, such as Gaussian process, Bayesian inference-based models and so on. Accuracy and efficiency of these methodologies may degrade for characterizing the model bias when more system inputs are considered in the prediction model due to the curse of dimensionality for regression-based approaches. This paper proposes a copula-based approach for model bias identification without suffering the curse of dimensionality. The main idea is to build general statistical relationships between the model bias and the model prediction including all system inputs using copulas so that possible model bias distributions can be effectively identified at any new design configurations of the system. Two engineering case studies whose dimensionalities range from medium to high will be employed to demonstrate the effectiveness of the copula-based approach.
Technical Paper

The Development of HFE Space Claims for Combat Vehicles

Discuss the basics of posturing and positioning of the full range of occupants necessary to cover the required anthropometric demographics in combat vehicles, both ground and air, since there are similarities to both and that they are both very different than the traditional automotive packaging scenarios. It is based on the Eye Reference Point and the Design Eye Point. Discuss the three Reach Zones: Primary, Secondary and Tertiary. Discuss Vision Zones and potentially ground intercepts. Discuss body clearances, both static and dynamic. Discuss the basic effects of packaging occupants with body armor with respect to SRP's and MSRP's.
Journal Article

Subjective and Objective Effects of Driving with LED Headlamps

This study was designed to investigate how the spectral power distribution (SPD) of LED headlamps (including correlated color temperature, CCT) affects both objective driving performance and subjective responses of drivers. The results of this study are not intended to be the only considerations used in choosing SPD, but rather to be used along with results on how SPD affects other considerations, including visibility and glare. Twenty-five subjects each drove 5 different headlamps on each of 5 experimental vehicles. Subjects included both males and females, in older (64 to 85) and younger (20 to 32) groups. The 5 headlamps included current tungsten-halogen (TH) and high-intensity discharge (HID) lamps, along with three experimental LED lamps, with CCTs of approximately 4500, 5500, and 6500 K. Driving was done at night on public roads, over a 21.5-km route that was selected to include a variety of road types.
Technical Paper

Cycle-Resolved Investigation of In-Cylinder and Exhaust NO in a Spray-Guided Gasoline Direct-Injection Engine: Effect of Intake Temperature and Simulated Exhaust Gas Recirculation

The formation of NO was investigated in a spray-guided spark-ignition direct-injection gasoline engine. The influence of variations in intake air temperature and simulated exhaust gas recirculation was examined in an optical single-cylinder engine, fueled with iso-octane. Cycle-resolved simultaneous measurements of OH-chemiluminescence, NO laser induced fluorescence, and fast NO exhaust gas sampling allowed a detailed view of the formation process of NO in this engine. Overall, it was found that cycle-resolved information is needed to explain the differences found between operating conditions, since the initial high stratification of fuel leads to large spatial gradients in the NO concentration. Averaged in-cylinder NO distributions do not adequately reflect the formation process rather than show a smoothed distribution that may even be counter-intuitive based on averaged chemiluminescence data.
Technical Paper

Design Optimization and Reliability Estimation with Incomplete Uncertainty Information

Existing methods for design optimization under uncertainty assume that a high level of information is available, typically in the form of data. In reality, however, insufficient data prevents correct inference of probability distributions, membership functions, or interval ranges. In this article we use an engine design example to show that optimal design decisions and reliability estimations depend strongly on uncertainty characterization. We contrast the reliability-based optimal designs to the ones obtained using worst-case optimization, and ask the question of how to obtain non-conservative designs with incomplete uncertainty information. We propose an answer to this question through the use of Bayesian statistics. We estimate the truck's engine reliability based only on available samples, and demonstrate that the accuracy of our estimates increases as more samples become available.
Technical Paper

A Dual-Use Enterprise Context for Vehicle Design and Technology Valuation

Developing a new technology requires decision-makers to understand the technology's implications on an organization's objectives, which depend on user needs targeted by the technology. If these needs are common between two organizations, collaboration could result in more efficient technology development. For hybrid truck design, both commercial manufacturers and the military have similar performance needs. As the new technology penetrates the truck market, the commercial enterprise must quantify how the hybrid's superior fuel efficiency will impact consumer purchasing and, thus, future enterprise profits. The Army is also interested in hybrid technology as it continues its transformation to a more fuel-efficient force. Despite having different objectives, maximizing profit and battlefield performance, respectively, the commercial enterprise and Army can take advantage of their mutual needs.
Technical Paper

A Two-Tracer LIF Strategy for Quantitative Oxygen Imaging in Engines Applied to Study the Influence of Skip-Firing on In-Cylinder Oxygen Contents of an SIDI Engine

The effect of skip-firing (which is often applied in optical engine work) on the available in-cylinder oxygen concentration was investigated with a laser-induced fluorescence imaging setup that combines the measurement of fluorescence signals from toluene and 3-pentanone to quantitatively determine the distribution of molecular oxygen. We describe in detail the image processing procedure for this measurement. The reduction of in-cylinder oxygen when switching from skip-fired to continuous-fired engine operation is measured and compared to traditional exhaust measurements.
Technical Paper

A New Approach to Modeling Driver Reach

The reach capability of drivers is currently represented in vehicle design practice in two ways. The SAE Recommended Practice J287 presents maximum reach capability surfaces for selected percentiles of a generic driving population. Driver reach is also simulated using digital human figure models. In typical applications, a family of figure models that span a large range of the target driver population with respect to body dimensions is positioned within a digital mockup of the driver's workstation. The articulated segments of the figure model are exercised to simulate reaching motions and driver capabilities are calculated from the constraints of the kinematic model. Both of these current methods for representing driver reach are substantially limited. The J287 surfaces are not configurable for population characteristics, do not provide the user with the ability to adjust accommodation percentiles, and do not provide any guidance on the difficulty of reaches that are attainable.
Technical Paper

Variance Reduction Techniques for Reliability Estimation Using CAE Models

Traditional reliability assessment methods based on physical testing can require prohibitively large sample sizes in many applications. This has led manufacturers to employ virtual testing using CAE models in place of physical testing. However, when the CAE models are not valid, the resulting reliability assessment may be unreliable. In this paper we develop theory and methodology in which traditional physical testing can be used in conjunction with CAE models to create a new type of accelerated testing that requires smaller sample sizes than traditional test plans while exhibiting robustness with respect to inaccuracies in the CAE models. These test plans are implemented by physically testing a biased sample of products and employing a variance reduction technique such as importance sampling. The CAE model is used as a prior belief for failure probability from which one can derive the sampling plan which minimizes the variance.
Technical Paper

Particulate Emissions in GDI Vehicle Transients: An Examination of FTP, HWFET, and US06 Measurements

With increasingly stringent light duty particulate emissions regulations, it is of great interest to better understand particulate matter formation. Helping to build the knowledge base for a thorough understanding of particulate matter formation will be an essential step in developing effective control strategies. It is especially important to do this in such a way as to emulate real driving behaviors, including cold starts and transients. To this end, this study examined particulate emissions during transient operation in a recent model year vehicle equipped with a GDI engine. Three of the major federal test cycles were selected as evaluation schemes: the FTP, the HWFET, and the US06. These cycles capture much of the driving behaviors likely to be observed in typical driving scenarios. Measurements included particle size distributions from a TSI EEPS fast-response particle spectrometer, as well as real-time soot emissions from an AVL MSS soot sensor.
Journal Article

Cost-Effective Reduction of Greenhouse Gas Emissions via Cross-Sector Purchases of Renewable Energy Certificates

Over half of the greenhouse gas (GHG) emissions in the United States come from the transportation and electricity generation sectors. To analyze the potential impact of cross-sector cooperation in reducing these emissions, we formulate a bi-level optimization model where the transportation sector can purchase renewable energy certificates (REC) from the electricity generation sector. These RECs are used to offset emissions from transportation in lieu of deploying high-cost fuel efficient technologies. The electricity generation sector creates RECs by producing additional energy from renewable sources. This additional renewable capacity is financed by the transportation sector and it does not impose additional cost on the electricity generation sector. Our results show that such a REC purchasing regime significantly reduces the cost to society of reducing GHG emissions. Additionally, our results indicate that a REC purchasing policy can create electricity beyond actual demand.
Journal Article

Low-Order Contact Load Distribution Model for Ball Nut Assemblies

Ball nut assemblies (BNAs) are used in a variety of applications, e.g., automotive, aerospace and manufacturing, for converting rotary motion to linear motion (or vice versa). In these application areas, accurate characterization of the dynamics of BNAs using low-order models is very useful for performance simulation and analyses. Existing low-order contact load models of BNAs are inadequate, partly because they only consider the axial deformations of the screw and nut. This paper presents a low-order load distribution model for BNAs which considers the axial, torsional and lateral deformations of the screw and nut. The screw and nut are modeled as finite element beams, while Hertzian Contact Theory is used to model the contact condition between the balls and raceways of the screw and nut. The interactions between the forces and displacements of the screw and nut and those at the ball-raceway contact points are established using transformation matrices.
Technical Paper

Recent Aircraft Tire Thermal Studies

A method has been developed for calculating the internal temperature distribution in an aircraft tire while free rolling under load. The method uses an approximate stress analysis of each point in the tire as it rolls through the contact patch, and from this stress change the mechanical work done on each volume element may be obtained and converted into a heat release rate through a knowledge of material characteristics. The tire cross-section is then considered as a body with internal heat generation, and the diffusion equation is solved numerically with appropriate boundary conditions at the wheel and runway surface. Comparisons with buried thermocouples in actual aircraft tires shows good agreement.
Technical Paper

A Network-Based Expert System for Comparative Analysis of Pulley Assembly Methods

The pulleys employed in automotive accessory drive systems very often consist of a two piece assembly; a multitude of fastening techniques are used in completing the assembly. There are numerous assembly methods and a variety of distinct pulley configurations dictated by the various automobile manufacturers in accordance with individual accessory drive needs. An expert system is being developed to evaluate the merit of multiple assembly alternatives for a specific pulley application. The expert system provides a consistent evaluation tool for assembly alternatives, balancing the influence of product cost, strength and quality considerations. The knowledge-based system is implemented in an expert system shell called AGNESS (A Generalized Network-based Expert System Shell). The expert system judges the acceptability of various pulley assembly techniques, assigning a high “merit value” to the better designs and proportionately lower values to less desirable designs.
Technical Paper

Some Observations on the International Coalition Strategies in the Development of Chinese Automobile Industry

Since the end of W.W.II, many countries have embarked on various to develop a national automobile industry to spur the economic growth of the country, to meet the rising domestic demand for automobiles, and to compete in the world markets. Can these countries achieve these objectives and at the same time retain their national independence in the automobile industry from the domination of the foreign multinational automobile manufacturers? This paper addresses these questions by examining first, the records of Latin America (Argentina, Brazil, Mexico), South Korea and Taiwan in Asia Pacific Region; it then attempts to determine to what extent their experiences may be transferrable to the Chinese automobile industry which is currently undergoing modernization. For the purpose of this paper, the automobile industry encompasses only passenger vehicles.
Technical Paper

Selection Families of Optimal Engine Designs Using Nonlinear Programming and Parametric Sensitivity Analysis

The selection process of key engine design variables to maximize peak power subject to fuel economy and packaging objectives is formulated as an optimization problem readily solved with nonlinear programming. The merit of this approach lies not in finding a single optimal engine, but in identifying a family of optimal designs dependent on parameter changes in the constraint set. Sensitivity analysis of the optimum to packaging parameters, fuel economy parameters, and manufacturing parameters is presented and discussed in the context of product development decisions.
Technical Paper

Mathematical Modeling in Plane Strain Bending

Springback is one of the main problems in sheet metal bending operations. Theoretically, an accurate description of strain distribution and stress distribution is required in order to predict the springback behavior of a bending component. Prediction of strain distribution needs a good geometrical model while prediction of stress distribution needs both an accurate strain description and an accurate stress-strain relationship. In this paper, a new model is developed for strain calculation in plane strain bending. The displacement of the neutral surface, the thickness change, the stress and strain distributions over the sheet thickness, the bending moment and the springback curvature are examined using this new model and useful conclusions are obtained. The new model is also compared with Hill's pure bending model, the membrane theory (plus post-processing) and the shell theory. The application ranges and the limitations of the membrane theory and the shell theory are discussed.
Technical Paper

Life Cycle Assessment and Design of Instrument Panels: A Common Sense Approach

The U.S. EPA initiated the Common Sense Initiative (CSI) to develop “Cleaner, Cheaper, Smarter” environmental policy and management practices. This paper addresses the application of life cycle design and assessment tools to automotive instrument panels (IP) as part of the Automotive Manufacturing Sector CSI pilot project investigation. For this study, an “average IP” was modeled based on the instrument panels of three mid-sized U.S. car models: 1995 Chevrolet Lumina, 1996 Dodge Intrepid and 1996 Ford Taurus. This “average IP” consisted of seventeen different materials and weighed over 22 kg (49 lbs.). A life cycle inventory analysis was conducted to evaluate the environmental burdens associated with materials production, manufacturing, use, and retirement. A thorough evaluation of solid waste production and energy consumption was completed and partial inventories of air emission and water effluent releases were also conducted.