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White Paper

Studies into Additive Manufacturing for In-Space Manufacturing

2017-06-26
WP-0001
NASA has embarked on an ambitious program to integrate additive manufacturing techniques and to develop processes for the microgravity environment. The most recent example of this program is the successful launch and deployment of the first 3D printer on the International Space Station. In this one-year effort, students were required to meet a series of milestones to design, manufacture, and test their ideas in close cooperation with members of the NASA Exploration Augmentation Module (EAM) concept team.The participants in this project were tasked with thinking of new solutions using AM that would simultaneously be recyclable with minimal loss in mechanical properties but also have the capacity for high mechanical properties. Working in interdisciplinary teams, the participant teams investigated the use of recycled materials, characterization, testing, modeling, and tool development.
Technical Paper

Examination of High Frequency Characterization Methods for Mounts

2001-04-30
2001-01-1444
The knowledge of frequency-dependent dynamic stiffnesses of mounts, in axial and flexural motions, is needed to determine the behavior of many automotive sub-systems. Consequently, characterization and modeling of vibration isolators is increasingly becoming more important in mid and high frequency regimes where very few methods are known to exist. This paper critically examines some of the approximate identification methods that have been proposed in the literature. Then we present a new experimental identification method that yields frequency-dependent multi-dimensional dynamic stiffnesses of an isolator. The scope is however limited to a linear time-invariant system and our analysis is restricted to the frequency domain. The new characterization method uses two inertial elements at both ends of an isolator and free boundary conditions are maintained during testing.
Technical Paper

Serpentine Accessory Belt Drive Tool: Virtual Prototyping for V-Ribbed Belt Drives

2001-04-30
2001-01-1424
Serpentine accessory belts are commonly used in industries such as automotive and general machinery. The purpose of this analytical tool is to provide design engineers the capability to model belt drive systems using ADAMS (Automated Dynamic Analysis of Mechanical Systems). The generated ADAMS models can be used to analyze several different characteristics concerning V-Ribbed belt drive systems. The general solution of the governing nonlinear equations provides the coupled longitudinal and transverse response of the translating belt drive system. Typical simulation outputs include pulley hubloads, belt impact dynamic forces, and belt slip rates at the pulleys.
Technical Paper

Optimization of Vehicle Warm-up Using Simulation Tools

2001-05-14
2001-01-1705
A comprehensive simulation method is presented for the optimization of vehicle warm-up. Sophisticated one dimensional simulation methods based on network theory are used for flow simulation to limit computation time and guarantee high simulation quality. Partial integration of three dimensional flow simulation methods help to improve accuracy. Simulation sub-models for the engine, the HVAC system, and the passenger cabin are combined to simulate the warm-up process of the vehicle. This functionality is implemented in a modern software tool named KULI to support the development engineer as good as possible. Steady state and transient simulation are used to optimize the warm-up behavior.
Technical Paper

Comparison of CFD Simulation Methods and Thermal Imaging with Windscreen Defrost Pattern

2001-05-14
2001-01-1720
The measured windscreen defrost pattern for a saloon car has been compared with two CFD simulation methods and with the results obtained using a thermal imaging camera. The objectives were to determine: if CFD could be used with confidence to simulate defrost performance; the difference between the two CFD methods; the ability of the thermal imaging technique to predict defrost performance; the most appropriate use of these techniques during an HVAC development programme. There was a good comparison between the defrost pattern on the windscreen and the results from the thermal imaging camera and the two CFD methods. The CFD methods have been shown to be suitable for fault finding and recommending their use is reinforced for development work of ducts and vents in the HVAC system. Airflow direction and distribution could be implied from the thermal camera images, which makes it a suitable tool for fine tuning duct and vent designs at the final stages of the design programme.
Technical Paper

Noise Source Identification in a Cab Interior

2001-04-30
2001-01-1630
Nearfield Acoustical Holography (NAH) has traditionally been utilized in the identification of noise sources on separable geometry of the wave equation. Recent advances have utilized the Boundary Element Method (BEM) to extend the source identification to noise sources with arbitrary geometry. However, this generalized NAH leads to the solution of a discrete ill-posed problem that requires solution through Singular Value Decomposition (SVD) in conjunction with numerical regularization. Robust numerical regularization schemes have recently been implemented in commercial software COMET/Acoustics® [1, 2] so as to fully automate the noise source identification procedure, and render it applicable to complex, practical problems. An application involving noise source identification on the interior of an earthmoving equipment cab is presented to demonstrate the capability of generalized NAH. The NAH reconstructed velocities on the surface of the cab are compared with the input velocities.
Technical Paper

Progress in the Optimized Application of Simulation Tools in Vehicle Air Conditioning

2001-05-14
2001-01-1699
The paper focuses on the usage of simulation tools during the development of vehicle air-conditioning systems. The integration of simulation is explained at every stage of the process. It differentiates at which step the 3-D simulation properties are needed and where the advantages of 1-D tools decide its use. For each demand the most targeting way of calculation has to be chosen, facing properties like precision, hardware needs and especially modeling as well as calculation time along to the tightened development schedule. Examples are given from system layout to detailed optimization.
Technical Paper

A Software Tool for Noise Quality and Brand Sound Development

2001-04-30
2001-01-1573
For noise quality and brand sound design of passenger cars a unique software tool is currently used by our clients world-wide to evaluate and optimise the interior noise quality and brand sound aspects of passenger cars on an objective basis. The software tools AVL-VOICE and AVL-COMFORT are designed for the objective analysis of interior noise quality, for benchmarking, for the definition of noise quality targets and most important for effective vehicle sound engineering. With this tool, the target orientated implementation of the required interior noise quality or brand sound by predictable hardware modifications into passenger cars - for tailor made joy of driving - becomes feasible. The use of this tools is drastically reducing vehicle evaluation time and sound engineering effort when compared with traditional jury subjective evaluation methods and standard acoustic NVH optimisation procedures.
Technical Paper

An Energy Source Simulation Method to Predict Sound Radiation

2001-04-30
2001-01-1524
An energy source simulation method (ESSM) has been developed to determine sound energy density. Using this approach, a specified intensity boundary condition on the surface of a vibrating body is approximated by superimposing energy density sources placed inside the body. The unknown strengths for these sources are then found by minimizing the error on the boundary, using a least squares technique. The superposition of these energy density sources should then approximate the sound radiating from the body. The approach was evaluated in two-dimensions for a circle, square, and a more general geometry. The ESSM proved an excellent tool for predicting the energy density provided that power radiated uniformly in all directions. However, the ESSM could not accurately predict the directional characteristics of the energy density field if the power radiated significantly higher from one side of an object than other sides.
Technical Paper

Frame Resonance of High Air Flow Resistivity Plastic Foams: Properties to Improve Acoustical Absorption of Composite Multi-Layered Systems

2001-04-30
2001-01-1558
The optimization of acoustical properties of multi-layered materials used in the automotive industry requires a good understanding and characterization of the various component layers. This is a particular concern in the case of headliners where performance must be balanced with packing space demands. These composite structures when used with flexible urethane foams provide good stiffness and light weight, but their acoustic performance can be sub-optimal. Measurements undertaken with poro-elastic high airflow resistivity foams highlighted frame resonances which, if exploited, might significantly improve the acoustical performance of this system. A new modeling technique based on a pseudo-macroscopic description of the poro-elastic material in the framework of a four-pole network will be used to explain these frame resonances. This formulation exploits the electro-acoustical analogy in transmission line theory.
Technical Paper

Excitation and Measurement of BSR in Vehicle Seats

2001-04-30
2001-01-1552
Buzz, Squeak, and Rattle (BSR) tests are commonly employed in the automotive industry as a diagnostic. The resulting signals are typically analyzed using established (historical) metrics such as A-weighted SPL or stationary loudness (ISO532B). However, due to the non-stationary nature of these signals, traditional metrics often fail to fully describe the signals in question. Compounding the issue is the fact that some specifications state that the test specimen is to produce ‘no objectionable noises’ when subjected to representative excitation. This is a very vague and debatable statement that normally cannot be settled by subjective observations alone. Within this paper, sound quality and statistical metrics are employed for several BSR signals acquired during forced response testing of a seat. Results are presented for two different boundary conditions and alternative signal processing tools are presented.
Technical Paper

Sound Quality Equivalent Modeling for Virtual Car Sound Synthesis

2001-04-30
2001-01-1540
The pressure on development cycles in the automotive industry forces the acoustical engineers to create awareness of sound quality in the early stages of development, perhaps even before a physical prototype is available. Currently, designers have few tools to help them listen to their “virtual” models. For the design of a synthesis platform of in-vehicle binaural sound, the sound should be modeled with almost identical sound quality perception. A concept is presented where the total sound of a vehicle is split in a number of components, each with its own sound characteristics. These characteristics are described in a signal model that allows the analysis of an existing sound into a limited number of signal components: orders-frequency spectra, time envelopes and time recordings.
Technical Paper

Novel Design of a Multi-Function Acoustics Laboratory for the Testing and Evaluation of Automotive Acoustics Systems and Components

2001-04-30
2001-01-1489
The acoustic performance requirements of vehicle interior trim elements and sound package elements have increased significantly in recent years. Additionally, the burden of developing these products has been shifted from the Original Equipment Manufacturers (OEMs) to suppliers. To aid in developing lightweight, low cost, and high performance parts, a flexible acoustic testing facility was designed for use in many different applications. Specific, purpose-built chambers for only one type of measurement are typically not cost effective facilities.
Technical Paper

Use of Simulation Tools in EGR Development Process

2001-05-14
2001-01-1747
During the development process of the EGR, several CAE tools were used. The overall load results as a combination of static, dynamical and temperature induced load. The inputs were known from experiments and engine test stand. The influence of different gasket assembly possibilities onto the pre-stress in the structure was subject to several static analysis. The dynamic behavior was addressed because of the engine induced random vibrations into the EGR system. Natural frequencies and modes were used to show potential for improvements and power spectral density analysis was used the evaluate the statistical stress distribution. Fluid distribution and structure temperature was obtained from CFD analysis with conjugate heat transfer.
Technical Paper

Diesel Fuel Lubricity - Base Fuel Effects

2001-05-07
2001-01-1928
Many modern diesel fuel injection equipment designs rely totally on the fuel to provide lubrication. The ability of a diesel fuel to lubricate diesel fuel injection equipment has become commonly referred to as its “lubricity”. If a diesel fuel has insufficient lubricity then the performance of the fuel injection equipment can be compromised resulting in reduced durability and increased vehicle emissions. We have been studying diesel fuel lubricity since the early 1990s using a test rig. The test rig consists of a motored distributor type fuel injection pump, injectors and a fuel handling/circulation system. This paper reviews test rig results on a total of twenty three different base fuels. The pump test rig results are compared to the inspection properties of the test fuels and conclusions derived.
Technical Paper

Mobility and fuel economy of hybrid-driven vehicles in terrain~Results from computer simulation

2000-06-12
2000-05-0394
An important requirement for the application of hybrid drives in future terrain vehicles is their competitiveness with regard to the driving properties and the fuel economy. Therefore, a two-axle, all-wheel-driven military transport vehicle equipped with a serial hybrid propulsion system has been regarded and examined by computer simulation. The tool, used for this purpose, is the simulation program ORSIS, (Off Road Systems Interactive Simulation), which has been developed at the University of the Federal Armed Forces in Hamburg. By generating a realistic surrounding area with reproducible conditions ORSIS allows an objective comparison of different vehicle types and the investigation of the influence of modified vehicle parameters. The paper presents results from computer simulations which include acceleration and braking procedures, determination of maximum drawbar pull, and the estimation of fuel consumption under realistic conditions by driving on determined routes.
Technical Paper

"Nickel electroformed" tools development through stereolithography (SLA) for sheet metal forming~An evaluation study

2000-06-12
2000-05-0272
Currently, advancements in Rapid Prototyping (RP) technologies have led to considerable amount of research activities and has been playing a major role in the area of tooling development for which Rapid Tooling (RT) term was coined. While rapid prototyping techniques are employed to make prototype tools, the basic idea of the rapid tooling is to produce prototype and zero series parts by using prototype tools so the parts truly represent the future production. This paper will present an evaluation of a RP and RT technique in developing tools (punch and dies) for sheet metal forming, which had been manufactured and tested. Both punch and die have been manufactured by combining Stereolithography (SL), RP technique, with nickel electroforming process. The stereolithography technique that had been utilized in developing models for the tools had been built with modeling pattern called Accurate Clear Epoxy Solid (ACES).
Technical Paper

"Quick" tools development through stereolithography (SLA) for sheet metal forming~An evaluation study

2000-06-12
2000-05-0270
Currently, advancements in Rapid Prototyping (RP) technologies have led to considerable amount of research activities and has been playing a major role in the area of tooling development for which Rapid Tooling (RT) term was coined. Rapid prototyping techniques are employed to make prototype tools. While, the basic idea of the rapid tooling is to produce prototype and zero series parts by using prototype tools so the parts truly represent the future production. This paper will present an evaluation of a RP & RT technique in developing tools (punch and dies) for sheet metal forming, which had been manufactured and tested. Both punch and die have been manufactured directly from Stereolithography (SL). The stereolithography technique that had been utilized in developing models for the tools had been built with modeling pattern called QuickCast infiltrated with Aluminum-Filled Epoxy, designated as Quick Tool.
Technical Paper

Reconstruction of Twenty Staged Collisions with PC-Crash's Optimizer

2001-03-05
2001-01-0507
When vehicle collisions are reconstructed using a discrete kinetic time forward simulation program, many trials have to be performed to reach a point where the simulation results are close to the actual ones. The pre-impact speeds and directions of travel of each vehicle are the main variables that affect the post-impact motion of the vehicles. However, other factors, such as the exact resultant position where the impact forces are exchanged, the vehicle positions with respect to each other at impact, and the coefficient of restitution are important variables that also affect the results. When a number of impact parameters are unknown, a reconstruction can take a great deal of time. An optimizer tool in PC-Crash is designed to minimize reconstruction time and error by automatically varying a selected number of impact parameters, comparing the resulting simulation for each combination of parameters with the actual incident.
Technical Paper

Contact Pressure Distribution of Piston Rings -Calculation Based on Piston Ring Contour -

2001-03-05
2001-01-0571
The piston ring design using low tangential force to reduce friction loss has become a general trend in engine development - especially in passenger car engine - in recent years. This trend emphasizes the importance of stable sealing function that does not require much tangential force. Thus, it is important to grasp the correct pressure distribution between the ring and the cylinder. Reliable and accurate calculation to understand the pressure distribution has been an issue for many years among the engineers. In this report, we propose a new calculation method based on the piston ring contour in a free condition. Generally, the piston ring contour is calculated to achieve its correspondence to a given pressure distribution. By analyzing inversely, the pressure distribution is calculated when a ring contour is given. But as is well known, the solution is often unstable in inverse analyses. We introduced the idea of the method of least squares to avoid this problem.
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