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Viewing 1 to 30 of 1155
2011-04-12
Technical Paper
2011-01-0510
Megumu Oshima, Kanya Nara, Tatsuhiko Yoshimura
We have constructed a design review system in which Full Process and Quick Design Review processes are selectively used according to the degree of newness in a design change. The Full Process Design Review is conducted for a review of system or part designs having a high level of newness and the tools and process used in this review were standardized. The Quick Design Review is newly developed design review process that could be conducted in a quicker and simpler manner for designs involving a medium level of newness in order to effectively prevent design-related problems. The Quick Design Review uses a changes list and Design Review Based on Failure Mode (DRBFM) [1] worksheets to focus on the changed points. This method enables the engineers involved to identify problems and to devise solutions efficiently and effectively through discussions.
2004-11-16
Technical Paper
2004-01-3348
Marcelo R.A.C. Tredinnick, Marcelo Lopes de Oliveira e Souza
In this work we study the stability of digital controls of flexible/Vibratory aerospace/automobile systems by the graph norm technique, occurring in sampled-data control systems due to sampling period variations. To do so, this work tries to establish regions (graphs) of stability and instability in a Banach Space, the distances (norms) between them and a given design to detect analytically and/or numerically its margins of stability or conditions of instability. Based on that, we sketch the first steps for a design methodology of stable digital controllers of flexible/vibratory systems embedded in a sampled-data system with adjustable sampling periods of A/D and D/A converters. A short tutorial about the graph norm technique is also given and some theoretical results as well numerical results are shown. This work was done in two folds to unmask the stability secrets hidden in a general sampled-data control system, until today not revelated.
2004-07-19
Technical Paper
2004-01-2322
S. A. Walker, J. Tweed, J. W. Wilson, R. K. Tripathi
The development of a Green’s function approach to ion transport greatly facilitates the modeling of laboratory radiation environments and allows for the direct testing of transport approximations of material transmission properties. Using this approach radiation investigators at the NASA Langley Research Center have established that simple solutions can be found for HZE ions by ignoring nuclear energy downshifts and dispersion. Such solutions were found to be supported by experimental evidence with HZE ion beams when multiple scattering was added. Lacking from the prior solutions were range and energy straggling and energy downshift and dispersion associated with nuclear events. In a more recent publication it was shown how these effects can be incorporated into the multiple fragmentation perturbation series. Analytical approximations for the first two perturbation terms were presented and the third term was evaluated numerically.
2014-04-01
Journal Article
2014-01-1018
Robert V. Petrach, David Schall, Qian Zou, Gary Barber, Randy Gu, Laila Guessous
Coatings have the potential to improve bearing tribological performance. However, every coating application process and material combination may create different residual stresses and coating microstructures, and their effect on bearing fatigue and wear performance is unclear. The aim of this work is to investigate coating induced residual stress effects on bearing failure indicators using a microstructural contact mechanics (MSCM) finite element (FE) model. The MSCM FE model consists of a two-dimensional FE model of a coated bearing surface under sliding contact where individual grains are represented by FE domains. Interactions between FE domains are represented using contact element pairs. Unique to this layered rolling contact FE model is the use of polycrystalline material models to represent realistic bearing and coating microstructural behavior. The MSCM FE model was compared to a second non-microstructural contact mechanics (non-MSCM) model.
2013-10-07
Technical Paper
2013-36-0355
Diego Muniz Benedetti, Ricardo Luiz Utsch de Freitas Pinto, Ricardo Poley Martins Ferreira
In this paper it is presented an analysis of the longitudinal and lateral-directional stability characteristics of paragliders. The paragliders stability analysis is part of the thesis named “Paragliders Flight Dynamics”, submitted to the Department of Mechanical Engineering of the Federal University of Minas Gerais (UFMG) - Brazil - in partial fulfillment of the requirements to obtain the master's degree in mechanical engineering. The full thesis presents a complete theoretical analysis of paragliders flight dynamics providing useful information for paragliders conceptual design optimization, and representing a first initiative to incentivize the international aeronautical engineering community to dedicate attention to this particular field.
2011-04-12
Journal Article
2011-01-0731
M. Shariyat, Mahboobeh Rajabi Ghahnavieh
Beam-type structural elements are generally utilized in construction of majority of the automotive structures, e.g. the buses, trailers, and solid axles. These components are usually subjected to spatially-random or uncertain load conditions during their service lives. Moreover, material properties of the beams-type structural elements may vary from a sample to another in a random manner. The situation will be more complex when both material properties and load conditions exhibit random natures in the spatial domain. In the present paper, an algorithm is presented to assess the probabilistic behavior of the beam-type vehicle's components in relation with the strength and deflection requirements. A consistent finite element reliability model that may be employed for beams with arbitrary inclinations under simultaneous spatially-random loading conditions and random material properties is introduced.
2011-04-12
Journal Article
2011-01-0728
Amandeep Singh, Zissimos Mourelatos, Efstratios Nikolaidis
Reliability is an important engineering requirement for consistently delivering acceptable product performance through time. As time progresses, the product may fail due to time-dependent operating conditions and material properties, component degradation, etc. The reliability degradation with time may increase the lifecycle cost due to potential warranty costs, repairs and loss of market share. Reliability is the probability that the system will perform its intended function successfully for a specified time interval. In this work, we consider the first-passage reliability which accounts for the first time failure of non-repairable systems. Methods are available in the literature, which provide an upper bound to the true reliability which may overestimate the true value considerably. Monte-Carlo simulations are accurate but computationally expensive.
2011-04-12
Technical Paper
2011-01-0727
Erik Wilhelm, Alexander Wokaun
Evaluating options for reducing the environmental impact of light duty vehicles is complicated by the number of technologies being actively researched. In this work, various alternative transportation fuels such as ethanol, biodiesel, hydrogen, and electricity as well as advanced materials and drive-train concepts are analyzed for their environmental benefits compared to conventional diesel and gasoline vehicles. To objectively evaluate the impact of technology and fuel options on various stakeholder criteria under uncertainty (e.g. fuel and technology costs), it is necessary to consider how the technology may be applied to a broad set of vehicle designs. The heuristic vehicle design method uses rules from first principles and engineering practice to ensure vehicles in the design set (virtual fleet) are composed of self-consistent technology options.
2011-04-12
Journal Article
2011-01-0729
Bart Zalewski
Engineering systems are often too complex and their behavior cannot be determined using closed form or exact methods. To circumvent this problem, numerical methods, such as boundary element method, have been formulated to obtain approximate solutions to partial differential equations, which describe the behavior of the physical engineering systems. However, the inherent uncertainty in constitutive formulation causes uncertainties in the solutions obtained by numerical methods and undermines their validity. Conventional analysis does not account for material uncertainty, which is, however, accounted for in the design phase. This paper addresses the impact of uncertain shear modulus for plane strain linear elasticity problems on the numerical solutions obtained using boundary element method. The uncertainty is modeled using fuzzy approach.
2011-04-12
Journal Article
2011-01-1080
Vijitashwa Pandey, Efstratios Nikolaidis, Zissimos Mourelatos
Multi-attribute decision making and multi-objective optimization complement each other. Often, while making design decisions involving multiple attributes, a Pareto front is generated using a multi-objective optimizer. The end user then chooses the optimal design from the Pareto front based on his/her preferences. This seemingly simple methodology requires sufficient modification if uncertainty is present. We explore two kinds of uncertainties in this paper: uncertainty in the decision variables which we call inherent design problem (IDP) uncertainty and that in knowledge of the preferences of the decision maker which we refer to as preference assessment (PA) uncertainty. From a purely utility theory perspective a rational decision maker maximizes his or her expected multi attribute utility.
2010-10-17
Technical Paper
2010-36-0519
Jean-Pierre Coyette, Julien Manera
Abstract Numerical simulation techniques are widely used in automotive and aircraft sectors. The optimization of industrial products with respect to acoustic performance requires appropriate modeling strategies in order to handle various noise sources and different propagation paths. The present paper focuses on the application of finite element techniques (FE) to the solution of vibro-acoustic and aero-acoustic problems. State-of-the-art FE techniques are reviewed and illustrated by appropriate examples.
1999-10-19
Technical Paper
1999-01-5632
Gregor A. Dirks
A general outline of the motivation of the research project „Technology Navigator“ and the contents of work is given, together with details of the methodology under development. The impact of the introduction of new technology is analyzed from the view of an aircraft manufacturer, in order to derive a methodology for the support of technology scheduling. Important features of this methodology are the consideration of the whole family of aircraft addressed, the planning of technology readiness and corresponding investment and it’s impact on the cash flow curve. Where forecasts or other uncertainties are involved a statistical approach is chosen.
2011-06-13
Technical Paper
2011-38-0005
Jason Mickey, Eric Loth, Colin Bidwell
A new technique is proposed for computing particle concentrations and fluxes with Lagrangian trajectories. This method calculates particle concentrations based on the volume of a parcel element, or cloud, at the flux plane compared against the initial volume and is referred to as the Lagrangian Parcel Volume (LPV) method. This method combines the steady-state accuracy of area-based methods with the unsteady capabilities of bin-based methods. The LPV method results for one-dimensional (1D) unsteady flows and linear two-dimensional (2D) steady flows show that a quadrilateral element shape composed of a single parcel (with four edge particles) is capable of accurately predicting particle concentrations. However, nonlinear 2D flows can lead to concave or crossed quadrilaterals which produce significant numerical errors.
2011-06-13
Technical Paper
2011-38-0004
Peng Ke, Xinxin Wang
Lagrangian approach has been widely adopted in the droplet impingement analysis for aircraft icing simulation. Some improvements were proposed, including: 1) The heat and mass transfer consideration in droplet dynamics; 2) More efficient droplet localization method, which could and facilitated to find the initial cell in Eulerian grid; 3) New computation method of impingement efficiency, which uses the cover ratio to transform the impingement efficiency of arbitrary impinged region to that of the cell element of body surface and avoids the iterative computation to find the trajectories reaching the corner of the panel or cell element. A numerical solver was built and integrated with the capabilities to deal with super-cooled large droplet (SLD) conditions by considering the splashing and bouncing of SLD. The computational results were validated with the experiment data, which shown good agreements in the impingement limitations and tendency.
2011-06-13
Technical Paper
2011-38-0022
Marco Fossati, Rooh-ul-Amin Khurram, Wagdi G. Habashi
The irregular shapes that glaze ice may grow into while accreting over the surface of an aircraft represent a major difficulty in the numerical simulation of long periods of in-flight icing. In the framework of Arbitrary Lagrangian-Eulerian (ALE) formulations, a mesh movement scheme is presented, in which frame and elasticity analogies are loosely coupled. The resulting deformed mesh preserves the quality of elements, especially in the near-wall region, where accurate prediction of heat flux and shear stresses are required. The proposed scheme handles mesh movement in a computationally efficient manner by localizing the mesh deformation. Numerical results of ice shapes and the corresponding aerodynamic coefficients are compared with the experimental results.
2011-06-13
Technical Paper
2011-38-0069
Daniel R. Adriaansen, Cory Wolff, Frank Mcdonough
The Current Icing Product (CIP) provides an hourly diagnosis of the severity of icing occurring based on multiple data sources. Pilot reports (PIREPs) and surface observations (METARs), as well as satellite, numerical weather prediction (NWP) model, radar, and lightning data are all utilized within the algorithm. The accurate identification of cloud base is a large factor in the algorithm's determination of icing severity. Current methods employ the METAR observation of ceiling to identify the cloud base over a specified area within the CIP domain. The temperature from the Rapid Update Cycle (RUC) NWP model at the height of the observed METAR ceiling can be utilized as a proxy for the amount of condensate in the cloud. The likelihood of a large amount of condensate in the identified cloud increases with increasing cloud base temperature. As the amount of liquid water diagnosed by CIP severity increases, so does the estimated icing severity.
2011-10-18
Technical Paper
2011-01-2770
Lejun Chen PhD, Ronald Patton
This work is motivated through a research study ADDSAFE funded by the European Commission, following an interest in implementing mixed linear parameter varying (LPV) H_/H✓ model-based fault detection and diagnosis (FDD) methodology for detecting nonlinear actuator faults for flight control system. The main design goal is to maximize the robustness of the residual signal to uncertainty and disturbances whilst also achieving the specific minimum sensitivity of the residual signal to faults. The specific minimum sensitivity index used is based on the H_ index concept and is extended to the LPV FDD system problem. This allows the fault signature for multiple sensor and actuator faults to be reconstructed simultaneously, facilitating the robust isolation of faults rather than just their detection.
2004-11-16
Technical Paper
2004-01-3236
Sandro Aparecido Baldacim, Nivaldo Cristofani, Carlos do Nascimento Santos, José Rui Lautenschlager
Lightning is a high voltage and high current phenomenon and it originates by build up of electrical charge in the air or, more commonly, in clouds. It is constituted of an electric current peak of short duration (0,5 ms) and high intensity (200 kA), followed by a low intensity (400 A) but high duration (1s) periods. The lightning effects in aircraft can be divided in two groups: direct effects (physical effects such as melting, rupture, damage of surfaces and structures due to conduction of lightning current or high power magnetic force) and indirect effects (electromagnetic fields generating levels of transient voltage and current on interconnecting wiring and cable leads within the equipment circuits eventually damaging internal components).
2004-07-19
Technical Paper
2004-01-2397
Simon Appel, Ricardo Patrício, Hans Peter de Koning, Olivier Pin
The calculation of linear conductors for a thermal lumped parameter (TLP) model, to be used with ESATAN (ref 1.) or SINDA, is one of the last parts of the thermal model preparation that is not yet fully automated. Most users calculate the conductors by hand or have their own special spreadsheets, or other tools, which can calculate some of these for a series of combinations of simple shaped TLP-nodes. For TLP-nodes with more complex shapes these tools cannot be used. The current paper presents two generally applicable methods to automate the generation of the linear conductors for thermal lumped parameter models
2004-07-19
Technical Paper
2004-01-2388
C. D. Thompson, Brienne Shkedi
The International Space Station (ISS) Environmental Control and Life Support System (ECLSS) is designed to be maintainable. During the 3 years since the ISS US Lab became operational, there have been numerous ECLSS Orbital Replacement Units (ORU’s) launched and returned to maintain the ECLSS operation in the US segments. The maintenance logistics have provided tools for maintenance, replaced limited life ORU’s and failed ORU’s, upgraded ECLSS hardware to improve reliability and placed critical spares onboard prior to need. In most cases, the removed ORU’s have been returned for either failure analysis and repair or refurbishment. This paper describes the ECLSS manifesting history and maintenance events and quantifies the numbers of ECLSS items, weights, and volumes.
2012-10-02
Technical Paper
2012-36-0526
Gregorio G. Azevedo, Marcelo Bustamante, Julio A. Cordioli, Samir N. Y. Greges, Jeff Weisbeck, Andre de Oliveira
The Hybrid FE-SEA method is a recently developed numerical technique that deals with the so-called mid-frequency problem. Such problems involve the dynamic analysis of systems that include, at the same frequency range, components with high and low modal density. Systems with a reduced number of modes are usually modeled using deterministic methods, as the Finite Element (FE) Method, while modal dense systems need to be treated by means of statistical methods such as the Statistical Energy Analysis (SEA). Neither FE nor SEA can properly describe a system that displays the mid-frequency behavior due to a prohibitive computational cost (FE) or the lack of accuracy (SEA). The floor structure of an aircraft is a typical case of a mid frequency problem, where the floor beams are relatively rigid and have very few modes while the floor panels have a very high modal density.
2012-10-22
Technical Paper
2012-01-2230
Yeong-Ren Lin, Yang Hu, Lei Zhou, David Woodburn, Thomas Wu, Louis C. Chow, Quinn Leland
In the aviation community, there is a high priority to develop all-electric aircraft. Electro-mechanical actuation systems would replace traditional, large, heavy and difficult-to-maintain hydraulic actuation systems. This movement from hydraulic actuation to electrical actuation enhances the flexibility to integrate redundancy and emergency system in future military aircraft. Elimination of the hydraulic fluid removes the possibility of leakage of corrosive hydraulic fluid and the associated fire hazard, as well as environmental concerns. The switch from hydraulic to electrical actuation provides additional benefits in reduced aircraft weight, improved survivability and improved maintainability. The heat load in an electro-mechanical actuation (EMA) is highly transient and localized in nature; therefore a phase change material could be embedded in the heat generating components to store peak heat load.
2012-10-22
Technical Paper
2012-01-2135
Vanchana Raul, Pranav Orpe
The quality of an embedded application depends not only on how well it satisfies functional requirements but also on performance efficiency of the system. In embedded systems, non-functional requirements like memory requirements, play a very important role, and often impact significantly the embedded system's performance and overall cost of implementation. Embedded Systems usually have constrained resources like memory. Hence, choosing a correct method of verifying memory requirements is extremely critical. This Paper will give an overview of methodologies for performing different Memory Analyses to determine the correctness and consistency of memory requirements for airborne software and verifying efficient memory usage as required by the RTCA DO-178B guidelines. Different memory analyses methodologies like Memory Map Analysis, Stack Analysis and Heap Analysis are explained with current technology involved.
2014-09-30
Technical Paper
2014-36-0193
Luciano Magno Frágola Barbosa, Francelle Maria Oliveira Maciel, José Eduardo Mautone de Barros
Abstract The aim of this work is to present the preliminary performance studies of the unmanned, lightweight (less than 10 kg), supersonic research aircraft. The studies comprise the typical mission for the aircraft's first supersonic version, based on the aerodynamic, thrust, and mass characteristics presented in a previous work. The aircraft, named as “Pohox”, is an Unmanned Air Vehicle, or “UAV”, and is intended to be the flying test bed for a multi cycle engine capable to provide thrust in subsonic, transonic and supersonic regimes. Different tools have been developed to perform the analysis. In the analysis, different flight paths are considered in order to provide insights in terms of fuel consumption, altitude and speed gain. Aircraft ‘excess power’ diagrams have been generated, to provide guidance for the definition of the flight paths to be analyzed. Drag dependency with Mach number is considered in the analysis.
2014-11-04
Technical Paper
2014-36-0785
Augusto Amador Medeiros, Zargos Neves Masson, Pablo Giordani, Julio Cordioli
Abstract With the increase in aircraft transportation and, consequently, aircraft noise in the last decades, measurement of acoustic liner impedance under grazing flow has become a point of interest. Different indirect methodologies have been developed by independent research groups to solve this problem. The Mode-Matching technique and, more recently, the Two-Port method are examples of developed methodologies that use acoustic pressure measurements in a test rig where a liner sample is subject to grazing mean flow to educe its impedance. In this paper, both methods are explained, implemented and used to educe the acoustic impedance of different liner samples in a recently developed grazing flow impedance eduction test rig. Additionally, both methods are compared based on their computational cost and limitations.
2014-09-30
Technical Paper
2014-36-0508
Luciano Magno Frágola Barbosa, Paulo Henriques Iscold Andrade de Oliveira
Abstract One of the critical tasks of aircraft design is the definition of mass of aircraft's main items, and the aircraft mass distribution. Depending on the type of aircraft (e.g. commercial, general aviation, highly-maneuverable) different types of mass distribution data or trend curves are available; and in general these curves are based on the existing aircraft. But some lack of data is noticeable in terms of solar aircraft, i.e. the available information in terms of mass trends does not fulfill the needs of the designers of this type of aircraft. Considering this perspective, the main motivation of this study is to provide some information, in terms of mass trends and mass analysis for sun-powered aircraft, which could fill part of the gap, and stimulate other efforts in the same direction. Through this work, studies of mass breakdown of different examples of sun-powered aircraft are presented.
2014-09-30
Technical Paper
2014-36-0390
Juliano F. Mologni, Anderson S. Nunes, Cesareo L. R. Siqueira, Diogo L. Figueiredo, Jefferson C. Ribas, Arismar C. S. Junior, Marco A. R. Alves
Abstract Radar Cross Section (RCS) is the equivalent effective area of a given target intercepting a radar wave. In other words, RCS is a measure of how detectable a solid is with radar. For the past years, several electromagnetic numerical codes were used to calculate the RCS of aircrafts including the well known and commonly used Finite Element Method (FEM), Finite Difference Time Domain (FDTD) and Method of Moments (MoM). An incident planar wave is used to simulate the radar signal. Today a hybrid method known as Finite Element Boundary Integral (FEBI) solves a RCS model using the advantages of both FEM and MoM. This paper shows a series of RCS benchmarks listed in the literature comparing the results and performance of FEM, IE and FEBI. In order to show the state of the art of electromagnetic numerical codes and a more realistic analysis, several RCS of aircraft models are presented using FEBI and a true radar source.
2016-04-05
Journal Article
2016-01-0497
Brian Falzon, Wei Tan
Abstract The development of the latest generation of wide-body carbon-fibre composite passenger aircraft has heralded a new era in the utilisation of these materials. The premise of superior specific strength and stiffness, corrosion and fatigue resistance, is tempered by high development costs, slow production rates and lengthy and expensive certification programmes. Substantial effort is currently being directed towards the development of new modelling and simulation tools, at all levels of the development cycle, to mitigate these shortcomings. One of the primary challenges is to reduce the extent of physical testing, in the certification process, by adopting a ‘certification by simulation’ approach. In essence, this aspirational objective requires the ability to reliably predict the evolution and progression of damage in composites. The aerospace industry has been at the forefront of developing advanced composites modelling tools.
2015-05-01
Journal Article
2015-01-9082
Branislav Sredanovic, Djordje Cica
Abstract The most efficient way to reduce friction and heat generation at the cutting zone is to use advanced cooling and lubricating techniques. In this paper, an experimental study was performed to investigate the capabilities of conventional, minimal quantity lubrication (MQL) and high pressure cooling (HPC) in the turning operations. Process parameters (feed, cutting speed and depth of cut) are used as inputs to the developed artificial neural network (ANN) and the adaptive networks based fuzzy inference systems (ANFIS) model for prediction of cutting forces, tool life and surface roughness. Results obtained by the models have been compared for their prediction capability with the experimentally determined values and very good agreement with experimental results was observed.
2016-01-05
Journal Article
2015-01-9086
Geethanjali Gadamchetty, Abhijeet Pandey, Majnoo Gawture
The three parameter Ramberg-Osgood (RO) method finds popular usage for extracting complete stress-strain curve from limited data which is usually available. The currently popular practice of assuming the plasticity to set in only at the Yield point provides computational advantage by separating the complete nonlinear curve, obtained from RO method, into elastic and plastic regions. It is shown, with an example problem, that serious errors are committed by using this method if one compares the obtained results with results of complete stress-strain curve. In the present work we propose a simple Taylor series based approach based on RO method to overcome the above deficiency. This method is found to be computationally efficient. The proposed method is applicable for stress-strain curves of materials for which RO method provides a good approximation.
Viewing 1 to 30 of 1155

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