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Sökning: hsv:(TEKNIK OCH TEKNOLOGIER) hsv:(Maskinteknik) hsv:(Rymd och flygteknik) > Linköpings universitet

  • Resultat 1-10 av 132
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1.
  • Munjulury, Raghu Chaitanya, et al. (författare)
  • Knowledge-based future combat aircraft optimization
  • 2016
  • Ingår i: 30th Congress of the International Council of the AeronauticalSciences (ICAS 2016). - Bonn : International Council of Aeronautical Sciences (ICAS). - 9781510834552 ; , s. 273-280
  • Konferensbidrag (refereegranskat)abstract
    • Future combat aircraft inherently conceal all the components internally essentially for stealth reasons. The geometry is optimized for subsonic and supersonic flight area distribution and the components and payload to be fitted inside the aircraft. The basic requirements to accomplish are fuel consumption, mission profile, and military performance. Analytical methods comprise of a quick aerodynamic and structural optimization. The result obtained is then compared with multi-fidelity aero-structural analysis
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2.
  • Shetty, Sandeep (författare)
  • Optimization of Vehicle Structures under Uncertainties
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Advancements in simulation tools and computer power have made it possible to incorporate simulation-based structural optimization in the automotive product development process. However, deterministic optimization without considering uncertainties such as variations in material properties, geometry or loading conditions might result in unreliable optimum designs. In this thesis, the capability of some established approaches to perform design optimization under uncertainties is assessed, and new improved methods are developed. In particular, vehicle structural problems which involve computationally expensive Finite Element (FE) simulations, are addressed.The first paper focuses on the evaluation of robustness, given some variation in input parameters, the capabilities of three well-known metamodels are evaluated. In the second paper, a comparative study of deterministic, reliability-based and robust design optimization approaches is performed. It is found that the overall accuracy of the single-stage (global) metamodels, which are used in the above study, is acceptable for deterministic optimization. However, the accuracy of performance variation prediction (local sensitivity) must be improved. In the third paper, a decoupled reliability-based design optimization (RBDO) approach is presented. In this approach, metamodels are employed for the deterministic optimization only while the uncertainty analysis is performed using FE simulations in order to ensure its accuracy.In the fifth paper, two new sequential sampling strategies are introduced that aim to improve the accuracy of the metamodels efficiently in critical regions. The capabilities of the methods presented are illustrated using analytical examples and a vehicle structural application.It is important to accurately represent physical variations in material properties since these might exert a major influence on the results. In previous work these variations have been treated in a simplified manner and the consequences of these simplifications have been poorly understood. In the fourth paper, the accuracy of several simple methods in representing the real material variation has been studied. It is shown that a scaling of the nominal stress-strain curve based on the Rm scatter is the best choice of the evaluated choices, when limited material data is available.In this thesis work, new pragmatic methods for non-deterministic optimization of large scale vehicle structural problems have been developed. The RBDO methods developed are shown to be flexible, more efficient and reasonably accurate, which enables their implementation in the current automotive product development process.
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3.
  • Tarroc Gil, Sergi, et al. (författare)
  • Zonal Model Based Aircraft Passenger Thermal Comfort Comparative Study
  • 2022
  • Ingår i: 33th Congress of the International Council of the Aeronautical SciencesStockholm, Sweden. - : International Council of the Aeronautical Sciences (ICAS). - 9781713871163 ; , s. 312-322
  • Konferensbidrag (refereegranskat)abstract
    • Computational simulations have become during the last decades an essential tool to be used every day sooner in the design chain within the aerospace industry, leading to better decision making and more efficient concepts. However, in the aircraft design field, the thermal comfort of the passengers is not assessed until late design stages due to the complexity and high computational cost of simulating the flow inside it. The present work has the aim to show the Zonal Model approach as a solid early design simulation alternative to conventional CFD. A complete Fractional Step based Zonal Model solver is proposed, able to provide first estimations to the two-dimensional fluid solution, for a given cabin concept, with a low computational cost associated. This solver has also integrated its own automatized mesh generation algorithm along with a Radial Basis Functionsmorphing tool. With this method, a set of comparative studies have been performed for comparing several cabin design parameters attending to the thermal comfort of passengers and crew, giving a demonstration of the capabilities that this Zonal Model approach has for early aircraft design optimization and decision making.
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4.
  • Eek, Magnus (författare)
  • On Credibility Assessment in Aircraft System Simulation
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The aeronautical industry is becoming increasingly reliant on Modeling and Simulation (M&S) for use throughout all system development phases, for system verification, and end-user training. To justify and to utilize the full potential of today’s model-based approach, the development of efficient and industrially applicable methods for credibility assessment of M&S efforts is a key challenge.This work addresses methods facilitating credibility assessment of simulation models and simulator applications used in aircraft system development. For models of individual aircraft subsystems, an uncertainty aggregation method is proposed that facilitates early model validation through approximate uncertainty quantification. The central idea is to integrate information obtained during component level validation directly into the component equations, and to utilize this information in model level uncertainty quantification.In addition to methods intended for models of individual subsystems, this work also proposes a method and an associated tool for credibility assessment of large-scale simulator applications. As a complement to traditional document-centric approaches, static and dynamic credibility information is here presented to end-users directly during simulation. This implies a support for detecting test plan deficiencies, or that a simulator configuration is not a suitable platform for the execution of a particular test. The credibility assessment tool has been implemented and evaluated in two large-scale system simulators for the Saab Gripen fighter aircraft. The work presented herein also includes an industrially applicable workflow for development, validation, and export of simulation models.
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5.
  • Safavi, Edris, et al. (författare)
  • Implementation of collaborative multidisciplinary design optimization for conceptual design of a complex engineering product
  • 2016
  • Ingår i: Concurrent Engineering - Research and Applications. - : Sage Publications. - 1063-293X .- 1531-2003. ; 24:3, s. 251-265
  • Tidskriftsartikel (refereegranskat)abstract
    • This study investigates the performance of the collaborative multidisciplinary design optimization framework and how it facilitates the knowledge integration process. The framework is used to design and optimize an innovative concept of a tidal water power plant. The case study helps to highlight the challenges that may occur during implementation. The result is presented as a modified framework with less implementation difficulties. The improved framework shows significant reduction in design time and improvement in collaborative design optimization for a design team. The geometry of the product is optimized to minimize weight and maximize the power generated by the turbine with respect to some mechanical constraints.
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6.
  • Shetty, Sandeep, et al. (författare)
  • An evaluation of simple techniques to model the variation in strain hardening behavior of steel
  • 2017
  • Ingår i: Structural and multidisciplinary optimization (Print). - Bonn : Springer. - 1615-147X .- 1615-1488. ; 55:3, s. 945-957
  • Tidskriftsartikel (refereegranskat)abstract
    • It is important to consider variations in material parameters in the design of automotive structures in order to obtain a robust and reliable design. However, expensive tests are required to gain complete knowledge of the material behavior and its associated variation. Consequently, due to time and cost constraints, simplified material scatter modeling techniques based on scatter data of typical material properties provided by the material suppliers are used at early design stages in simulation-based robustness studies. The aim of this paper is to study the accuracy of the simplified scatter modeling methods in representing the real material variation. The simplified scatter modeling methods are evaluated by comparing the material scatter obtained by them to the scatter obtained by complete tensile tests, which are obtained after detailed timeconsuming experimental investigations. Furthermore, an accuracy assessment is carried out based on selected responses from an axially-crushed, square tube made from DP600 steel.
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7.
  • Stekovic, Svjetlana, 1967-, et al. (författare)
  • Towards the elaboration of the European Code of Practice for TMF crack growth
  • 2016
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • In recent years, there has been an increasing interest towards the environmental impact of air travel. As a result, it is of vital importance to the European aviation industry to reduce the engine emissions. For this purpose, ACARE set new challenging targets aiming to reduce emissions, fuel consumption and raising temperature capabilities. This will ultimately be achieved by the introduction of novel engine design and new materials able to sustain complex loadings from take-off, cruise, descent and shut down. It is a prerequisite to understand the impact of such environments in current alloys.Specifically, Thermo-Mechanical Fatigue (TMF), which occurs at the rim of turbine discs, aerofoils and rear structures need to be assessed. At these locations, the harsh thermal transients during take-off and descent may cause the formation of cracks.  A previous European project on TMF, which ended in 2005, has been successful at evaluating and addressing issues related to thermo-mechanical fatigue testing. This project led to the elaboration of a code of practice for TMF studies, which has been implemented by testing houses and equipment manufacturers worldwide. A European project has recently been awarded, under the umbrella of both `Horizon 2020' and Clean Sky 2, aiming to evaluate and model TMF crack initiation and growth.TMF crack growth (CG) methods are essential to demonstrate that structural components meet the certification requirements of being tolerant at handling damages and the presence of melt anomalies. They are also needed to assess remnant lives in cracked turbine components such as vanes. However, crack growth in TMF loading cycles cannot be currently reliably measured experimentally nor predicted by existing CG models. Therefore, isothermal propagation data are used to conservatively handle TMF effects, which can lead to over-designed components and loss of engine efficiency. Our project aims to address those deficiencies.
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8.
  • Björnsson, Andreas (författare)
  • Automated layup and forming of prepreg laminates
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Composite materials like carbon fiber-reinforced polymers (CFRPs) present highly appealing material properties, as they can combine high strength with low weight. In aerospace applications, these properties help to realize lightweight designs that can reduce fuel consumption. Within the aerospace industry, the use of these types of materials has increased drastically with the introduction of a new generation of commercial aircraft. This increased use of CFRP drives a need to develop more rational manufacturing methods.For aerospace applications, CFRP products are commonly manufactured from a material called prepreg, which consists of carbon fibers impregnated with uncured polymer resin. There are two dominant manufacturing technologies for automated manufacturing using prepreg, automated tape layup and automated fiber placement. These two technologies are not suitable for all types of products, either due to technical limitations or a combination of high investment costs and low productivity. Automation alternatives to the two dominant technologies have been attempted, but have so far had limited impact. Due to the lack of automation alternatives, manual manufacturing methods are commonly employed for the manufacturing of complex-shaped products in low to medium manufacturing volumes.The research presented in this thesis aims to explore how automated manufacturing systems for the manufacturing of complex CFRP products made from prepreg can be designed so that they meet the needs and requirements of the aerospace industry, and are suitable for low to medium production volumes. In order to explore the area, a demonstrator-centered research approach has been employed. A number of demonstrators, in the form of automated manufacturing cells, have been designed and tested with industrial and research partners. The demonstrators have been used to identify key methods and technologies that enable this type of manufacturing, and to analyze some of these methods and technologies in detail. The demonstrators have also been used to map challenges that affect the development of enabling methods and technologies.Automated manufacturing of products with complex shapes can be simplified by dividing the process into two steps. Thin layers of prepreg are laid up on top of each other to form flat laminates that are formed to the desired shape in subsequent forming operations. The key methods and technologies required to automate such a system are methods and technologies for automated prepreg layup, the automated removal of backing paper and the forming of complex shapes. The main challenges are the low structural rigidity and tacky nature of prepreg materials, the extensive quality requirements in the aerospace industry and the need for the systems to handle a wide array of prepreg shapes.The demonstrators show that it is possible to automate the manufacturing of complexshaped products using automated layup and forming of prepreg laminates. Tests using the demonstrators indicate that it is possible to meet the quality requirements that apply to manual manufacturing of similar products.
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9.
  • Kihlman, Henrik, et al. (författare)
  • 6DOF metrology-integrated robot control
  • 2003
  • Ingår i: SAE Technical Paper Series. - Montreal, QC, Canada : Society of Automotive Engineers. - 0148-7191.
  • Konferensbidrag (refereegranskat)abstract
    • This paper describes ongoing research into Metrology-integrated robot control. The research is a part of an ongoing EU funded aircraft industry project – ADFAST*. The ADFAST project tries to implement the use of industrial robots in low-volume production, high-demand-on-accuracy operations and for dynamic force compensation. To detect and compensate deflection in industrial robots during a process, the robot uses a metrology system. The metrology system supervises the tool center point of the robot as it executes its processes. Leica has recently released a new metrology system; the LTD800, which measures distances with laser interferometry and can simultaneously measure orientation of targets, through photogrammetry, using an additional camera on top of the measuring unit. This paper will describe theory and results from tests performed on integrating the LTD800 with the robot.
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10.
  • Munjulury, Raghu Chaitanya, et al. (författare)
  • A comprehensive computational multidisciplinary design optimization approach for a tidal power plant turbine
  • 2017
  • Ingår i: Advances in Mechanical Engineering. - London : Sage Publications. - 1687-8132 .- 1687-8140. ; 9:3, s. 1-13
  • Tidskriftsartikel (refereegranskat)abstract
    • Multidisciplinary design optimization has become a powerful technique to facilitate continuous improvement of complex and multidisciplinary products. Parametric modeling is an essential part with tremendous impact on the flexibility and robustness of multidisciplinary design optimization. This article investigates the effect of relational and non-relational parameterization techniques on the robustness and flexibility of the conceptual design of a multidisciplinary product. Bench marking between relational and non-relational parameterization and their effect on flexibility and robustness indicate that the relational parameterization is an efficient method in the multidisciplinary design optimization process. The inherent properties of the method contribute to an efficient parametric modeling with improved communication between different disciplines. This enhances the performance of the multidisciplinary design optimization process and allows a more flexible and robust design. The considered disciplines are computer-aided design, computational fluid dynamics, finite element analysis, and dynamic simulation. A high-fidelity geometry created in a computer-aided design environment is computer-aided design centric approach and later used in computational fluid dynamics, finite element analysis for a better understanding of the product as it leads to precise outcomes. The proposed approach is implemented for the conceptual design of a novel product, a tidal power plant developed by Minesto AB using a multidisciplinary design optimization process.
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