NCK NaCCAS - sekce letadel


Recent Submissions

Now showing 1 - 5 of 5
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    Modifications of a simple I-beam and its effects on the stress state
    (Taylor & Francis, 2016-12-20) Cejpek, Jakub; Juračka, Jaroslav
    The motivation for this work is a desire for a deeper understanding of the structural failures in a composite glider wing, which has been tested in the laboratories of the Institute of Aerospace Engineering, Faculty of Mechanical Engineering, Brno University of Technology. To understand the causes of the encountered failures, one has to consider the effects of all the stages in the design, manufacturing and testing of the wing. This paper focuses only on the design stage. The presented facts were obtained from a finite element analysis. The geometry used for the analysis is that of the tested specimens. This allows validating the results by the comparison of the deformation and strains measured during the laboratory tests. The analysis starts with a simple I-beam loaded by three-point-bending. In the next step a cantilever is added. Several more modifications follow, changing the I-beam to the wing. The case evaluation considers the interaction between normal (material direction 1) and inter-laminar shear stresses in the upper flange. The goal of this paper is to quantify the effect of each design change in the wing structure and loading on the stress plane 1-31.
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    Dimensionally Stable Laminates Under Thermal Loading and Their Applications
    (EDP Sciences, 2019-12-17) Symonov, Volodymyr
    There exist many types of structures, which are required to have stable dimensions within a wide range of temperatures. The specific nature of composites allows finding special conditions when a laminate stacking sequence can provide zero thermal expansion coefficients in one or more directions. This allows the structure being designed to have the same dimensions in a wide range of temperatures. This work is aimed to find mathematical conditions, which guarantee in-plane zero CTE at least in one direction. As an application of thermally stable laminates a rotating disk is chosen. The mathematical model for such a disk is presented. Among investigated materials there was not found any of them, which can be used to layup a laminate with zero CTEs in two directions. However, all investigated materials can be used to layup many laminates with zero CTE in one or another direction. Moreover, it was discovered a laminate might have a zero CTE, if the lamina has zero or negative CTE at least in one direction. It was found the stresses, which appear in a laminated disk caused by centripetal forces, are insignificantly low in comparison to the thermal ones within the investigated ranges of angular velocity and temperature.
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    Aerodynamic shape optimization of an airliner elastic wing
    (EDP Sciences, 2017-11-08) Navrátil, Jan
    Aerodynamic shape optimization of a common airliner elastic wing is presented and compared with optimization of the same wing assuming rigid structure. A gradient-based optimization approach is applied in connection with adjoint method used for calculation of gradients of aerodynamic forces. The initial wing shape is parameterized by Free Form Deformation technique. The aerodynamics of the elastic wing is calculated using the fluid-structure interaction method which couples computational fluid dynamic solver with linear structural solver.
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    Failure Index Based Topology Optimization for Multiple Properties
    (Brno University of Technology, 2017-05-15) Löffelmann, František
    Aim of the presented work is to introduce a method which is being coded. It works in conjunction with an open-source finite element solver CalculiX. One of the topology optimization methods - The Bi-directional Evolutionary Structural Optimization method (BESO) was chosen due to its simplicity, which is used in the way of python code standing above FE solver. Two test examples are presented. First demonstrates ability to achieve results similar to compliance based topology optimization on short beam leading to solid-void structure. Second example shows possibility to switch among different materials with regard to their allowable stresses.
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    Wake vortex gliding
    (2015-06-29) Zikmund, Pavel
    Airplanes and birds can save energy by flying in formation. The energy is harvested from the wake vortex of the formation leader. This paper brings flight performance feasibility study of an extreme formation when a big airliner is followed by a small UAV. Models of B 747 wake vertices are laid out and parameters of the UAV designed for flight in the wake vortex are introduced. Regions with sufficient energy for gliding flight are analysed for different vortex models.