scholarly journals MODAL AND FLUTTER ANALYSIS OF THE SAILPLANE LAK-17B USING NUMERICAL METHODS

Transport ◽  
2014 ◽  
Vol 29 (1) ◽  
pp. 84-89 ◽  
Author(s):  
Marius Andrikaitis ◽  
Algimantas Fedaravičius
Keyword(s):  
Finite Element ◽  
Numerical Methods ◽  
Finite Element Model ◽  
Normal Modes ◽  
Element Model ◽  
Current Work ◽  
Lattice Method ◽  
Flutter Analysis ◽  
Doublet Lattice Method

The objective of current work is to determine the V–g and V–f diagrams for the sailplane’s LAK-17B empennage using numerical methods. The article considers the following problems: development of finite element model of the sailplane LAK-17B; normal modes calculation using created finite element model; flutter analysis of sailplane LAK-17B using doublet lattice method.

Characterization of Nonlinear Coupled Dynamics in Sandwich Structures

2008 ◽  
Author(s):  
Ioannis T. Georgiou
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Geometric Nonlinearity ◽  
Sandwich Structures ◽  
Normal Modes ◽  
Element Model ◽  
Nonlinear Normal Modes ◽  
High Fidelity ◽  
Coupled Dynamics ◽  
Nonlinear Normal

In this work, the nonlinear coupled dynamics of a sandwich structure with hexagonal honeycomb core are characterized in terms of Proper Orthogonal Decomposition modes. A high fidelity nonlinear finite element model is derived to describe geometric nonlinearity and displacement and rotation fields that govern the coupled dynamics. Contrary to equivalent continuum models used to predict vibration properties of lattice and sandwich structures, a high fidelity finite element model allows for a quite detailed description of the distributed complicated geometric nonlinearity of the core. It was found that the free dynamics excited by a blast load and the forced dynamics excited by a harmonic force posses POD modes which are localized in space and time. The processing of the simulated dynamics by the Time Discrete Proper Transform forms a means to study the nonlinear coupled dynamics of sandwich structures in the context of nonlinear normal modes of vibration and reduced order models.

scholarly journals Numerical investigation of the mechanical properties of the additive manufactured bone scaffolds fabricated by FDM: the effect of layer penetration and post-heating

2017 ◽  
Author(s):  
Saman Naghieh ◽  
Mohammad Reza Karamooz-Ravari ◽  
Mohsen Badrossamay ◽  
Ehsan Foroozmehr
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Elastic Modulus ◽  
Numerical Methods ◽  
Finite Element Model ◽  
Compression Test ◽  
Element Model ◽  
Element Analysis ◽  
Bone Scaffolds

In recent years, thanks to additive manufacturing technology, researchers have gone towards the optimization of bone scaffolds for the bone reconstruction. Bone scaffolds should have appropriate biological as well as mechanical properties in order to play a decisive role in bone healing. Since the fabrication of scaffolds is time consuming and expensive, numerical methods are often utilized to simulate their mechanical properties in order to find a nearly optimum one. Finite element analysis is one of the most common numerical methods that is used in this regard. In this paper, a parametric finite element model is developed to assess the effects of layers penetration׳s effect on inter-layer adhesion, which is reflected on the mechanical properties of bone scaffolds. To be able to validate this model, some compression test specimens as well as bone scaffolds are fabricated with biocompatible and biodegradable poly lactic acid using fused deposition modeling. All these specimens are tested in compression and their elastic modulus is obtained. Using the material parameters of the compression test specimens, the finite element analysis of the bone scaffold is performed. The obtained elastic modulus is compared with experiment indicating a good agreement. Accordingly, the proposed finite element model is able to predict the mechanical behavior of fabricated bone scaffolds accurately. In addition, the effect of post-heating of bone scaffolds on their elastic modulus is investigated. The results demonstrate that the numerically predicted elastic modulus of scaffold is closer to experimental outcomes in comparison with as-built samples.

Analysis of the Influence of Blade Pattern Characteristics on the Forced Response of Mistuned Blisks With a Cyclic CMS-Based Substructure Model

2010 ◽  
Author(s):  
Andreas Hohl ◽  
Lars Panning ◽  
Jo¨rg Wallaschek
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Vibrational Energy ◽  
Normal Modes ◽  
Element Model ◽  
Forced Response ◽  
Symmetry Approach ◽  
Full Structure ◽  
Value Decomposition

In turbomachinery applications bladed disks and blisks are subjected to high dynamic loads due to fluctuating gas forces. The dynamic excitation results in high vibration amplitudes which can lead to high cycle fatigue failures (HCF). Herein, the blades are almost identical but differ due to wear or small manufacturing tolerances. These small deviations of the blade properties can lead to a localization of the vibrational energy in single blades and even higher risk of HCF. Intentional mistuning, for example an alternating alignment of two different blades AB around the blisk, has been studied in literature to decrease the sensitivity against statistical mistuning. Using a Component Mode Synthesis (CMS) based mistuning model the influence of intentional mistuning on blisks is analyzed in this paper. Therein, the CMS of the disk is calculated with a fast and accurate cyclic symmetry approach. Therefore, the CMS of the disk can be calculated with one disk segment of the underlying Finite Element Model. The so called Wave Based Substructuring (WBS) is used to reduce the (numerous) coupling degrees of freedom between the disk and the blades with a truncated set of waves. The orthogonal waves are derived with a Singular Value Decomposition or a QR decomposition from the normal modes at the coupling degrees of freedom (DOF) calculated by a cyclic modal analysis of the full structure. In a case study the Reduced Order Model (ROM) of a spatial Finite Element Model is used to determine the influence of intentional mistuning with additional statistical mistuning on the forced response of blisks.

Flutter Optimized Design for a Aircraft Horizontal Tail Base on Optimus Software

2014 ◽  
Vol 684 ◽  
pp. 58-63
Author(s):  
Da Qian Zhang ◽  
Xiao Dong Tan ◽  
Zi Lei Zhang ◽  
Xin Ping Fu
Keyword(s):  
Finite Element ◽  
Wind Tunnel ◽  
Similarity Theory ◽  
Dynamic Pressure ◽  
Unsteady Aerodynamics ◽  
Element Model ◽  
Scale Model ◽  
Optimized Design ◽  
Lattice Method ◽  
Doublet Lattice Method

Based on the similarity theory, the horizontal tail scale model is designed and manufactured. Subsonic doublet lattice method is used to calculate unsteady aerodynamics, V-g method is used to solve the flutter determinant. Optimus software is used to optimize the thickness of the skin. The constraint condition is the frequency, MAC value and flexibility, and the objective function is flutter dynamic pressure. Flutter velocity of horizontal tail model optimized decreased 6%,and flutter frequency increased greatly. Horizontal tail scale model was test in wind tunnel. The finite element calculate results was very close with wind tunnel results, which verify the correctness of the finite element model and optimization models.

On Updating of Finite Element Model Using Optimization Method

1997 ◽  
Author(s):  
Wolfgang G. Luber
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Natural Frequencies ◽  
Normal Modes ◽  
Mathematical Optimization ◽  
Element Model ◽  
Optimization Method ◽  
Mode Shapes ◽  
Initial Structure ◽  
Error Localization

Abstract An error localization and update method is presented which examines the elastic and dynamic behavior of the structure by means of deflections stemming from a discrete load case and from normal mode shapes of the structure respectively as well as the information of the change of natural frequencies. The main objective of the study is to provide an economical and reliable error localization method for aeronautical structures. A finite element model of the elastic structure must be available before testing the real structure to determine the optimal positioning of sensors. The error localization is based on sensitivity methods and on nonlinear mathematical optimization codes. Displacements for selected load cases and normal modes are taken as constraints. Minimum sizing changes with respect to the initial structure is used as objective function. Numerical examples with different structures show that the proposed methods can accurately detect the variations in stiffness in certain cases.

The Study of Mechanical Behaviors Performance of Bearing Form's Influence on Small-Radius Bridge

2011 ◽  
Vol 255-260 ◽  
pp. 776-780
Author(s):  
Mao Qi Li
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Reaction Force ◽  
Bending Moment ◽  
Element Model ◽  
Small Radius ◽  
Structural Method ◽  
Mechanical Behaviors ◽  
Lattice Method ◽  
Longitudinal Bending

With the structural method, the "bending - twisting" coupling of the curve bridge is possible. As the small-radius bridge’s radius become smaller and smaller, the "Bending-Twisting" coupling become more and more common in order to discuss and verify the mechanical behaviors performance of supports' influence on small-radius bridge. This is done by changing the small-radius bridge’s supporting approach, using girder lattice method to construct a finite element model, analysis on a small-radius bridge of supporting longitudinal bending moment, torque and the influence of reaction force. The data shows that the double supports can reduce the small-radius bridge’s torque, make the medial and lateral support bearings equal reaction, make the small-radius bridge’s mechanical behaviors performance more reasonable, but was less affected by longitudinal bending moment. This conclusion of the small-radius bridge is significant to the designing work in the future.

Sign in / Sign up

Export Citation Format

Share Document