Complex Eigenvalue Analysis Applied to an Aircraft Brake Vibration Problem

1995 ◽  
Author(s):  
Denis J. Feld ◽  
Dana J. Fehr
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Friction Force ◽  
Mode Shape ◽  
Element Model ◽  
Eigenvalue Analysis ◽  
Complex Eigenvalue ◽  
Friction Forces ◽  
Model Complex ◽  
Complex Eigenvalue Analysis

Abstract A conventional finite element model of an aircraft wheel and brake is extended to include forces responsible for friction-induced noise. Responses of aircraft brake vibration modes change the normal force across the brake friction interfaces, and consequently the friction forces. The resulting friction force variations are assembled in the form of a supplemental stiffness matrix and added to the finite element model. Complex eigenvalue analysis that includes the friction force variations provides frequency and mode shape information, as well as an assessment of the predicted mode stability. A predicted unstable vibration mode compares very well to operating mode shape data determined from instrumented tests. Hardware modifications to reduce a brake noise in an aircraft cabin were based on beneficial trends found from exercising the model. Implementation of the hardware modifications on the aircraft successfully suppressed the noise.

The Design and Size Optimization of the New FCEV Subframe Based on Hypermesh Platform

2011 ◽  
Vol 328-330 ◽  
pp. 435-440
Author(s):  
Jun Liao ◽  
Lan Shan ◽  
Yan Feng
Keyword(s):  
Finite Element ◽  
Comparative Analysis ◽  
Finite Element Model ◽  
Mode Shape ◽  
High Strength Steel ◽  
High Strength ◽  
Element Model ◽  
Strength Analysis ◽  
Size Optimization ◽  
Optimal Size

The establishment of FCEV finite element model of the subframe is based on Hypermesh platform, and a new subframe structure is designed in accordance with the stiffness and strength analysis on the original subframe in all conditions. High-strength steel materials are used to optimize the design of this new structure, which result in the optimal size. Through the comparative analysis of the strength, stiffness, mode shape and quality on new subframe and the original one, it is verified that the design of the new subframe is reasonable and feasible.

On a Perturbation Method for the Analysis of Unsteady Belt-Drive Operation

2004 ◽  
Vol 72 (4) ◽  
pp. 570-580 ◽  
Author(s):  
Michael J. Leamy
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Perturbation Method ◽  
Element Model ◽  
Contact Forces ◽  
Steady Solution ◽  
Belt Drive ◽  
Friction Forces ◽  
Direct Contrast ◽  
Validity Criteria

A perturbation method is presented for use in analyzing unsteady belt-drive operation. The method relies on the important assumption that for operating states close to steady operation, the friction state (i.e., whether the belt is creeping or sticking at any location on the pulley) is similar to that of the well-known steady solution in which a lone stick arc precedes a lone slip arc (Johnson, K. L., 1985, Contact Mechanics, Cambridge U.P., London, Chap. 8; Smith, D. P., 1999, Tribol. Int., 31(8), pp. 465–477). This assumption, however, is not used to determine the friction force distribution, and, in fact, the friction forces in the stick zone are found to be nonzero, in direct contrast to the steady solution. The perturbation analysis is used to derive expressions for the span tensions, the pulley tension distributions, the contact forces between the belt and the pulleys, and the angular velocity of the driven pulleys. Validity criteria are developed which determine bounds on the operation state for which the assumed friction state is upheld. Verification of response quantities from the perturbation solution is accomplished through comparison to quantities predicted by an in-house dynamic finite element model and excellent agreement is found. Additionally, the finite element model is used to verify the key assumption that a lone slip arc precedes a lone stick arc.

Real Asymmetric Matrix Eigenvalue Analysis for Dynamic Instability Problems

2000 ◽  
Author(s):  
Heewook Lee ◽  
Noboru Kikuchi
Keyword(s):  
Control Systems ◽  
Eigenvalue Problems ◽  
Dynamic Instability ◽  
Eigenvalue Analysis ◽  
Complex Eigenvalue ◽  
Friction Forces ◽  
Matrix Eigenvalue ◽  
Complex Eigenvalues ◽  
Complex Eigenvalue Analysis ◽  
Matrix Eigenvalue Problems

Abstract Complex eigenvalue analysis is widely used when the dynamic instability of the structure is in doubt due to friction forces, aerodynamic forces, control systems, or other effects. MSC/NASTRAN upper Hessenberg method and MATLAB eigenvalue solver produce fictitious nonzero real parts for real asymmetric matrix eigenvalue problems. For dynamic instability problems, since nonzero real parts of complex eigenvalues determine the unstable eigenvalues, the accuracy of real parts becomes crucial. The appropriate double shift QR or the QZ algorithms are applied to eliminate fictitious nonzero real parts and produce only authentic complex eigenvalues for real asymmetric matrix eigenvalue problems. Numerical examples are solved using the double shift QR and the QZ algorithms, and the results are compared with the results of MSC/NASTRAN upper Hessenberg method and MATLAB solvers.

The Research of Drive Roll’s Dynamics Characteristics

2014 ◽  
Vol 597 ◽  
pp. 498-501
Author(s):  
Shao Hai Li
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Mode Shape ◽  
Vibration Mode ◽  
Element Model ◽  
Set Up ◽  
Drive Roll ◽  
Ansys Workbench

In order to research the dynamic characteristics of drive roll, finite element model of the drive roll was set up by ANSYS/Workbench. The drive roll’s natural frequency and vibration mode concerned in reality were acquired based on modal analysis, deformation trend and size of each mode shape were analysed, then deformation of the weak positions about each mode was cleared, and some measures about improving its dynamic characteristics were proposed, all of these offered a support to strengthen drive roll’s damping property.

Model updating of finite element model using optimisation routine

2016 ◽  
Vol 88 (5) ◽  
pp. 665-675 ◽  
Author(s):  
Bimo Prananta ◽  
Toni Kanakis ◽  
Jos Vankan ◽  
Rien van Houten
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Objective Function ◽  
Mode Shape ◽  
Model Updating ◽  
Element Model ◽  
Design Parameters ◽  
Shape Error ◽  
Content Type ◽  
Small Aircraft

Purpose The present paper aims to describe the model updating of a small aircraft dynamic finite element model (FEM) to improve its agreement with ground vibration test (GVT) data. Design/methodology/approach An automatic updating method using an optimization procedure is carried out. Instead of using dedicated updating tools, the procedure is implemented using standard MSC/NASTRAN because of wide availability of the software in small aircraft industries. The objective function is defined to minimize the differences in the natural frequency and the differences in the mode shape between the analytical model and the GVT data. Provision has been made to include the quantification of confidence in both the GVT data and in the initial model. Parameter grouping is carried out to reduce the number of design parameters during the optimization process. Findings The optimization module of standard finite element (FE) software can be effectively used to reduce the differences between the GVT and the FEM in terms of frequency and mode shape satisfactorily. The strategy to define the objective function based on minimizing the mode shape error can reduce the improvement in the frequency error. The required user interference can be kept low. Originality/value The most important contribution of the present paper concerns the combination of strategies to define the objective function and selection of the parameters.

scholarly journals Finite Element Model Updating of Satellite Sailboard Based on Sensitivity Analysis

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Haitao Luo ◽  
Wei Wang ◽  
Jia Fu ◽  
Lichuang Jiao
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Modal Analysis ◽  
Mode Shape ◽  
Vibration Mode ◽  
Model Updating ◽  
Element Model ◽  
Acceleration Response ◽  
Modal Frequency

The modal analysis of a satellite sailboard finite element model is carried out to accurately investigate the response of a satellite sailboard in a complex loaded space environment through simulation. The basic excitation vibration test of the satellite sailboard is used to perform model matching and a correlation test. Appropriate design variables are selected through sensitivity analysis. Modal analysis data and vibration table excitation test response data are used to modify the finite element model. After optimization, the orthogonality of the simulated vibration mode and experimental vibration mode is good. The low-order frequency errors in the simulation model are less than 5%, the high-order errors are less than 10%, and the modal confidence MAC values are above 0.8. The modal frequency and mode shape are closer to the experimental modal frequency and mode shape, respectively. The simulation and test acceleration response of the modified finite element model of a honeycomb panel are compared under the two conditions of sine sweep and random vibration. The acceleration response curves of reference points are consistent, and amplitude and frequency errors are within acceptable limits. The model updating effect is evident, which provides good reference for research on satellites and other aerospace products.

Arched Vaults Made of Corrugated Sheets: Natural Vibration Frequencies

2019 ◽  
pp. 18-24
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Building Structures ◽  
Friction Forces ◽  
Modeling Process ◽  
The Difference ◽  
Russian Norms ◽  
The Finite Element Model

According to the recent Russian norms, when designing building structures, it is necessary to conduct a dynamic analysis of wind loads, which previously was required not in all cases. In arched vaults of profiled arched self-supporting flooring, it was not always necessary to determine the frequencies and forms of natural vibrations. These parameters can be established using the finite element method. Taking into consideration the complex and lengthy modeling process of arched vaults, in particular the contact areas in regular transverse joints, a large number of finite elements in the models and, as a consequence, considerable time for their calculation, it was necessary to identify a sufficient level of detailing of a finite element model for correct calculations of frequencies and forms of vibrations considered in the operation of structures. The influence of the detailing of the finite element model of arched vaults made of profiled flooring on the determination of their natural frequency is revealed. To substantiate the parameters of the finite element model, it was studied how the results of the calculation was influenced by edge effects, the presence of friction in the joints of corrugations of the profiled flooring, the influence of rubber gaskets in the joints on the work of the arched vault. Much attention is paid to the features of the design scheme associated with the choice of the number of sheets of profiled flooring, taking into account the contact nodes, friction forces, etc. It is established that the first vibration frequency is little dependent on the number of sheets of corrugated flooring and the presence of rubber gaskets in the joints. For subsequent frequencies, the difference can be significant.

A Coupled Frequency and Time Domain Approach for Hydroelastic Analysis of Very Large Floating Structure

2021 ◽  
Author(s):  
Dengshuo Chen ◽  
Xingya Feng ◽  
Chao Hou ◽  
Jianfei Chen
Keyword(s):  
Finite Element ◽  
Structural Analysis ◽  
Finite Element Model ◽  
Elastic Deformation ◽  
Mode Shape ◽  
Time Domain ◽  
Element Model ◽  
Floating Structure ◽  
Hydrodynamic Analysis ◽  
Hydroelastic Analysis

Abstract This paper develops a practical approach based on Python that couples the hydrodynamic analysis with the structural analysis, in order to solve the hydroelastic problem of Very Large Floating Structure (VLFS). The hydrodynamic analysis is carried out by solving linear 3D diffraction and radiation problems in the frequency domain, while the structural analysis is performed by a time-domain nonlinear finite element model. The coupling is realized by a generalized mode expansion method where the elastic deformation of the VLFS is regarded as extended radiation mode in the water. We consider a pontoon-type floating plate in regular waves. Analytical mode shape functions are used for representing the VLFS elastic deformations. The Mindlin plate theory is used for the finite element model. Convergence study of structure mode shape numbers, hydrodynamic model mesh and finite element model mesh is carefully carried out. Good agreements of the vertical displacement of the floating plate are found compared with experimental data and numerical results in the literature. Our simulation results show that the dynamic response of the VLFS is significantly influenced with consideration of its elastic deformation in the waves, and we see the influence is more pronounced in relatively shorter waves. The proposed approach is shown promising for hydroelastic analysis for more complex VLFS in realistic ocean seastates.

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