Determination of Full Set Elastic Constants for Composite Materials on Basis of Frequency Response Analysis, FEA, and GA

2008 ◽  
Author(s):  
Arcady Soloviev ◽  
Anton Bychkov ◽  
Maria Shevtsova
Keyword(s):  
Finite Element ◽  
Frequency Response ◽  
Elastic Constants ◽  
Orthotropic Materials ◽  
Vibration Modes ◽  
Dynamic Tests ◽  
Good Efficiency ◽  
Static Tests ◽  
Orthotropic Composite

The number of engineering problems includes the identification of anisotropic composite elastic constants determination. We developed an experimentally - analytical technique for identification of all elastic constants of orthotropic materials. The offered technique is substantially based on measurement of eigenfrequencies and semi quantitative analysis of natural vibration modes, instead of wave propagation speed and fields of vibrational displacement used by other acoustic methods. The developed method of the elastic composite and piezoelectric materials properties identification is implemented in linked MATLAB – Comsol Multiphysics combining the finite element analysis (FEA) of oscillations dynamics and minimization of some functional, which type is determined by particularity of a solved problem. These techniques complement the early designed by authors’ FEM-based methods for orthotropic composite static tests. The offered dynamic tests include an evaluation of specimen’s frequency response, determination of natural frequencies and vibration modes of specimens both in natural experiments and numerical finite element simulations. The identification process consists of several stages. In series of static tests are determined all allowable modules. Further a complete matrix of elastic constant is constructed, but some modules specified by approximated values (in particular, interlaminar shear modules). A series of dynamic tests executed in which the periodical excitation of samples and the frequency response is recorded by means of piezoelectric actuators and sensors. Then on basis of early defined (in static tests and with use of mix rule) modules of composite and experimentally founded eigenfrequencies by means of FEM the vibration natural modes are identified. By combination of FEM, genetic algorithm (GA) and Levenberg-Marquardt minimization method the specification of composite mechanical properties is evaluated. Application of developed technique to orthotropic composite used in aviation structures (polymeric composite spar of the helicopter main rotor blade) is explicitly illustrated. The obtained results have shown a good efficiency of proposed identification methods. We demonstrate that proposed approach provides best reliability and shows small dependence on metering equipment precision.

scholarly journals Determination of anisotropic elastic parameters from morphological parameters of cancellous bone for osteoporotic lumbar spine

2021 ◽  
Author(s):  
Christoph Oefner ◽  
Elena Riemer ◽  
Kerstin Funke ◽  
Michael Werner ◽  
Christoph-Eckhard Heyde ◽  
...  
Keyword(s):  
Finite Element ◽  
Lumbar Spine ◽  
Cancellous Bone ◽  
Elastic Constants ◽  
Bone Volume ◽  
Human Bone ◽  
Homogenization Theory ◽  
Elastic Parameters ◽  
Anisotropic Elastic

AbstractIn biomechanics, large finite element models with macroscopic representation of several bones or joints are necessary to analyze implant failure mechanisms. In order to handle large simulation models of human bone, it is crucial to homogenize the trabecular structure regarding the mechanical behavior without losing information about the realistic material properties. Accordingly, morphology and fabric measurements of 60 vertebral cancellous bone samples from three osteoporotic lumbar spines were performed on the basis of X-ray microtomography (μCT) images to determine anisotropic elastic parameters as a function of bone density in the area of pedicle screw anchorage. The fabric tensor was mapped in cubic bone volumes by a 3D mean-intercept-length method. Fabric measurements resulted in a high degree of anisotropy (DA = 0.554). For the Young’s and shear moduli as a function of bone volume fraction (BV/TV, bone volume/total volume), an individually fit function was determined and high correlations were found (97.3 ≤ R2 ≤ 99.1,p < 0.005). The results suggest that the mathematical formulation for the relationship between anisotropic elastic constants and BV/TV is applicable to current μCT data of cancellous bone in the osteoporotic lumbar spine. In combination with the obtained results and findings, the developed routine allows determination of elastic constants of osteoporotic lumbar spine. Based on this, the elastic constants determined using homogenization theory can enable efficient investigation of human bone using finite element analysis (FEA).

scholarly journals Determination of the frequencies and forms of free vibrations of pentagonal plates by the finite-element method

2020 ◽  
pp. 61-66
Author(s):  
A. Grigorenko ◽  
M. Borysenko ◽  
O. Boychuk
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Free Vibrations ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Rigid Attachment ◽  
Equivalent Mass ◽  
Practical Convergence ◽  
Element Method

Frequencies and modes of free vibrations of an isotropic thin pentagonal plate of regular shape with various configurations of rigid attachment at the edges are determined using the finite element method (FEM). The results obtained for some pentagonal plates are compared with the results obtained for square plates of an equivalent mass with corresponding boundary conditions. We present the vibration modes of the studied plates and the topology of the vibration modes for some of the considered plates corresponding to the square plates with free edges and rigidly fixed edges. The reliability of the obtained results is ensured by the use of a substantiated mathematical model, the correct formulation of the problem and the practical convergence of the calculated frequencies when using the FEM.

A Study on Determination of Electrical Impedance and Frequency Characteristics of a Subway System Using Finite Element Analysis

2013 ◽  
Author(s):  
Sorin Deleanu ◽  
David C. Carpenter
Keyword(s):  
Finite Element ◽  
Frequency Response ◽  
Railway Track ◽  
Return Current ◽  
Rail Track ◽  
Current Path ◽  
Subway System ◽  
Subway Train ◽  
Analytical Approaches

The paper provides a description of the analysis of a subway system (track-in-tunnel) by using FEM analysis and comparing to classical analytical approaches by Carson, Pollaczek, Bickford and Tylavsky. Reviews of methods to determine self and mutual impedance for electrified railroads are provided. These methods include frequency response and are directly applicable to a three-rail track DC track system. The analytic impedance models are built on Carson-Pollaczek–Bickford equations, adjusted by Tylavsky, for two situations: when the ground is perfectly insulated and when considering the earth return current. For the latter, the authors assume a return current path only through the tunnel concrete structure below the railway track support structure. The model is extended by considering the effects of the soil beneath under tunnel as a conductor. The solution of finite element method (FEM) applied for the determination of impedance for the three-rail track subway train configuration, modeled and examined, consists of computational analysis based upon minimizing the energy of electromagnetic field. The paper continues by examining the frequency effects on the track and system. The track/trolley model developed by Tylavsky was modified such that the trolley feeder is provided by the power rail and used to calculate the return current through the traction rails. The subway train, supplied with a rectified DC power, is subjected to a significant harmonic content, which may affect the signal and control circuits. Both experimental data and preliminary analytical and numerical calculations are presented, showing the variation of resistances and inductances of the running track with the current magnitude and frequency response. In the study, a large frequency range was considered (15Hz to 5000Hz) in order to cover all of the significant frequencies used for control and signal systems in common tracks configurations, and for which measurements have been carried. It is then shown that the power and signaling characteristics of the modeled system can predict the magnitude of the perturbation current for different values of frequency. The current density profile is illustrated for the case of a concrete tunnel structure in a subway application. The last section consists of a discussion regarding future developments and further work.

scholarly journals Measuring scheme for determination of loads acting on the side frame of the bogie from a wheelset

2021 ◽  
Vol 264 ◽  
pp. 05035
Author(s):  
Rustam Rahimov ◽  
Anastasia Nekrasova ◽  
Larisa Ogorodnikova ◽  
Grigory Lisovsky ◽  
Dilfuza Zairova ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Strain Gauges ◽  
Theoretical Studies ◽  
The Finite Element Method ◽  
Dynamic Tests ◽  
Accuracy Of Measurements ◽  
Measuring Scheme ◽  
Element Method

The study aims to develop a measuring circuit to determine the loads acting on the side frame of the bogie from the wheelset when the wagon is moving. The paper reviews and analyzes experimental methods for measuring the vertical and lateral forces acting on the side frame of the bogie from the wheelset when the wagon is moving. Theoretical studies of the stress-strain state of the side frame of a freight wagon bogie were carried out using the finite element method under the action of loads on the axle opening from the wheelset. As a result of theoretical studies by the finite element method, the places for the installation of strain gauges were determined, and a method for processing the received signals was selected. The developed measuring scheme makes it possible to determine the spatial force effect acting on the side frame of the bogie from the wheelset, which makes it possible, without increasing the number of measuring channels in the equipment, to reduce the number of strain gauges for measuring the considered loads while running dynamic tests. In addition, it improves the accuracy of measurements of vertical loads, with the help of which the coefficient of dynamic addition of unsprung parts of the bogie is calculated.

Tire Vibration Modes and Effects on Vehicle Ride Quality

1993 ◽  
Vol 21 (1) ◽  
pp. 23-39 ◽  
Author(s):  
R. W. Scavuzzo ◽  
T. R. Richards ◽  
L. T. Charek
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Operating Conditions ◽  
Modal Testing ◽  
Ride Quality ◽  
Vibration Modes ◽  
Inflation Pressure ◽  
Passenger Cars ◽  
Element Modeling ◽  
Road Surfaces

Abstract Tire vibration modes are known to play a key role in vehicle ride, for applications ranging from passenger cars to earthmover equipment. Inputs to the tire such as discrete impacts (harshness), rough road surfaces, tire nonuniformities, and tread patterns can potentially excite tire vibration modes. Many parameters affect the frequency of tire vibration modes: tire size, tire construction, inflation pressure, and operating conditions such as speed, load, and temperature. This paper discusses the influence of these parameters on tire vibration modes and describes how these tire modes influence vehicle ride quality. Results from both finite element modeling and modal testing are discussed.

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