Modal Analysis of the Setar: A Numerical–Experimental Comparison

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Hossein Mansour
Keyword(s):  
Modal Analysis ◽  
Laser Doppler Vibrometer ◽  
Mode Shapes ◽  
Experimental Comparison ◽  
Fe Model ◽  
Fe Method ◽  
Wide Range ◽  
Structural Details ◽  
Orthotropic Properties ◽  
Structural Mode

The setar, a Persian long-necked lute, is analyzed by means of experimental modal analysis and finite element (FE) method. The experimental analysis is performed using a combination of impulse hammer and laser Doppler vibrometer (LDV), which has led to the extraction of structural mode shapes, natural frequencies, and modal dampings. The FE model is developed taking into account structural details, such as orthotropic properties of the wood, direction of the grains, nonideal joints, and the effect of strings preload. Numerical results are shown to be in a very good agreement with the experimental data over a wide range of frequencies.

Output-Only Modal Analysis of an Internal Unreachable Module Embedded in a Space Electronic Equipment

2012 ◽  
Author(s):  
Lassaad Ben Fekih ◽  
Georges Kouroussis ◽  
David Wattiaux ◽  
Olivier Verlinden ◽  
Christophe De Fruytier
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Degrees Of Freedom ◽  
Transverse Direction ◽  
Mode Shapes ◽  
Fe Model ◽  
Fe Method ◽  
Numeric Model ◽  
Stiffness Matrices ◽  
Output Only

An approach is proposed to identify the modal properties of a subsystem made up of an arbitrary chosen inner module of embedded space equipment. An experimental modal analysis was carried out along the equipment transverse direction with references taken onto its outer housing. In parallel, a numerical model using the finite element (FE) method was developed to correlate with the measured results. A static Guyan reduction has led to a set of master degrees of freedom in which the experimental mode shapes were expanded. An updating technique consisting in minimizing the dynamic residual induced by the FE model and the measurements has been investigated. A last verification has consisted in solving the numeric model composed of the new mass and stiffness matrices obtained by means of a minimization of the error in the constitutive equation method.

Dynamic Analysis of Indian Railway Integral Coach Factory Bogie

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Srihari Palli ◽  
Ramji Koona ◽  
Rakesh Chandmal Sharma ◽  
Venkatesh Muddada
Keyword(s):  
Dynamic Response ◽  
Modal Analysis ◽  
Fe Model ◽  
Fe Method ◽  
Harmonic Response ◽  
Natural Modes ◽  
Modes Of Vibration ◽  
Indian Railway ◽  
Secondary Suspension ◽  
Railway Sleeper

Dynamic response of railway coach is a key aspect in the design of coach. Indian railway sleeper and 3 tier AC coaches consist of two railway bogies, where the central distance of the center of gravity between the bogies is 14.9 m. Analysis of railway bogie forms a basis for investigating the behaviour of the coach as a whole. The current work carried out is, vehicle dynamic response in terms of Eigen frequency modal analysis and harmonic analysis of a Indian railway 6 Ton Integral Coach Factory (ICF) bogie using finite element (FE) method. The entire bogie model is discretized using solid92 tetrahedral elements. The primary and secondary suspension systems are modelled as COMBIN14 elements in the FE model of the bogie. Modal analysis of the bogie model using Block Lanczos method in ANSYS is carried out to extract first few natural modes of vibration of the bogie. The roll mode frequency attained in Modal analysis is in good agreement with the fundamental frequency calculated analytically. Sinusoidal excitation is fed as input to bottom wheel points to analyse the harmonic response of the bogie in terms of displacement at different salient locations. Harmonic response results reveal that the bogie left and right locations are more vulnerable than the locations near the centre of gravity of the bogie.

3D Modal Analysis of a Loaded Tire with Binary Random Noise Excitation

2019 ◽  
Vol 48 (3) ◽  
pp. 207-223
Author(s):  
Ipar Ferhat ◽  
Rodrigo Sarlo ◽  
Pablo A. Tarazaga
Keyword(s):  
Modal Analysis ◽  
High Frequency ◽  
Random Noise ◽  
Real Life ◽  
Laser Doppler Vibrometer ◽  
Static Condition ◽  
Three Dimensions ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Testing Techniques

ABSTRACT Modal analysis of tires has been a fundamental part of tire research aimed at capturing the dynamic behavior of a tire. An accurate expression of tire dynamics leads to an improved tire model and a more accurate prediction of tire behavior in real-life operations. Therefore, the main goal of this work is to improve the tire-testing techniques and data range to obtain the best experimental data possible using the current technology. With this goal in mind, we propose novel testing techniques such as piezoelectric excitation, high-frequency bandwidth data, and noncontact vibration measurement. High-frequency data enable us to capture the coupling between the wheel and tire as well as the coupling between airborne and structure-borne noise. Piezoelectric excitation eliminates the dynamic coupling of shakers and the inconsistency of force magnitude and direction of impact hammers as well as added mass effect. Noncontact vibration measurements using three-dimensional (3D) scanning laser Doppler vibrometer (SLDV) are superior to accelerometers because of no mass loading, a high number of measurement points in three dimensions, and high sensitivity. In this work, a modal analysis is carried out for a loaded tire in a static condition. Because of the highly damped nature of tires, multiple input excitation with binary random noise signal is used to increase the signal strength. Mode shapes of the tire are obtained and compared using both accelerometers and SLDV measurements.

Dynamic Properties of a Heliostat Structure Determined by Numerical and Experimental Modal Analysis

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
J. Felipe Vásquez-Arango ◽  
Reiner Buck ◽  
Robert Pitz-Paal
Keyword(s):  
Modal Analysis ◽  
Vortex Shedding ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Simple Approach ◽  
Operating Conditions ◽  
Mode Shapes ◽  
Fe Model ◽  
Damping Coefficients ◽  
Operating Points

An experimental and numerical modal analysis was performed on an 8 m2 T-shaped heliostat structure at different elevation angles. The experimental results were used to validate a finite element (FE) model by comparing natural frequencies and mode shapes. The agreement between experiments and simulations is good in all operating points investigated. In addition, damping coefficients were determined experimentally for each mode, in order to provide all necessary information for the development of a dynamic model. Furthermore, potentially critical operating conditions caused by vortex shedding were identified using a simple approach.

scholarly journals Experimental Analysis and Multiscale Modeling of the Dynamics of a Fiber-Optic Coil

Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 582
Author(s):  
Özkan Kahveci ◽  
Caner Gençoğlu ◽  
Tuncay Yalçinkaya
Keyword(s):  
Measurement Errors ◽  
Fiber Optic ◽  
Structural Data ◽  
Testing Procedure ◽  
Mode Shapes ◽  
Fe Model ◽  
Estimation Model ◽  
Dimensional Parameter ◽  
Aerospace Applications ◽  
Wide Range

Fiber-optic gyroscopes (FOGs) are common rotation measurement devices in aerospace applications. They have a wide range of diversity in length and in the winding radius of the coil to meet system requirements. Every dimensional parameter in the coil influences the dynamic response of the system, eventually leading to measurement errors. In order to eliminate the errors and to qualify the system, after the design and production stages, a deep and comprehensive testing procedure follows. In this study, the dynamic behavior of a quadrupole wound fiber-optic coil is investigated. First, pre-wound fiber-optic coils are tested with an impact modal test, where the mode shapes and natural frequencies are determined with structural data acquisition. For the modal analysis, a finite element (FE) model is developed where a representative volume element (RVE) analysis is also included to properly consider the influence of the microstructure. The experimental and numerical results are compared and validated. Moreover, an estimation model is proposed for a type of coil with different fiber lengths. Finally, the estimated coil set is produced and tested employing the same methodology in order to illustrate the capacity of the developed framework.

Hydroelastic Response of a Ship Structural Detail to Seakeeping Loads Using a Top-Down Scheme

2012 ◽  
Author(s):  
François-Xavier Sireta ◽  
Quentin Derbanne ◽  
Fabien Bigot ◽  
Šime Malenica ◽  
Eric Baudin
Keyword(s):  
Fatigue Life ◽  
Life Assessment ◽  
Mode Shapes ◽  
Fe Model ◽  
Structural Detail ◽  
Top Down ◽  
Local Pressure ◽  
Ship Structure ◽  
Fine Mesh ◽  
Structural Details

In order to investigate the local response of a ship structure, it is necessary to transfer the seakeeping loading to a 3DFEM model of the structure. A common approach is to transfer the seakeeping loads calculated by a BEM method to the FEM model. Following the need to take into account the dynamic response of the ship to the wave excitation, some methods based on a modal approach have been recently developed that include the dry structural modes in the hydro-structure coupling procedure and allow to compute the springing and whipping response of the ship structure to the seakeeping loads. In the context of the fatigue life assessment of a structural detail, a very fine FE model is required. A very large number of seakeeping loading cases also need to be considered to account for all the conditions encountered by the ship through its life. It becomes then clear that because of the CPU time issue, the whole FE model can not be very fine. This is why a hierarchical top-down analysis procedure is commonly used, in which the global ship structure is modelled in a coarse manner using one finite element between web frames. The structural details are modelled separately using a fine meshing. Such top-down methods are commonly used for the estimation of the quasi-static response of structural details to the seakeeping loads. This paper presents a methodology in which a top-down method is used to estimate the springing response of a ship structural detail loaded with wave pressure, and its fatigue life. The global dry structural modes are transferred to the detail fine model using the shape functions of the finite elements of the global model. The hydrodynamic pressures are computed directly on the fine mesh model, avoiding any interpolation error. The imposed displacements at the fine mesh boundary are computed using the same method that is used to transfer the structural mode shapes, and the local pressure induced loads and inertia loads are applied on the fine mesh nodes. This method is applied for the calculation of the elongation of a strain gauge which is installed in the passage way of an ultra large container ship.

Fitness-for-Service of a Column Equipment Containing Dent Defects Based on API 579 Level 3 Analysis and Considering the Dynamic Loads

2016 ◽  
Author(s):  
Zhiyuan Han ◽  
Guoshan Xie ◽  
Liang Sun ◽  
Minzhen Zhao ◽  
Haiyan Qian ◽  
...  
Keyword(s):  
Dynamic Load ◽  
Structural Integrity ◽  
Wind Load ◽  
Dynamic Loads ◽  
Mode Shapes ◽  
Fe Model ◽  
Fe Method ◽  
Column Equipment ◽  
Earthquake Load ◽  
Level 3

Fitness-for-service assessment of a pressurized component containing dents or other mechanical damage is important to ensure the operational safety and structural integrity of the damaged equipment. In the present study, the API 579 level 3 fitness-for-service analysis were performed for a column equipment containing dent defects, and the main difficulty is to determine the applied dynamic load, especially when considering wind load and earthquake load at high order mode shapes. To solve this problem, a simplified method combining the analytic calculation and finite element (FE) method were proposed in this study. At the first step, the wind load and earthquake load on different segments of the column without defect were calculated by analytic methods according to Chinese code GB4710. Then the critical load combination determined in step one were applied on a whole column FE model containing 6 dent defects with different dimensions. Based on the FE simulation, the stress linearization were performed for strength check, and buckling analysis were performed buckling collapse failure respectively. The results of strength check and critical buckling load showed that the column containing dents under static load and dynamic load conditions was acceptable for continued operation based on API 579 level 3 analysis. Thus, the methodology developed in this study provides an available fitness-for-service assessment for dents in column equipment and enables the consideration of dynamic loads.

System Identification and Reduction of Vibrations of Piping in Different Conditions

2013 ◽  
Author(s):  
Gereon Hinz ◽  
Klaus Kerkhof
Keyword(s):  
System Identification ◽  
Boundary Conditions ◽  
Modal Analysis ◽  
Model Updating ◽  
Steel Structure ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Piping System ◽  
Fe Model ◽  
Model Studies

Safe operation, availability and lifetime assessment of piping are of utmost concern for plant operators. The knowledge on how failures in piping and its support construction are reflected in changes of the dynamic behavior (eigen-frequencies, -modes and damping) is a useful basis for System Identification and Structural Health Monitoring (SHM). Modal analysis of complex piping, the identification of system changes and the use of vibration dampers in piping still constitute challenges. In this study three different piping systems are investigated: 1. In the first piping system at a chemical plant, which is supported by a tall steel structure fixed at the base, piping-elbow forces at the top of the building cause large vibration amplitudes. Tuned mass dampers (TMD) for minimizing vibration amplitudes were first tested in the laboratory of MPA Stuttgart and then designed for the piping system in the plant for preventing failures. 2. Another piping system is reported that is excited at resonance frequency to cause failure due to in-plane bending in an elbow with local wall thinning. 3. Finally, a large piping system at a lignite power plant is investigated under ambient vibration to detect changes in boundary conditions. Experimental Output Only Modal Analysis (OOMA) and Operational Modal Analysis (OMA), FE-model studies and model-updating are performed. Changes in the natural frequencies and corresponding mode shapes due to through-wall cracks or changing boundary conditions were observed.

Experimental and numerical investigation on dynamic parameters of broaching machine

2015 ◽  
Vol 231 (10) ◽  
pp. 1907-1920
Author(s):  
Shenshun Ying ◽  
Shiming Ji ◽  
Yangyu Wang ◽  
Zhixin Li ◽  
Lvgao Lin ◽  
...  
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Damping Ratio ◽  
Experimental Results ◽  
Mode Shapes ◽  
Fe Model ◽  
Dynamic Parameters ◽  
Machine Structure

Dynamic properties of the whole broaching machine structure greatly contribute to the broaching quality and efficiency. However, it is hard to measure the dynamic parameters because they will change during operation compared with the static results from classic experimental modal analysis. This study is to examine the dynamic parameters of broaching machine LG7120KT using both the numerical finite element (FE) method and the experimental operational modal analysis (OMA). Firstly, FE analysis model of the broaching machine with the real dimension is constructed and calculated. Second, experimental results are obtained from OMA in practical broaching process, which can be used to identify steady-state modes. Modal parameters including mode shapes, damping ratio, and natural frequencies are examined, using both LMS SCADAS III-305 system and PolyMAX method in OMA. The numerical and experimental results show high agreement in their calculated natural frequencies. From the modal analysis results, it is also found the vibration normal to cutting direction can be greatly reduced by adjusting broaching speed. From the topology optimization result based on the already correlated FE model, we redesigned a lightweight machine structure with a better dynamic performance, due to its lower displacement of broaching machine at force point and its higher first-order natural frequency. The experimental and numerical results in this paper help to design the structural parameters of broaching machine and propose a better broaching process.

scholarly journals DYNAMIC BEHAVIOR OF A CABLE-STAYED FOOTBRIDGE OVER RIVER VRBAS IN BANJA LUKA

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Marina Latinović ◽  
Zoran Mišković ◽  
Marko Popović
Keyword(s):  
Domain Decomposition ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Dynamic Behavior ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Fe Model ◽  
Modal Assurance Criterion ◽  
Frequency Domain Decomposition ◽  
Banja Luka

This paper presents a dynamic behavior analysis of an old cable-stayed footbridge over river Vrbasin Banja Luka. Identification of modal parameters, of this prone to vibrations footbridge structure,was performed using Operational Modal Analysis with Frequency Domain Decomposition method.Experimental test setups and obtained results, compared to the numerical values obtained by FEmodel updating, are shown. Modal Assurance Criterion was used for the confirmation of theuniqueness of experimentally obtained mode shapes, and also for the comparison of FE model modeshapes to the experimentally obtained ones, in the locations of measurement.

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