scholarly journals A MODIFICATION OF AN ESTIMATION METHOD OF THE NATURAL FREQUENCY OF A CUBE FORM MICRO SATELLITE

2018 ◽  
Vol 6 (7) ◽  
pp. 121-131
Author(s):  
Kei-Ichi Okuyama ◽  
Shigeru Hibino ◽  
Misuzu Matsuoka ◽  
Sidi A. Bendoukha ◽  
Aleksander Lidtke
Keyword(s):  
Mechanical Property ◽  
Aluminum Alloy ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Estimation Method ◽  
Longitudinal Direction ◽  
Practical Method ◽  
Lateral Direction ◽  
Satellite Structure ◽  
Vibration Tests

Micro satellites must survive severe mechanical conditions during their launch phase. One design requirement for rockets is the stiffness requirement, i.e. the natural frequencies requirement. In the early stages of satellite development, presumption of the natural frequency of a satellite may be difficult. The material used for the structure of many micro satellites is an aluminum alloy. The structure subsystem occupies a large portion of the satellite mass, and the elastic modulus of this aluminum alloy is larger than that of other subsystems. Therefore, the mechanical property of the aluminum alloy cannot be used to represent the mechanical property of the whole satellite.  The density of an actual satellite differs from the density of the aluminum alloy.  Therefore, when estimating the minimum natural frequency, the size and the elastic modules of an actual satellite structure must be used. When using an actual satellite structure, the estimated minimum natural frequencies of the lateral direction and the longitudinal direction during the ascent phase are in agreement with the measured values acquired by the vibration tests. In order to shorten a process of satellite development, this paper describes a practical method for estimating the natural frequency of a cube-shaped micro satellite This paper is a modified version of the previous paper [1] using new measurement results.

scholarly journals AN ESTIMATION METHOD OF THE NATURAL FREQUENCY OF A CUBE FORM MICRO SATELLITE

2018 ◽  
Vol 6 (3) ◽  
pp. 88-97
Author(s):  
Kei-ichi OKUYAMA ◽  
Shigeru HIBINO ◽  
Misuzu MATSUOKA ◽  
Aleksander LIDTKE
Keyword(s):  
Mechanical Property ◽  
Aluminum Alloy ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Estimation Method ◽  
Longitudinal Direction ◽  
Practical Method ◽  
Lateral Direction ◽  
Satellite Structure ◽  
Vibration Tests

Micro satellites must survive severe mechanical conditions during their launch phase. One design requirement for rockets is the stiffness requirement, i.e. the natural frequencies requirement. In the early stages of satellite development, presumption of the natural frequency of a satellite may be difficult. The material used for the structure of many micro satellites is an aluminum alloy. The structure subsystem occupies a large portion of the satellite mass, and the elastic modulus of this aluminum alloy is larger than that of other subsystems. Therefore, the mechanical property of the aluminum alloy cannot be used to represent the mechanical property of the whole satellite.  The density of an actual satellite differs from the density of the aluminum alloy.  Therefore, when estimating the minimum natural frequency, the size and the elastic modules of an actual satellite structure must be used.  When using an actual satellite structure, the estimated minimum natural frequencies of the lateral direction and the longitudinal direction during the ascent phase are in agreement with the measured values acquired by the vibration tests. In order to shorten a process of satellite development, this paper describes a practical method for estimating the natural frequency of a micro satellite.

scholarly journals KARAKTERISTIK DINAMIKA STRUKTUR SATELIT MIKRO LAPAN-TUBSAT

2010 ◽  
Vol 3 (2) ◽  
Author(s):  
Robertus Heru Trihajanto ◽  
Sugiarmadji HPS
Keyword(s):  
Resonance Frequency ◽  
Dynamic Characteristic ◽  
Natural Frequency ◽  
Normal Modes ◽  
Longitudinal Direction ◽  
Mode Shapes ◽  
Al Alloy ◽  
Fem Modeling ◽  
Lateral Direction ◽  
Structural Dynamic

The TUBSAT-LAPAN micro satellite is planned to be launched using PSLV rocket. The design constraints of the mechanical system of the satellite are able to accomodate structural requirment for PSLV, which are first resonance frequency in the rocket longitudinal axis 90 Hz and first resonance frequency in the lateral axis 45 Hz. Therefore, the structural dynamic characteristic data of the satellite is important to be evaluated, such as natural frequency and mode shapes of the satellite structures, The normal modes analysis made is done usingh Finite Element Methods commercial software NASTRAN. To simplify the FEM modeling the satellite components inside the compartmens is replaced by a dummy load simulating their contribution to satellite mass, centerof gravity and inertia, which was made by the same material as the satellite's structure, i.e. Al-Alloy 2024T351. Meanwhile, the FEM modeling for both the UHF antena used the Stainless Steel materials as the real antena. The analysis results show that the lowest local natural frequency of the satellite occurs on the UHF antena. The first natural frequency of the antena structures in lateral direction is 52,29 Hz. The first natural frequency of the satellite in lateral direction 151.47 Hz completing the satellite integration, vibration test was done to the satellite. The test shows that the first global frequency is 72-75 Hz in the lateral direction and 148 Hz in longitudinal direction. Structural dynamic characteristic of TUBSAT_LAPAN micro satellite in free flying condition are also analyzed using no-constraint condition to check the safe separation clearance scenario. The results show that the first natural frequencies for satellite structures (combination) become very small, less than 0.00032 Hz. But, the lowest of the first natural frequency for UHF antena structures is almost constant, 52.30 Hz in lateral direction.

Dynamic Characteristic of an Artificial Wing Mimicking a Beetle Hind Wing

2011 ◽  
Author(s):  
Ngoc San Ha ◽  
Nam Seo Goo ◽  
Tailie Jin ◽  
Quoc Viet Nguyen ◽  
Hoon Cheol Park
Keyword(s):  
Dynamic Characteristic ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Hind Wing ◽  
Damping Factor ◽  
Laser Sensor ◽  
Lateral Direction ◽  
Structural Dynamic ◽  
Artificial Wing ◽  
Beetle Hind Wing

Biomimetics is one of the most important paradigms as researchers seek to invent better engineering designs over human history. However, the observation of insect flight is a relatively recent work. Several researchers have tried to address the aerodynamic performance of flapping creatures and other natural properties of insects, although there are still many unsolved questions. In this study, we have attempted to investigate the structural dynamic characteristic of an artificial wing that mimicked the wing shape and main venation structure of a beetle hind wing using a non contact measurement method. The structural dynamic characteristic of the artificial wing was measured and compared to the real beetle hind wing by determining the natural frequencies and damping factor. The artificial wing was glued with the cyanoacrylate adhesive at the wing base onto the acrylic stand which was attached to the base of a shaker. The shaker produces the translation motion in the lateral direction of the wing plane. A non-contact laser sensor was used to measure the displacement history of the painted spots on the hind wing. A Bru¨el & Kjær FFT analyzer was adopted to calculate the frequency response functions where the natural frequencies of the wing structure can be extracted. The fundamental natural frequency of artificial wing is 51.3 Hz while the natural frequency of the beetle hind wing is 48.8 Hz. In addition, the wing structures were lightly damped with damping factor around 3.1% that is close to the one of beetle hind wing. We found that, in terms of the wing elasticity, the plastic wing frame of artificial wing was suitable for beetle-like flight.

Measurement of Young’s Modulus and Shear Modulus of Some Structures Welded Using Flux Cored Wire by Vibration Tests

2014 ◽  
Vol 216 ◽  
pp. 151-156 ◽  
Author(s):  
Liviu Bereteu ◽  
Mircea Vodǎ ◽  
Gheorghe Drăgănescu
Keyword(s):  
Shear Modulus ◽  
Arc Welding ◽  
Natural Frequencies ◽  
Free Vibrations ◽  
Vibration Modes ◽  
Cored Wire ◽  
Flux Cored Arc Welding ◽  
Longitudinal Elastic Modulus ◽  
Vibration Tests ◽  
Non Destructive

The aim of this work was to determine by vibration tests the longitudinal elastic modulus and shear modulus of welded joints by flux cored arc welding. These two material properties are characteristic elastic constants of tensile stress respectively torsion stress and can be determined by several non-destructive methods. One of the latest non-destructive experimental techniques in this field is based on the analysis of the vibratory signal response from the welded sample. An algorithm based on Pronys series method is used for processing the acquired signal due to sample response of free vibrations. By the means of Finite Element Method (FEM), the natural frequencies and modes shapes of the same specimen of carbon steel were determined. These results help to interpret experimental measurements and the vibration modes identification, and Youngs modulus and shear modulus determination.

scholarly journals Effects of Elliptical Hole on the Correlation of Natural Frequency with Buckling Load of Basalt Laminates Composite Plates

2020 ◽  
Vol 27 (1) ◽  
pp. 216-225
Author(s):  
Buntheng Chhorn ◽  
WooYoung Jung
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Basalt Fiber ◽  
Orientation Angle ◽  
Elliptical Hole ◽  
Composite Plates ◽  
Buckling Load ◽  
Mode Shapes ◽  
Geometric Ratio

AbstractRecently, basalt fiber reinforced polymer (BFRP) is acknowledged as an outstanding material for the strengthening of existing concrete structure, especially it was being used in marine vehicles, aerospace, automotive and nuclear engineering. Most of the structures were subjected to severe dynamic loading during their service life that may induce vibration of the structures. However, free vibration studied on the basalt laminates composite plates with elliptical cut-out and correlation of natural frequency with buckling load has been very limited. Therefore, effects of the elliptical hole on the natural frequency of basalt/epoxy composite plates was performed in this study. Effects of stacking sequence (θ), elliptical hole inclination (ϕ), hole geometric ratio (a/b) and position of the elliptical hole were considered. The numerical modeling of free vibration analysis was based on the mechanical properties of BFRP obtained from the experiment. The natural frequencies as well as mode shapes of basalt laminates composite plates were numerically determined using the commercial program software (ABAQUS). Then, the determination of correlation of natural frequencies with buckling load was carried out. Results showed that elliptical hole inclination and fiber orientation angle induced the inverse proportion between natural frequency and buckling load.

scholarly journals A Vibration-Based Structural Health Monitoring System for Transmission Line Towers

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 515 ◽  
Author(s):  
Long Zhao ◽  
Xinbo Huang ◽  
Ye Zhang ◽  
Yi Tian ◽  
Yu Zhao
Keyword(s):  
Structural Health Monitoring ◽  
Transmission Line ◽  
Natural Frequency ◽  
Health Monitoring ◽  
Structural Changes ◽  
Natural Frequencies ◽  
Transmission Tower ◽  
Health Monitoring System ◽  
Wind Speeds ◽  
Before And After

In this paper, we present a vibration-based transmission tower structural health monitoring system consisting of two parts that identifies structural changes in towers. An accelerometer group realizes vibration response acquisition at different positions and reduces the risk of data loss by data compression technology. A solar cell provides the power supply. An analyser receives the data from the acceleration sensor group and calculates the transmission tower natural frequencies, and the change in the structure is determined based on natural frequencies. Then, the data are sent to the monitoring center. Furthermore, analysis of the vibration signal and the calculation method of natural frequencies are proposed. The response and natural frequencies of vibration at different wind speeds are analysed by time-domain signal, power spectral density (PSD), root mean square (RMS) and short-time Fouier transform (STFT). The natural frequency identification of the overall structure by the stochastic subspace identification (SSI) method reveals that the number of natural frequencies that can be calculated at different wind speeds is different, but the 2nd, 3rd and 4th natural frequencies can be excited. Finally, the system was tested on a 110 kV experimental transmission line. After 18 h of experimentation, the natural frequency of the overall structure of the transmission tower was determined before and after the tower leg was lifted. The results show that before and after the tower leg is lifted, the natural frequencies of each order exhibit obvious changes, and the differences in the average values can be used as the basis for judging the structural changes of the tower.

Vibration of Beams with a Single Delamination under Axial Loading

2011 ◽  
Vol 675-677 ◽  
pp. 477-480
Author(s):  
Dong Wei Shu
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Analytical Solutions ◽  
Axial Load ◽  
Natural Frequencies ◽  
Axial Loading ◽  
Composite Beams ◽  
Mode Shapes ◽  
Equilibrium Conditions ◽  
Monotonic Relation

In this work analytical solutions are developed to study the free vibration of composite beams under axial loading. The beam with a single delamination is modeled as four interconnected Euler-Bernoulli beams using the delamination as their boundary. The continuity and the equilibrium conditions are satisfied between the adjoining beams. The studies show that the sizes and the locations of the delaminations significantly influence the natural frequencies and mode shapes of the beam. A monotonic relation between the natural frequency and the axial load is predicted.

scholarly journals Ambient Vibration Tests of an Arch Dam with Different Reservoir Water Levels: Experimental Results and Comparison with Finite Element Modelling

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Sergio Vincenzo Calcina ◽  
Laura Eltrudis ◽  
Luca Piroddi ◽  
Gaetano Ranieri
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Water Levels ◽  
Arch Dam ◽  
Experimental Results ◽  
Ambient Vibration ◽  
Reservoir Water ◽  
Ambient Vibration Tests ◽  
Vibration Properties ◽  
Vibration Tests

This paper deals with the ambient vibration tests performed in an arch dam in two different working conditions in order to assess the effect produced by two different reservoir water levels on the structural vibration properties. The study consists of an experimental part and a numerical part. The experimental tests were carried out in two different periods of the year, at the beginning of autumn (October 2012) and at the end of winter (March 2013), respectively. The measurements were performed using a fast technique based on asynchronous records of microtremor time-series. In-contact single-station measurements were done by means of one single high resolution triaxial tromometer and two low-frequency seismometers, placed in different points of the structure. The Standard Spectral Ratio method has been used to evaluate the natural frequencies of vibration of the structure. A 3D finite element model of the arch dam-reservoir-foundation system has been developed to verify analytically determined vibration properties, such as natural frequencies and mode shapes, and their changes linked to water level with the experimental results.

Inoculation and Fading of Sr-Modified A356.2 Aluminum Alloy in Squeeze Casting

2016 ◽  
Vol 850 ◽  
pp. 671-678
Author(s):  
Jian Wei Niu ◽  
Lie Jun Li ◽  
Hai Jun Liu ◽  
Ji Xiang Gao ◽  
Chuan Dong Ren
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Aluminum Alloy ◽  
Hydrogen Absorption ◽  
Deleterious Effect ◽  
Squeeze Casting ◽  
Eutectic Silicon ◽  
Direct Reading ◽  
Air Bag ◽  
Fading Rate

The inoculation and fading behavior of Sr-modified aluminum alloy A356. 2 were studied for air bag bracket produced by squeeze casting. The effects of Sr, P, B contents and casting temperature on the microstructure and eutectic silicon morphology in different periods of inoculation were investigated by SEM and direct-reading Spectrometer. The influence of inoculation fading rate and addition of Sr on the casting mechanical properties and hydrogen absorption was studied. The experimental results showed that the inoculation process was completed in 1 h, and the eutectic silicon morphology can be maintained in almost subsequent 40 h after the addition of Sr. The fading rate decreased appreciably with the increase of casing temperature, P and B contents. The deleterious effect of the inoculation fading of Sr on the casting mechanical property can be compensated by the squeeze casting.

PNEUMATIC VIBROISOLATION SYSTEM OF THE BASE DESK WITH NATURAL FREQUENCY REGULATION

2021 ◽  
Vol 113 ◽  
pp. 91-100
Author(s):  
Radka JÍROVÁ ◽  
Lubomír PEŠÍK
Keyword(s):  
Natural Frequency ◽  
Automotive Industry ◽  
Natural Frequencies ◽  
Dynamical Behaviour ◽  
Operating Conditions ◽  
Frequency Regulation ◽  
The Stability ◽  
Short Time

Vibroisolation systems of base desks for machine and testing facilities usually cannot effect efficient changing of their own frequencies according to operating conditions. Especially in the case of the automotive industry, the possibility of changing natural frequencies is very desirable. During varying operating conditions, the vibroisolation system needs to be regulated easily and quickly regarding the minimisation of dynamical forces transmitted to the ground and to ensure the stability of the testing process. This paper describes one of the options of tuning the base desk at a relatively short time and by sufficient change of own frequencies, which decides the dynamical behaviour of the whole system.

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