FFT Analyzer Research Articles

1003 FFTアナライザの周波数応答関数による金属/セラミックス系複合焼結体の振動減衰特性の測定(GS04-1 材料加工)

1003 FFTアナライザの周波数応答関数による金属/セラミックス系複合焼結体の振動減衰特性の測定(GS04-1 材料加工)

Experimental study to identify the effect of type of coupling on unbalance using frequency spectrum analysis

Any defect in machine will affect vibration behavior and nature of this effect is different for different faults. Understanding and practicing the fundamentals of rotating shaft parameters is the first step in reducing unnecessary vibration, reducing maintenance costs and increasing machine uptime. Hence condition monitoring based on vibration measurements can be used to identify those defects qualitatively. Vibration signals give early indication of mechanical failures such as misalignment, unbalance and bent shaft etc. The present study deals with experimental investigation of unbalance with the help of FFT analyzer and its unique vibration spectrum for different types of couplings such as jaw coupling, flexible flange coupling and rigid coupling. Understanding and practicing the fundamentals of rotating shaft parameters is the first step in reducing unnecessary vibration, reducing maintenance costs and increasing machine uptime. Many researchers have reported unbalance related faults show dominant peak at 1×. For experimental identification of unbalance an experimental setup is constructed and frequency spectrum is acquired for jaw coupling, flexible flange coupling and rigid flange coupling. These acquired spectrums are compared with available literature for confirmation of experiment results. The experimental results are in close agreement with results available in literature.

Cutting tool condition monitoring by analyzing surface roughness, work piece vibration and volume of metal removed for AISI 1040 steel in boring

The vibration is one of the intensive problems in boring process. Machining and tool wear are affected more by vibration of tool due to length of boring bar. The present work is to estimate the effect of cutting parameters on work piece vibration, roughness on machined surface and volume of metal removed in boring of steel (AISI1040). A laser Doppler vibrometer (LDV) was used for online data acquisition and a high-speed FFT analyzer used to process the AOE signals for work piece vibration. A design of experiments was prepared with eight experiments with two levels of cutting parameters such as spindle rotational speed, feed rate and tool nose radius. Taguchi method has been used to optimize the cutting parameters and a multiple regression analysis is done to obtain the empirical relation of Tool life with roughness of machined surface, volume of metal removed and amplitude of work piece vibrations.

FFT アナライザの周波数応答関数による多孔質焼結材の振動減衰機構の同定

ABSTRACTIn the fields of an eco-friendly automobile, an advanced industrial machine, and a precision electronic device, controlling of vibrational behavior of the sintering parts obtained from powder metallurgy is required. In this paper, the vibration behavior of porous material made by powder metallurgy is investigated by a FFT analyzer. Pure Cu powders (Average particle size: 36 µm, 89 µm) are used as initial substances. The powder is compressed by a metal die with 100～200 MPa, and a plate shaped Cu compact is made. Using a high vacuum furnace, the green compact is heated from room temperature with 10 ˚C/min, and is sintered at 700～1000 ˚C for 1 hour. By changing the powder particle size, the compaction pressure, and the sintering temperature, some kinds of sintered Cu porous plates which had various microstructures, varied porosity, and different mechanical properties are sintered. For the sintered Cu porous plate obtained, microstructure observation, tensile test and vibration test are performed. The vibration behavior of the sintered Cu porous plates is analyzed from the frequency response function of the FFT analyzer. The damping coefficient of the sintered Cu porous plate depends on the porosity and the open pore ratio. The vibrational behavior of the sintered material is able to be easily measured by FFT analyzer.

G051056 振動する液面上に保持された液滴の保持位置と液面波形の関係([G051-05]流体工学部門,一般セッション : 液膜・液滴)

It is known that a droplet is held on the vertically vibrating pool of the same kind of liquid. When the frequency of oscillation is at the resonance of the apparatus, the droplet is found to a certain position on the pool regardless of the initial dropped position. In this case, the lifetime of a droplet is as long as several hours, perhaps because of the larger amplitude of vibration acceleration than the gravity as previously reported. Then we investigated waveform at the resonance frequency to clarify the relationship with the position where the droplet is retained. The amplitude, phase, and average displacement of the surface of oscillating pool were measured by a laser displacement meter and FFT analyzer. The average displacement is relevant to the position of a droplet, while the amplitude and phase are not; in the distribution where the regression plane of the average displacement is subtract, its minimum position is almost the same as the retained droplet.

수송 트레일러의 충격흡수장치 개발 (IV) - 동력경운기 적재함의 연결히치, 판스프링, 쇽업쇼바 -

Purpose: This study was conducted to analyze the vibration absorption effect for the agricultural product transportation-trailer equipped with vibration absorbable connecting hitch, leaf spring suspension, and shock absorber simultaneously (HLS), comparing with the trailer equipped with vibration absorbable connecting hitch only(H), trailer equipped with connecting hitch and leaf spring suspension (HL), and existing trailer with no vibration absorption device (E). Methods: Vertical accelerations were measured at driver seat and front, middle, rear parts of trailer bottom with no load for 4 types of transportation-trailer, and analyzed using FFT analyzer. Results: The magnitude of average vibration accelerations occurred up to 20 Hz, at this low frequencies the severe damage for agricultural products could be represented, was lower (maximum 6 times) for HLS trailer compared with H trailer. And vibration absorption effect for HLS trailer was also higher up to 40-80 Hz and 80-100 Hz, but the difference was less. At driver seat, the vibration absorption effect was high severely for HL and HLS trailer, and the magnitude of vibration acceleration was showed less difference in comparing at trailer bottom. Conclusions: From the test results, it could be recommended that the agricultural products transportation trailer should be equipped with vibration absorption device of HLS.

Hygrothermal effects on free vibration of delaminated woven fiber composite plates – Numerical and experimental results

The present study deals with numerical and experimental investigations on free vibration behavior of woven fiber Glass/Epoxy delaminated composite plates subjected to elevated temperatures and moistures. A composite plate model based on first order shear deformation theory (FSDT) with provision of mid plane square delamination is considered for free vibration of delaminated composite plates subjected to hygrothermal loading. An eight noded quadratic isoparametric element with five degrees of freedom per node is used in the formulation. A series of experiments is conducted to obtain natural frequencies of vibration for woven fiber Glass/Epoxy delaminated composite plates using B&K FFT analyzer with PULSE software, which agree reasonably well with the numerical values. Teflon film is embedded in the laminate, simulating the presence of delamination. The effects of temperature, moisture, delamination size and different boundary conditions on the natural frequencies of composite plates are investigated. The results indicate that the vibration behavior is greatly influenced by the delamination and hygrothermal parameters involved in the study.

High intensity air ultrasound source for determining ultrasound microphone sensitivity up to 400 kHz

A broadband air jet ultrasound source, RSS101U-H, for animal bioacoustics research produces broadband ultrasound to at least 400 kHz. Free field reciprocity calibration of ½” condenser microphones on-axis, grid caps removed, using sine wave excitation by the method of Rudnick and Stein [JASA 20, pp 818-825, (1948)] was made (previously used to 280 kHz [JASA 67, p 7, (1980)]). Measurement from 5 kHz to 100 kHz was made in 1 kHz bins via an FFT analyzer. A communications receiver was used from 40 kHz to 400 kHz. The sensitivity of a ¼” microphone was determined from the free field of the reciprocity ½” microphone source. Air jet ultrasound level at 80 mm distance was then determined with the ¼“ microphone. Communications receiver 2.5 kHz bandwidth data was reduced to 1 kHz bin values. Air humidity sound absorption was determined via ANSI 1.26. The ¼” microphone sensitivity and broadband source sound level results in 1 kHz bands to 400 kHz are presented. Air jet spectral level was 97 dB re 20 uPa @ 75 kHz to 57 dB @ 400 kHz. This can be used to rapidly determine the sensitivity of any air ultrasound microphone over this frequency range.

Vibrational Analysis of Quarter Car Vehicle Dynamic System Subjected to Harmonic Excitation by Road Surface

A front suspension of Hyundai Elantra 1992 model is assigned as quarter car model and is considered for the performance study. Modeling the dynamic performance of an automobile car system represents a complex task and forms an important step in its design procedure. In this paper the stationary response of quarter car vehicle model moving with a constant velocity over a rough road is considered for the performance study. For this a simplified model and experimental set up is developed. The deterministic impulses due to road profile are given by an eccentric cam which gives input motion to front suspension acting as a follower of the cam. The displacements obtained by FFT analyzer at upper mount of shock absorber were compared with the analytical and MATLAB results.

Experimental investigation on detection of air gap eccentricity in induction motors by current and vibration signature analysis using non-invasive sensors

The contents of this paper reports an experimental investigation carried out to detect the air gap eccentricity faults under varying load conditions using non-invasive transducers to monitor the current and vibration signals as a diagnostic medium. Experimental results of vibration signature analysis using Micro-Electro-Mechanical Systems (MEMS) accelerometer and Motor Current Signature Analysis (MCSA) using Hall Effect current transducers are compared and found nearly common signatures. Spectral analysis is carried out using decimation in time Fast Fourier Transform algorithm using FFT analyzer. This study also examines the usefulness of vibration signature analysis using MEMS to detect the eccentricity faults in developing a compact, miniaturized and cost effective instrument.

VIBRATIONAL ANALYSIS OF QUARTER CAR VEHICLE DYNAMIC SYSTEM SUBJECTED TO HARMONIC EXCITATION BY ROAD SURFACE

A front suspension of Hyundai Elantra 1992 model is assigned as quarter car model and is considered for the performance study. Modeling the dynamic performance of an automobile car system represents a complex task and forms an important step in its design procedure. In this paper the stationary response of quarter car vehicle model moving with a constant velocity over a rough road is considered for the performance study. For this a simplified model and experimental set up is developed. The deterministic impulses due to road profile are given by an eccentric cam which gives input motion to front suspension acting as a follower of the cam. The displacements obtained by FFT analyzer at upper mount of shock absorber were compared with the analytical and MATLAB results.

0206 交流磁場下の磁性流体ホールの光入出力特性(OS2 機能性流体とその先進応用,オーガナイズドセッション)

Experimental study on the optical input-output characteristics of a hole formed with magnetic fluid and thin annular permanent magnet in the alternating magnetic fields were performed by using the photodiode sensor system. The hole of magnetic fluid was driven by the Helmholtz coil. The expansion and contraction motions of magnetic fluid hole in high frequency region was measured with the photodiode sensor system. The light intensity through the magnetic fluid hole was measured by the photodiode sensor system. The output signal was analyzed by a FFT analyzer. The optical input-output characteristics of the magnetic fluid hole in alternating fields were revealed.

217 リニアローラガイド用キャリッジの固有振動解析と減衰能評価

This paper analyzes the natural vibration of a single carriage of linear roller guides. The carriage was excited by an impulse hammer through an added mass and its response was detected by an accelerometer. The acceleration was analyzed by an FFT analyzer. The linear roller guide has three rigid body modes. The motion directions of these modes are roll, pitch and radial direction. The natural frequencies and compliances were measured changing the added mass. The mathematical model of carriage was proposed for identifying the natural frequencies, compliances and damping ratios of each mode. This mathematical model includes the roller model. The contact stiffness between roller and raceway is modeled as linear spring. Moreover, assuming the vibration damping is caused by interaction of roller and raceway, the damping force is modeled. This mathematical model can calculate the natural frequencies and compliances well. And the damping capacity of carriage is evaluated as damping ratios of each mode.

Performance evaluation of musical instruments using computer controlled test setup

A computer based test setup was developed to determine the performance of musical instruments. Various local markets (Tanjore and Kumbakonam in Tamil Nadu and Simpadipura in Karnataka) were surveyed and information was collected on timbers being used for making musical instruments and also for exploring the possibility of making musical instruments from plantation species. Different musical instruments like veena, chitra veena and dholak were got fabricated (with the assistance of skilled persons proficient in making these items) using plantation timbers such as Artocarpus hirsutus Lam., Bombax ceiba Linn.,Melia dubia Cav. and Swietenia mahagoni (L.) Jacq. A PC based dual channel FFT analyzer and 0.62 cm inch condenser microphones along with preamplifier were employed for the analysis of wave front generated by the musical instruments (both traditional as well as fabricated by the artists). The wave front generated by the musical instruments (veena, chitra veena and dholak) is picked up by the microphone (kept near the musical instrument) and sound spectrum is recorded using FFT analyzer. The data obtained on sound spectrum generated by musical instruments were analyzed and found the suitability of species for musical instruments based on frequency spectrum and elastic properties. The outcome of research will be useful for music industries involved in fabrication of musical instruments by way of suggesting alternate timber species.

Real-time tool condition monitoring of face milling using acousto-optic emission â an experimental approach

In metal cutting, as a result of the cutting motion, the surface of work piece will be influenced by cutting parameters, cutting force, vibrations, etc. The effects of vibrations have been paid little attention. Accurate detection of the tool conditions under given cutting conditions is very important so that worn tools can be identified and replaced in time. Objective of the present work is to predict the effects of displacements due to vibration during face milling and to examine the correlation of surface roughness along with progression of tool wear at different machining combinations so as to develop a base for online tool condition monitoring system. A laser doppler vibrometer and FFT analyser are used for online data acquisition and subsequent processing of signals. The encouraging results of the work pave the way for the development of a real-time and reliable tool-condition-monitoring system.

Silenced sounds of a long gone past.

The extended millenary galleries of rock art are among the pre‐historical treasures in Portugal, a vast territory to explore. In search of the known but elusive proofs of music making, we have encountered specific types of ceremonial rocks that have been silent, with no memory of their use. For the first time, an approach has been made for studying the special 〈little holes rocks〉, or 〈rochas com covinhas〉, with an innovative systematic methodology. We are using a measuring‐grid created for this purpose, an FFT analyzer, and digital recordings in two stages: (1) Acoustical analysis of the sound produced in the flat surfaces and in the holes, and comparison between the signals from different depths and shapes; (2) Observation, in the area, of the amplitude and repercussion of the formulated sound, recurring to readings in strategic positions surrounding the rocks. By attesting the musical exploitation of these pre‐historical objects, there is an attempt to contribute to the understanding of how important was sound and its abstract organization in the development of the human race. Analytical charts, images, and recordings will illustrate the research here presented. [Work supported by Fundacao para a Ciencia e a Tecnologia, Portugal.]

Unsteady Swirling Flows Arising in Straight Tubes

The objective of this study is to clarify the occurrence of the high-speed mode of unsteady swirling flows in straight tubes. The unsteady flows generated in the tube were measured by means of a semiconductor-type pressure transducer and an FFT analyzer. The high-speed mode measured has rotational speed which is approximately equal to or higher than the peripheral velocity of the swirling flow. The unsteady flow is due to cell rotation in the circumferential direction of the tube. The occurrence of the high-speed mode was confirmed, and the characteristics (rotational speed, pressure amplitude, and phase) of this mode were clarified. In order to understand the measured unsteady flows, the three dimensional vortex core profiles were discussed based on the distributions of the pressure amplitude and phase.

Prediction of vibration amplitude from machining parameters by response surface methodology in end milling

Decreasing vibration amplitude during end milling process reduces tool wear and improves surface finish. Mathematical model has been developed to predict the acceleration amplitude of vibration in terms of machining parameters such as helix angle of cutting tool, spindle speed, feed rate, and axial and radial depth of cut. Central composite rotatable second-order response surface methodology was employed to create a mathematical model, and the adequacy of the model was verified using analysis of variance. The experiments were conducted on aluminum Al 6063 by high-speed steel end mill cutter, and acceleration amplitude was measured using FFT analyzer. The direct and interaction effect of the machining parameter with vibration amplitude were analyzed, which helped to select process parameter in order to reduce vibration, which ensures quality of milling.

S1105-1-2 ジャーナル軸受で支えられた回転体の振動([S1105-1]トライボロジーの基礎と応用(1))

An experimental apparatus of journal bearings for rotor vibration was used in this study. A rotor, composed of a shaft, a weight, one piece of a clutch and a slight disk having many slits for pulse generation, was supported by a pair of journal bearings. The rotor was rotated by an electric motor and then separated from it. The vibrations of the rotor, at the journal and at the weight, were measured with gap sensors and laser displacement sensors. Vibration of rotor supported by journal bearings was analyzed with FFT analyzer. Frequencies of critical speed and oil whip are shown in comparison with each other.

Research on Simulation Optimization and Experiment of Dynamical Vibration Absorption Boring Bar with Damping

The build-in dynamical vibration absorption system with damping is applied to increase the dynamic stiffness of a boring bar. According to construction and vibration features, multi flexible body dynamical model of the vibration absorption system is built up by using the software of ADAMS and ANSYS. Also the vibration characteristic of an actual boring bar is analyzed by using SA-78 2ch FFT analyzer. Through the analysis of simulation results and experimental data the accuracy of the model is validated. On this basis the influence of the radial stiffness coefficient of rubber brushes, the damping coefficient of damping fluid and the mass of heavy turning body on the vibration system is discussed by using the vibration analyses module of ADAMS. The simulation results verify the feasibility of the initial structure design; establish the design key points in the actual design. The multi flexible body dynamical model of the vibration absorption system has been simulated, optimized and analyzed. And optimized parameters are obtained finally. With these optimized parameters, actual dynamical vibration absorption boring bar with damping can be designed, and the dynamic stability of the bar is enhanced thereby.