Structural Intensity Measurement Research Articles

Localization of contact-type failure based on frequency down-conversion of elastic vibration by measurement of structural intensity

Localization of contact-type failure based on frequency down-conversion of elastic vibration by measurement of structural intensity

Detection of contact-type failure by measurement of structural intensity of low-frequency vibration caused by frequency down-conversion of elastic vibrations

Detection of contact-type failure by measurement of structural intensity of low-frequency vibration caused by frequency down-conversion of elastic vibrations

角速度計を用いたはりの振動インテンシティ計測

角速度計を用いたはりの振動インテンシティ計測

130 実験モード解析を用いた振動インテンシティ計測法の開発(波動・インテンシティ,OS-9 モード解析とその応用関連技術,総合テーマ「伝統を,未来へ!」)

This paper discusses a new method for structural intensity measurement based on the modal expansion of structural intensity for flexural vibration on beams. The intensity field indicates the magnitude and the direction of vibratory energy flows at any point in a structure. The sensor array which is composed of two or four accelerometers is often used to measure the intensity vector at any point. On the other hand, we had proposed the modal expansion of intensity. The expansion can be used to estimate the intensity field from the modal properties evaluated by the experimental modal analysis. In this paper, we propose a new measurement method for intensity on beam and discuss the detail condition of the method. Then the numerical and experimental demonstrations are carried out to show the usefulness of the proposed method.

G1000-5-5 モード展開に基づく振動インテンシティ計測法の実験的検討(機械力学・計測制御部門一般講演(5):音響・波動,社会変革を技術で廻す機械工学)

This paper discusses a new method for structural intensity measurement based on the modal expansion of structural intensity for flexural vibration on beams. The intensity field indicates the magnitude and the direction of vibratory energy flows at any point in a structure. The sensor array which is composed of two or four accelerometers is often used to measure the intensity vector at any point. On the other hand, we had proposed the modal expansion of intensity. The expansion can be used to estimate the intensity field from the modal properties evaluated by the experimental modal analysis. In this paper, we propose a new measurement method for intensity on beam and discuss the detail condition of the method. Then the numerical and experimental demonstrations are carried out to show the usefulness of the proposed method.

Measurement of structural intensity using boundary element method-based nearfield acoustical holography

The regularization method for measurement of structural intensity (SI) using boundary element method (BEM)-based nearfield acoustical holography (NAH) is proposed. Spatial derivatives of normal displacement are necessary to obtain the structural intensity. The derivative operations amplify high-wavenumber component of measurement noise and contaminate the measurement result of SI. To overcome this difficulty, regularization method for measurement of SI using fast Fourier transform-based NAH has been introduced. In this paper, this regularization method is modified for the BEM-based NAH. The BEM-based NAH avoids the aperture replication problem; therefore, measurement aperture for BEM-based NAH can be set smaller than that for FFT-based NAH. The effectiveness of the proposed method is demonstrated by experiments.

Measurement of structural intensity using patch near-field acoustical holography

Measurement of power flow in a structure, called the structural intensity (SI), is essential for vibration control and noise reduction. The near-field acoustical holography (NAH)-based measurement method is suitable to analyze the interrelationship between SI and acoustic intensity (AI) because NAH-based methods provide measurements of SI and AI simultaneously. Use of NAH requires the measurement of a pressure field over a complete surface located exterior to the structure. Therefore, if the measurement aperture is smaller than the structure, reconstructed results from the pressure on the finite aperture are seriously contaminated. This finite aperture effect prevents implementation of this NAH-based method on an actual large-scale structure such as a ship. Patch NAH and regularization method for SI measurement are applied to overcome this difficulty. This method enables implementation of the NAH-based SI measurement method in a large-scale structure. The effectiveness of this method is demonstrated by experiment.

Characterisation of a dissipative assembly using structural intensity measurements and energy conservation equation

It is possible to get from complex velocity maps obtained by optical measurements (holographic interferometry, laser doppler vibrometry, etc.) and wavenumber processing, useful quantities to study energy flows in structures such as intensity, power flow, forces, localisation of sources and sinks of energy. In this paper, scanning laser vibrometer measurements on two-plate assembly are used to determine the dissipating power by the joints from the above-mentioned energetic quantities. The average power flow over lines parallel to the junction is computed using the proposed method in order to check a one-dimensional model of power flow distribution along the other dimension. An approximate energy conservation law of flexural vibration which gives good results on beam structures and measurement data are used to determine the dissipation characteristic of joints.

Measurement of Structural Intensity of a Shell Based on Finite Element Method

Article Measurement of Structural Intensity of a Shell Based on Finite Element Method was published on October 1, 2005 in the journal Journal of the Mechanical Behavior of Materials (volume 16, issue 4-5).

On the application of B-spline approximation in structural intensity measurement

Evaluation of structural intensity in engineering structures is a field of increasing interest in connection with vibration analysis and noise control. In contrast to classical techniques such as modal analysis, structural intensity indicates the magnitude and direction of the vibratory energy travelling in the structures, which yields information about the positions of the sources/sinks, as well as the energy transmission path. Since structural intensity is directly related to the energy level, proper damping treatments and mechanical modifications can then be adopted to dissipate or divert the structure borne sound efficiently and effectively [1]. Since the first introduction and early developments of structural intensity concept [2–4], many measurement methods and numerical prediction approaches have been proposed. For measurement on plate-like structures (plates, shells and their assemblies, etc.), the determination of structural intensity requires the information of surface velocity and stress, as well as the associated phase relationship between them. The initial works [2–4] on structural intensity measurement are mainly conducted with contact transducers such as accelerometers and strain gauges. Later, to overcome the obvious drawbacks of such method, e.g. additional weight introduced by the sensors, non-contact measurement method is proposed based on near-field acoustic [5]. Currently, optical measurement using laser Doppler vibrometer (LDV) or scanning

Regularization method for measurement of structural intensity using nearfield acoustical holography

The regularization method for measurement of structural intensity using nearfield acoustical holography is proposed. Spatial derivatives of normal displacement are necessary to obtain the structural intensity. The derivative operations amplify high-wave-number components of measurement noise. Therefore, the estimation of an appropriate wave-number filter is crucial for implementation of the measurement of structural intensity. In conventional methods, this wave-number filter is determined from the flexural wavelength. And the same wave-number filter is applied to obtain all spatial derivatives. As a result, structural intensity obtained from the pressure hologram, whose signal-to-noise ratio is low, is seriously contaminated by the noise. To overcome this difficulty, regularization theory is applied to determine the appropriate wave-number filter for each order of derivatives. The effectiveness of the proposed method is demonstrated by experiments.

A method for structural intensity measurement on a plate by using the spectral element method

A method for structural intensity measurement on a plate by using the spectral element method

振動インテンシティ計測によるはりの板厚予測に関する研究(O.S.4-2 樹脂材料の特性および振動インテンシティ,OS4:ダイナミクス・コントロールの基礎とその応用技術)

振動インテンシティ計測によるはりの板厚予測に関する研究(O.S.4-2 樹脂材料の特性および振動インテンシティ,OS4:ダイナミクス・コントロールの基礎とその応用技術)

Characterizing mechanical system integrity using structural surface intensity

Many structural intensity measurements have been made on simple beam and plate-like structures to determine source strengths and transmission paths. When analyzing more complex structures it is often difficult to compute the intensity throughout the depth of an element. Using a method developed by Pavic [G. Pavic, J. Sound Vib. 115, 405–422 (1987)], the structural surface intensity (SSI) is computed on a gearbox housing using an array of accelerometers and strain gauges. The focus of this research is to use SSI as a machinery fault indicator, with the objective of developing a method that is more sensitive than other conventional diagnostic methods. Experimental data were taken on a gearbox from the Mechanical Diagnostic Test Bed (MDTB) at the Penn State Applied Research Laboratory as the gearbox was run to failure. The changes in energy flow are analyzed and characterized to provide criteria for fault detection. Analysis of the data indicates that significant changes in structural surface intensity occur as geartooth faults develop and that SSI can be more sensitive than other traditional indicators. [This research was supported by the Multidisciplinary University Research Initiative for Integrated Predictive Diagnostics (Grant No. N00014-95-1-0461) sponsored by the Office of Naval Research.]

267有限要素法を援用した構造体の振動インテンシティ計測

Many studies about structural intensity (SI) measurement, which is useful to know transmission paths of the vibration energy in a body, have been reported. Most of the works, however, have been done only for thin bodies, such as beams or plates because of the difficulty in measuring interior vibration distribution in thick structures. In this paper, a new SI measurement method applicable to thick bodies is proposed. In the method, the entire vibration distribution in the structure is estimated form limited number of the measured partial surface vibration data with the aid of dynamic analysis of finite element method (FEM). The entire SI distribution is calculated using the estimated vibration and stress distributions. Several SI measurements for thick vibrating bodies have been successfully carried out by the proposed method.

In-plane pulsed carrier speckle interferometry for structural surface intensity measurement

In-plane pulsed carrier speckle interferometry for structural surface intensity measurement

In-plane pulsed carrier speckle interferometry for structural surface intensity measurement

Experimental validation of structural intensity analytical and Finite Element calculations has traditionally relied on accelerometer and strain gauge point-wise measurements, although more recently laser vibrometry has been applied. Whole field measurements of structural intensity has been limited to out-of-plane component analysis using holographic interferometry, and is suitable only for plate and membrane studies. This paper describes a novel form of in-plane Electronic Speckle Interferometry. The interferometer has been developed specifically to assess the suitability of whole field speckle metrology for structural intensity analysis in three dimensional solids and objects, which require simultaneous in-plane velocity and strain measurements. A resonant beam is examined using the optical technique, with comparative data obtained from contact transducers.

The measurement of structural intensity on a plate with nonuniform thickness

A method to measure the structural intensity on a plate with non-uniform thickness is presented and demonstrated with experimental results. The method is an extension of the wave decomposition method, previously demonstrated on uniform thickness beams. It treats a plate as a superposition of beams, and relies only upon local rather than global vibration measurements. The average thickness in the local region of the measurement points is the plate thickness used in the calculations of the power levels.

FINITE DIFFERENCING METHODS FOR THE MEASUREMENT OF DYNAMIC BENDING STRAIN

Finite differencing formulations for dynamic bending strain are used to define measurement methods for autospectral, spatial and time history predictions of dynamic bending strain. These measurement methods provide predictions of dynamic bending strain in both nearfield and farfield regions from discrete measurements of displacement, velocity or acceleration. The differencing formulations considered use either three- or four-point finite differencing requiring simultaneous measurements at three or four positions, respectively. The number of simultaneous measurements required is reduced to two if the response is stationary and frequency response methods are used. The main limitation of these differencing methods is that the spatial extent of the measurement array precludes the prediction of dynamic bending strain at locations such as a clamped boundary where dynamic strain is usually largest. Experimental results are presented demonstrating autospectral, spatial and time history predictions of dynamic strain in both nearfield and farfield regions, and sources of errors in predictions are discussed. As structural intensity is given by the product of dynamic stress and velocity, the work presented here is also of interest for structural intensity measurements, particularly in nearfield regions when evanescent waves cannot be neglected.

Active noise control procedures in a generic composite helicopter cabin

Composite materials are used more and more in the helicopter domain, instead of metal structures, which leads toward a degradation of the acoustic comfort in the cabin because of the decreasing mass and low performances of composites. So, active control procedures can be used in addition to passive treatments. The paper deals with the feasibility of active noise control procedures in order to reduce the radiated noise generated in a composite helicopter cabin, through the mechanical deck. A generic composite fuselage is excited by four shakers to simulate the noise produced by the four gear box fastenings. Four decorrelated random signals are generated to produce forces equal to about 1 N into the 500–3000 Hz band. Modal analysis and structural intensity measurements are achieved on the mechanical deck, and pressure fields are acquired in two parallel planes. Moreover, theoretical acoustic modes of the cavity are computed with a FEM model. These different data allow one to analyze the structural behavior of the mechanical desk and the structure–cavity coupling. Four piezoelectric actuators, located in front of the excitations, are controlled by feedforward algorithms to reduce the pressure fields with different types of error sensors and cost functions.