Reconstruction of the Force Applied to a Plate in the Time Domain From Sound Pressure Measurements

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Chuan-Xing Bi ◽  
Long Hu ◽  
Yong-Bin Zhang ◽  
Xiao-Zheng Zhang
Keyword(s):  
Time Domain ◽  
Sound Pressure ◽  
Microphone Array ◽  
Near Field ◽  
Impulse Response Function ◽  
Time History ◽  
Pressure Measurements ◽  
Concentrated Force ◽  
Vibration Responses ◽  
The Time Domain

Abstract This paper provides a non-contact approach to reconstruct the distributed or concentrated force applied to a plate in the time domain. This approach is based on sound pressure measurements and is realized by coupling the techniques of real-time near-field acoustic holography (RT-NAH) and force reconstruction. A microphone array is used to measure the sound pressures in the near field of the plate. The measured sound pressures are taken as the inputs of the RT-NAH to reconstruct the vibration responses, including the normal acceleration, velocity, and displacement, on the surface of the plate. With the reconstructed vibration responses, the equation of motion governing the forced vibration can be further processed to reconstruct the force applied to the plate in the time domain. In the process of reconstructing the vibration responses, a displacement–pressure impulse response function is derived for the first time and is used in the RT-NAH. Results of numerical simulations as well as experiments demonstrate that the proposed approach can identify the location of the force accurately and reconstruct the time history of the force effectively, thereby helping to diagnose the mechanical cause of the radiated noise.

Separating Multiple Moving Sources by Microphone Array Signals for Wayside Acoustic Fault Diagnosis

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Wei Xiong ◽  
Qingbo He ◽  
Zhike Peng
Keyword(s):  
Fault Diagnosis ◽  
Time Domain ◽  
Feature Matching ◽  
Matching Pursuit ◽  
Microphone Array ◽  
Time Frequency ◽  
Moving Sources ◽  
The Time Domain ◽  
Envelope Spectrum ◽  
Threshold Setting

Wayside acoustic defective bearing detector (ADBD) system is a potential technique in ensuring the safety of traveling vehicles. However, Doppler distortion and multiple moving sources aliasing in the acquired acoustic signals decrease the accuracy of defective bearing fault diagnosis. Currently, the method of constructing time-frequency (TF) masks for source separation was limited by an empirical threshold setting. To overcome this limitation, this study proposed a dynamic Doppler multisource separation model and constructed a time domain-separating matrix (TDSM) to realize multiple moving sources separation in the time domain. The TDSM was designed with two steps of (1) constructing separating curves and time domain remapping matrix (TDRM) and (2) remapping each element of separating curves to its corresponding time according to the TDRM. Both TDSM and TDRM were driven by geometrical and motion parameters, which would be estimated by Doppler feature matching pursuit (DFMP) algorithm. After gaining the source components from the observed signals, correlation operation was carried out to estimate source signals. Moreover, fault diagnosis could be carried out by envelope spectrum analysis. Compared with the method of constructing TF masks, the proposed strategy could avoid setting thresholds empirically. Finally, the effectiveness of the proposed technique was validated by simulation and experimental cases. Results indicated the potential of this method for improving the performance of the ADBD system.

scholarly journals Convolution-based time-domain simulation for fluidelastic instability in tube arrays

2021 ◽  
Author(s):  
Mingjie Zhang ◽  
Ole Øiseth
Keyword(s):  
Impulse Response ◽  
Response Function ◽  
Time Domain ◽  
Impulse Response Function ◽  
Time Domain Simulation ◽  
Unit Step ◽  
Tube Arrays ◽  
Unit Impulse ◽  
The Time Domain ◽  
Unit Impulse Response

AbstractA convolution-based numerical algorithm is presented for the time-domain analysis of fluidelastic instability in tube arrays, emphasizing in detail some key numerical issues involved in the time-domain simulation. The unit-step and unit-impulse response functions, as two elementary building blocks for the time-domain analysis, are interpreted systematically. An amplitude-dependent unit-step or unit-impulse response function is introduced to capture the main features of the nonlinear fluidelastic (FE) forces. Connections of these elementary functions with conventional frequency-domain unsteady FE force coefficients are discussed to facilitate the identification of model parameters. Due to the lack of a reliable method to directly identify the unit-step or unit-impulse response function, the response function is indirectly identified based on the unsteady FE force coefficients. However, the transient feature captured by the indirectly identified response function may not be consistent with the physical fluid-memory effects. A recursive function is derived for FE force simulation to reduce the computational cost of the convolution operation. Numerical examples of two tube arrays, containing both a single flexible tube and multiple flexible tubes, are provided to validate the fidelity of the time-domain simulation. It is proven that the present time-domain simulation can achieve the same level of accuracy as the frequency-domain simulation based on the unsteady FE force coefficients. The convolution-based time-domain simulation can be used to more accurately evaluate the integrity of tube arrays by considering various nonlinear effects and non-uniform flow conditions. However, the indirectly identified unit-step or unit-impulse response function may fail to capture the underlying discontinuity in the stability curve due to the prespecified expression for fluid-memory effects.

scholarly journals Analytical and Numerical Analysis of the Dynamics of a Moonpool Platform–Wave Energy Buoy (MP–WEB)

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4083
Author(s):  
Kong ◽  
Liu ◽  
Su ◽  
Ao ◽  
Chen ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Time Domain ◽  
Impulse Response Function ◽  
Radiation Force ◽  
Resonance Phenomenon ◽  
Hydrodynamic Performance ◽  
Wave Forces ◽  
Diffraction Radiation ◽  
The Time Domain

In this work the hydrodynamic performance of a novel wave energy converter configuration was analytically and numerically studied by combining a moonpool and a wave energy buoy, called the moonpool platform–wave energy buoy (MP–WEB). A potential flow, semi-analytical approach was adopted to assess the total (incident, diffraction, radiation) wave forces acting on the device, and the wave capture and energy efficiency performance of this configuration was assessed, both in the time and frequency domain. The performance of the two configurations, single float and double float, were analyzed and compared in terms of diffraction force, added mass radiation force, motion, and power in the frequency domain. Using an impulse response function-based (IRF) method, the frequency domain results were converted in the time domain. The same parameters in the time domain were derived and the main results were confirmed. Wave energy conversion efficiency was significantly increased due to the resonance phenomenon inside the moonpool.

scholarly journals Vibration of a Laminated Beam with a Delamination Including Contact Effects

2004 ◽  
Vol 11 (3-4) ◽  
pp. 157-171 ◽  
Author(s):  
W. Ostachowicz ◽  
A. Żak
Keyword(s):  
Time Domain ◽  
Dynamic Contact ◽  
Equation Of Motion ◽  
Newmark Method ◽  
The Finite Element Method ◽  
Laminated Beam ◽  
Contact Algorithm ◽  
Vibration Responses ◽  
Newton Raphson ◽  
The Time Domain

Certain results are presented in this paper on damped vibration of a laminated cantilever beam with a single closing delamination. In order to investigate this task the finite element method has been applied in the current study. For modelling the beam higher order shear deformation beam finite elements have been used. The vibration of the beam is investigated in the time domain using a dynamic contact algorithm developed by the authors. The algorithm is based on the Newmark method and also incorporates a Newton-Raphson based procedure for resolving the equation of motion. The time series obtained from solving the equation of motion have been subsequently analysed in the frequency domain by using FFT (Fast Fourier Transform). The vibration responses of the beam due to various harmonic and impulse excitations, at different delamination locations, and for different delamination lengths, as well as changes in the dissipation of damping energy due to the delamination, have all been considered in the paper.

scholarly journals Transient Response of an Impacted Beam and Indirect Impact Force Identification Using Strain Measurements

1994 ◽  
Vol 1 (3) ◽  
pp. 267-278 ◽  
Author(s):  
Hyungsoon Park ◽  
Youn-sik Park
Keyword(s):  
Impulse Response ◽  
Impact Force ◽  
Impulse Response Function ◽  
Time History ◽  
Impulse Response Functions ◽  
Transverse Impact ◽  
History Of ◽  
Convolution Approach ◽  
The Time Domain ◽  
The Impact

The impulse response functions (force-strain relations) for Euler–Bernoulli and Timoshenko beams are considered. The response of a beam to a transverse impact force, including reflection at the boundary, is obtained with the convolution approach using the impulse response function obtained by a Laplace transform and a numerical scheme. Using this relation, the impact force history is determined in the time domain and results are compared with those of Hertz's contact law. In the case of an arbitrary impact, the location of the impact force and the time history of the impact force can be found. In order to verify the proposed algorithm, measurements were taken using an impact hammer and a drop test of a steel ball. These results are compared with simulated ones.

Travelers’ exposure to vibrations and noise depending on the type of transport – the results of pilot research

2019 ◽  
Vol 570 (3) ◽  
pp. 23-27
Author(s):  
Magdalena Matys ◽  
Kamil Piotrowski ◽  
Dominik Mleczko ◽  
Paweł Pawlik
Keyword(s):  
Air Pollution ◽  
Time Domain ◽  
Public Transport ◽  
Sound Pressure ◽  
Heavy Traffic ◽  
Pressure Level ◽  
Point Of View ◽  
Vibration Acceleration ◽  
Passenger Cars ◽  
The Time Domain

For some time residents of big cities have been encouraged to change their means of transport, that is, to swap passenger cars for public transport vehicles. This is meant to help to reduce the problems associated with heavy traffic and air pollution. The authors of the article decided to check if such a change is also beneficial from the point of view of comfort and health of a person who uses public transport. For this purpose values of vibration acceleration and sound pressure level to which Cracow’s commuters are exposed to have been analyzed, depending on the type of vehicle they choose. In this respect measurements have been carried out for passenger cars, buses and trams. Two vehicle models of each type, significantly different from each other (old and new) have been selected for the tests. The measurements during a few trips in each type of vehicle on a predetermined route have been conducted. This article presents a comparison of measured values of vibroacoustic parameters in the time domain. It attempts to assess vibration and noise parameters, taking into account their impact on the health and comfort of the traveler.

A study of brake disc modal behaviour during squeal generation using high-speed electronic speckle pattern interferometry and near-field sound pressure measurements

2000 ◽  
Vol 214 (3) ◽  
pp. 285-296 ◽  
Author(s):  
M Reeves ◽  
N Taylor ◽  
C Edwards ◽  
D Williams ◽  
C. H. Buckberry
Keyword(s):  
High Speed ◽  
Sound Pressure ◽  
Surface Deformation ◽  
Speckle Pattern ◽  
Near Field ◽  
Electronic Speckle Pattern Interferometry ◽  
Brake Disc ◽  
Pressure Measurements ◽  
Near Field Sound ◽  
Field Sound

The out-of-plane surface vibration of a brake disc during naturally excited squeal has been investigated using a combination of high-speed electronic speckle pattern interferometry (ESPI) and near-field sound pressure measurements. Both techniques provide visualization and quantification of the time-resolved surface velocity. A mathematical description of disc brake squeal modal behaviour is proposed that predicts accurately all of the experimentally observed interferometry and sound field measurements. The complex mode description proposed here is in agreement with that proposed by others for drum brake squeal. This assumes that two identical diametral modes are excited simultaneously, identical except for a spatial and temporal phase shift. The use of a near-field microphone array provided a convenient multipoint, non-contacting vibration probe which may find use in the study of other vibrations characterized by high surface amplitudes and efficient sound radiation. The high-speed ESPI provided a real-time visualization of surface deformation analogous to double- pulsed holographic interferometry, with the benefit of giving a true time series of the surface deformation during a single vibration cycle.

scholarly journals Scattering of an Impact Wave by a Crack in a Composite Plate

1992 ◽  
Vol 59 (3) ◽  
pp. 596-603 ◽  
Author(s):  
S. K. Datta ◽  
T. H. Ju ◽  
A. H. Shah
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Impact Load ◽  
Near Field ◽  
Boundary Integral ◽  
Transition Elements ◽  
Element Discretization ◽  
Crack Tips ◽  
Time Domain Response ◽  
The Time Domain

The surface responses due to impact load on an infinite uniaxial graphite/epoxy plate containing a horizontal crack is investigated both in time and frequency domain by using a hybrid method combining the finite element discretization of the near-field with boundary integral representation of the field outside a contour completely enclosing the crack. This combined method leads to a set of linear unsymmetric complex matrix equations, which are solved to obtain the response in the frequency domain by biconjugate gradient method. The time-domain response is then obtained by using an FFT. In order to capture the time-domain characteristics accurately, high-order finite elements have been used. Also, both the six-node singular elements and eight-node transition elements are used around the crack tips to model the crack-tip singularity. From the numerical results for surface responses it seems possible to clearly identify both the depth and length of this crack.

scholarly journals Calculations of near-field emissions in frequency-domain into time-dependent data with arbitrary wave form transient perturbations

2012 ◽  
Vol 1 (2) ◽  
pp. 26
Author(s):  
Y. Liu ◽  
B. Ravelo ◽  
J. Ben Hadj Slama
Keyword(s):  
Time Domain ◽  
Near Field ◽  
Wave Spectrum ◽  
Computational Method ◽  
Time Dependent ◽  
Dependent Data ◽  
Wave Form ◽  
Frequency Dependent ◽  
Transient Electromagnetic ◽  
The Time Domain

This paper is devoted on the application of the computational method for calculating the transient electromagnetic (EM) near-field (NF) radiated by electronic structures from the frequency-dependent data for the arbitrary wave form perturbations i(t). The method proposed is based on the fast Fourier transform (FFT). The different steps illustrating the principle of the method is described. It is composed of three successive steps: the synchronization of the input excitation spectrum I(f) and the given frequency data H0(f), the convolution of the two inputs data and then, the determination of the time-domain emissions H(t). The feasibility of the method is verified with standard EM 3D simulations. In addition to this method, an extraction technique of the time-dependent z-transversal EM NF component Xz(t) from the frequency-dependent x- and y- longitudinal components Hx(f) and Hy(f) is also presented. This technique is based on the conjugation of the plane wave spectrum (PWS) transform and FFT. The feasibility of the method is verified with a set of dipole radiations. The method introduced in this paper is particularly useful for the investigation of time-domain emissions for EMC applications by considering transient EM interferences (EMIs).

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