Optimal design of shear vertical wave electromagnetic acoustic transducers in resonant mode

2020 ◽  
Vol 64 (1-4) ◽  
pp. 639-647
Author(s):  
Zhichao Cai ◽  
Zhenyong Zhao ◽  
Lan Chen ◽  
Guiyun Tian
Keyword(s):  
Permanent Magnets ◽  
Signal To Noise Ratio ◽  
Acoustic Resonance ◽  
Element Model ◽  
Response Characteristic ◽  
Resonant Mode ◽  
Thickness Measurement ◽  
Frequency Interval ◽  
Resonant Amplitude ◽  
The Common

In this paper, a new electromagnetic acoustic resonance (EMAR) transducer is proposed for precise thickness measurement in specimen. The new EMAR is composed of a mirror symmetric coil (MSC) and a pair of Nd-Fe-B permanent magnets with the different polarity for enhancing the generation and detection of resonant signals. Firstly, a finite element model was established to simulate the distributions of Lorentz force produced by new EMAR and the resonant process of shear waves. Furthermore, the relationship between the frequency response characteristic of the new EMAR and the common EMAR were explored. Finally, to verify the performance of the EMAR, several experiments were performed. Compared with the common EMAR transducer, the resonant amplitude of the new EMAR transducer was increased by 121.74% and the signal-to-noise ratio was increased by 28.35%, and the resonance frequency interval of the new EMAR was twice that of the common mode in the frequency domain simulation experiment, this advantage effectively reduced the error rate of measurement. The results show that the new EMAR transducer with mirror coil structure has higher accuracy in thickness detection of specimens.

Measurement of Adhesive Bonding Strength With an EMAT in the Resonant Mode

2019 ◽  
Vol 2 (4) ◽  
Author(s):  
Tianhao Liu ◽  
Haiqiang Zhou ◽  
Cuixiang Pei ◽  
Zhenmao Chen
Keyword(s):  
Attenuation Coefficient ◽  
Bonding Strength ◽  
Adhesive Bonding ◽  
Signal To Noise Ratio ◽  
Plate Thickness ◽  
Acoustic Resonance ◽  
Resonant Mode ◽  
Imperfect Interface ◽  
Electromagnetic Acoustic Transducer ◽  
Strength Evaluation

Abstract The electromagnetic acoustic resonance (EMAR) method with shear wave is sensitive to boundary conditions and plate thickness. In this paper, a new noncontact ultrasonic testing method based on the electromagnetic acoustic transducer (EMAT) in the resonant mode is proposed for the bonding strength evaluation in metal-based adhesive structures. Different from the conventional pulse-echo method using short-burst excitation for bonding inspection, the attenuation coefficient feature of the resonant ultrasonic signal with long-burst excitation is applied to increase the signal-to-noise ratio (SNR) and detecting sensitivity of the EMAT for adhesive bonding strength evaluation. A theoretical model for adhesive bonding testing with EMAT signals in the resonant mode is established. To extract the signal feature representing the reflection coefficient, the time-domain signal was processed by Hilbert transformation and exponential curve fitting. Through the simulation on the received signal, the correlation between the attenuation coefficient of the exponent fitted curve and the strength on the adhesive imperfect interface were confirmed. Finally, the proposed correlation is verified by an experiment on stainless steel plates bonded with polymethyl methacrylate plates by epoxy adhesion via a permanent magnetic EMAT.

Free Vibration Analysis for Tapered Cross-Section Steel-Concrete Composite Material Beam

2017 ◽  
Vol 893 ◽  
pp. 380-383
Author(s):  
Jun Xia ◽  
Z. Shen ◽  
Kun Liu
Keyword(s):  
Finite Element ◽  
Composite Material ◽  
Cross Section ◽  
Vibration Analysis ◽  
Free Vibration Analysis ◽  
Element Model ◽  
Composite Beams ◽  
Shear Connection ◽  
The Common ◽  
Interlayer Slip

The tapered cross-section beams made of steel-concrete composite material are widely used in engineering constructions and their dynamic behavior is strongly influenced by the type of shear connection jointing the two different materials. The 1D high order finite element model for tapered cross-section steel-concrete composite material beam with interlayer slip was established in this paper. The Numerical results for vibration nature frequencies of the composite beams with two typical boundary conditions were compared with ANSYS using 2D plane stress element. The 1D element is more efficient and economical for the common tapered cross-section steel-concrete composite material beams in engineering.

The Influence Region Analysis for the Delayed Resonator Vibration Absorber

2001 ◽  
Author(s):  
Giulio Grillo ◽  
Nejat Olgac
Keyword(s):  
Vibration Suppression ◽  
Vibration Absorber ◽  
Primary System ◽  
Frequency Interval ◽  
Vibration Absorption ◽  
Region Analysis ◽  
The Common ◽  
Resonator Vibration ◽  
Three Degree Of Freedom ◽  
Tuned Vibration Absorber

Abstract This paper presents an influence region analysis for an actively tuned vibration absorber, the Delayed Resonator (DR). DR is shown to respond to tonal excitations with time varying frequencies [1–3]. The vibration suppression is most effective at the point of attachment of the absorber to the primary structure. In this study we show that proper feedback control on the absorber can yield successful vibration suppression at points away from this point of attachment. The form and the size of such “influence region” strongly depend on the structural properties of the absorber and the primary system. There are a number of questions addressed in this paper: a) Stability of vibration absorption, considering that a single absorber is used to suppress oscillations at different locations. b) Possible common operating frequency intervals in which the suppression can be switched from one point on the structure to the others. A three-degree-of-freedom system is taken for as example case. One single DR absorber is demonstrated to suppress the oscillations at one of the three masses at a given time. Instead of an “influence region” a set of “influence points” is introduced. An analysis method is presented to find the common frequency interval in which the DR absorber operates at all three influence points.

scholarly journals SAR Images Co-registration Based on Gradient Descent Optimization

2019 ◽  
Vol 9 (2) ◽  
pp. 2361-2367
Keyword(s):  
Gradient Descent ◽  
Cross Correlation ◽  
Dynamic Method ◽  
Signal To Noise Ratio ◽  
Gaussian Kernel ◽  
Sar Images ◽  
Registration Process ◽  
Coarse Registration ◽  
The Common ◽  
Fine Registration

The target of the registration process is to get the disagreement between two captured images for the same area to candidate the transformation matrix that is used to map the points in one image to its congruent in the other image for the same area. A dynamic method is demonstrated in this paper to improve registration process of SAR images. At first, smoothing filtering is used for noise reduction based on gaussian-kernel filter to set aside the pursue-up amplification of noise. Then; area based matching method, cross correlation, is used to perform a coarse registration. The output of the coarse registration is directly applied to the regular step gradient descent (RSGD) optimizer as a fine registration process. The performance of the demonstrated method was evaluated via comparison with the common used corner detectors (Harris, Minimum Eigenvalues, and FAST). Mean square error (MSE) and peak signal-to-noise ratio (PSNR) are the main factors for the comparison. The results show that the demonstrated approach preserves the robustness of the registration process and minimizes the image noise.

The Research for Extension Software Data Structure

2010 ◽  
Vol 121-122 ◽  
pp. 849-853
Author(s):  
Xiao Mao Wu ◽  
Hui Ming Guo ◽  
Yong Quan Yu
Keyword(s):  
Data Structure ◽  
Software Design ◽  
Element Model ◽  
Structure Model ◽  
The Common ◽  
Matter Element Model

In this paper, we analyze the data structure of design of matter-element model from the level of software design, combined with the features of the common used data structure and matter-element model in Extenics, finally propose a new data structure model, which adapt to computation, reasoning and transformation using matter-element model.

scholarly journals Doppler Imaging of Non-radially Pulsating Stars

2000 ◽  
Vol 175 ◽  
pp. 264-267 ◽  
Author(s):  
S. Jankov ◽  
E. Janot-Pacheco ◽  
N.V. Leister
Keyword(s):  
Signal To Noise Ratio ◽  
Doppler Imaging ◽  
High Signal ◽  
Be Stars ◽  
Time Resolved ◽  
Pulsating Stars ◽  
Fourier Frequency ◽  
Doppler Image ◽  
Be Star ◽  
The Common

AbstractIn addition to the common applications (temperature, magnetic field, abundance distributions) the Doppler Imaging technique can also be applied to non-radial stellar pulsations (NRP). Due to their rapid rotation, the Be stars are ideal candidates for Doppler Imaging. However, for the stars for which the periodic temporal line profile variability is produced by multiple mode NRP, the classical Doppler image in not an appropriate representation. When the corotating frequencies of existing pulsation modes are non-zero, the reference frame in which the resulting NRP is quasi-stationary cannot be defined. The technique can be applied “mode-by-mode”, which is illustrated in time-wavelength and Fourier frequency domain, using the time-resolved sequence of high resolution, high signal-to-noise ratio spectra of the Be star ζ Oph.

scholarly journals Yokeless Axial Flux Surface-Mounted Permanent Magnets Machine Rotor Parameters Influence on Torque and Back-Emf

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3418
Author(s):  
Stanisław J. Hajnrych ◽  
Rafał Jakubowski ◽  
Jan Szczypior
Keyword(s):  
Permanent Magnets ◽  
Torque Ripple ◽  
Air Gap ◽  
Electric Machine ◽  
Axial Flux ◽  
Flux Surface ◽  
Cogging Torque ◽  
Torque Density ◽  
3D Fea ◽  
The Common

The paper presents the results of a 3D FEA simulations series of a dual air gap Axial Flux (AF) electric machine with Surface-Mounted Permanent magnets (SPM) with parameterized rotor geometry. Pole number and pole span influence on back-emf, as well as cogging and ideal electromagnetic torques angular characteristics were investigated for each model with the common segmented yokeless stator with concentric windings. Synchronous and BLDC drives supply were used to estimate back-emf distortion. Ideal torque ripple and cogging torque spectra were analyzed. It was concluded that the number of poles closer to the number of slots with ~0.8 pole span tends to yield good torque density with the lowest cogging torque, back-emf distortion and ideal torque ripple.

Vibration Control With Magnetically Mounted Piezoelectric Actuators

2008 ◽  
Author(s):  
J. C. Collinger ◽  
W. C. Messner ◽  
J. A. Wickert
Keyword(s):  
Vibration Control ◽  
Permanent Magnets ◽  
Control Method ◽  
Contact Stiffness ◽  
Unit Length ◽  
Piezoelectric Actuators ◽  
Coupled System ◽  
Element Model ◽  
Magnetic Attraction ◽  
Piezoelectric Control

A novel vibration control method utilizing magnetically mounted piezoelectric actuators is described. Piezoelectric actuators are bonded to permanent magnets, which are attached to the surface of a steel cantilever beam through their magnetic attraction. The magnetic-piezoelectric control mounts are an alternative to traditional epoxy attachment methods for piezoelectrics which allows easy in-the-field reconfiguration. In model and laboratory measurements, the beam is driven through base excitation and the resonant shunt and synchronized switching techniques are applied to two magnetic-piezoelectric control mounts to attenuate vibration. The coupled system is discretized using a Galerkin finite element model that incorporates relative axial motion between the beam and the mounts, which is governed by the sticking contact stiffness per unit length of the beam-magnet interface. The control mounts are designed using a magnetic array configuration which increases the attraction force for a given magnet thickness. Results show that the magnetic-piezoelectric control mounts provide attenuation, while also providing the flexibility to easily adjust the actuators along the length of the beam.

scholarly journals Force Magnitude Reconstruction Using the Force Transmissibility Concept

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Y. E. Lage ◽  
N. M. M. Maia ◽  
M. M. Neves
Keyword(s):  
Experimental Data ◽  
A Priori ◽  
Element Model ◽  
Direct And Inverse Problems ◽  
Force Magnitude ◽  
Mdof Systems ◽  
Applied Forces ◽  
Force Transmissibility ◽  
The Common ◽  
Hybrid Methodology

This paper proposes the reconstruction of forces, based on the direct and inverse problems of transmissibility in multiple degree of freedom (MDOF) systems. The objective and novelty are to use the force transmissibility to calculate reactions given the applied loads (and vice versa). This method, relating two sets of forces, proves to be an alternative to the common inverse problem based on the measurement of FRFs and operational accelerations to determine operational forces, as it can be advantageous in some cases. This implies thea prioriknowledge of the transmissibility of the structure, either experimentally or numerically. In this study a finite element model is built, describing with enough accuracy the dynamic behavior of the structure. The numerical model will play a key role in the construction of the transmissibility matrix; this will be used to evaluate either the reaction or the applied forces, using experimental data. This constitutes a hybrid methodology, which is validated experimentally. The authors present several comparisons between reconstructed and experimentally measured sets of forces. It is shown that the proposed method is able to produce good results in the reconstruction of the forces, underlining its potential for other structures and possible applications.

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