scholarly journals Theoretical study on the sensitivity of dynamic acoustic force measurement through monomodal and bimodal excitations of rectangular micro-cantilever

2021 ◽  
Author(s):  
Cagri Yilmaz ◽  
Ramazan Sahin ◽  
Eyup Sabri Topal
Keyword(s):  
Phase Shift ◽  
Driving Forces ◽  
Oscillation Amplitude ◽  
Single Frequency ◽  
Measurement Sensitivity ◽  
Simultaneous Application ◽  
Excitation Scheme ◽  
Improve Measurement ◽  
Frequency Excitation ◽  
Micro Cantilever

Abstract We present a detailed analysis on measurement sensitivity of dynamic acoustic forces via numerical simulation of the micro-cantilever responses. The rectangular micro-cantilever is regarded as a point mass in the dynamic model of forced and damped harmonic oscillator. We use single- and bimodal-frequency excitation schemes for actuation of the micro-cantilever in the presence of dynamic acoustic forces. In bimodal-frequency excitation scheme, the micro-cantilever is excited at its first two eigenmode frequencies simultaneously as opposed to single-frequency excitation. First, we numerically obtain micro-cantilever deflections by solving the Equations of Motions (EOMs) constructed for the first two eigenmodes. Then, we determine oscillation amplitude and phase shift as a function of acoustic force strength within different frequency regions. Moreover, we relate amplitude and phase shift to virial and energy dissipation in order to explore the interaction between flexural modes in multifrequency excitation. The simulation results point out that bimodal-frequency excitation improves the measurement sensitivity of dynamic acoustic forces at particular frequencies. Herein, simultaneous application of driving forces enables higher sensitivities of observables and energy quantities as acoustic force frequencies become around the eigenmode frequencies. For our case, we obtain the highest phase shift (approximately 178 degrees) for the acoustic force strength of 100 pN at the frequency of around 307.2 kHz. Therefore, this method can be easily adapted to improve measurement sensitivity of dynamic acoustic forces in a wider frequency window.

scholarly journals Virial and Energy Dissipation in Measurement of Dynamic Acoustic Forces Using Bimodal-frequency Excitation of Micro-cantilever Array

2021 ◽  
Vol 4 (1) ◽  
pp. 332-340
Author(s):  
Cagri Yilmaz ◽  
Eyup Sabri Topal
Keyword(s):  
Energy Dissipation ◽  
High Sensitivity ◽  
Mathematical Framework ◽  
Force Frequency ◽  
Force Measurements ◽  
Excitation Scheme ◽  
Frequency Bands ◽  
Cantilever Array ◽  
Frequency Excitation ◽  
Micro Cantilever

Virial and energy dissipation, related to oscillation observable responses, possess complementary information regarding acoustic force measurements. In this paper, we introduce a mathematical framework describing the analytic relationship between oscillation observables and energy quantities at the second eigenmode in the measurement of dynamic acoustic forces. We utilize a bimodal-frequency excitation scheme for actuation of the micro-cantilever array to obtain high-sensitivity frequency bands. Herein, we analyze the virials of acoustic force interaction and the energy dissipation levels on the domain of acoustic force frequency. For our case, we obtain the high-frequency bands of around 200-270 kHz and 440-570 kHz for the force strengths in the range of 4.0-36.0 pN. In addition, results of virials and dissipated power with respect to acoustic force strengths are introduced for low- and high-sensitivity frequency regions. Therefore, the energy quantities can be robustly utilized to determine high-sensitivity frequency windows in the measurement of dynamic acoustic forces.

Estimation of the Linearized Damping Coefficients of a Squeeze-Film Vibration Isolator

1987 ◽  
Vol 201 (3) ◽  
pp. 181-191 ◽  
Author(s):  
R Stanway ◽  
R Firoozian ◽  
J E Mottershead
Keyword(s):  
Single Frequency ◽  
Squeeze Film ◽  
Experimental Facility ◽  
Vibration Isolator ◽  
New Approach ◽  
Filtering Algorithm ◽  
Damping Coefficients ◽  
Performance Predictions ◽  
Frequency Excitation ◽  
Extract Information

In this paper the authors present experimental confirmation of the feasibility of a new approach to the estimation of the four damping coefficients associated with a squeeze-film vibration isolator. The design and construction of the experimental facility is described in detail. A time-domain filtering algorithm is applied to process the displacement responses to single-frequency excitation and thus extract information on the linearized dynamics of the squeeze-film. The estimated coefficients are validated by comparing performance predictions with those obtained from spectrum analysis and from short-bearing theory. The significance of the results is discussed and suggestions are made for further work in this area.

Two-Frequency Oscillation With Combined Coulomb and Viscous Frictions

2002 ◽  
Vol 124 (4) ◽  
pp. 537-544 ◽  
Author(s):  
Gong Cheng ◽  
Jean W. Zu
Keyword(s):  
Steady State ◽  
Dry Friction ◽  
Single Frequency ◽  
Friction Oscillator ◽  
One Stop ◽  
Frequency Excitation ◽  
Stop Motion ◽  
The One ◽  
Coulomb Dry Friction ◽  
Mass Spring

In this paper, a mass-spring-friction oscillator subjected to two harmonic disturbing forces with different frequencies is studied for the first time. The friction in the system has combined Coulomb dry friction and viscous damping. Two kinds of steady-state vibrations of the system—non-stop and one-stop motions—are considered. The existence conditions for each steady-state motion are provided. Using analytical analysis, the steady-state responses are derived for the two-frequency oscillating system undergoing both the non-stop and one-stop motions. The focus of the paper is to study the influence of the Coulomb dry friction in combination with the two frequency excitations on the dynamic behavior of the system. From the numerical simulations, it is found that near the resonance, the dynamic response due to the two-frequency excitation demonstrates characteristics significantly different from those due to a single frequency excitation. Furthermore, the one-stop motion demonstrates peculiar characteristics, different from those in the non-stop motion.

Dynamic analysis of nonlinear time-varying spur gear system subjected to multi-frequency excitation

2018 ◽  
Vol 25 (6) ◽  
pp. 1210-1226 ◽  
Author(s):  
Yi Yang ◽  
Mengjuan Xu ◽  
Yang Du ◽  
Pan Zhao ◽  
Yiping Dai
Keyword(s):  
Spur Gear ◽  
Numerical Results ◽  
Gear System ◽  
Working Environment ◽  
Single Frequency ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Time Varying ◽  
Harmonic Excitations ◽  
Frequency Excitation

Due to the complex working environment, gear systems always suffer from multiple excitations in actual engineering. This paper concerns the frequency response characteristics of a nonlinear time-varying spur gear system subjected to multi-frequency excitation. Firstly, a single degree-of-freedom gear pair model is established with consideration of the gear backlash, time-varying mesh stiffness and multiple harmonic excitations. Then, using the multiple time scales method, a comprehensive theoretical study is conducted to analyze various resonant cases including primary, parametric and combination resonances. Besides, parametric studies are accomplished to reveal the effects of the multi-frequency excitation on gear dynamics and to provide some useful references for reducing the vibration level. With the help of the fifth-order Runge–Kutta method, the numerical results are obtained to verify the validity of the analytical solutions and to emphasize the significances of the multi-frequency excitation. In addition, a comparison is performed between the numerical results and the published experimental results to validate the proposed gear model. Results show that the presence of the multi-frequency excitation will introduce the interaction between different harmonic excitations, which significantly affects the nonlinear vibration characteristics of a spur gear system. The proposed gear model with multi-frequency excitation could be more reliable and universal than that with single-frequency excitation. In addition, the results of parametric study could provide some suggestions to designers and researchers attempting to obtain desirable dynamic behaviors of a gear system subjected to multi-frequency excitation.

scholarly journals Close Frequency Pairs in Delta Scuti Stars

2002 ◽  
Vol 185 ◽  
pp. 326-327
Author(s):  
K.M. Bischof ◽  
M. Breger
Keyword(s):  
Phase Shift ◽  
Power Spectra ◽  
Phase Changes ◽  
Single Frequency ◽  
Sufficient Data ◽  
Amplitude Variability ◽  
Pulsation Mode ◽  
Delta Scuti ◽  
Close Frequency ◽  
Scuti Stars

AbstractThe power spectra of several δ Scuti stars show close peaks with similar frequencies and amplitudes. Apart from possible observational problems, this can be interpreted in terms of two separate pulsation modes with similar, close frequencies or an artifact of amplitude variability of a single pulsation mode. If sufficient data are available, it is possible to distinguish between the two hypotheses on the basis of expected systematic phase changes associated with the amplitude variations of an assumed single frequency. This phase-shift test has been applied to modes found for BI CMi. In this paper we present the evidence for one of the close frequency pairs found in this star.

Study-Planning with Science and Compliance as the Driving Forces

1991 ◽  
Vol 10 (3) ◽  
pp. 381-386
Author(s):  
Mildred S. Christian
Keyword(s):  
Quality Assurance ◽  
Driving Forces ◽  
Final Report ◽  
Simultaneous Application ◽  
Senior Staff ◽  
Team Members ◽  
Study Planning ◽  
Scientific Principles ◽  
End Times ◽  
Study Director

Science and compliance are not competing forces. Only by simultaneous application of scientific principles and compliance requirements can appropriate, replicable safety evaluations be produced. Our organization has developed a system, identified as Telstar, by which teams that include members from each department are assigned to each study before its initiation and continue to be involved with the study until issue of the final report. This team is identified on the basis of appropriate expertise and experience and representation of appropriate areas. The Telstar team for each study includes the study director/report coordinator, the principal technician, the animal care technician, the data specialist, the information specialist, and the quality assurance auditor. Start and end times are assigned to each study period, including protocol approval, the various phases of study conduct and critical phase audits, specific raw data audits, beginning and ending of the in-life phase meetings, preparation of intermediate and final tables, review of tables, review of report results with senior staff, report writing by the study director, submission of report to senior staff, revision times, submission of report to quality assurance for audit, final review by study director after the quality assurance audit, final review by management (including review of the quality assurance audit results for the report), and report issue. Throughout the study, various team members interact with the study director, and scheduling is checked at twice-weekly management meetings, allowing study design and milestones to be modified if necessary. Use of this project team, with the study director coordinating specialists from each area, results in a quality product that meets all needs.

Measuring the flow through a model engine inlet system containing a plenum and runners

2001 ◽  
Vol 215 (8) ◽  
pp. 955-964 ◽  
Author(s):  
C. T. Shaw ◽  
D. J. Lee ◽  
S. H. Richardson ◽  
S Pierson
Keyword(s):  
Turbulence Intensity ◽  
Internal Combustion Engines ◽  
Laser Doppler Anemometry ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Recirculation Region ◽  
Ring Vortex ◽  
Measurement Sensitivity ◽  
Inlet System ◽  
Improve Measurement

This paper describes an experiment carried out in a model of an inlet system containing a plenum chamber and runners. Such inlet systems are commonly found on petrol internal combustion engines where the cylinders are arranged in a V-configuration. Measurements of velocity, turbulence intensity and pressure drop across the system have been made and a detailed error analysis carried out. These measurements are suitable for the validation of results obtained from computational fluid dynamics (CFD) software. Particular attention has been paid to reducing turbulence intensity levels at the inlet of the system, with additional entry lengths and smooth bell-mouth profiles being used. At each measurement point the laser Doppler anemometry (LDA) system has been tuned by hand to improve measurement sensitivity. Seeding of the flow has been an important factor and water droplets produced by a medical nebulizer have been used. Errors in velocity measurement vary throughout the flowfield, with a strong dependency on turbulence levels. From the results a relatively simple three-dimensional flow structure is found with the inlet flow separating on entry to the plenum, forming a ring vortex with a central jet within it. This jet turns from the horizontal to the vertical to enter the open runner, forming a separation bubble on the upstream side of the runner. A large slow-moving recirculation region forms in the plenum downstream of the open runner. From measurements of turbulence intensities, large values of around 40 per cent are found at the plenum-runner interface and in the recirculation region. This means that the flow is essentially time dependent even for notionally steady state conditions.

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