Resonant Frequency Analysis Research Articles

Fuzzy Analysis of Resonance Frequencies for Structural Inspection of an Engine Cylinder Block

Summary: A new inspection technique for complex mechanical structures is proposed in this paper, where a fuzzy inference system carries out structural inspection. The inputs to the fuzzy inference system are the elements of a fault signature, an array of numbers prepared with use of below 5 kHz resonance frequencies of faultless and a number of faulty specimens. Advantage: Below 5 kHz resonance frequencies are easier and less expensive to obtain compared to higher frequency ones. Limit: Due to high expenses of experiments, reliable finite element models were alternatively used to obtain resonance frequencies of the faulty specimens. Results: The developed fuzzy inference system in this research accurately located an under-surface fault in an engine cylinder block.

Analysis of resonance frequency at six-step induction motor drive with long cable connection in a geothermal plant

Analysis of resonance frequency at six-step induction motor drive with long cable connection in a geothermal plant

Veering and merging analysis of nonlinear resonance frequencies of an assembly bladed disk system

This paper presents an investigation of the eigenvalues of veering and merging phenomena of a bladed disk system with contact features (an assembly bladed disk system). Of particular interest are the vibrational characteristics at rotational speed intervals at which the eigenvalue loci exhibit veering and merging phenomena. Furthermore, the current work attempts to investigate the interactions between the disk-dominated and blade-dominated families of modes in an assembly bladed disk system. In this regard, a representative model of an assembly bladed disk system is proposed, implementing an improved Euler-Bernoulli beam to model the rotating blade. The coupled equations of the bladed disk system are discretized using the modal functions which satisfy the eigenvalue problem. The change in modal properties of a blisk system with rotational speed is initially depicted to provide a reference for the analysis of a nonlinear system. Thereafter, the modal spectrum of the assembly bladed disk system is computed and analyzed by a frequency-domain method. Numerical analysis reveals that coupling interaction induces a series of eigenvalue veering and merging phenomena and that the modal frequencies at low rotational speeds are significantly affected by the nonlinearity of contact features. In particular, corresponding analysis of the mechanisms of these phenomena is presented. Furthermore, the present work also investigates the sensitivity of a low rotational speed interval and merging phenomena to several parameters.

Mechanical performance of rubberized cement paste with calcium sulfoaluminate cement addition

Due to an increasing amount of waste tires produced yearly, environmental concerns arise as waste tires in landfills pose both a fire hazard, and a habitat for rodents and mosquitos. As a result, the reuse of waste tires in the form of waste rubber in concrete has been attempted. Previous research work has shown that the inclusion of waste rubber in concrete results in a drastic decrease in compressive strength. The limitations regarding the use of rubberized concrete are related to the interfacial transition zone between rubber and paste. Due to mismatch in free surface energy between rubber and cement paste, an interfacial gap is often reported to be present. This investigation aims to determine the effect of expansive cement, specifically calcium sulfoaluminate cement (CSA), has on the performance on rubberized cement samples, and its effect on the interfacial transition zone. A comprehensive experimental plan was carried out including pullout and compressive tests, scanning electron microscopy (SEM) imaging of fractured surface, and non-destructive tests through resonant frequency and dynamic mechanical analysis (DMA); furthermore, a temperature sweep via DMA was done to determine damping factor as a function of temperature. Results from compressive strength indicate a marked increase in the performance of rubberized samples with expansive cement. Pullout results, dynamic modulus and damping ratio values, shrinkage measurements, and scanning electron microscopy (SEM) imaging validate the hypothesis that a decreased interfacial gap at the rubber-paste interface obtained from using expansive cement results in increased mechanical performance.

국내 택배용 딸기의 적정 완충포장 시스템 개발

Due to the rapid increase in cyber shopping mall of agricultural products, the parcel delivery service industry also increased, making it necessary to design an optimum packaging for agricultural products. And Due to the recent increase in strawberry consumption, there is also a need for a packaging system for parcel delivery service. In order to establish the criteria for optimum cushioning packaging design of strawberries, the bioyield strength of strawberries by storage time was measured through the ASABE test standards, and the peak acceleration in the resonance frequency and resonance frequency bands of strawberries was measured through the vibration test regulated in the ASTM test specifications. Tray cup pad and corrugated fiberboard box of delivery strawberries were designed using FEM theoretical analysis of contact stress and resonant frequency. In addition, an optimum packaging system was developed with a cushioning and vibration design considering the impact characteristics when distributing agricultural products. Through the performance evaluation and on-site evaluation of the optimum packaging system of strawberries for parcel delivery service, the random PSD test results of the delivery showed a 74% reduction in the acceleration level, and the actual distribution test of the delivery showed that the damage rate of strawberries was not more than 6.7%, indicating that it was possible to use the optimum packaging of strawberries for delivery.

Correlation of Thermo-Elastic Material and Corrosion Behavior of Refractory Castables by In-Situ Measurements

Corrosion is one of the most common wear mechanisms of refractories. Corrosive attacks lead to chemical and microstructural changes. Hot corrosion compromises chemical and/or physical interactions. Thus, the process is complex and not yet fully understood. Currently, corrosion is investigated post mortem by means of X-ray diffraction or scanning electron microscopy. These methods have the drawback that some information is lost on cooling. In-situ measurements, however, take measurements within the process. In resonant frequency and damping analysis (RFDA), a sample is excited to vibrate by a mechanical impulse. The vibrating sample emits an acoustic signal. This is recorded with a microphone and evaluated by means of Fast Fourier Transformation (FFT). We measured the change of the frequency of a low cement castable during the corrosion process. Further simplified experiments with less complex materials were done to confirm the results. Distinctive points of the curves could be correlated to specific corrosion phenomena, like melting or infiltration. The applied methods include a first characterization of the material with open porosity, density and in-situ high-temperature (HT)-RFDA measurements as well as a study of the slag behavior.

Multi-technique damage monitoring of concrete beams: Acoustic Emission, Digital Image Correlation, Dynamic Identification

Acoustic Emission (AE), Digital Image Correlation (DIC) and Dynamic Identification (DI) techniques are used to analyse crack formation and propagation in plain concrete pre-notched beam specimens subject to three-point bending. Four dimensional scales are considered and scale effects on fracture energy, bending strength, and AE energy per unit area are investigated. The energy brittleness numbers are calculated for the different beam sizes to characterise the fragility of the specimens. For the larger sample, the principal strain directions obtained by DIC are put in relation with the crack path, while the analysis of resonant frequencies is used to correlate the bending stiffness reduction to the crack advancement.

太赫兹平行平板金属波导T型腔中消逝模共振频率的理论分析

太赫兹平行平板金属波导T型腔中消逝模共振频率的理论分析

Modeling ultrasonic wave propagation in a dental implant - Bone system

The evolution of the bone-implant interface reflects the implant osseointegration and bond strength, thereby determining the overall implant stability in the jawbone. Quantitative ultrasound represents a promising alternative technique to characterize the interfacial integrity, precisely due to the fact that those waves propagate essentially along the bone-implant interface, and are therefore influenced by its state. This study reports a numerical investigation of ultrasonic wave propagation for a commercial implant-jawbone system in which the thickness and mechanical properties of the interfacial layer (corresponding to the interphase) are systematically varied through the application of a rule of mixtures, in order to mimic the evolution from a dominantly soft tissue - like medium up to a fully healed bone.A simple figure of merit is devised in terms of an RMS-like (root mean square) factor based on the implant displacements, that evolves continuously and significantly with the bone “healing” process, thereby providing unequivocal information on the nature of the investigated bone-implant interface.The results show that the wave propagation pattern is primarily dictated by the impedance mismatch rather than by the interface thickness. This study validates the concept of quantitative ultrasonic testing as a sensitive alternative to the widespread resonant frequency analysis, thereby opening the way for future sensitivity analyses that will address more refined bone-implant interface pathologies such as those observed in the clinical realm.

Design and analysis of microcantilever beams based on arrow shape

In this work, we present the design and analysis of microcantilever beams based on arrow shape. Effect of rectangular step length and width as well as free end width of beam have been investigated on various characteristics of proposed microcantilever beams. The proposed microcantilever beams were fabricated from silicon dioxide material using wet bulk micromachining in 25 wt.% TMAH at 75 °C. Vibration analysis of the microcantilever beams was carried out using a laser vibrometer. A FEM software, ANSYS, was used primarily for numerical analysis of resonance frequency, and to examine the effect of rectangular step length as well as free end width of microcantilever beam on its resonance frequency. Furthermore, ANSYS was employed to determine the maximum deflection, torsional end rotation and quality factor of proposed microcantilever beams. Additionally, effects of bottom gap and rectangular step length on quality factor of proposed microcantilever beams at lower and higher bottom gaps have also been investigated. The fundamental transverse bending mode frequency for a proposed microcantilever beam comprising rectangular step length of 50 μm and free end width 0 μm is approximately 48% higher than that of the conventional rectangular profile microcantilever beam of width 40 μm. Furthermore, maximum deflection and torsional end rotation obtained for a proposed microcantilever beam having rectangular step length 190 μm and beam free end width 40 μm are found as 680% and 800%, respectively, higher than that of the rectangular beam of length 200 μm and thickness 40 μm.

Analysis of Resonance and Anti-Resonance Frequencies in a Wireless Power Transfer System: Analytical Model and Experiments

This brief presents a magnetic coupling wireless power transfer system configured in a series-series topology and operating at both resonance and anti-resonance frequencies which occur due to the parasitic coil capacitances. It is shown that their effects on system dynamics cannot be ignored. A mathematical model based on circuit theory is developed and the analytical solution for the power transferred to an electrical load is derived. A technique for extracting coil parameters such as resistance, inductance and capacitance from impedance measurements is proposed. The complete model is first experimentally verified and then used for further numerical investigations.

Lamb wave scattering, conversion and resonances in an elastic layered waveguide with a surface-bonded rectangular block

Numerical and experimental studies of guided waves diffraction by surface-bonded obstacles of rectangular shape serving as a preliminary model for realistic stiffeners are presented. The simulations are performed within the semi-analytical hybrid approach based on the frequency-domain spectral element method and the boundary integral equation method employing integral transforms of Green’s matrices. The mathematical model is verified by comparison with the results calculated by the finite element method and with experimental data. The developed hybrid method allows investigating the scattering of each of the excited guided elastic waves separately, so along with the evaluation of diffraction eigenfrequencies, the conversion of Lamb waves at the obstacle is carefully analyzed. Analysis of complex resonance frequencies demonstrates that eigenfrequencies have large absolute values of the imaginary parts, that explains the absence of strong resonances. Nevertheless, eigenfrequencies with smallest absolute values of imaginary part pronounce themselves in resonance scattering of Lamb waves.

A Low-cost broadband high gain circularly polarized cylindrical loop-monopole composite antenna for satellite communications

A unidirectional low-cost broadband high gain circularly polarized (CP) cylindrical loop-monopole composite antenna is presented for a navigation system, satellite system, GPS (1.575 GHz) and GLONASS (1.602 GHz) bands. The antenna has a simple structure with coaxial feeding, and is used to achieve circular polarization with an orthogonal shorting strip. The proposed antenna is designed by metal and no external feeding network is used, so antenna is less in cost and low in complexity. An optimized antenna is designed and measured, the measured results agree well with the simulated results. The results show good performance of impendence bandwidth (IBW) with approximately 58.8% (1.2–2.2) GHz and the simulated 3-dB axial-ratio bandwidth (ARBW) of approximately 18.5% (1.45–1.75 GHz). Moreover, the measured broadside antenna gain is stable and almost constant of average value 9.5 dBi with less than 0.3 dB variation within the 3 dB ARBW. The mathematical analysis of resonance frequency is also studied for a cylindrical loop and monopole radiators.

Resonant frequency analysis of dental implants

Dental implant stability influences the decision on the determination of the duration between implant insertion and loading. This work investigates the resonant frequency analysis by means of a numerical model.The investigation is done numerically through the determination of the eigenfrequencies and performing steady state response analyses using a commercial finite element package. A peri-implant interface, of simultaneously varying stiffness, density and layer thickness is introduced in the numerical 3D model in order to probe the sensitivity of the eigenfrequencies and steady state response to an evolving weakened layer, in an attempt to identify the bone reconstruction around the implant.For the first two modes, the resonant frequency is somewhat insensitive to the healing process, unless the weakened layer is rather large and compliant, like in the very early stages of the implantation. A “Normalized Healing Factor” is devised in the spirit of the Implant Stability Quotient, which can identify the healing process especially at the early stages after implantation.The sensitivity of the resonant frequency analysis to changes of mechanical properties of periprosthetic bone tissue seems relatively weak.Another indicator considering the amplitude as well as the resonance frequency might be more adapted to bone healing estimations. However, these results need to be verified experimentally as well as clinically.

Correlated mode analysis of a microwave driven ICP source

Microwave and optical measurements are correlated to identify the mode evolution in a miniature, microwave driven, inductively coupled plasma (ICP) source. The very compact design of the source is derived from previous work (Porteanu et al 2013 Plasma Sources Sci. Technol. 22 035016). Microwave spectroscopy of the system resonances during the simultaneous microwave excitation of the plasma (‘Hot-S-Parameter’ spectroscopy) is a novel method to determine the electron density and to identify the type of coupling mode. The method corresponds directly to the kind of numerical simulations employed. The purpose of this analysis is finally to find the minimum power necessary to drive the source into the ICP mode. The efficiency of microwave energy transfer to the plasma is also discussed. Nitrogen at pressures between 50 and 1000 Pa and a gas flow of 150 sccm is used as test plasma, for which the electron density is determined. Analysis of the microwave resonance frequency shows that the electron density exceeds 1019 m−3 at 50 Pa for 11 W and at 1000 Pa for 26 W absorbed power. 3D theoretical analysis of this source confirms that at this electron density an ICP mode is present.

Resonant Frequency Analysis of Capacitive Micromachined Ultrasonic Transducers (CMUTs) with Layered Membranes

Resonant Frequency Analysis of Capacitive Micromachined Ultrasonic Transducers (CMUTs) with Layered Membranes

Controlling the effective bending stiffness via out-of-plane rotational resonances in elastic metamaterial thin plates

In this work, we investigate the effective parameters of elastic metamaterial thin plates. We find that the out-of-plane rotational resonances can lead to a resonant behavior in the effective bending stiffness of metamaterial thin plates, which provides a route to tune the effective bending stiffness independently, from positive to negative values, and even infinity. By using resonant frequency analysis for metamaterial plates with different sizes, we have verified the resonant nature of the effective bending stiffness. Moreover, by designing a new type of elastic metamaterial plate with enhanced moment of inertia, we demonstrate a convenient way to tune the frequency regime of negative bending stiffness to overlap with that of negative mass density, and thus realize a band of negative group velocity. With the effective mass density and bending stiffness being independently tunable, the resonance properties of the elastic metamaterial thin plate can be engineered efficiently. Our work demonstrates a unique approach for manipulating flexural waves in elastic metamaterial thin plates.

Floating Hemispherical Helical Antenna: Analysis of Gain, Efficiency and Resonant Frequency

This paper reports the effect of seawater conductivity on gain, efficiency and resonant frequency of a hemispherical helical antenna. The size of the copper ground plane for the hemispherical antenna can be reduced using conductive seawater as part of the ground plane for the antenna. Seawater increases the gain from 6 dBi to 8 dBi but with a decreased efficiency. The simulated radiation efficiency of the antenna on water surface is 61%. This paper also reports the design of a low cost floating buoy. The buoy provides a waterproof setup for the circuitry and antenna. The buoy can be effectively used for shallow water coastal monitoring.

A closed-form approach for the resonant frequency analysis of clamped rectangular microplates under distributed electrostatic force

This paper proposes a fast-converged reduced-order model for small vibrations of electrostatically actuated rectangular microplates around their deformed states. On this foundation, one-mode analysis method and thus closed-form analytical expressions are developed for the fundamental resonant frequency analysis. Numerical multi-mode analysis is conducted to investigate the convergence. It is concluded that the one-mode analysis method can give a converged solution, which demonstrates that the proposed model has a faster convergence than previous models where multi modes are needed. The directly calculated resonant frequencies by the closed-form expressions are in good agreement with the numerical results by FEM simulations with less than 5% variation before pull-in. Parametric study shows the closed-form expressions are applicable to the cases in which the thickness is less than 1/20 of the length and width under a nominal length to width ratio of 1∼2.5, and the gap distance is less than or equal to the thickness of the microplate. Additionally, a kind of electrostatic configurations based on multilayer microplates, capacitive micromachined ultrasonic transducers (CMUTs), were used to experimentally validate the closed-form expressions and good agreement was observed.

Modeling the effect of osseointegration on dental implant pullout and torque removal tests.

Osseointegration of dental implants is a key factor for their success. It can be assessed either by destructive (eg, pullout or torque extraction), or nondestructive methods (eg, resonant frequency analysis). However, as of today there is a scarcity of models that can relate the outcome of destructive tests to the level of osseointegration. To study various percentages of bone to implant bonding (tie) using finite element simulations. While evolutions of the bone mechanical properties are not explicitly taken into account, emphasis is put on the 3-dimensional variable extent of the bone-implant bonding, its statistical distribution, and its influence on the measurable extraction and torque loads, seeking to obtain a quantitative relationship. We performed numerical simulations of randomly tied implants and calculated the evolution of the pullout force as well as that of the extraction torque. Within simplifying assumptions for the osseointegration represented by a tie (as opposed to frictional) constraint, the results of this work indicate that the torque test is more discriminant than the extraction one, while both cannot really discriminate osseointegration levels below a relative variation of 20%.