Displacement Node Research Articles

Design and Analysis of Ultrasonic Composite Transducer with a Quarter-wave Taper Transition Horn

Based on the electromechanical equivalent circuit theory, equations related to the resonance frequency and the magnifying coefficient of a quarter-wave vibrator and a quarter-wave taper transition horn were deduced, respectively. A series of 3D models of ultrasonic composite transducers with various conical section length was also established. To reveal the influences of the conical section length and the prestressed bolt on the dynamic characteristics (resonance frequency, amplitude, displacement node, and the maximum equivalent stress) of the models and the design accuracy, finite element (FE) analyses were carried out. The results show that the addition of prestressed bolt increases the resonance frequency and causes the displacement node on the center axis to move towards the small cylindrical section. As the conical section length rises, the increment of resonance frequency reduces and tends to a stable value of 360 Hz while the displacement of the node on the center axis becomes lager and gradually approaches 1.5 mm. Furthermore, the amplitude of the output terminal is stable at 16.18 μm under 220 V peak-topeak (77.8 VRMS) sinusoidal potential excitation. After that, a prototype was fabricated and validated experiments were conducted. The experimental results are consistent with that of theory and simulations. It provides theoretical basis for the design and optimization of small-size, large-amplitude, and high-power composite transducers.

Study on the Axial Compression Postbuckling Similitude Model of the Stiffened Cylindrical Shell with Dimple Imperfections

The body of the new‐type dry gas holder is a large stiffened cylindrical shell. Limited by the test site and economic conditions, the buckling characteristics of such holders are generally studied through scale model experiments. Taking the longitudinal‐ring rectangular stiffened cylindrical shell as the research object, the generalized similitude condition and scaling principle formula of the structure are derived innovatively based on Donnell’s assumption and the energy method. By means of displacement loading and node coordinates updating, dimple imperfections are introduced into the ideal structure of the stiffened cylindrical shell, and then, the complete similitude and partial similitude analysis of axial compression nonlinear buckling for imperfect structures are carried out. The analysis results show that the complete similitude analysis of stiffened cylindrical shell axial‐compression nonlinear buckling can be realized accurately; the partial similitude model for stiffened cylindrical shell axial‐compression nonlinear buckling can better predict the buckling characteristics of its prototype structures, and the closer the Poisson’s ratio between the model and the prototype materials is, the more accurate the prediction results are. Meanwhile, the generalized similitude condition and scaling principle formula derived based on the energy method can provide useful reference for the model design and experimental verification of the axial compression buckling of the stiffened cylindrical shell with local geometric imperfections.

Phononic band gap of a quarter-wave stack for enhanced piezoelectric energy harvesting

Extraordinary phenomenon (e.g., band gap) exhibited by a phononic crystal (PnC) has recently been incorporated into piezoelectric energy harvesting (PEH) as a means to amplify input waves for improving the power generation capability. For a systematic design of PnC-based PEH using band gap reflection, it is required to identify a standing wave pattern (i.e. location of nodes and antinodes) in order to determine the optimal placement of a piezoelectric layer. In this context, we propose a quarter-wave stack (QWS)-based PEH system under elastic waves. The foundational idea of this study is to manipulate a standing wave pattern formed in a host medium by considering the phase change within the QWS. The key to creating an optimal standing wave for PEH is to intentionally form a displacement node at the interface between the host medium (here, continuous copper bar) and QWS at a target design frequency; thereby, the placement of the piezoelectric layer can be systematically determined in order that its center is aligned with the strain antinode to generate the maximum output power. To deeply explore the effect of the standing wave pattern on the output performances of the QWS-based PEH system, two key parameters are thoroughly investigated: 1) the number of unit cells and 2) the excitation frequency. Numerical analysis results suggest the followings: First, an increase in the number of unit cells corresponds to the effect of amplifying input loading for enhanced PEH; thereby, the output performances increase gradually and converge asymptotically. Second, since the standing wave pattern varies with the excitation frequency, the electroelastic coupling varies accordingly. These new findings provide guidelines on design parameters that can be manipulated to yield the best performance of the QWS-based PEH system under elastic waves for various potential applications.

Resonant Tuning of Langevin Transducers for Ultrasonically Assisted Machining Applications.

This article provides a fundamental study into the trade-offs between the location of piezoceramic elements, resonant frequency, and achievable ultrasonic vibration amplitude at the working end of the bolted Langevin-style transducers (BLTs) for ultrasonically assisted machining (UAM) applications. Analytical models and finite-element (FE) models are established for theoretical study, which are then validated by experiments on four real electromechanical transducers. The results suggest that resonant frequency and oscillation amplitude of the BLTs depend essentially on the dimensions of the system and the location of the piezoceramic elements. The highest resonant frequency and the maximal vibration are achieved when the piezoceramic elements are at the longitudinal displacement node, where the highest effective electromechanical coupling coefficient value is exhibited. However, the minimal resonant frequency and the lowest vibration, which is almost equal to zero, are observed when the piezoceramic elements are located at the displacement antinode. In addition, the longitudinal displacement node locations are dependent on the resonant frequency of the devices rather than the locations of the piezoceramic elements.

Fouling reduction using the resonance vibration in membrane separation of whole milk

Resonance vibration mitigated membrane fouling during whole milk filtration by submerged membrane system with hollow fibers of polyvinylidene fluoride. Resonance vibration extended the filtration duration (70 kPa) by 54 times, compared with no vibration. Resonance vibration was found more effective for fouling reduction than mechanical vibration, at which module is vibrated mechanically without resonance effect. Fouling reduction performance of resonance vibration was not affected by packing density because every fiber oscillates at resonance vibration. Larger lateral displacement and smaller wave node were favored for fouling reduction. Use of long fiber for filtration decreased the frequency, but increased lateral displacement.

Дія радіаційної сили в звуковому полі на сферичну краплю в околі вільної поверхні ідеальної рідини

Acoustic radiation force effect on a liquid spherical drop placed in the vicinity of an ideal liquid free surface is studied. The problem of determination of the radiation forces acting on an obstacle in ideal liquid is formulated with respect to the Lagrange coordinate system. Thus, the radiation pressure is defined as time-averaged value of the acoustic pressure over the obstacle surface. This approach is adequate if, at determining of the acoustic pressure in a fluid, the deviation of the pressure from the harmonic law in time domain is taken into account in the obstacle vicinity. An action of the acoustic radiation force on a spherical drop of ideal liquid placed in turn in a liquid by its free plane surface is studied here for the case of the incident plane sound wave propagating perpendicularly to the liquid boundary. As a result, the liquid sphere is appeared to be located in the standing sound wave of pressure which has its displacement node at the free surface. Problem solution is obtained as a three step procedure. Initially, solution of the problem of an incident wave scattering at the drop is derived. With making use of the results obtained, the second step encompasses determining of hydrodynamic forces acting on the liquid spherical drop with their subsequent averaging over the suitable time interval at the third step. It is found there frequencies of the incident wave exist that provide zero radiation force acting on the drop which is immobile in this case. These equilibrium positions of the spherical drop could be stable or unstable with respect to the incident wave frequency variation.

On the Acoustic Radiation Force Acting Upon a Rigid Spherical Particle Near the Free Liquid Surface

The action of the acoustic radiation force on a rigid spherical particle near the free liquid surface on which a plane sound wave is normally incident is studied. A standing sound pressure wave with displacement node at the free surface results from the interference between the incident and scattered waves. The dependence of the radiation force on the frequency, the radius of the particle, and the distance between it and the liquid surface is established. It is found out that the nodes and antinodes of the standing sound wave are the equilibrium positions of the particle. The antinodes are stable equilibrium positions, while the nodes are unstable equilibrium positions. It is confirmed that the radiation force causes particles to group at the antinodes in the sound field.

Numerical Simulation for the Effects of Ice Thickness on the Overhead Transmission Cable Tension

A model of single span overhead transmission cable was established in this paper, based on nonlinear finite element theory, combined with supports displacement method and node equilibrium method, form-finding analysis was carried out for the model of single span overhead transmission cable, the cable tension of model was compared with the theoretical calculation value, and the correctness of the model was verified. Then update cable model was analyzed, the sag, tension and ends tilt of cable under different ice thickness was discussed. This paper provided a reliable method for on-line monitoring the safety of overhead transmission cable in icing conditions.

Diagnostic value of multidetector computed tomography for renal sinus fat invasion in renal cell carcinoma patients

ObjectiveAlthough renal sinus fat invasion has prognostic significance in patients with renal cell carcinomas (RCCs), there are no previous studies about the value of multidetector computed tomography (MDCT) about this issue in the current literature. Materials and methodsA total of 863 consecutive patients (renal sinus fat invasion in 110 patients (12.7%)) from single institutions with surgically-confirmed renal cell carcinoma who underwent MDCT between 2010 and 2012 were included in this study. The area under the curves (AUCs) of the receiver operating characteristic (ROC) analysis was used to compare diagnostic performance. Reference standard was pathologic examination. Weighted κ statistics were used to measure the level of interobserver agreement. Multivariate logistic regression model was used to find the predictors for renal sinus fat invasion. Image analysis was first performed with axial-only CT images. A second analysis was then performed with both axial and coronal CT images. A qualitative analysis was then conducted by two reviewers who reached consensus regarding tumor size, decreased perfusion, tumor margin, vessel displacement, and lymph node metastasis. The reference standard was pathologic evaluation. ResultsThe AUCs of the ROC analysis were 0.881 and 0.922 for axial-only images and 0.889 and 0.902 for combined images in both readers. The AUC of tumor size was 0.884, a similar value to that of the reviewers. In multivariate analysis, tumor size, a linear-nodular or nodular type of fat infiltration, and an irregular tumor margin were independent predicting factors for perinephric fat invasion. ConclusionMDCT shows relatively high diagnostic performance in detecting perinephric fat invasion of RCC but suffers from a relatively low PPV related to low prevalence of renal sinus fat invasion. Applying tumor size alone we could get similar diagnostic performance to those of radiologists. Tumor size, fat infiltration with a nodular appearance, and an irregular tumor margin were predictors for perinephric invasion.

Finite Element Analysis of Bullet Penetration Circular Sandwich Plate

A nonlinear dynamic finite element method based on ANSYS/LS-DYNA is used to simulate the physical process of a bullet penetrating circular sandwich plate at a speed of about 400 m/s. In the simulation, Lagrange algorithm, Johnson-Cook and Crushable-foam constitutive model are choosed. Energy time history curve, impact force time history curve, Von-Mises stress nephogram and displacement nephogram are obtained. At the same time, stress time history curve of the maximum stress element and displacement time history curve of the maximum displacement node are obtained. Compared with the non-sandwich plate, it is found that the use of sandwich plate can reduce the total mass, inner plate stress and displacement, and can protect inner plate well.

Structural Design and Simulation of a Piezoelectric Peristaltic Pump Driven by Circumferential Traveling-Wave

This paper proposes a new type of piezoelectric peristaltic pump driven by circumferential traveling-wave. The disk drive stator consists of an annular metal elastic base and a piezoelectric ceramic ring bonded to the metal elastic base with special welding adhesive. The vibration displacement function of composite vibrator was built. One end of the drive stator is divided into four sections. And it will generate mechanical deformation in circumferential direction to extrude the fluid in the tube when two-phase voltages with 90º difference and amplitude of 120V are added to each group consist of two relative sections and voltage of 0 is added to the other end of the drive stator. The actuation sequences can affect the flowing direction of the fluid. This pump has the advantages of simple structure, small size, light weight, low energy consumption and no electromagnetic interference. In this paper,the finite element model of the drive stator was also built by using ANSYS software, and relevant ANSYS harmonic response analysis was carried out. The results demonstrate that the positive and negative displacement of the maximal displacement node can satisfy the extrusion of silicon tube to the fluid and siphonage, and the corresponding resonance frequency can be operated. According to the simulation results the structure of the drive stator was determined.

Static and Dynamic Responses of a Composite Engine Mounting Structure

In this paper fiber reinforced laminated composite for engine mount model are investigated by finite element method. Static analysis is carried out to find out the maximum displacement point or node on the bottom plate, on which the displacement is optimized. Different ply orientation and combinations of 0°/45°, 0°/90° and 0°/45°/90° are then studied under sinusoidal and dynamic load conditions to examine the effect of ply orientation on the structure’s displacement transportation, and to get the optimized ply orientation combination, which inherit least displacement from the excitation on the top plate. The result shows that the laminate with ply orientation of 0°/90° is the best as the Z-displacement on the bottom is considered.

Experimental Study on Vibration Characteristics of Acoustic System in Ultrasonic Vibration Lapping

In this paper, the natural frequency and the vibration mode of the lapping tool in ultrasonic vibration lapping are analyzed, the resonance mechanism of the lapping tool is researched by establishing its mechanical model and displacement equation, and the experimental study is carried out in ultrasonic vibration lapping of engineer ceramics. The conclusions include: 1) The natural frequency of the designed lapping tool is ; 2) The acoustic system in ultrasonic vibration lapping is simplified to equivalent many-degrees of freedom system, while the damp is ignored, the lapping tool is resonant with itself-natural frequency, the joint of the horn and the lapping tool is a displacement node, and the whole system is in resonant condition. 3）While the experimental condition is no-load and ultrasonic, the vibration frequency of the lapping tool is 21.3125 , which is further closed to the calculated natural frequency, at that time the amplitude of the lapping tool is maximal and the system is in resonant condition. Moreover, while the resonance frequency of the horn and the lapping tool is different, the good vibration effect of the lapping tool can be obtained by adjusting the excitation frequency of generator.

The Transformer Simulation and Performance Testing in Ultrasonic Vibration Assisted Grinding System

According the designing theory of transformer, it could be designed by big end diameter, magnification, area index and other parameters. then theoretical resonance length, small end diameter, displacement node, magnification factor, shape factor and other parameters of the transformer could be determined. This model can be built by ANSYS and vibration performance of transformer can be judged by numerical analysis. Finally, the performance of the transformer vibration would be tested and analyzed.

Transfection effect of microbubbles on cells in superposed ultrasound waves and behavior of cavitation bubble

The combination of ultrasound and ultrasound contrast agents (UCAs) is able to induce transient membrane permeability leading to direct delivery of exogenous molecules into cells. Cavitation bubbles are believed to be involved in the membrane permeability; however, the detailed mechanism is still unknown. In the present study, the effects of ultrasound and the UCAs, Optison™ on transfection in vitro for different medium heights and the related dynamic behaviors of cavitation bubbles were investigated. Cultured CHO-E cells mixed with reporter genes (luciferase or β-gal plasmid DNA) and UCAs were exposed to 1MHz ultrasound in 24-well plates. Ultrasound was applied from the bottom of the well and reflected at the free surface of the medium, resulting in the superposition of ultrasound waves within the well. Cells cultured on the bottom of 24-well plates were located near the first node (displacement node) of the incident ultrasound downstream. Transfection activity was a function determined with the height of the medium (wave traveling distance), as well as the concentration of UCAs and the exposure time was also determined with the concentration of UCAs and the exposure duration. Survival fraction was determined by MTT assay, also changes with these values in the reverse pattern compared with luciferase activity. With shallow medium height, high transfection efficacy and high survival fraction were obtained at a low concentration of UCAs. In addition, capillary waves and subsequent atomized particles became significant as the medium height decreased. These phenomena suggested cavitation bubbles were being generated in the medium. To determine the effect of UCAs on bubble generation, we repeated the experiments using crushed heat-treated Optison™ solution instead of the standard microbubble preparation. The transfection ratio and survival fraction showed no additional benefit when ultrasound was used. These results suggested that cavitation bubbles created by the collapse of UCAs were a key factor for transfection, and their intensities were enhanced by the interaction of the superpose ultrasound with the decreasing the height of the medium. Hypothesizing that free cavitation bubbles were generated from cavitation nuclei created by fragmented UCA shells, we carried out numerical analysis of a free spherical bubble motion in the field of ultrasound. Analyzing the interaction of the shock wave generated by a cavitation bubble and a cell membrane, we estimated the shock wave propagation distance that would induce cell membrane damage from the center of the cavitation bubble. (E-mail: kodama@tubero.tohoku.ac.jp)

Load characteristics of high power sandwich piezoelectric ultrasonic transducers

Based on the equivalent circuit theory, the load characteristics of high power piezoelectric ultrasonic sandwich transducers are studied. Two types of loads are studied. One is liquid load as in ultrasonic cleaning, and the other is solid load as in ultrasonic drilling and machining. The effect of load and structure of the transducer on the resonance frequency of the transducer is analyzed. It is shown that the effect of load on the resonance frequency of sandwich transducers with different structures is different. For liquid load as in ultrasonic cleaning, the effect of the load on the resonance frequency of the sandwich transducer with symmetrical structure is the largest. It is the smallest for the transducer with its displacement node in the back metal cylinder. For solid load as in ultrasonic drilling and machining, the effect of the load on the resonance frequency of the sandwich transducer with its displacement node in the front metal cylinder is the largest. It is also the smallest for the transducer with its displacement node in the back metal cylinder. On the other hand, for some applications, such as ultrasonic drilling, when the lateral dimension of the tool is much less than that of the transducer, its effect on the resonance frequency of the transducer is small. The conclusions are useful in designing vibrating systems for different ultrasonic applications.

Optimization of the performance of the sandwich piezoelectric ultrasonic transducer.

The resonance and antiresonance frequency, the effective electromechanical coupling coefficient, and the mechanical quality factor of a sandwich piezoelectric ultrasonic transducer are studied and optimized. The effect of the thickness of thick piezoelectric element electrodes on the transducer performance is analyzed. The effect of the length and position of the piezoelectric elements in the transducer is also studied. It is shown that, although using thick electrodes is beneficial for releasing heat produced by the piezoelectric elements, the effective electromechanical coupling coefficient and the mechanical quality factor are reduced. The length and the position of the piezoelectric elements affect the performances of the transducer. Increasing the length of the piezoelectric elements decreases the mechanical quality factor, but the effective electromechanical coupling coefficient increases. When the length reaches a certain value, the effective electromechanical coupling coefficient reaches a maximum value. When the piezoelectric elements are located at the geometrical center or the displacement node, the effective electromechanical coupling coefficient and the mechanical quality factor are maximized.

Free in-plane vibration of isotropic non-rectangular plates

A numerical study for the free in-plane vibration of non-rectangular plate is presented in this paper. The plate is defined by four curved boundaries using eight points and natural co-ordinates to map the geometry. The displacement nodes are introduced at the boundary of the plate as well as inside the perimeter. Each displacement node has two degrees of freedom and much higher order polynomials than the ones used for the geometric representation are used to represent the displacement fields. Using the energy functional, the matrix equation is obtained and solved for natural frequencies and associated mode shapes. Numerical results are calculated first for rectangular plates with three sets of boundary conditions and then compared with the data published in the literature by other researchers. Additional results are also presented and discussed in this paper for the in-plane vibration of rhombic and circular–annular–sector plates.

Path following and critical points for contact problems

This work is concerned with the problem of tracing the equilibrium path in large displacement frictionless contact problems. Conditions for the detection of critical points along the equilibrium path are also given. By writing the problem as a system of non-linear B-differentiable functions, the non-differentiability due to the presence of the unilateral contact constraints is overcome. The path-following algorithm is given as a predictor-corrector method, where the corrector part is performed using Newton's method for B-differentiable functions. A new type of displacement constraints are introduced where the constraining displacement node may change during the corrector iterations. Furthermore it is shown that, in addition to the usual bifurcation and limit points, bifurcation is possible or the equilibrium path may have reached an end point even if the stiffness matrix is non-singular.

3-D simulations of solar and stellar convection and magnetoconvection

We present the key components of a 3-D code designed for simulating the hydrodynamics and magnetohydrodynamics of stellar atmospheres and envelopes. Some particular properties of the code are: (1) the ability to handle strong stratification (extensive simulations with bottom/top pressure ratios of 3×104 have been performed, and simulations with pressure ratios of 5×106 are being initiated); (2) a detailed treatment of the radiating surface; (3) a functional form of the subgrid-scale diffusion designed to minimize the influence on resolved motions; (4) boundary conditions open to flows. The top boundary allows the transmission of short period waves, while the bottom boundary condition was designed to enforce a displacement node for radial pressure modes.