Plane Diaphragm Research Articles

Theoretical and experimental study on the effect of plane diaphragm tension on dynamic stability of liquid in a hemispherical tank under vertical excitation

The dynamic stability of a liquid in a hemispherical tank covered with a plane diaphragm under vertical excitation was studied both theoretically and experimentally. In the analysis, the liquid was assumed to be incompressible, non-viscous, and irrotational, and the plane diaphragm was a clamped circular membrane. The equation of motion was derived using the Galerkin method. The central frequency and width parameter of the instability region, in which parametric vibration occurred, were obtained using the Hsu’s method. In the experiment, two silicon test membranes with a diameter of 500 mm and thicknesses of 0.22 mm and 0.34 mm, were used as test plane diaphragms. Each test membrane was uniformly tensioned in the radial direction at ten points that were uniformly spaced along the circumference of the edge of the membrane. The central frequency and instability regions were measured by vertically exciting the test tank and measuring their responses using a laser Doppler vibrometer. The effect of diaphragm tension on parametric instability regions is presented in this paper. A comparison of the instability region between the experimental and the theoretical results showed that they were in good agreement, including in the case of a free surface.

Theoretical and experimental study on the effect of plane diaphragm tension on hydroelastic coupled vibrations in a hemispherical tank

In this study, to simulate liquid sloshing in a spacecraft fuel tank, the effect of tension of a plane diaphragm on the hydroelastic coupled vibration of the liquid in a hemispherical tank was investigated both analytically and experimentally. In the theoretical analysis, the liquid was assumed to be incompressible, non-viscous, and irrotational, and the plane diaphragm corresponded to a clamped circular membrane. The influence of tension of the diaphragm on the natural frequency was investigated. In addition, its natural frequencies and vibration modes were compared with those of a liquid in a cylindrical tank. The comparison revealed that the natural vibration characteristics of a liquid in a hemispherical tank approximate those of a liquid with the same volume in a cylindrical tank. In the experiment, two silicon test membranes with diameters of 500 mm, one 0.22 mm thick and the other 0.34 mm thick, were used as plane diaphragms. Each test membrane was uniformly tensioned in the radial direction at ten points that were uniformly spaced along the circumference of the edge of the membrane. The natural frequencies were measured by tapping the test membranes with a finger and conducting an FFT analysis of the response. The vibration modes were measured by exciting the membranes acoustically and measuring their responses using a scanning laser Doppler vibrometer. A comparison between the experimental and theoretical results showed that they were in good agreement, even in the case of an empty tank. This demonstrates the validity of the theoretical analysis and accuracy of the experimental results.

NODAL REACTIONS AND COEFFICIENTS OF THE STIFFNESS MATRIX OF A FINITE ELEMENT BASED ON THE REPRESENTATION OF DISPLACEMENTS BY POLYNOMIALS

The study of prismatic bodies with constants along one of the coordinates of mechanical and geometric parameters is most appropriate to conduct on the basis of the semianalytical finite element method (NMSE). Its essence is a combination of finite element sampling and decomposition of displacements in the characteristic direction by a system of trigonometric coordinate functions.In [8, 15], a variant of the semivanalytic finite element method for the calculation of prismatic bodies when used as a system of coordinate functions of Fourier series was developed. The use of trigonometric series provides maximum efficiency of the semi-analytical finite element method, however, only the boundary conditions corresponding to the object's support on an absolutely rigid in its plane and flexible diaphragm can be satisfied at the ends of the body.As a result of the performed researches, the basis of the representation of displacements by polynomials is obtained, which allows to significantly expand the range of boundary conditions at the ends of the body. In this case, it isnot possible to reduce the solution of the initial spatial boundary value problem to a sequence of two-dimensional problems, so a reasonable choice of appropriate polynomials becomes especially important.Both the conditionality of the matrix of the system of separate equations and, consequently, the convergence of integration algorithms for its solution, and the universality of the approach to the possibility of satisfying different variants of boundary conditions at the ends of the body depend on their correct choice.In addition, the question of methods of integration in the calculation of the coefficients of the stiffness matrix of a finite element (CE), which is quite common, due to the significant complexity of this procedure.

Design, fabrication and experimental studies of compliant flexure diaphragm for micro pump

This study reports the performance of piezo actuated compliant flexure diaphragm for micropump and MEMS application. To achieve the high performance of diaphragm at the low operating voltage compliant flexure diaphragm design is introduced. Very limited work has done on the diaphragms of micropump. Large numbers of mechanical micropumps have used plane diaphragms. The central deflection of diaphragm plays an important role in defining the micropump performance. The flow rate of mechanical type micropump strongly depends on the central deflection of diaphragm. In this paper compliant flexure diaphragms are designed for micropump to achieve higher deflection at lower operating voltage. Finite element analysis of compliant flexure diaphragm with single layer PVDF (Polyvinylidene fluoride) actuator is simulated in COMSOL. Compliant flexure diaphragms with a different number of flexures are analyzed. The central deflection of compliant flexure diaphragms is measured for driving voltages of 90V to 140V in 10 steps. The deflection of the compliant flexure diaphragm mainly depends on flexure width and length, the number of flexures in the diaphragm, PVDF thickness, diaphragm thickness and driving voltage. Use of compliant flexure diaphragm for micropump will reduce the mass and driving voltage of micropump. An attempt is made to compare the results of compliant flexure diaphragms with plane diaphragms. From the experimental results it is noticed that the compliant flexure diaphragm deflection is twice that of the plane diaphragm at same driving voltage. Deflection of three flexure and four flexure compliant diaphragms is 10.5µm and 11.5µm respectively at 140V.

Temperature Compensation Fiber Bragg Grating Pressure Sensor Based on Plane Diaphragm

Pressure sensors are the essential equipments in the field of pressure measurement. In this work, we propose a temperature compensation fiber Bragg grating (FBG) pressure sensor based on the plane diaphragm. The plane diaphragm and pressure sensitivity FBG (PS FBG) are used as the pressure sensitive components, and the temperature compensation FBG (TC FBG) is used to improve the temperature cross-sensitivity. Mechanical deformation model and deformation characteristics simulation analysis of the diaphragm are presented. The measurement principle and theoretical analysis of the mathematical relationship between the FBG central wavelength shift and pressure of the sensor are introduced. The sensitivity and measure range can be adjusted by utilizing the different materials and sizes of the diaphragm to accommodate different measure environments. The performance experiments are carried out, and the results indicate that the pressure sensitivity of the sensor is 35.7 pm/MPa in a range from 0 MPa to 50 MPa and has good linearity with a linear fitting correlation coefficient of 99.95%. In addition, the sensor has the advantages of low frequency chirp and high stability, which can be used to measure pressure in mining engineering, civil engineering, or other complex environment.

Effect of flexure beam geometry and material on the displacement of piezo actuated diaphragm for micropump

In this paper, we present a COMSOL analysis of flexure diaphragm for piezo actuated valveless micropump. Diaphragms play an important role in micropumps, till now plane diaphragms are commonly used in micropumps. Use of compliant flexure hinges in diaphragm and other MEMS application is one of the new approach to achieving high deflection in diaphragm at low operating voltage. Flexures hinges in diaphragm acts as simply supported beam. Out-off plane compliance value and stiffness is considered for the selection of proper flexure for diaphragm. Diaphragm material also plays an important role in the diaphragm central deflection. Factor considered for diaphragm material selection is resilience; it is the ratio of yield stress to static modulus. Higher is the resilience will leads to higher deflection generated, it also imparts good compliance. Based on the resilience beryllium copper, stainless steel and brass materials are selected for diaphragm analysis. Simulations have been performed using COMSOL multiphysics. This study reports the effect of flexure hinge geometry and diaphragm material on the central deflection of diaphragms and compared with existing plane diaphragm. Simulation results illustrates that the deflection of three flexure diaphragm with 2mm width and 2mm length flexure is 6.75µm for stainless steel, 10.89 for beryllium copper and 12.10µm for brass, at 140V which is approximately twice that of plane diaphragm deflection. The maximum in both plane and three flexure diaphragm deflection is obtained for brass diaphragm compared to stainless steel and beryllium copper.

Modeling of compliant flexure diaphragm for micropump

A number of mechanical micropumps have been proposed, many of those have been designed using plane diaphragms. Diaphragm is the essential part in mechanical type of micropump. Performance of the diaphragm can be improved by varying diaphragm geometry; use of compliant flexure in the diaphragm will improve the diaphragm deflection. In this paper, we present a FE analysis of stainless steel flexure diaphragm with different number of rectangular flexures using ANSYS. Simulations have been performed and results obtained for different flexure diaphragm from the Finite element modeling (FEM) compared with the plane diaphragm to decide the better diaphragm for piezoelectric mechanical type micropump. The central deflection is studied for driving voltage of 90-120V. Single layer PVDF actuator of 52µm thickness is considered for simulation. The great advantage of using compliant flexure in micropump diaphragm is that it can achieve higher deflection at a low driving voltage.

Experimental studies on the dynamic stability of liquid in a spherical tank covered with diaphragm under vertical excitation

Experimental studies are conducted on the liquid sloshing characteristics in a spherical tank covered with a flexible diaphragm. A spherical acrylic tank with 145.2mm radius is used as a test tank, and is filled with water. Silicon diaphragms, plane or hemispherical type, with 0.2mm thickness are used as test diaphragms. The test tank is harmonically excited in the vertical direction by an electro-dynamic exciter. During the test, vibrations due to parametric instability occur when the excitation frequency is twice the natural frequency. Parametric instability regions for some natural modes are measured and are presented in the excitation frequency–excitation acceleration diagram for three cases: liquid surface is uncovered (i.e., free surface), covered with a plane diaphragm, and covered with a hemispherical diaphragm, with the volume of filling water being changed appropriately.

Absolute micro pressure measurements based on a high-overload-resistance sensor

Presented is a piezoresistive absolute micro pressure sensor, which is of great benefit for altitude location. In this investigation, the design, fabrication and testing of the sensor are carried out. By analysing the stress distribution on sensitive elements using the finite-element method (FEM), a novel structure through the introduction of beams into the standard bossed diaphragm is built up. The proposed configuration presents its advantages in terms of sensitivity and overload resistance compared with the standard bossed diaphragm and conventional plane diaphragm structures. The sensor is fabricated based on silicon bulk micromachining technology, and the detailed processing program is discussed. Calibration data obtained through measurements are in good agreement with the results of the FEM analysis. Testing results demonstrate that the sensor features a high sensitivity of 11.098 µV/V/Pa in the operating range of 500 Pa at room temperature, and a high-overload resistance (200 times overload) to protect it from being destroyed under atmospheric environment. Owing to the excellent performance, the sensor can be applied for measuring absolute micro pressure lower than 500 Pa.

Silicon capacitive pressure transducer with increased modulation depth

Implementing the potentialities of silicon capacitive pressure sensors requires the solution to a number of design-technology and structure-circuitry problems. This work demonstrates the application of three-electrode capacitive transducers in silicon capacitive pressure sensors. IC technology is shown to provide the best possibility for fabricating three-electrode capacitive transducers with linear dependence of relative impedance versus the diaphragm deflection and, hence, versus applied pressure, the electrodes being flat. It is proposed to position a movable electrode on the diaphragm. It is shown that the real dependence of the relative impedance versus applied pressure in the case of capacitive sensors with a plane diaphragm can be approximated by a straight line with sufficient precision. The area of the electrodes being 0.25 times the area of the diaphragm, the approximation error is less than 1%, while the relative deflection of the centre of the diaphragm varies from −1.0 to 0.8. The sensitivity in this case is only 15% less than the highest possible one for capacitive transducers with flat electrodes. When the relative deflection of the centre of the diaphragm varies in the ranges −1.0–0 and 0–0.3, the approximation error is less than 0.2%. Experimental results are in good agreement with a theoretical analysis of silicon sensors with plane diaphragms.

Loudspeaker of plane diaphragm type

A loudspeaker of plane diaphragm type has a skin-like material with smaller diameter than that of the plane diaphragm pasted thereon so that the skin-like material will not stick out of the diaphragm surface and the edge piece surrounding it can securely support the plane diaphragm, preventing unpleasant noises and split vibrations.

Calculation of parameters for cathodic corrosion protection of hydraulic structures

1. Cathodic corrosion protection of metallic elements of hydraulic structures has in recent years been extensively used; until recently, one of the drawbacks of cathodic protection has been the lack of methods of mathematical analysis. 2. At the B. E. Vedeveev All-Union Scientific-Research Institute of Hydraulic Engineering, we have developed a method of calculating the parameters of cathodic protection hydroelectric stations metal structures, based on the solution of problems in the electric-field theory and taking account of the principal operational conditions of the structure. 3. The author suggests a model for calculating the parameters of cathodic protection of metal structures, the surfaces of which can be approximated by a plane (sluice gates, grids, sheet-pile walls, and diaphragms); calculations and nomograms are presented for determining the cathodic protection parameters under a wide range of operating conditions.

Occultation of Beta Scorpii by Jupiter on May 13, 1971

PHOTOELECTRIC observations of the occultation of the star β Scorpii by Jupiter were carried out at our field station at Kavalur on the night of May 13–14, 1971, at the cassegrain focus of the 38 cm reflecting telescope. Our photometric record was made by photographing a CRO trace in order to record the true light emission curve during the immersion and emersion phases of the occultation. The record was calibrated by photographing seconds pulses from a quartz clock simultaneously. A thin glass plate behind the focal plane diaphragm allowed continuous visual monitoring of the Jovian limb and the occultation phenomenon.

1491. Manometric glass vessel with plane diaphragm: A P Alekseev et al, Zavodsk Lab, 37 (5), 1971, 627 ( in Russian)

1491. Manometric glass vessel with plane diaphragm: A P Alekseev et al, Zavodsk Lab, 37 (5), 1971, 627 ( in Russian)

Photoelectric Occultation Observations of Regulus and the Pleiades

The dual channel photometer is mounted on the tailpiece of the 32-in.ƒ/16 reflector at McCormick Observatory’s Fan Mountain Station. A 50-50 beam splitting mirror distributes the light to two EMI 6256 S/A photomultipliers. A focal plane diaphragm admits an area of sky of 100 sec2 of arc, and UBV or narrow-band filters are used to isolate spectral regions. The photoelectrons are fed through preamplifiers and amplifiers to a specially designed integrated-circuit photon counting instrument. The preamplifiers are attached as closely as possible to the photomultiplier anodes, while the remaining circuits are housed separately. A Sony TC-200 stereo tape recorder is used to record the output signal from the counter, and an oscilloscope is used for real-time monitoring of the counter operation during occultations.

The size effect and the non-local Boltzmann transport equation in orifice and disk geometry

A variational approximation is obtained for the resistance (or total entropy production) of a circular orifice in a plane diaphragm at which the scattering is specular. It is found that the Ohm's law prediction must be multiplied by a correction factor of the order of unity and added to the `small orifice' Knudsen contribution. The results for the intermediate regime can be applied to the transport of electricity and heat by electrons and to phonons which are dominated by elastic scattering (e.g. by crystal imperfections). Results are also obtained for the case when the diaphragm separates materials of different mean free path. It is shown that the above problems are equivalent to the determination of the spreading resistance of a small disk-shaped electrode. The mathematical method is based on the formulation of an integral equation over the region of the disk with a kernel containing the Green function for the infinite medium Boltzmann equation.

Absorption of Sound in Mixtures of Oxygen and Water Vapor

The attenuation of sound waves in mixtures of oxygen and water vapor contained in a tube has been measured at frequencies between 90 and 1200 cps. The tube was terminated at one end by a fixed reflector and at the other by a plane diaphragm producing the sound waves. The impedance of the diaphragm/gas-column system was investigated near natural modes of the tube and analyzed by means of a circle diagram to yield the attenuation coefficient. The frequency of maximum absorption of sound was found to be a quadratic function of the water-vapor concentration. The value of the vibrational specific heat for oxygen was found to be (0.0332+0.0015) R.