Development of an improved mathematical model for the dynamic response of a sphere located at a viscoelastic medium interface

A comprehensive investigation on the static and dynamic responses of a sphere located at elastic and viscoelastic medium interfaces is performed in this study. First, the mathematical models commonly used for predicting the static displacement of a sphere located at an elastic medium interface are presented and their performances are compared. After that, based on the finite element analyses, an accurate mathematical model to predict the static displacement of a sphere located at an elastic medium interface valid for different Poisson’s ratios of the medium and small and large sphere displacements is proposed. Then, an improved mathematical model for the dynamic response of a sphere located at a viscoelastic medium interface is developed. In addition to the Young’s modulus of the medium and the radius of the sphere, the model takes into account the density, Poisson’s ratio and viscosity of the medium, the mass of the sphere and the radiation damping. The effects of the radiation damping, the Young’s modulus, density and viscosity of the medium and the density of the sphere on the dynamic response of the sphere located at a viscoelastic medium interface are explored. The developed model can be used to understand the dynamic responses of spherical objects located at viscoelastic medium interfaces in practical applications. Furthermore, the proposed model is a significant tool for graduate students and researchers in the fields of engineering, materials science and physics to gain insight into the dynamic responses of spheres located at viscoelastic medium interfaces.

Fabrication and Characterization of Annular-Shaped Piezoelectric Micromachined Ultrasonic Transducer Mounted with Pb(Zr,Ti)O3-Based Monocrystalline Thin Film

In this study, we propose an annular-shaped piezoelectric micromachined ultrasonic transducer (pMUT) based on a Pb(Zr,Ti)O3-based monocrystalline thin film. This pMUT is expected to increase the resonance frequency while maintaining displacement sensitivity, making it superior to an island-shaped pMUT, which is a conventional design. To demonstrate the validity of this assumption, annular- and island-shaped pMUTs with a 60-μm-diameter diaphragm were prototyped and characterized. As a result, the annular-shaped pMUT exhibited a resonance frequency of 11.9 MHz, a static displacement sensitivity of 2.35 nm/V and a transmitting figure-of-merit (FOM) of 28 nm∙MHz/V. On the other hand, the island-shaped pMUT exhibited a resonance frequency of 9.6 MHz and a static displacement of 2.5 nm/V and an FOM of 24 nm∙MHz/V. Therefore, the annular-shaped pMUT was experimentally demonstrated to provide a higher FOM compared to the island-shaped pMUT. In addition, the annular-shaped pMUT with the optimal dimensions is found to be able to keep a relatively large fabrication margin. This is an advantageous point for the practical device fabrication. We believe this design has a potential to become a standard design for high-performance pMUT devices.

Design of MEMS magnetic actuator for MEMS fourier transform infrared spectrometer

The objective of this thesis is to design MEMS magnetic actuator for MEMS FTIRS. The actuator consists of moving part and fixed part. The moving part uses rotation-to-translation motion conversion mechanism to achieve large translation, which includes four trapezoidal plates, central ring, anchoring springs and connection springs. The fixed part of the actuator consists of four solenoids. The actuator can be integrated with separately fabricated micromirror plate to achieve high surface quality translation micromirror for FTIRS. The actuator is capable of eliminating titling by controlling the four solenoids individually. The MEMS magnetic actuator has been designed and simulated to be able to output a static displacement of 370micrometers. The stress has been analyzed for the moving part of the actuator. The actuator fixed part has been designed. Dynamic analysis has been conducted for the moving part of the actuator. The moving part of the actuator has been fabricated using MetalMUMPs.

Displacements in the Cationic Motif of Nonstoichiometric Fluorite Phases Ba1−xRxF2+x as a Result of the Formation of {Ba8[R6F68–69]} Clusters: III. Defect Cluster Structure of the Nonstoichiometric Phase Ba0.69La0.31F2.31 and Its Dependenceon Heat Treatment

The defect structure of Ba0.69La0.31F2.31 single crystals in as-grown state and after annealing at 1173 K for 336 h was studied by X-ray diffraction analysis. Both crystals belong to the CaF2 structure type (sp. gr. Fm3¯m). They have vacancies in the main anion motif and interstitial fluorine anions in Wyckoff positions 48i and 4b. Relaxation (static displacement of some main anions to Wyckoff position 32f) is observed in the annealed crystal. It was established that annealing leads to a change in the type of displacement of the main anions in Wyckoff positions 8c from dynamic to static. Displacement of La3+ cations to Wyckoff position 32f is observed in both crystals. A model of the defect structure of Ba0.69La0.31F2.31 is proposed, according to which interstitial fluorine anions and La3+ cations are aggregated into [Ba14−nLanF64+n] clusters with the cuboctahedral anionic core formed by interstitial fluorine anions in Wyckoff positions 48i. Ba2+ cations are located in the cluster in the centers of the faces, and the La3+ cations are shifted by 0.24 Å from the vertices of the cluster along the three-fold axis towards the center of the cluster. The study establishes the relationship between the defect structure of crystals and their structurally sensitive properties, and to develop approaches to their management.

ANALISIS TEGANGAN ALAT UJI BENDING PIPA SKALA LABORATORIUM MENGGUNAKAN FINITE ELEMENT ANALYSIS

Proses pengerolan yang banyak digunakan di industri skala kecil seperti bengkel, workshop dan lain-lain masih dilakukan secara manual. Pembuatan mesin bending pipa dengan proses ini memerlukan perencanaan yang tepat dengan cara mengetahui terlebih dahulu tegangan yang bekerja pada pipa agar tidak melebihi tegangan maksimumnya. Tegangan maksimum dalam perencanaan dan pembuatan mesin merupakan suatu dasar yang sangat penting untuk diketahui. Tujuan penelitian ini adalah untuk mendapatkan hasil simulasi tegangan yang terjadi pada alat bending pipa skala laboratorium yang mengalami pembebanan menggunakan perangkat lunak Solidworks 2020. Proses simulasi dilakukan dengan variasi pembebanan 700 N, 500 N dan 100 N. Proses Simulasi dilakukan dengan beberapa langkah pengerjaan, yaitu menginputkan data material baik material roller maupun material pipa yang akan dilakukan pengerolan. Data material yang diinputkan dapat berupa modulus elastisitas, poissons’ratio, yield strength dan lain-lain. Langkah selanjutnya diinputkan pemodelan roller bending dengan solidworks, setelah itu dilakukan simulasi metode elemen hingga (finite element analysis) menggunakan software Solidworks 2020. Selanjutnya dari proses simulasi telah dilakukan diperoleh tegangan bending maksimum sebesar 265,1 MPa, sedangkan static displacement maksimum sebesar 2,161 e1 mm.

Positional control of a parallel kinematics mechatronic manipulator linear drive

The research is part of the current work on the design and research of precision actuators with parallel kinematics, designed to guide and orient of various objects. To protect the sensitive load and the supporting platform from undesirable disturbances above the permissible ones, as well as to limit the time of transient processes and the consumed power, a method for planning the trajectory of the linear actuator stem when operating in positional mode is proposed. The article describes an algorithm for calculating the parameters of the trajectory of an object under specified restrictions on speed, acceleration and acceleration derivative, and also proposes an algorithm for implementing control along a planned trajectory for a modern microprocessor system, which implements the dependence of speed on movement. The advantage of the proposed control method is the elimination of the cumulative effect of the static displacement error while observing dynamic constraints, as well as the possibility of using algorithms in both closed-loop and open-loop drives based on various types of electric motors. The article presents the results of computer simulation of an open-loop drive operating according to the proposed algorithm, the advantages and disadvantages of this approach are noted.