Mojtaba Ghodsi

Development of Magnetostrictive Resonant Torsional Vibrator

In this paper, the design, construction, and operation of a magnetostrictive resonant torsional vibrator are described. To generate torsional vibration, two magnetostrictive patches are bonded on an aluminum horn. Two magnetic fields, longitudinal and circumferential, are applied into the patches. As a result, the magnetostrictive patches vibrate torsionally based on the Wiedemann effect. The magnetostrictive patches are made of 2V permendur, which has isotropic magnetic properties. The principle of the torsional vibrator is explained, and differential equations of torsional vibration of the horn are derived. A torsional horn is designed for a resonant frequency of 8515 Hz. The experimental results show that the torsional angle of the tip of the horn is 5.44× 10-6 rad. This type of vibrator is exploited in applications that require torsional vibration, such as miniature ultrasonic motors or ultrasonic-assisted bone drilling system. In other words, the vibrator is used as an actuator.

Investigation of Effect on Vibrational Behavior of Giant Magnetostrictive Transducers

Resonant magnetostrictive transducers are used for generating vibrations in the sonic and ultrasonic range of frequency. As the mechanical properties of magnetostrictive materials change according to different operating conditions (i.e., temperature, mechanical prestress, and magnetic bias), the vibrational behavior of the transducer changes too. effect is the change in the Young modulus of the ferromagnetic material and it has to be considered as it leads to changes in the dynamics of the transducer. This paper deals with the study of such effect from both theoretical and experimental point of view. effect on behavior of the transducer based on Terfenol-D is analytically described as a function of different operating conditions focusing on effects on resonance frequency, mode shape, and moreover experimentally the quality factor. Results of resonance frequency prediction have been validated with experiments and good agreement has been seen.

Piezoelectric Transducers on Curved Dispersive Bending Wave and Poke-Charged Touch Screens

Ferroelectric thin films of lead zirconate titanate Pb(Zr0.52,Ti0.48)O3(PZT) and bismuth titanate Bi4Ti3O12(BiT) were prepared by photochemical metal-organic deposition as electromechanical transducers used in optoelectronic devices. Both solutions were deposited on flat and convex amorphous glass substrates to poke-charge the device or detect the touch point coordinate on new generation of free-shaped screens. The effects of optimization on UV exposure, precursor type and annealing temperature (600–800 °C) were investigated on microstructural, optical and ferroelectric properties of deposited thin films. Suppressing the non-uniformity of the film thicknesses due to repetitive deposition, actually there is no structural difference between the two types of substrates and their effects on the film properties. Polarization-voltage hysteresis loops showed relatively larger remnant polarization of P r = 9.3 µC/cm2 and 6.1 µC/cm2 for optimized UV-irradiated PZT and BiT thin films, respectively, than uncured samples.

Effect of forging on ferromagnetic properties of low-carbon steel

Mechanical work usually has adverse effect on magnetic properties of soft magnetic materials. It reduces saturation magnetic flux density, decreases drastically magnetic permeability, widens hysteresis loop and decreases magnetostriction coefficient which leads to less strain under certain magnetic field intensity. This paper presents a practical way to improve magnetic properties of low-carbon steel, which had already been deformed by forge technique.

Analytical, numerical and experimental investigation of a giant magnetostrictive (GM) force sensor

Purpose – This paper aims to investigate a novel giant magnetostrictive (GM) force sensor using Terfenol-D rod. Design/methodology/approach – First of all, principle of GM force sensor based on positive magnetostriction of Terfenol-D is presented. Then, design procedure of the GM force sensor is stated. Magnetic properties such as B-H curve and permeability of Terfenol-D are measured by a novel experimental setup and the results are used in analytical model, sensitivity estimation and numerical simulations. Then, an analytical model is presented and a numerical simulation using CST Studio Suite 2011 software is done. So as a result of numerical simulations, optimum geometry of the GM force sensor is obtained related to the condition in which the GM force sensor has highest sensitivity. After that, the sensor is fabricated using the simulation results and is tested by means of an experimental setup. Characteristic curve of the GM force sensor in several conditions is measured and the optimum operational co...

Thickness and thermal processing contribution on piezoelectric characteristics of Pb(Zr-Ti)O3 thick films deposited on curved IN738 using sol–gel technique

Lead zirconate-titanate (PZT) thick films of perovskite structure Pb(ZrxTi1-x)O3 were fabricated on the curved surface of IN738 nickel-based supper alloy substrate up to 15 µm thickness using sol–gel deposition technique without polyvinylpyrrolidone. The films were heated at 200℃ with 10 wt% excess PbO, pyrolyzed at 400℃, and subsequently annealed at 650℃, 700℃, and 800℃. Au and Pt thin films were deposited as bottom and top electrodes, respectively. PZT films of different thicknesses and thermal treatment conditions were characterized to investigate the effect of process on crystalline phase development, orientation, and microstructure morphology. Thereby, formation of fairly smooth, semi-dense, and crack-free random orientated thick films as well as an increase in the average grain size and stress relaxation was observed as the film thickness increased. Having optimized the coating process, intrinsic and extrinsic dielectric, ferroelectric and piezoelectric properties were measured as a function of the film thickness, orientation, grain size, and domain wall motions to evaluate the remnant polarization (Pr = 7.6–17.5 µC/cm2), coercive field (Ec = 2.5–4 kV/cm), permittivity (ɛr = 276–326), dielectric loss (tanδ(%) = 2.7–3), and piezoelectric charge coefficient (d33 = 71–145 pm/V) of the PZT thick films prepared potentially to be used as high bandwidth 1–5 MHz structural health monitoring transducers.

Design and Implementation of an Accurate, Portable, and Time-Efficient Impedance-Based Transceiver for Structural Health Monitoring

Reducing maintenance costs while increasing the safety and reliability, especially in moving structures, needs a reliable nondestructive analyzer. The aim of this research is to provide a practical solution for this problem based on high-frequency excitation of stationary and moving structures by propagating standing Lamb waves in the range of 1 to 1000 kHz. The proposed solution comprises of a controlled frequency swept signal source, a number of piezoelectric sensors, a portable analyzer, and a rotary mechanism. Measuring the accurate electromechanical impedance (EMI) is made possible by monitoring the applied voltages, currents, and phase differences accurately. In this study, design and implementation of a low-cost, compact, and portable transceiver is explored for periodic structural health monitoring of a proposed rotary structure using EMI technique. The compactness of the proposed system is an essential requirement for rotary structures as compared with bulky, heavy, and expensive impedance analyzers. Challenges in design and development of such a system are discussed in this paper, together with mitigations to make the system functional and practical. An experimental study is carried out in frequency domain to measure the real and imaginary parts of impedance spectrum of piezo-transducers. The results show that the portable transceiver has the capability to detect structural incipient damages before any catastrophic failure, thus avoiding undesirable shut down during the operation.

Design and Experimental Implementation of a Beam-Type Twin Dynamic Vibration Absorber for a Cantilevered Flexible Structure Carrying an Unbalanced Rotor: Numerical and Experimental Observations

This paper presents experimental and numerical results about the effectiveness of a beam-type twin dynamic vibration absorber for a cantilevered flexible structure carrying an unbalanced rotor. An experimental laboratory prototype setup has been built and implemented in our laboratory and numerical investigations have been performed through finite element analysis. The proposed system design consists of a primary cantilevered flexible structure with an attached dual-mass cantilevered secondary dynamic vibration absorber arrangement. In addition, an unbalanced rotor system is attached to the tip of the flexible cantilevered structure to inspect the system response under harmonic excitations. Numerical findings and experimental observations have revealed that significant vibration reductions are possible with the proposed dual-mass, cantilevered dynamic vibration absorber on a flexible cantilevered platform carrying an unbalanced rotor system at its tip. The proposed system is efficient and it can be practically tuned for variety of design and operating conditions. The designed setup and the results in this paper can serve for practicing engineers, researchers and can be used for educational purposes.

Design and simulation of multi-resonance sonic transducer using Terfenol-D

Terfenol-D resonant transducers have some advantages, such as high energy density and high vibrational amplitude, that make them suitable for working in a wide range of application. On the contrary, the main drawback is that operating frequency is fixed and correspond to the resonance frequency of the device itself. If working frequency is far away from the resonance, efficiency of the transducer decreases suddenly. In this paper, an attempt to design and simulation of a multi-resonance sonic transducer is presented. The idea is to increase the range of operating frequencies of about 1.5 kHz. This can be obtained by exploiting ΔE effect in Terfenol-D in response to changes in mechanical preload and magnetic bias. Design procedure is validated by a finite element commercial software and effects of changing resonance frequency in vibrational mode shape of the transducer are presented. The magnetic circuit of the transducer is designed to minimize flux leakage and it is simulated with ANSYS12. Results of this paper can help to design the more flexible transducer in operating frequency and modal shape.

Comparative discussion between first and second modes of Terfenol-D transducer

Terfenol-D resonance transducer has high energy-density and high vibration amplitude. These features make them good selection for using in different applications such as liquid atomizers and sonar transducers. Operating mode of the Terfenol- D transducer plays an important role in efficiency of it. It can also change some parameters of the transducer such as quality factor. In this paper, experimental comparative study between first and second longitudinal modes of vibration in the Terfenol-D transducer is presented. It contains the mechanical quality factor, band with frequency and also effect of changing Young modulus in resonance frequency and mode shape. For this purpose, a resonance transducer for working in 3 kHz in first mode and 8.25 kHz in second mode has been designed and fabricated. In design procedure, preload mechanism location is considered as nodes. Quality factor and bandwidth is calculated experimentally and resonance frequency and mode shape has been calculated both with analytical method and ANSYS12 FEM commercial software. Results show that higher quality factor in the second mode shape and this mode shows lower sensitivity with Young modulus .