Key Engineering Materials Vols. 334-335

Abstract: Rotary and linear ultrasonic motors were developed in the present paper using metal-PZT composite piezoelectric stator transducer configuration. The transducer consists of a concentric PZT tube and a metal tube, which structurally improve the reliability of the stator transducer. The developed transducer can provide a free vibration velocity of 0.9 m/s under 100 Vp-p at the resonant state. The rotary motor and linear motor use the developed transducer as the driving component, which produces the rotational motion to drive the motor. The rotary motor is able to achieve about 700 rpm no-load speed, above 2 mNm torque, maximum 70 mW output power and 50% efficiency under driving voltage of 80 Vp-p. The linear motor produces rotational motion and linear motion simultaneously. The linear speed of 5 mm/s can be achieved under the driving voltage of 50 Vp-p under no-load state. Under the loaded state, maximum 8 N load has been observed to be moved by the motor at a speed of 0.6 m/s. The maximum output power and efficiency of the linear motor are 9 mW and 11%, respectively.

Abstract: In the present work, the FGM monomorph actuator was developed and applied in the impedance pump. The actuator was fabricated using electrophoretic deposition (EPD). Two starting materials, pure PZT and doped PZT, were mixed to form four different compositions. The actuator was then fabricated by sequential deposition of the four compositions layer by layer on the substrate and followed by sintering to full density. The actuator shows both piezoelectric property and microstructural gradient across the layers. The actuator is able to achieve a bending displacement of nearly 2 mm at resonant frequency. It has been successfully applied to the impedance pump as the actuating component. The pumping action comes from the periodic compression by the actuator to induce a net flow. Maximum flow was observed at the resonant frequency of the actuator. A flow rate of about 9 ml/min was generated.

Abstract: Piezoelectric bimorphs were assessed for their capabilities to be used as control actuators for vibration suppression of the print circuit boards (PCBs). Plate structures made of FR-4, a widely used industrial-grade material for manufacture of PCBs, were considered. An advanced and structured control algorithm, linear quadratic regulator with output feedback (LQROF), was used for active vibration control of the PCB structures. Experimental results showed that the LQROF control is a more robust algorithm than the classic control using the direct velocity feedback, and piezoelectric bimorph actuators present a great potential for active vibration control of the PCBs, and smart composites with embedded actuators.

Abstract: The response time of a rotor system on a magnetorheological(MR) fluid squeeze film damper was measured experimentally. The effects of rotating speed, step voltage and rotor imbalance on the response time were dealt with. It is shown that the MR fluid damper rotor system is a second-order dynamic system. The rapid response time defined by the time taken for the vibration amplitude to rise (fall) from 10 % (or 90%) to 90 % (or 10%) of the vibration amplitude difference between the initial and final states is 0.05~0.7s in applying a step voltage and 0.01~1.225s in dropping a step voltage, respectively. It is impossible for the response time to be within a few milliseconds. The response time is determined not only by magnetic field strength, MR fluid specification, rotational speed, but operation mode of the power supply. There is a zero initial delay time at either applying or dropping the step voltage, which is caused by the magnetizing or de-magnetizing process.

Abstract: The controllability of a magnetorheological(MR) fluid squeeze film damper under a sinusoidal magnetic field was experimentally studied on a flexible rotor. It is shown that the frequency of the excitation magnetic field has a great effect on the controllability of the MR fluid damper. As the magnetic field frequency increases, the controllability of the MR fluid damper significantly reduces. There is a maximum frequency of the magnetic field for a given magnetic field strength or a minimum strength of the magnetic field for a given magnetic field frequency to make the dynamic behavior of the MR damper be controllable. When the magnetic field frequency is over the maximum one or the magnetic field strength is less than the minimum one, the controllability of the MR fluid damper almost completely disappears and the dynamic behavior of the MR fluid damper with the sinusoidal magnetic field is the same as that without the magnetic field.

Abstract: In this paper, the TiNi fiber reinforced / Polycarbonate(PC) composite material is developed, and its properties is studied. Conducting fatigue experiments, shape memory effect of the material for preventing fatigue crack growth are investigated. The fatigue behavior and crack propagation are observed under increasing temperature with a SEM servo-pulser, which is a fatigue testing instrument with scanning electron microscope. As the results, the effectiveness of fatigue resistance is confirmed. The shape memory effect and expansion behavior of the matrix caused by increasing temperature create the effect of the fatigue crack propagation control. It is verified that the controlling of fatigue crack growth is attributed to the compressive stress field in the matrix which is caused by shrinkage of the TiNi fibers above austenitic finishing temperature (Af).

Abstract: The propagation of shear horizontal (SH) wave is studied in a tri-material composed of a piezomagnetic layer and two semi-infinite piezoelectric half-spaces. These materials are hexagonal (6mm) crystals. A dispersion relation is exactly derived. The numerical results show the existence of the SH wave and its dispersion characteristics. These may be useful for the applications of piezoelectric-piezomagnetic media in the microwave technology.

Abstract: Recently, zirconia has been considered as a suitable material for surface coating nanosized TiO2 for use as an electrode in a solar cell application. In this study, the TiO2 (P-25) coated ZrO2 was synthesized from P-25 TiO2 and coated with zirconium n-propoxide in the range of 2.5-50 wt.%. The surface of the TiO2 coated with ZrO2 were examined by X-ray diffraction (XRD) analysis, high resolution transmission electron microscope (HRTEM), which showed zirconia could coat onto the P-25 TiO2 surface. Any excess of zirconia has been deposited as separated particles. Peaks for tetragonal zirconia were observed from the XRD patterns in zirconia-coated P-25 containing more than 20 wt. % of zirconia after calcinations at 500 °C, 800 °C and 1300 °C. In addition, peaks of anatase could be observed from XRD patterns of the samples after calcination at 1300°C. The results show that coating zirconia onto the TiO2 grain surfaces may act to retard the phase transformation from anatase to rutile.

Abstract: Aerodynamic surfaces for subsonic flight vehicles are usually designed primarily with the cruise condition in mind. With this objective in mind, the design of these aerodynamic surfaces, which usually exist as airfoils on the vehicles, are in general suboptimal for actual situation because they must be used for takeoff, landing, and maneuver in addition to cruise condition [1]. Therefore, it would be always desirable to design an airfoil with the ability to adapt to its current flow condition and alter its shape to remain the efficiency at any speed. The present paper reports a design of an airfoil with NACA 0012 profile which aims to deform the airfoil shape under the actuation the shape memory alloy (SMA) actuators embedded in it. The SMA actuators design to alter the aerodynamic lift and drag in a subsonic flow. The feasibility of the design is examined and discussed in the light of the change in lift to drag ratio and the power budget of the actuation.

Abstract: Unsymmetrical carbon fibre/epoxy composites with bonded piezoelectric fibre actuators were investigated as a means to shape change, or morph, composite structures. A carbon fibre cantilever was examined along with its response to applied strains (from piezoelectric actuators), with emphasis on the characterisation of shape/deflection and the reproducibility of the shape/deflection of the structure.