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[en] The Twymann-Green interferometry is applied to measure surface deformations of mechanical components in industrial areas with non-contact since it requires relatively simple optical arrangement. In this study, a tapered canti-lever beam was used to measure out-of-plane displacement by Twymann-Green interferometry. The surface of the specimen was polished to be shown as that of a mirror. Fringes observed from the specimen with a shiny surface include speckle noise and are similar to those obtained from the specimen sprayed by white paint. Gussian blur which is a commercial software is used to eliminate high frequency speckle noise. Phase shifted four fringes using PZT were captured and were used to calculated phased image. Experimental results of the tapered canti-levered plate analyzed by 4-step phase shifting method are close to the theoretical expectation.
[en] In the temperature range from room temperature to 973 K and the mechanical loading range from 0.1 to 3 MPa, a Li2TiO3 pebble bed was successively loaded and the packing behaviour of the bed was observed. Deformation caused by the mechanical loading is partly relaxed when the bed is heated without the load. After a large numbers of thermal and mechanical loading cycles, the packing factor of the bed increased from the initial packing factor of 66.9% to finally about 68.5%. This progressive increase in packing leads to production of a cavity region at the top of the pebble bed, therefore it is important to obtain a high initial packing factor.
[en] The parametric effects of a PZT beam that is simultaneously used as a vibration absorber and a power harvester were investigated in this study. A cantilever beam paved with PZT layers and with added tip mass has been widely used as a harvester or sometimes as a Dynamic vibration absorber (DVA). However, the beam is rarely considered a collocated device. In this study, the first step was theoretical derivation of a distributed beam covered with bimorph PZT layers. Then, the beam was attached to a 1DOF vibratory main system. Two indicators for vibration absorption and power harvesting were defined. Numerical results demonstrated that the lumped mass ratio favored both of the abilities, but that the DVA mass ratio influenced these two abilities in exactly the opposite way. The conjunction of a harvester circuit into a DVA shifted its resonance frequency up to 5 % (an extreme case of open circuit R→∞). Simultaneous power harvesting diminished the absorption capability up to 35 % for each set of mass ratios. To achieve the maximum degree of power harvesting, a corresponding load resistance that somewhat increases with the lumped mass ratio is applied. Experimental results verified the existence of the best load resistance, but the measured harvested curve was lower than the theoretical calculation because of structure damping and deviations of PZT material properties
[en] In some space applications, such as space navigation and vibration control of the large space structures, micro-acceleration transducers are required and have to be calibrated accurately. Unfortunately, providing extremely small static and quasi-static stimuli (accelerations) for the calibration of the micro-acceleration transducer has been a challenging task. This paper proposes a novel piezo-driven micro-inclination stage (PMIS) that can produce both discrete and continuous tumbles in a gravity field so that extremely small static and quasi-static stimuli (accelerations) can be obtained from a tiny component of the gravity constant. The proposed PMIS, which is driven by the lead zirconate titanate (PZT) stack, employs a rhombic mechanism to provide the PZT stack with a proper preload for the purpose of outputting a bidirectional force. To produce accurate static and quasi-static stimuli, the hysteresis non-linearity inherent in PZT stack is compensated by employing the strain feedback based adaptive control where the hysteresis property is identified online using the controlled auto-regressive moving average model. Furthermore, to improve the resolution of strain feedback, the strain sensitivity is maximized through structure optimization of the rhombic mechanism. The experimental results demonstrated that the proposed PMIS can produce minimal micro-inclination of (corresponding to the induced micro-acceleration of ) with the frequency ranging from 0 (DC) to 2 Hz. (paper)
[en] Shock-induced depoling of the ferroelectric ceramic PZT 95/5 is utilized in a number of pulsed power devices. Several experimental and theoretical efforts are in progress in order to improve numerical simulations of these devices. In this study we have examined the shock response of normally poled PZT 95/5 under uniaxial strain conditions. On each experiment the current produced in an external circuit and the transmitted waveform at a window interface were recorded. The peak electrical field generated within the PZT sample was varied through the choice of external circuit resistance. Shock pressures were varied from 0.6 to 4.6 GPa, and peak electrical fields were varied from 0.2 to 37 kV/cm. For a 2.4 GPa shock and the lowest peak field, a nearly constant current governed simply by the remanent polarization and the shock velocity was recorded. Both decreasing the shock pressure and increasing the electrical field resulted in reduced current generation, indicating a retardation of the depoling kinetics
[en] Electric field and aging time are two important factors that affect the mechanical strength and long-term reliability of lead zirconate titanate or PZT actuators. In the present work, a commercial PZT-5A aged four years was examined using ball-on-ring (BoR) mechanical testing under coupled electric fields. The electric field range of −3Ec to +3Ec (Ec, coercive electric field) was studied (i.e., −3Ec, −Ec, 0, +Ec, +2Ec, and +3Ec) with a controlled electric loading path. A Weibull distribution was used to interpret the mechanical strength data. With an electric field preloaded from 0 to −3Ec, it was found that subsequent increases in the electric field resulted in an asymmetrical V-shaped curve of mechanical strength against the electric field. The bottom of the V curve was located near the zero electric field level. Microscopy analysis showed that pores were the strength limiter for the tested PZT under electromechanical loadings. (technical note)
[en] The field of energy harvesting has drawn an increased amount of interest due to the rapid development of wireless sensors and self-powered devices. Currently, there is limited information regarding the impact of coupling both thermal and mechanical excitations in a single material and its energy harvesting capabilities. This paper demonstrates the use of Lead Zirconate Titanate (PZT) as a coupled thermal and mechanical energy harvesting device. PZT ceramic was subjected to different thermal and mechanical loading conditions. Under pure mechanical cycling the sample consistently generated the least power output averaging less than 200 nW. An increase in power output was observed under mechanical cycling and higher temperatures. A peak power of 500 nW was seen under both, thermal cycling, as well as under coupled thermal-mechanical cycling. This study demonstrated the feasibility to harvest different waste energies from a single device. (paper)
[en] For high electrical loads, the electromechanical characteristics of PZT actuators are impacted by nonlinearities. This work presents a procedure, derived from nonlinear analysis, to assess separately the electrostriction and the elastostriction parameters of bulk PZT ceramics. A detailed investigation has shown that the electrostriction is dominant in actuator applications, while the elastostriction affects sensor applications. Further, the relationship between electrostriction and polarization in PZT material is discussed
[en] This paper describes the methods applied to the some chemical analysis of PZT ceramics during processing, and particularly in the finished ceramic, since small compositions changes can produce marked changes in final piezoelectric properties. Data on two samples (powder and high-fired ceramic material) are presented. The major constituents - Pb,Zr and Ti; nine trace elements and compound concentrations - Nb,C, Si, Al, Sr, free lead oxide, acid-insoluble matter, free oxygen and crystalline phases were determined using x-ray fluorescence, x-ray diffraction, thermal neutron activation, direct combustion, atomic absorption, vacuum fusion/gas chromatography, gravimetry, titrimetry and spectrophotometry. The major constituents were determined by more than one method, with good agreement between the various methods. (author)