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[en] This study puts forward the consequence of poling direction on piezoelectric materials operating in longitudinal (d 33) mode. It has been mathematically presented that piezoelectric strain coefficients get altered due to poling direction. Further, this concept was developed theoretically to investigate the effect of poling angle on sensing and actuation capabilities of the piezoelectric materials particularly operating in d 33 mode. To demonstrate the effect, a cantilever based interdigitated electrode configuration has been considered with different materials including 0.3BaTiO3-0.7NaNbO3 (BT-NNb), K0.475Na0.475Li0.05(Nb0.92Ta0.05Sb0.03) (KNLNTS), Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) and Pb[ZrxTi1-x] (PZT-5A) . In addition to poling direction, the effect of electrode width and electrode separation distance was also investigated. Upon poling tuning, enhanced was displayed only by BT-NNb and PMN-PT due to large difference between magnitudes of piezoelectric strain coefficients. On the other hand, in terms of sensing and actuation substantial increment was observed these two materials while the performance of PZT-5A deteriorated with increasing poling angle. An increment of 4400% and 87% was observed in BT-NNb and PMN-PT respectively in actuation while sensing performance increased by ∼2460% and ∼210% for BT-NNb and PMN-PT respectively. (paper)
[en] Energy harvesting is a research area that has seen greatly increased interest in recent years. This paper presents experimental efforts to validate analytically predicted energy generating performance of piezoelectric harvesters for use in a pressure-loaded system. The energy harvesters adopted in this article are simply supported, partially covered piezoelectric unimorph circular diaphragms designed to capture energy from fluctuating pressure and convert it into electrical energy. The design itself has been presented in earlier work; however there is a lack of experimentally validated models in the literature for these kinds of harvesters. This paper presents experimental results showing that when key factors such as the bonding layer in the composite harvesting structure are considered, the experimental results coincide with the analytical predictions
[en] A study on smart seats for railroad vehicles was conducted using piezoelectric (PZT) sensors. For this purpose, the concept of passenger friendly smart seats was defined, and a PZT sensor was selected as the optimum sensor based on this concept. Using PZT sensors, simulation tests were performed using a sub-scale model railroad vehicle. In these tests, the main functions of the smart seats were extracted and simplified to improve the effectiveness of the simulation tests. Based on the test results, the system for smart seats proposed in this paper was successfully verified using PZT sensors and the dedicated operation software for the system. This paper will contribute to the improvement of services in high-speed rail systems through advances in ticket checking tasks.
[en] We analyze the first-order gradient effects in micro piezoelectric-bimorph circular plate (PBCP) power harvesters by including the first-order gradient terms in the energy density functions. Considering that the dimension of a PBCP is much smaller in the thickness direction than the in-plane dimensions, the gradient effects can be focused on analysis of the strain-gradient effects in the thickness direction through choosing the strains and the electric displacements as the independent constitutive variables. The paper has shown theoretically that the first-order gradient effects have induced shift in the natural frequency of a PBCP structure and resulted in a small change in the harvester performance. (paper)
[en] Researchers at the Department of Energy's Sandia National Laboratories and the University of Kentucky are developing an entirely different approach to space mirrors: a thin-film, ultralight deployable mirror made out of a ''smart'' material that changes shape when struck by electrons fired by a computer-controlled electron gun.(c) 2000 Optical Society of America
[en] Highlights: • Fabricating the ternary (1-x)K0.5Na0.5Nb1-ySbyO3-zSrZrO3-xBi0.5Na0.5HfO3 ceramics by the conventional solid-state reaction method; • Constructing R-O-T multiphase coexistence in the range of 0.03£x£0.05, 0.04£y£0.06, 0.01£z£0.025; • Attaining the high d33 (470 ± 5 pC/N) and a relatively high TC (244 °C). (1 − x)K0.5Na0.5Nb1 − ySbyO3-zSrZrO3-xBi0.5Na0.5HfO3 (KNNS-SZ-BNH) lead-free ceramics were developed by the conventional solid-state reaction method. Effects of the additives (Bi0.5Na0.5HfO3, SrZrO3 and Sb5+) on their phase structure, microstructure, and electrical properties were investigated. The rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary can be established in the ceramics with 0.03 ≤ x ≤ 0.05, 0.04 ≤ y ≤ 0.06, and 0.01 ≤ z ≤ 0.025, and then their piezoelectric properties were improved. The ceramics with x = 0.03, y = 0.04 and z = 0.01 possess the optimum piezoelectric properties (d33 = 470 ± 5 pC/N, kp = 0.51 ± 0.02, and TC = 244 °C). We believe that R-O-T multiphase coexistence is mainly responsible for the enhancement of piezoelectric properties.
[en] The disturbances in a semi-infinite piezoelectric medium excited by a constant polarized tangential electric field for a finite interval of time and heated by sources of heat, distributed continuously over a plane parallel to the free surface of the medium, which vary according to a ramp-type function of time, are investigated. The problem is solved using methods of transform calculus and, finally, the results are plotted graphically. (author)