• Advances in aircraft and spacecraft science
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• 제2권3호
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• pp.275-302
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• 2015

Theoretical and numerical assessments of approximate evaluations and simplified analyses of piezoelectric structures transverse shear modal effective electromechanical coupling coefficient (EMCC) are presented. Therefore, the latter is first introduced theoretically and its approximate evaluations are reviewed; then, three-dimensional (3D) and simplified two-dimensional (2D) plane-strain (PStrain) and plane-stress (PStress) piezoelectric constitutive behaviors of electroded shear piezoceramic patches are derived and corresponding expected short-circuit (SC) and open-circuit (OC) frequencies and resulting EMCC are discussed; next, using a piezoceramic shear sandwich beam cantilever typical benchmark, a 3D finite element (FE) assessment of different evaluation techniques of the shear modal effective EMCC is conducted, including the equipotential (EP) constraints effect; finally, 2D PStrain and PStress FE modal analyses under SC and OC electric conditions, are conducted and corresponding results (SC/OC frequencies and resulting effective EMCC) are compared to 3D ones. It is found that: (i) physical EP constraints reduce drastically the shear modal effective EMCC; (ii) PStress and PStrain results depend strongly on the filling foam stiffness, rendering inadequate the use of popular equivalent single layer models for the transverse shear-mode sandwich configuration; (iii) in contrary to results of piezoelectric shunted damping and energy harvesting popular single-degree-of-freedom-based models, transverse shear modal effective EMCC values are very small in particular for the first mode which is the common target of these applications.

• 토지주택연구
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• 제5권2호
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• pp.99-106
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• 2014

이 연구에서는 주택과 도시 시설물에 적용이 가능하고, 시설물의 수요특성에 적합한 맞춤형 하이브리드형 에너지블록을 압전과 전자기 유도방식을 동시에 활용하여 개발하고자 하였다. 이를 위하여 에너지하베스팅 블록의 종류별 특성과 요구조건을 분석하고 그에 따른 에너지블록의 개선방향 및 적용방안을 도출하였다. 이러한 방안에 따라 선행연구에서 개발된 프로토타입 에너지블록의 특성 및 성능과 이 연구에서 개발된 하이브리드 에너지블록과의 성능을 비교분석 하였다. 비교결과, 하이브리드 에너지 블록이 기존 프로토타입에 비하여 1회 가진 시 12.7배, 그리고 5회 연속가진 시 28.9배의 출력을 나타냈다. 이는 연구목적인 W급의 전기에너지 생산목적에 부합되는 것으로, 주택 및 도시시설물에 적용이 가능할 것으로 사료된다.

• 한국전기전자재료학회논문지
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• 제25권7호
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• pp.511-515
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• 2012

A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 24 piezoelectric cantilevers and a vehicle load transfer mechanism. Applying a vehicle load transfer mechanism rather than directly installing energy harvesters under roads decreases the area of road construction and allows more energy harvesters to be installed on the side of the road. The power generation amount with respect to the vehicular velocity change was assessed by installing the vehicle load transfer mechanism and the energy harvester in the form of speed bumps and underground. The energy harvester installed in a speed bump form generated power of 7.61 mW at the vehicular velocity of 20 km/h. Also, power generation of the energy harvester installed in the underground form was 63.9 mW at the vehicular velocity of 28 km/h. Although the number of piezoelectric cantilevers was reduced by 1/3 to 24 in comparison to the previous research results with 72 piezoelectric cantilevers, similar power generation characteristic value was obtained within the vehicular velocity of 20 km/h by altering the vehicle load transfer mechanism and cantilever vibration method.

• Smart Structures and Systems
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• 제26권3호
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• pp.391-401
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• 2020

The present article reports the feasibility of the electrical energy generation from ambient low-frequency vibration using a piezoelectric material mounted on a bimorph cantilever beam actuator. A corresponding higher-order analytical model is developed using MATLAB in conjunction with finite element method under low-frequency with both damped and undamped conditions. An alternate model is also developed to check the material and dimensional viability of both piezoelectric materials (mainly focussed to PVDF and PZT) and the base material. Also, Genetic Algorithm is implemented to find the optimum dimensions which can produce the higher values of voltage at low-frequency frequencies (≤ 100 Hz). The delamination constraints are employed to avoid inter-laminar stresses and to increase the fracture toughness. The delamination has been done using a Teflon sheet sandwiched in between base plates and the piezo material is stuck to the base plate using adhesives. The analytical model is tested for both homogenous and isotropic material characteristics of the base material and extended to investigate the effect of the different geometrical parameters (base plate dimensions, piezo layer dimensions and placement, delamination thickness and placement, excitation frequency) on the model responses of the bimorph cantilever beam. It has been observed that when the base material characteristics are homogenous, the efficiency of the model remains higher when compared to the condition when it is of isotropic material. The necessary convergence behaviour of the current numerical model has been established and checked for the accuracy by comparing with available published results. Finally, using the results obtained from the model, a prototype is fabricated for the experimental validation via a suitable circuit considering Glass fibre and Aluminium as the bimorph material.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.622-622
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• 2013

Piezoelectric energy harvesting (PEH) device refers to a power device for acquiring mechanical energy from the environment surrounding us which would otherwise be wasted and for converting it into usable electrical energy. While much work has been done on developing ZnO nanogenerator (NG) with nanowire arrays, there are some issues of not only scaling up its output power but also optimizing structure for operating feasibly in various conditions. Efficiency of NG is highly dependent on fixed orientation. But in many cases, it is not easy to predict where the pressure and vibration may come from. Furthermore, the direction of the applied mechanical stress is usually non-stationary and can be random in various practical applications. Therefore an omnidirectional PEH is needed.In this work, we investigate an omnidirectional PEH device consisting ZnO nanowires. We deposited spiral patterned ZnO seed layer on Kapton film. We deposited thin Cr layer on the ZnO seed layer using DC-sputter to form a passivation layer to retard un-expected growth of ZnO nanowires. We grew ZnO nanowires along the spiral arms using hydrothermal method. ZnO nanowires have been selectively grown from the ZnO sidewall without Cr layer and have the average length of$5{\mu}m$ and the average diameter of 40nm. We reduced the defect in the as-grown ZnO nanowires by O2 plasma using asher and by thermal treatment using RTA. Consequently, each nanowire has different directions to each other. This isotropic design can lead to the omnidirectional power generation. The morphology of NG is characterized with FESEM. Maximum output power of the device is measured by using a picoammeter and a nanovoltmeter.

• 한국전기전자재료학회논문지
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• 제25권10호
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• pp.766-772
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• 2012

Spring supported piezoelectric cantilever structures (SPCS) were fabricated for vibration-based energy harvester application. We selected four elastic springs (A, B, C, and D type) as cantilever's supporter, each elastic spring has a different spring constant (S). The C type of SPCS ($S_C$: 4,649 N/m) showed a extremely low resonance frequency of 81 Hz along with the highest power output of 38.5 mW while the A type of SPCS ($S_A$: 40,629 N/m) didn't show a resonance frequency while. Therefore, it is considered that the lower spring constant lead to a lower resonance frequency of the SPCS. In addition, a tip mass (18 g) at one end of the SPCS could further reduce the resonance frequency without heavy degradation of power output.

• 대한기계학회논문집A
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• 제34권7호
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• pp.867-872
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• 2010

자연계에 존재하지만 사용되지 못 하고 버려지는 에너지를 효과적으로 채집하여 배터리를 충전하거나 전기 장치에 전기 에너지를 공급하는 에너지 하베스팅에 대한 연구를 수행하였다. 압전재료는 물체의 움직임이나 진동으로부터 에너지를 채집하는 주요한 재료로 널리 연구되고 있다. 본 논문에서는 기존의 PZT 압전 특성을 개량하고자 압전-복합재료 발전소자(Piezo-Composite Generating Element, 이하 PCGE)를 도입하여 성능 예측모델을 제안하고 이를 실험적으로 검증하였다. PCGE는 탄소/에폭시, PZT, 유리/에폭시 층으로 구성된다. 제작 과정에서 적층된 PCGE는 오토클레이브 안에서 $177^{\circ}C$의 온도에서 성형되는데, 이때 PCGE 내부에 초기잔류응력이 발생하게 되어 압전재료의 성능이 변화하게 된다. 세 종류의 PCGE를 제작한 후 에너지 채집 실험을 수행하여 제안된 성능 예측모델의 타당성과 기계적 진동을 전기적 에너지로 변환되는 성능을 검증하였다. 실험 결과 이론적인 성능 예측모델이 실험 결과와 잘 일치함을 확인하였다.

• 한국전기전자재료학회논문지
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• 제24권6호
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• pp.515-518
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• 2011

In this work, we designed and fabricated a multilayer thin film Pb(Zr,Ti)$O_3$ cantilever with a Si proof mass for low frequency vibration energy harvesting applications. A mathematical model of a mu lti-layer composite beam was derived and applied in a parametric analysis of the piezoelectric cantilever. Finally, the dimensions of the cantilever were determined for the resonant frequency of the cantilever. W e fabricated a device with beam dimensions of about 4,930 ${\mu}M$ ${\times}$ 450 ${\mu}M$ ${\times}$ 12 ${\mu}M$, and an integrated Si proof mass with dimensions of about 1,410 ${\mu}M$ ${\times}$ 450 ${\mu}M$ ${\times}$ 450 ${\mu}M$. The resonant frequency, maximum peak voltage, and highest average power of the cantilever device were 84.5 Hz, 88 mV, and 0.166 ${\mu}Wat$ 1.0 g and 23.7 ${\Omega}$, respectively. The dimensions of the cantilever were determined for the resonance frequency of the cantilever.

• 한국전기전자재료학회논문지
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• 제27권1호
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• pp.27-32
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• 2014

In this paper, PZT piezoelectric ceramic specimens with 4 compositions (Zr/Ti=50/50, 53/47, 56/44, 58/42) in $Pb(Zr,Ti)O_3$ system were fabricated. We studied effects of poling strength and thermal aging on the temperature characteristics of eletromechanical coupling factor k31 of the specimens, which were poled with the DC electric fields, 1.5, 2.5 and 3.5 kV/mm respectively and thermally aged for an hour at $200^{\circ}C$. The eletromechanical coupling factor k31 of the specimen with the composition Zr/Ti= 53/47, nearest to the morphotropic phase boundary decreased the most greatly, irrelevant to the intensity of poling field, due to 1st thermal aging. And the temperature coefficient of eletromechanical coupling factor k31 was (-) in the tetragonal phase composition and (+) in the rhombohedral phase composition, which is reverse in the temperature coefficient of resonance frequency. It is interesting that eletromechanical coupling factor k31 of PZT ceramics is shown to be able to increase as temperature increase in the interval $-20{\sim}80^{\circ}C$.