• Smart Structures and Systems
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• 제11권3호
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• pp.241-259
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• 2013

This paper presents the optimum load-speed diagram evaluation for a linear micromotor, including multitude cantilever piezoelectric bimorphs, briefly. Each microbeam in the mechanism can be actuated in both axial and flexural modes simultaneously. For this design, we consider quasi-static and linear conditions, and a relatively new numerical method called the smoothed finite element method (S-FEM) is introduced here. For this purpose, after finding an optimum volume fraction for piezoelectric layers through a standard numerical method such as quadratic finite element method, the relevant load-speed curves of the optimized micromotor are examined and compared by deterministic topology optimization (DTO) design. In this regard, to avoid the overly stiff behavior in FEM modeling, a numerical method known as the cell-based smoothed finite element method (CS-FEM, as a branch of S-FEM) is applied for our DTO problem. The topology optimization procedure to find the optimal design is implemented using a solid isotropic material with a penalization (SIMP) approximation and a method of moving asymptotes (MMA) optimizer. Because of the higher efficiency and accuracy of S-FEMs with respect to standard FEMs, the main micromotor characteristics of our final DTO design using a softer CS-FEM are substantially improved.

• 반도체디스플레이기술학회지
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• 제3권2호
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• pp.27-33
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• 2004

This paper is concerned with development of a micro tensile testing machine for optical functional materials such as single or poly crystal silicon and nickel film. Two micro tensile testers have been developed for various types of materials and dimensions. One of the testers is actuated by a PZT and the other is actuated by a servo motor for a precise displacement control. The specifications of PZT actuated micro tensile tester developed are as follows: the volumetric size of tester is desktop sized of 710$\times$200$\times$270 $mm^3$; the minimum load capacity and the load resolution in the load cell of 1N are 3 mN and 0.1 mN respectively; the full stroke and the stoke resolution of piezoelectric actuator are 1 mm and 10nm respectively. A special automatic specimen installing equipment is applied in order to prevent unexpected deformation and misalignment of specimens during handling of specimen for testing.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.82-88
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• 2006

In People usually think that smart materials and smart structures have not been developed until recent years. But those kinds of sensors have already been used for sensing damage in a variety of materials and structures. Two typical examples are piezoelectric materials (e.g., PZT) and electric strain gauges. Load cell is an example that utilizes the piezoelectric property to measure the change in physical quantities occurred by applied loads, while strain gauges are used to measure the deformation of compressive and tension members. The feasibility of using smart materials is realized for a monitoring technology when those sensors are used to monitor damages at inside or outsider of the structures. In this study, a fundamental study on the development of self diagnostic smart concrete using PZT, and unsaturated polyester electric resistance sensor.

• 한국정밀공학회지
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• 제23권3호
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• pp.163-170
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• 2006

Thin films play an important role in many technological applications including microelectronic devices, magnetic storage media, MEMS and surface coatings. It is well known that a thin film's material properties can be very different front the corresponding bulk properties and thus there has been a strong need for the development of a miniature tester to measure the mechanical properties of a thin film. Two testers are designed and set up in small size of 62 mm width, 20 mm depth and 90-120 mm height to fit in a chamber of scanning electron microscope (SEM). One tester has a homemade 0.2 N load cell and a low-priced electromagnetic actuator. The other has a commercial 5 N load cell, a $52{\mu}m$ piezoelectric actuator and some novel grips. Two types of 3.5 microns thick polysilicon specimen are tested to prove the testers' applicability. The strain is measured by the two ways. Firstly, it is measured by an ISDG system in the atmosphere far the reference. Secondly, the same test is repeated in a SEM chamber to monitor the strain as an in-situ experiment. The strain is evaluated by observing the gap change between two markers.

• 한국공간구조학회논문집
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• 제6권3호
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• pp.35-41
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• 2006

구조물의 모니터링과 손상 및 진동예측에 많은 센서들이 사용되고 있으며, 압전소자 및 변형게이지는 재료 및 구조물의 손상에 사용되고 있다. 그러나 진동에 대한 실험은 미진한 실정이다. 압전소자는 구조물의 변형되었을 때 로드셀의 경우에서처럼 작용되는 외력을 전기적인 신호로 바꾸어주는 센서이다. 이를 이용하여, 철근 콘크리트 판에서 진동예측을 압전소자의 전압변화로 사용하였다. 본 연구는 판에서 압전소자를 사용하여 진동을 예측하기 위한 기초적 연구이다.

• 한국태양에너지학회 논문집
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• 제39권1호
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• pp.51-58
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• 2019

This paper deals with the operation of a hybrid power generation system made with photovoltaic cells and piezoelectric materials. The system can produce power from the wind as well as from the sun subject to their availability. Irrespective of the largeness of their power production, the power developed by both generators (i.e., phtovoltaic cells and piezoelectric cells) were combined and stored before it was applied to a load. Especially, the AC power (current) developed from each piezoelectric generator was converted by a full wave bridge rectifier and then combined prior to its storage in a capacitor. It was observed that the system can produce a maximum output power of 6.49 mW at loading resistance of $100{\Omega}$.

• 비파괴검사학회지
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• 제12권4호
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• pp.9-17
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• 1993

Three types of piezoelectric sensors to detect acoustic emission signals were developed and characterized. Epicentral displacement and velocity of a plate to have infinite boundary were calculated by convolution between a Green's function and a simulated source time function to show parabolic rising characteristic. The sensor calibration system set up was composed of a steel plate, a glass capillary, an indentor and a load cell indicator The transient elastic signals were detected by the sensors. The results were compared with the theoretical results and Fast Fourier Transformed. As the results, the sensor fabricated using a disk shape of a piezoelectric PZT element showed resonant characteristics. The sensors fabricated using a conical shape PZT element and a PVDF polymer film showed the wide band characteristics for particle displacement and velocity, respectively. The calculated results showed good agreements with the transient responses in the cases of the wide band sensors and it was confirmed that the simulated source time function had been properly assumed.

• 한국해양공학회지
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• 제29권1호
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• pp.34-44
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• 2015

A hydraulic tensile test machine (HSTM) is one of the devices used to obtain the flow stress of a material during high-speed elongation. This paper first describes some features of a newly built HSTM. The improvement histories of the upper and lower jigs, which are the most vital parts of the HSTM, are also presented. We have frequently witnessed test failures with 1st generation jigs and specimens due to slip between the jig and specimen. 2nd generation jigs provide more stable test results, but the use of a longer upper jig induces excessive vibration and consequently makes it difficult to attach an environment chamber. 3rd generation jigs have some advances in terms of the symmetric fastening between the upper jig and specimen, as well as an exemption from direct contact between the lower jig and specimen. The performance of an environment chamber is verified by high and low temperature tests. A high-speed displacement measurement system is introduced based on a high-speed camera and motion-tracking software with aid of a surface grid device for the specimen.