• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.9
• /
• pp.881-886
• /
• 2009

This paper presents a manipulation system consisting of a coarse/fine XY positioning system and an out-of-plane manipulator. The object of the system is to conduct tine positioning and manipulation of micro parts. The fine stage and the out-of-plane manipulator have compliant mechanisms with flexure hinges, which are driven by stack-type piezoelectric elements. In the fine stage, the compliant mechanism plays the roles of motion guide and displacement amplification. The out-of-plane manipulator contains three piezo-driven compliant mechanisms for large working range and fine resolution. For large displacement, the compliant mechanism is implemented by a two-step displacement amplification mechanism. The compliant mechanisms are manufactured by wire electro-discharge machining for flexure hinges. Experiments demonstrate that the developed system is applicable to a fine positioning and fine manipulation of micro parts.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.567-570
• /
• 2000

Thermal simulation of typical stack-type and newly proposed planar-type micro-gas sensors were studied by FEM method. the thermal analysis for the proposed planar structure including temperature distribution over the sensing layer and power consumption of the heater were carried using finite element method by computer simulation and well compared with those of typical stack-type micro-gas sensor. The thermal properties of the microsensor from thermal simulation were compared with those of an actual device to investigate the acceptability of the computer simulation.

• Progress in Superconductivity and Cryogenics
• /
• v.16 no.2
• /
• pp.42-46
• /
• 2014

In this study we investigated ac transport current losses in the face to face stack for the anti-parallel current flow, and compared the electromagnetic properties with those of the single SC tape as well as those of the same stack for the parallel current path. The gap between the SC tapes in the stack varied in order to verify the electromagnetic influence of the neighbors when current flows in opposite direction, and the model was implemented in the finite element method program by the commercial software, COMSOL Multiphysics 4.2a. Conclusively speaking, the loss was remarkably decreased for the anti-parallel current case, which is attributed the magnetic flux compensation between the SC layers due to the opposite direction of the current flows. As the gap between SC tapes was increased, the loss mitigation became less effective. Besides, the current density distribution is very flat cross the sample width for the narrower gap case, which is believed to be benefit for the power electric system. These results are all in good agreement with those predicted theoretically for an infinite bifilar stack.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.12 no.4
• /
• pp.467-472
• /
• 2012

In this paper, we present a finite element method (FEM) study on the space charge effects in organic light emitting diodes. The physical model covers all the key physical processes in OLEDs, namely charge injection, transport and recombination, exciton diffusion, transfer and decay as well as light coupling, and thin-film-optics. The exciton model includes generation, diffusion, and energy transfer as well as annihilation. We assumed that the light emission originates from oscillation which thus is embodied as exciton in a stack of multilayer. We discuss the accumulation of charges at internal interfaces and their signature in the transient response as well as the electric field distribution. We also report our investigation on the influence of the insertion of the emission layer (EML) in the bilayer structure.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.10 s.103
• /
• pp.1211-1216
• /
• 2005

Underwater acoustic transducers are widely used for SONAR application, whose important design parameters are shapes. materials, dimensions and supporting structures. Practical design method of transducers consists of manufacturing, experiments and modifications so that it requires much time and expenses. In this study, an analytical method was developed for the Tonpilz type transducers using the commercial finite element analysis code ATILA which can solve the electro-mechanical coupling problems. A finite element model was established including the transducer elements such as ceramic stack, head mass, tail mass, tensile bolt, and molding layers. The proposed model was verified and modified by comparing the in-air and in-water test results of prototypes. The developed analysis method will be effectively used for the sensitivity analysis of design parameters in transducer design process.

• Journal of Korea Foundry Society
• /
• v.40 no.6
• /
• pp.146-150
• /
• 2020

In general, hot metal castings contract and molds expand during the cooling step of a casting process. Therefore, it is important to consider both the casting and mold at the same time in a casting process analysis. For a more accurate analysis that includes the contact characteristics, matching each node of the casting and mold in the contact area is recommended. However, it is very difficult to match the nodes of the casting and the mold when generating elements due to the geometric problem of CAD model data. The present study proposes a mesh generation technique that considers mechanical contact between the casting and the mold in a casting analysis (finite element analysis). The technique focuses on the fact that the mold surrounds the casting. After generating the 3D elements for the casting, the surface elements of the casting in contact with the mold are projected inside the mold to create contact elements that coincide with the contact surface of the casting. It was confirmed that high-quality contact element information and a 3D element net can be automatically generated by the method proposed in this study.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.1407-1413
• /
• 2011

This paper studied on the VVVF Inverter for 1C4M propulsion system of railway traction. The paper includes the comparison along a VVVF Inverter electric power conversion element for an electric railcar(GTO, IGBT). These inverters are composed of high power IGBTs and controlled by compact control units. The stack is simplified and optimized by using plate bus and IGBT driver units of hybrid-type.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.1576-1577
• /
• 2007

As a intelligent valve piezoelectric valve is to applied to various fields of application. Piezoelectric valves have fast response time and good linearity for pressure control but its hysteresis displacement by its stack actuator influences on pressure control in electro-hydraulic braking. Solenoid valves are traditional element to control hydraulic pressure but this paper proposes piezoelectric valve for brake pressure control with hysteresis compensation.

• Advances in Automotive Engineering
• /
• v.1 no.1
• /
• pp.41-59
• /
• 2018

In the study, investigation of fiber- reinforced composite materials that can be an alternative to conventional steel was performed by finite element analysis with the help of software. Steel and composite materials have been studied on a four axle truck chassis model. Three-dimensional finite element model was created with software, and then analyzes were performed. The analyses were performed for static and dynamic/fatigue cases. Fatigue cases are formed with the help of design spectra model and fatigue analyses were performed as static analyses with this design spectra. First, analyses were performed for steel and after that optimization analyses were made for the AS4-PEEK carbon fiber composite and Eglass-Epoxy fiber composite materials. Optimization of composite material analyzes include determining the total laminate thickness, thickness of each ply, orientation of each ply and ply stacking sequence. Analyzes were made according to macro mechanical properties of composite, micromechanics case has not been considered. Improvements in weight reduction up to %50 provided at the end of the composite optimization analyzes with satisfying stiffness performance of chassis. Fatigue strength of the composite structure depends on various factors such as, fiber orientation, ply thickness, ply stack sequence, fiber ductility, ductility of the matrix, loading angle. Therefore, the accuracy of theoretical calculations and analyzes should be correlated by testing.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.3
• /
• pp.199-206
• /
• 2015

This paper deals with the vibration characteristics of stacked transducers composed of piezoelectric discs, which are main elements of ultrasonic sensors or actuators. The stacked transducers were devised in the sense of natural frequencies. Two- or three-layer transducers were fabricated with piezoelectric discs of different diameters. The natural frequencies were determined by the finite element analysis and they were verified by comparing them with experimental results. It appeared that the natural frequencies of the stacked piezoelectric transducers include the natural frequencies of the constituent piezoelectric discs and the natural frequencies caused by stacking. Based on these results, it would be possible to predict the vibration characteristics of the stacked piezoelectric transducers in a design process.