• Journal of Welding and Joining
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• v.16 no.4
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• pp.92-97
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• 1998

Because of the low melting temperature of solder, each temperature cycle initiates an irrecoverable creep deformation at the solder interconnection which connects the package body with the PCB. The crack starts and propagates from the position where the creep deformation is maximized. This work has tried to compare and analyze the thermal fatigue life of solder interconnection which is affected by the lead material, the size of die pad, chip thickness, and interface delamination of 48-Pin TSOP under the temperature cycle ($0^{\circ}C$~1$25^{\circ}C$). The crack initiation position and thermal fatigue life which are calculated by using FEA method are well matched with the results of experiments. The thermal Fatigue life of copper lead frame is extended around 3.6 times longer than that of alloy 42 lead frame. It is maximized when the chip size is matched with the length of the lead. It tends to be extended as the thickness of chip got thinner. As the interfacial delamination between die pad and EMC is increased, the thermal fatigue life tends to decrease in the beginning of delamination, and increase after the delamination grew after 45% of the length of die pad.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.3
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• pp.248-254
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• 2015

The strength and fatigue life of Satin and Twill-woven CF/epoxy composite(CFRP) have been investigated. Damage mechanism fatigue method has been used to assess fatigue damage accumulation. It is based on measured residual stiffness and residual strength of carbon-fiber reinforced plastic(CFRP) laminates under cyclic loading. Fatigue damage evolution in composite laminates and predict fatigue life of the laminates were simulated by finite element analysis(FEA) method. The stress analysis was carried out in MSC patran/Nastran. A modified Hashin's failure criterion di rmfjapplied to predict the failure of the experimental data of fatigue life but a Ye-delamination criterion was ignored because of 2D modeling. Almost linear stiffness and strength degradation were observed during most of the fatigue process. These stress distribution data were adopted in the simulation to simulate fatigue behavior and estimate life of the laminates. From the results, the predicted fatigue life is more conservatively estimated than the experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.537-544
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• 2015

This paper provided two types of design method on moving core type LOA and one type of design method on moving coil type LOA, and compared and examined each of its characteristics. In order to conduct parametric design process, voltage equation was used to schematize Lmin/K and L/M map, and the schematized map was used to determine Lmin, K or L, M. In order to meet requirements such as thrust force and input voltage and to satisfy the target values of Lmin, K or L, M, the types and sizes of each type were designed using geometry design process. 2-FEA was conducted for each of the designed model. After examining thrust force based on the location of the mover, Type-1 showed radical change in thrust force as movers moved, and Type-2 and Type-3 showed constant appearance of thrust force. The total volume of the designed LOA model was compared to select the model with highest thrust force density. Also, the weight of the mover for each model was compared in order to select the model that was predicted to have highest mechanical responsiveness and stroke characteristics.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.91-98
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• 2014

In this study, the first and second electronically controlled cooling systems for a bimodal tram were developed. The performance characteristics of the cooling systems were assessed experimentally with actual and identical conditions, and a simulation was run using ANSYS Fluent. The results of the experimental and FEA method were standardized. In order to confirm the reliability of the experimental method, the experiment was carried out by a testing institution. The low-volume flow-rate condition was found to be better, but the cooling system performed in a minimal condition. Therefore, it is important to find the optimum performance levels. The cooling system equipment was revised to determine the optimized design parameters, after which the cooling performance levels increased at the radiation area. Specifically, with a greater fan diameter. Through this study, the newly developed cooling system will be reevaluated after being mounted on an actual bimodal tram. This will lead to a completely domestically produced bi-modal tram cooling system.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.2
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• pp.144-150
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• 2008

Ships and offshore structures are exposed to wave and engine excitation loadings during navigation and cargo/ballasting operations. These excessive loads may cause damages to hull and may result loss of life the ship. Therefore, it is important to develop a system that allow accurate measurements of global hull loads. The objective of the study is developing a fiber optic monitoring system that is capable of monitoring, recording and warning of the vessel performance. A method for measurement of global loads on a vessel, using strain measurements from a network of fiber optic strain sensors and extensive finite-element analyses(FEA) with idealistic load cases, is presented. The method has been successfully validated on the idealized ship structure model with strain sensors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.10
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• pp.24-33
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• 2008

Optimal design of the direct-driven PM Wind Generator, combined with DEAS(Dynamic Encoding Algorithm for Searches) and FEM(Finite Element Method), has been proposed to maximize the Annual Energy Production(AEP) over the whole wind speed characterized by the statistical model of wind speed distribution. In particular, DEAS contributes to reducing the excessive computing time for the optimization process.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.38-40
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• 2009

In order to achieve a gearless construction of the wind energy conversion system(WECS), a low-speed generator should be used. Of the various candidate machine types, radial-field, multi-pole, permanent magnet, synchronous machines may be used for low-speed applications. So, this paper deals with the design of direct-coupled, multi-pole radial field machines with permanent magnet(PM) excitation for wind power applications for cogging torque reduction through the determination of optimum pole arc/pitch ratio. On the basis of an equivalent magnetic circuit method(EMCM) and a space harmonic method(SHM), an initial design is performed considering restricted conditions. And then, a detailed design is made using a non-linear finite element analyses(FEA). Finally, test results concerning generating characteristics are given to confirm the validation of the design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.6
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• pp.1004-1014
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• 2001

The fully automatic algorithm from initial finite element mesh generation to remeshing in two dimensional geometry is introduced using bubble packing method (BPM) for finite element analysis. BPM determines the node placement by force-balancing configuration of bubbles and the triangular meshes are made by Delaunay triangulation with advancing front concept. In BPM, we suggest two node-search algorithms and the adaptive/recursive bubble controls to search the optimal nodal position. To use the automatically generated mesh information in FEA, the new enhanced bandwidth minimization scheme with high efficiency in CPU time is developed. In the remeshing stage, the mesh refinement is incorporated by the control of bubble size using two parameters. And Superconvergent Patch Recovery (SPR) technique is used for error estimation. To verify the capability of this algorithm, we consider two elasticity problems, one is the bending problem of short cantilever beam and the tension problem of infinite plate with hole. The numerical results indicate that the algorithm by BPM is able to refine the mesh based on a posteriori error and control the mesh size easily by two parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.676-681
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• 2001

We usually divide the noise of exhaust system into pulsation noise and flow noise. Pulsation noise is the shock wave to occur when the burning gas of low pressure emits and include harmonic having basic frequency as the exhaust cycle of engine. Flow noise is the noise that is produced when gas flow emits into the atmosphere through the pipe and has the character of frequency like pink noise which has the high level of high frequency component. A muffler is divided into reflective type and absorptive type. We usually use the muffler compounding the property of them. In this study, it is the case of transfer matrix method that a muffler is compounded to analyze the elements of each section according to sound wave's proceed direction. But we use simple model. So, we use finite element method that takes short time to analyze. Acoustic analysis gives us transfer matrix to use FEA of SYSNOISE and we use STAR-CD for fluid analysis. We made database that is based on analytical results about the muffler of expansion type, extended type, offset type, reverse type, and perforated type and developed the muffler design system to perform work efficiently.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.96-96
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• 2009

The purpose of this study is to clarify the transitional behavior and main factor of excessive welding distortion caused by fabrication process of STS 304 vacuum vessel having double curvature for the efficient quality control of vacuum vessel. In order to do it, the predictive equations of the welding distortion in simple weldment of vacuum vessel were established by conventional finite element analysis. And the principal factor controlling the welding distortion was identified by evaluating the welding distortion of vacuum vessel in each fabrication process with FEA and simplified thermo elastic method. Based on the results, the principal factors of distortion of vacuum vessel were clarified as angular distortion and transverse shrinkage which are a source of excessive out-of plane distortion in the double curved vacuum vessel. It was expected that the FE analysis results of this study could contribute to establish the proper control method of welding distortion for double curved vacuum vessel.