• Proceedings of the KWS Conference
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• 2002.10a
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• pp.439-449
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• 2002

This paper reviews our recent research works on the interconnection technologies in electronic packaging and assembly. At the aspect of advanced joining methods, laser-ultrasonic fluxless soldering technology was proposed. The characteristic of this technology is that the oxide film was removed through the vibration excitated by high frequency laser change in the molten solder droplet. Application researches of laser soldering technology on solder bumping of BGA packages were carried out. Furthermore, interfacial reaction between SnPb eutectic solder and Au/Ni/Cu pad during laser reflow was analyzed. At the aspect of soldered joints' reliability, the system for predicting and analyzing SMT solder joint shape and reliability(PSAR) has been designed. Optimization design method of soldered joints' structure was brought forward after the investigation of fatigue failure of RC chip devices and BGA packages under temperature cyclic conditions with FEM analysis and experimental study. At the aspect of solder alloy design, alloy design method based on quantum was proposed. The macroproperties such as melting point, wettability and strength were described by the electron parameters. In this way, a great deal of the experimental investigations was replaced, so as to realize the design and research of any kinds of solder alloys with low cost and high efficiency.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.44-50
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• 2010

Structural vibration is a significant problem in many multi-part or multi-component assemblies. In aircraft industry, structures are composed of various fasteners, such as bolts, snap, hinge, weld or other fastener or connector (collectively "fasteners"). Due to these, prediction and design involving dynamic characteristics is quite complicated. However, the current state of the art does not provide an analytical tool to effectively predict structure's dynamic characteristics, because consideration of structural uncertainties (i.e. material properties, geometric tolerance, dimensional tolerance, environment and so on) is difficult and very small fasteners in the structure cause a huge amount of analysis time to predict dynamic characteristics using the FEM (finite element method). In this study, to resolve the current state of the art, a new approach is proposed using the FEM and probabilistic analysis. Firstly, equivalent elements are developed using simple element (e.g. bar, beam, mass) to replace fasteners' finite element model. Developed equivalent elements enable to explain static behavior and dynamic behavior of the structure. Secondly, probabilistic analysis is applied to evaluate the PDF (probability density function) of dynamic characteristics due to tolerance, material properties and so on. MCS (Monte-Carlo simulation) is employed for this. Proposed methodology offers efficiency of dynamic analysis and reality of the field as well. Simple plates joined by fasteners are taken as an example to illustrate the proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.165-171
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• 2016

A prosthetic knee for above-knee (AK) amputee is categorized into passive and active type. The passive prosthetic knee is generally made by elastic material. Although AK amputee can easily walk by using passive prosthetic leg, knee joint motions are not similar to ordinary persons. The active prosthetic leg can control the knee angle owing to the actuator and microprocessor. However, the active type is not cost-effective and the stability may be lost due to the malfunction of sensors. In order to resolve these disadvantages of passive and active type, a semi-active prosthetic knee which can control the knee angle is proposed in this work. The proposed semi-active one requires a less input energy but provides active type performance. In order to achieve this goal, in this work, a semi-active prosthetic knee using magneto-rheological (MR) damper for AK amputees is designed. The MR damper can support the weight of body by using less energy than actuator of active prosthetic. It can control knee angle by inducing the magnetic field at the time of stance phase. This salient characteristic is evaluated and presented in this work.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.151-159
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• 2003

The front 2 pieces of the 3-piece steel propeller shaft installed on a 8.5-ton truck were redesigned with a 1 -piece composite propeller shaft with steel yokes and spline parts to get the reduction of weight and the improvement of NVH characteristics. Based on the analysis of bending vibration, strength and cure-induced residual stresses of the composite propeller shaft, proper composite materials and stacking sequences were selected. The composite propeller shaft requires a reliable joining method between the shaft and steel end parts through a steel connector. From 3-D contact stress analyses of the laminated composite shaft with bolted Joints, the 3-row mechanical joint which satisfies the torque transmission capability has been designed. Several full-scale composite shafts were fabricated and tested to verify the design analyses. The design requirements are shown to be satisfied. With the newly designed composite shaft, the weight reduction more than 50% and improvements in NVH characteristics have been achieved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.276-280
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• 2020

A linear piezoelectric actuator that utilizes the elliptical motion of the two tips of the actuator is proposed. This device is easy to fabricate owing to its simple structure, consisting of three piezo ceramic benders and is suitable for use in micro robotic applications. A π-shaped structure, which was composed of four piezo ceramic benders, was constructed. Two of the benders were positioned on the center of the actuator, and the joints were attached at the ends of the cantilever. The other two benders were positioned on the side of the actuator and were attached between the joint and the tips. The actuator structure was designed to obtain the first bending mode of the horizontal vibration and the vertical vibration at the same frequency, resulting in elliptical motions at the tips. When two sinusoidal wave voltages with a 90-degree phase difference were applied to the two pairs of the actuator benders, elliptical motions were obtained at the tips. The driving characteristics of the prototype actuator were then measured using a laser doppler vibrometer.

• Structural Monitoring and Maintenance
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• v.3 no.4
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• pp.395-406
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• 2016

Modal parameter identification has received much attention recently for their usefulness in earthquake engineering, damage detection and structural health monitoring. The identification method based on Matrix Pencil technique is adopted in this paper to identify structural modal parameters, such as natural frequencies, damping ratios and modal shapes using impulse vibration responses. This method can also be applied to dynamic responses induced by stationary and white-noise inputs since the auto- and cross-correlation function of the two outputs has the same form as the impulse response dynamic functions. Matrix Pencil method is very robust to noise contained in the measurement data. It has a lower variance of estimates of the parameters of interest than the Polynomial Method, and is also computationally more efficient. The numerical simulation results show that this technique can identify modal parameters accurately even if the noise level is high.

• Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.312-321
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• 2016

Dynamic behaviour of a slider-crank mechanism associated with a smart flexible connecting rod is investigated. Effect of various mechanisms' parameters including crank length, flexibility of the connecting rod and the slider's mass on the dynamic behaviour is studied. Two control schemes are proposed for elastodynamic vibration suppression of the flexible connecting rod and also obtaining a constant angular velocity for the crank. The first scheme is based on feedback linearization approach and the second one is based on a sliding mode controller. The input signals are applied by an electric motor located at the crank ground joint, and two layers of piezoelectric film bonded to the top and bottom surfaces of the connecting rod. Both of the controllers successfully suppress the vibrations of the elastic linkage.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.295-302
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• 2000

Slab guideway, surface treatment, heat line installation, and joint connection for Automated Guideway Transit with rubber tire are researched. While the AGT with rubber tire is constructed in city, the precast slab guideway must be considered a reduction of the construction period and the noise under construction. which related with environment. To do that, a basic design and the structural analysis for the precast slab guideway with rubber tire are studied. The surface treatment and the heat line installation of that are also compared with currently used methods. Tining method is applied to the surface treatment adopted from the concrete pavement application currently in use. The connection method between the slab of bridge and precast guideway are suggested with a bolt type and a bond type. To minimize noise and vibration of the connection while the AGT is in driving, the slop connection method can be enhanced the serviceability.

• Journal of Korean Association for Spatial Structures
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• v.19 no.1
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• pp.37-44
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• 2019

Yangjindang house, which is located in Sang-ju province of South Korea, is one of the special Hanok structures dated back to Joseon dynasty. This study aims to examine structural safety of the Yangjindang wood frame building considering dynamic parameters such as the natural frequency and damping ratio. The numerical model of the wood frame building is implemented using Midas Gen, especially the wood joint where column and beam were connected. The behavior of the actual frame building was compared with the modeling results. In addition, structure responses such as shear force, axial force, flexural moment and deflections were calculated and compared with the allowable limits. Numerical results show that, generally, despite of some local members shear failure, Yangjindang's structural response does not exceed the limitation according to current standards.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.415-426
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• 2007

In a link motion punch press, numerous links are interconnected and each link executes a constrained motion at high speed. As a consequence, dynamic unbalance force and moment are transmitted to the main frame of the press, which results in unwanted vibration. This degrades productivity and precise stamping work of the press. This paper presents an effective method for reducing dynamic unbalance in a link motion punch press based upon kinematic and dynamic analyses. Firstly, the kinematic analysis is carried out in order to understand the fundamental characteristics of the link motion mechanism. Then design variable approach is presented in order to automate the model setup for the mechanism whenever design changes are necessary. To obtain the inertia properties of the links such as mass, mass moment of inertia, and the center of mass, 3-dimensional CAD software was utilized. Dynamic simulations were carried out for various combinations of design changes on some links having significant influences on kinematic and dynamic behavior of the mechanism.