• Structural Engineering and Mechanics
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• v.66 no.6
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• pp.729-736
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• 2018

This paper studies thermal buckling and post-buckling behaviors of functionally graded materials (FGM) tubes subjected to a uniform temperature rise and resting on elastic foundations via a refined beam model. Compared to the Timoshenko beam theory, the number of unknowns of this model are the same and no correction factors are required. The material properties of the FGM tube vary continuously in the radial direction according to a power function. Two ends of the tube are assumed to be simply supported and in-plane boundary conditions are immovable. Energy variation principle is employed to establish the governing equations. A two-step perturbation method is adopted to determine the critical thermal buckling loads and post-buckling paths of the tubes with arbitrary radial non-homogeneity. Through detailed parametric studies, it can be found that the tube has much higher buckling temperature and post-buckling strength when it is supported by an elastic foundation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.21-24
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• 2007

This paper deals with introduction of testing equipments for the evaluation of dynamic tensile characteristics of auto-body steel sheets and the crashworthiness of auto-body members. The servo-hydraulic high speed material testing machine was developed for tensile tests at the intermediate strain rate to obtain the tensile material properties at the strain rate under 500/sec. The split Hopkinson bar apparatus using the elastic wave was developed for dynamic material characteristics at the high strain rate ranged from 1,000 to 10,000/sec. The servo-hydraulic high speed crash testing machine is the equipment for the evaluation of the collapse load and crashworthiness of auto-body members. High speed carrying truck crashes to specimen with the maximum velocity of 17 m/sec.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.585-588
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• 2002

The USM uses friction between a mobile part (rotor) and a vibration part(stator), which is different from the principle of the conventional motor based on the interaction of electric and magnetic fields. In this thesis, a flat-type $L_1-B_8$ mode USM was designed and fabricated the characteristics of an ultrasonic vibration. The results of fabricated USM are as follows: (1) In case of ultrasonic motor with elastic-body of stainless, when applied voltage, frequency, pressing force of rotor were 50 [V], 27.9 [kHz], 1.5 [N], 5.0[mN m] respectively, the speed of revolution could be presented up to 0 [cm/s]. (2) In case of ultrasonic motor with elastic-body of brass, when applied voltage, frequency, pressing force of rotor were 50 [V], 21.4 [kHz], 1.5 [N], 1.4[mN m]respectively, the speed of rotor revolution was presented up to 0 [cm/s]. (3) The USM of elastic-body of stainless showing 1.17[%], somewhat low, in the maximum efficiency according to torque was superior to the USM of elastic-body of brass showing 0.34 [%]. The Flat-type $L_1-B_8$ mode USM had characteristics of typical drooping torque-speed, large torque and high speed, and operating in both directions by phase reversal.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.1
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• pp.1-6
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• 2015

Generating output characteristics of a ${\pi}$-type piezoelectric harvester depending on size of the ceramic and the elastic body were studied. The ${\pi}$-type piezoelectric harvester consists of a rectangular piezoelectric ceramic and a ${\pi}$ shaped elastic body. If the tensions is applied at both ends of an elastic body legs, the piezoelectric effect occurs at the ceramics through the form change of the elastic body. The structure of this ${\pi}$-type harvester can be used in a various area than an existing type generator, because it prevent from direct pressure to the ceramic. Generating characteristics of the harvester were analyzed by using finite element method program. The piezoelectric harvester was fabricated on the basis of analyzed results and attached on a frequency controllable vibrator to measure the output characteristics. And generating characteristics were defined by comparing analysis results and experimental results. The highest output voltage was obtained when the ceramic length, thickness were 20 mm, 0.5 mm in the analysis result. And experiment was performed by analysis results at low frequency region, output voltage was generated about 6 V.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.8
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• pp.635-639
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• 2013

Generating output characteristics of a EYE-type piezoelectric generator depending on ceramic size and materials of the elastic body were studied. EYE-type piezoelectric-generating device consist of the ceramic was attached between the both elastic body. piezoelectric-generating is that if the tension occurred at both ends of an elastic body, the piezoelectric effect occurs at ceramics through the form change of the elastic body. The structure of this EYE-type generator use various area. than a existing type generator, because the ceramic position of the directly force at does not apply. Resonance and output characteristics of the generator were analyzed by using FEM program. Generators were fabricated on the basis of analyzed results and attached on a frequency controllable vibrator to measure output characteristics. Also, the experimental results were compared with the simulated results. As a result, output characteristics of the generator increased depending on the increase in ceramic thickness. In case of increase in ceramic width, resonance frequency of the generator also decreased.

• Structural Engineering and Mechanics
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• v.57 no.5
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• pp.897-920
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• 2016

The objective is to determine the mechanical properties of the composites formed in two types, theoretically. The first composite includes micro-particles in a matrix while the second involves long, thin fibers. A fictitious, homogeneous, linear-elastic and isotropic single material named as effective material is considered during calculation which is based on the equality of the strain energies of the composite and effective material under the same loading conditions. The procedure is carried out with volume integrals considering a unique strain energy in a body. Particularly, the effective elastic shear modulus has been calculated exactly for small-particle composites by the same procedure in order to determine of bulk modulus thereof. Additionally, the transverse shear modulus of fiber reinforced composites has been obtained through a simple approach leading to the practical equation. The results have been compared not only with the outcomes in the literature obtained by different method but also with those of finite element analysis performed in this study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.231-234
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• 1998

In this study, the wind-mill type ultrasonic motor was fabricated, and then resonant frequency and vibration velocity characteristics of the stator were measured. Brass metal was pressed with umbrella-type using metal mold, then slot of 4 kind was processed in each of thickness. Among sixteen's stators, resonant frequency on vibration velocity was decreased remarkably in stator of higher resonant point, but resonant frequency on vibration velocity wasn't almost changed at lower resonant point of stator. The thickener thickness of elastic body, vibration velocity was decreased. The more slot of elastic body, vibration velocity was increased Applied voltage was changed from 10$V_{max}$ to 100$V_{max}$. Maximum vibration velocity value was 2.0[m/s].

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1365-1381
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• 2023

In this paper, a procedure for evaluating the structural integrity of the PCSG (Printed Circuit Steam Generator) unit block is presented with a simplified FE (finite element) analysis technique by applying the homogenization method. The homogenization method converts an inhomogeneous elastic body into a homogeneous elastic body with same mechanical behaviour. This method is effective when the inhomogeneous elastic body has repetitive microstructures, and thus the method was applied to the sheet assembly among the PCSG unit block components. From the method, the homogenized equivalent elastic constants of the sheet assembly were derived. The validity of the determined material properties was verified by comparing the mechanical behaviour with the reference model. Thermo-mechanical analysis was then performed to evaluate the structural integrity of the PCSG unit block, and it was found that the contact region between the steam header and the sheet assembly is a critical point where large bending stress occurs due to the temperature difference.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.33-38
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• 2013

In this study, both a finite element analysis and an experimental analysis are executed to investigate the mechanical characteristics of dielectric material effects on warpage. Also, viscoelastic material properties are measured by DMA and are considered in warpage simulation. A finite element analysis is done by using both thermal elastic analysis and a thermo-viscoelastic analysis to predict the nonlinear effects. For experimental study, specimens warpage of non-symmetric structure with body size of $22.5{\times}22.5$ mm, $37.5{\times}37.5$ mm and $42.5{\times}42.5$ mm are measured under the reflow temperature condition. From the analysis results, experimental warpage is not similar to FEA results using thermal elastic analysis but similar to FEA results using thermo-viscoelastic analysis. Also, its effect on substrate warpage is increased as core thickness is decreased and body size is getting larger. These FEA and the experimental results show that the nonlinear characteristics of dielectric material play an important role on substrate warpage. Therefore, it is strongly recommended that non-linear behavior characteristics of a dielectric material should be considered to control warpage of FCBGA substrate under conditions of geometry, structure and manufacturing process and so on.

• Journal of the Ergonomics Society of Korea
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• v.31 no.3
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• pp.455-461
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• 2012

The aim of this study was to investigate the appropriate elasticity of the textile material used for making women's girdle. Background: The elastic textiles have been used for making girdle. The hard type girdle gave high pressure on the body to make slim look. However, excessively high garment pressure caused negative effect to human bodies. This study studied the material giving proper garment pressure in girdle. Method: In this study five experimental girdles were made fabrics with various elasticities. The change of garment pressures and body girths were measured after subjects wearing the experimental girdles. The garment pressure was measured at 10 points. Body girths measured at abdomen, hip, and thigh. Results: The garment pressure of the commercial girdle was high at side of waistband, side femur and back gluteal fold. The experimental girdles made with high elasticity material definitely lowered garment pressure at those points. After wearing experimental girdle their abdomen and hip girths measurements were decreased. But, thigh girth was not reduced. Conclusion: The girdle made with excellent elasticity materials reduced garment pressure significantly and it made body slim as much as the commercial girdle except the thighs. Application: This study provides guideline for the developing girdle that applying optimum range of garment pressure with body slim effect.