• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.45-50
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• 2014

A vibration test coupon is prepared with nine plastic ball grid array packages on a printed circuit board using SnPb solders, and a random vibration test is conducted on the coupon. Life data from the test are analyzed, and it is shown that over the board, life data is location-dependent. For investigating this location dependency, a finite element model is developed and the equivalent stresses, which are defined based on the stress response functions at each node, are investigated. It is shown that one of the corner solder balls has the maximum equivalent stress at a package during the test. Finally, it is demonstrated that the maximum equivalent stress and durability life are inversely proportional.

• Tribology and Lubricants
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• v.30 no.3
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• pp.146-155
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• 2014

In this study, we conduct fretting corrosion tests on tin-plated brass coupons to investigate the effect of temperature on fretting corrosion for various span amplitudes. We prepare a coupled fretting corrosion specimens using a tin-plated brass coupon with a thickness of $10{\mu}m$. One specimen is a flat coupon and the other specimen is a coupon with a protuberance in 1 mm radius, which is produced using 2 mm diameter steel ball. We conduct fretting corrosion tests at $25^{\circ}C$, $50^{\circ}C$, $75^{\circ}C$, $100^{\circ}C$ by rubbing the coupled coupons together at the contact between the flat and protuberance coupons. We measure electric resistance of the contact during the fretting corrosion test period. There is increase in resistance with fretting cycles. It is found that rate of increase in electric resistance becomes faster with increase in testing temperature. Magnitude of friction coefficient increases with fretting span amplitudes. And, change in friction coefficient becomes desensitized to the increment in span amplitude. Assuming that failure cycle is the cycle with an electric resistance of $0.01{\Omega}$, we find that failure lifetime ($N_f$) decreases with increase in testing temperature. Furthermore, based on the assumption that the damage rate of the connector is inversely related to the failure cycle, we calculate the activation energy for fretting damage to be 13.6 kJ/mole by using the Arrhenius equation. We propose a method to predict failure cycle at different temperatures for span amplitudes below $30{\mu}m$. Friction coefficients generally increase with increase in span amplitude and decrease in testing temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.137-144
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• 2019

In coupon test of carbon fiber reinforced polymers (CFRP) as brittle materials, the converted strain derived from total deformation and effective length was introduced and its advantages were described. In general, measured value from strain gauge is used for determining the tensile properties of material, but it is not quite effective in CFRP because brittle material can not redistribute its stress and it only represents local behavior. For this reason, the converted strain response can be utilized effectively as a supplementary indicator, which evaluated the average value of tensile properties in brittle material and confirmed the strain measured by strain gauge. In addition, the converted strain clearly visualized 1) the effect of initial internal strain caused by fabrication errors and setup misalignment when applying gripping force and 2) post-response of partial rupture of CFRP caused by non-uniform strain distribution. non-uniform strain distribution.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.305-305
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• 2008

LTCC는 고주파영역에서 손실이 낮고 적층구조의 모듈제작이 가능하여 고주파용 모듈제작에 응용이 가능하다. 최근 수동소자가 내장된 ASM이나 FEM 등의 모듈은 그 집적도가 높고 기판의 두께가 감소함에 따라 소재의 고강도 특성이 요구되고 있다. 이와 같은 경향에 따라 Anorthite계 결정화 유리로 알려진 300MPa 이상의 고강도를 나타내는 CaO-Al2O3-SiO2계 소재가 선행 연구 과정을 통하여 개발되었다. 본 실험에서는 기 개발된 조성의 고강도 소재를 이용하여 RF부품에 적용하기 위한 테스트 쿠폰을 제작하였다. 고강도 소재를 이용하여 green sheet를 제조하고 수동소자인 R, L, C 등을 기판 내에 내장화 하기위해 LTCC 공정을 이용하여 각 층에 다양한 선폭 및 크기의 패턴을 인쇄한 뒤 적층하여 $900^{\circ}C$에서 소결하였다. 이 과정에서 공정에 대한 적용성이 각 공정별로 평가되었으며 완성된 테스트 쿠폰을 이용하여 소재의 전기적인 특성을 평가하였다.

• Asia Marketing Journal
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• v.13 no.3
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• pp.135-161
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• 2011

Social commerce is a more recent phenomenon and growing in number and size with the diffusion of social networking services. But it has not been studied as extensively. The purpose of this study is to investigate consumers' social commerce usage intention empirically. Using the theory of reasoned action suggested by Fishbein and Ajzen(1975), this study tests that perceived value created by social commerce affects social commerce usage intention. In this study, authors e identify to the conception of perceived value as a multidimensional construct, economic, psychology, and time value. This study is to analyze the effects of the value perceived by the consumer on attitude toward social commerce and the effects of the attitude and subjective norm on social commerce usage intention. Additionally, we examine the moderating role of coupon redemption effort in the relationship between attitude toward social commerce and usage intention. In order to evaluative the validity of the model, 258 questionnaires were collected from college students who frequently use SNS and accept new trend and technology using internet survey. All the instrument items used in this study were adapted from previous research and the data were analyzed using SPSS 18 and AMOS 7. This study proposed several hypotheses and conducted an experiment to test these hypotheses. Based on the data analysis results, it was found that economic and psychology value has significant effects on attitude toward the social commerce but time value had not the effect on attitude toward the social commerce. And the present study has also shown that both attitude toward the social commerce and subjective norm significantly influenced usage intention. This finding suggests that the theory of reasoned action effectively explains the social commerce usage intention. The result regarding the moderating effect of the coupon redemption effort has shown that the attitude toward social commerce and usage intention is moderated by consumer perception about coupon redemption.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.73-81
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• 2011

As high speed digital systems continue to use components with faster edge rate and clock speeds, transmission of the digital information, it can bring about many troubles. The increasing requirement for controlled impedance PCBs becomes both a critical success factor and a design challenge to implement a system. Especially, the noise sources in high frequency digital systems include the noise in power supply, ground and packaging, and they destroy the fidelity of signals. Therefore PCB design with impendence matching is needed to improve fidelity of signal in H/W. In this paper, we have developed an impedance control and analysis tool for multi-layer PCB design, and simulates the tracks controlled impedance with the test coupon. So, it can save the design time and support the economical PCB design.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.1
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• pp.28-39
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• 2016

This paper provides theoretical and experimental results to verify the crashworthiness of FH32 high-strength steel for arctic marine structures against ice impact. Assuming that side-shell structures of the Korean arctic research vessel, ARAON, with ice-notation PL10, collide with sheet ice, one-third-scale test specimens with a single transverse frame are manufactured. Impact-bending tests were conducted using a rigid steel striker that mimics sheet ice. Drop height was calculated by considering the speed at which sheet ice is rammed. Prior to impact-bending tests, tensile coupon tests were conducted at various temperatures. The impact-bending tests were carried out using test specimens fully fixed to the inside bottom frame of a cold chamber. The drop-weight velocity and test specimen deformation speed were measured using a high-speed camera and digital image correlation analysis (DICA). Numerical simulations were carried out under the same conditions as the impact-bending tests. The simulation results were in agreement with the test results, and strain rate was a key factor for the accuracy of numerical simulations.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.173-176
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• 2002

This paper describes the design procedure of composite parts for hingeless hub system of helicopter. These composite parts are composed of flexure and sleeve. The design of this composite flexure is an important technique in hingeless hub system since the rotor system stability and dynamic characteristics depends on this flexure characteristics. The objective of this research is to replace the existing metal hub parts with composite to improve the performance and stability. First, the coupon test of candidate composite material for hub parts was conducted. The hub parts was designed based on test results and the manufacturing possibility by using Fiber Placement System(FPS) was checked. Also the dynamic analysis and stress analysis of composite hub parts was conducted. Through this research, we will find out the possibility of replacing existing metal hub parts with composite.

• Journal of Power System Engineering
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• v.15 no.6
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• pp.5-10
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• 2011

A turbocharger is subjected to rapid temperature changes during thermal cyclic loads. In order to predict the thermo-mechanical failures, it's very important to estimate temperature distributions under the thermal shock test. This paper suggest the finite element techniques with the temperature histories, a constitutive material model and the mechanical constraints to calculate the thermal stresses and plastic strain distributions for the turbine housing. The first step was to develop a simple coupon approach to represent the failure mechanism of the classical design shapes and secondly applied the actual turbocharger to predict and validate the weak locations under the physical engine test.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.51-54
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• 2002

As digital systems continue to use components with faster edge rate and clock speeds, transmission of the digital information can take place many troubles. The increasing requirement for controlled impedance PCBs becomes both a critical success factor and a design challenge. Especially, the noise sources in digital system include the noise in power supply, ground and packaging due to simultaneous switching of signal, signal reflections and distortions on single and multiple transmission lines. This paper simulates the tracks controlled impedance with the test coupon. So, it can saves the design time and supports the economical PCB design.