• Composites Research
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• v.16 no.1
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• pp.1-12
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• 2003

This study developed SiC$_{p}$/A1$_2$O$_3$$_{f}$/Al composites for electronic packaging to which reinforcements were added with the volume fractions of 49%, 56% and 63% by the squeeze casting method. 0.8 wt. % of the inorganic binder as well as the A1$_2$O$_3$ fiber and SiC Particles with the volume fraction of 1:10 were added to the composites, which were produced in the newly designed mold. For the produced SiC/Al composites, the CTEs (coefficients of thermal expansion) were measured from 30 to 300 and compared with the FEM numerical simulation to analyze the temperature dependent properties. The experiment showed the CTEs of SiC$_{p}$/A1$_2$O$_3$$_{f}$/Al composites that were intermediate values of those of Rule of Mixture and Turner's Model. The CTEs were close to Turner's Model in the room temperature and approached the Rule of Mixture as the temperature increases. These properties analyzed from the difference of the average stress acting between the matrix and the reinforcements proposed in this study.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.303-306
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• 1994

Fundamental characteristics of giant magnetostrictive alloy $Terfenol-D(Tb_{0.3}Dy_{0.7}Fe_{1.9~1.95})$ are rreasured and discussed on the application for actuators. The magnetostriction is measured by laser displacement rreasuring system and the applied compressive stress is measured by load cell. Magnetostrictions increased as the applied compressive stresses increased. When the stress is 7 MPa, the magnetostriction is 1000 ppm at 1500 Oe. As the stresses iocreased from 0 to 14 MPa, the magnetic fields for saturating the magnetostriction also increased. The temperature increased during the experiment is $0.3^{\circ}C$, so the thermal expansion is negligible in these experirrents. The feedback or temperature control function should be added for the precise position control actuator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.216-216
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• 2004

본 논문은 우리가 일상 생활에서 접하는 에어컨의 핵심 부품인 열 교환기의 제작과정 중에서 확관 공정에서의 확관속도 최적화에 관한 것이다 여기서 열 교환기는 구멍 뚫린 박판형태의 방열핀과 이 구멍을 통과하는 구리재질의 관인 헤어핀의 2가지 주요 부품으로 구성되어있다 그리고 확관기(Fig. 1)에 있어서의 확관공정은 Fig. 2에서 보는 바와 같이 소성변형을 통한 관의 반지름 방향의 팽창으로 방열핀과 헤어핀을 결합시켜주는 높은 정밀도를 요구하는 작업이다.(중략)

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.1
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• pp.47-58
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• 2020

The interest in the use of shield TBM (Tunnel Boring Machine) on the tunnel excavation has been increased rapidly in Korea. The shield TBM tunnel is generally designed as non-drainage tunnel. Consequently, if water leakage through the segment joints happens, big problems on the usage and stability of tunnel can be occurred. In this study, the variation of waterproof capacity of hydrophilic rubber waterstop by the construction error and excessive displacement of segment was studied. In particular, the waterproof capacity of each of single and double layer arrangements of hydrophilic rubber waterstop was examined to verify the efficiency of the double layer arrangement. The test results show that the single layer and double layer hydrophilic rubber waterstop showed the same waterproof performance. hydrophilic rubber waterstop has favorable on the offset, however unfavorable on the gap.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.893-899
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• 2015

In the design of injection molds, the temperature distribution and deformation of the mold is one of the most important parameters that affect the flow characteristics, flash generation, and surface appearance, etc. Plastic injection analyses have been carried out to predict the temperature distribution of the mold and the pressure distribution on the cavity surface. As the input loads, we transfer the temperature and pressure results to the structural analysis. We compare the structural analysis results with the thermal expansion effect using the actual flash and step size of a smartphone cover part. To reduce the flash problem, we proposed a new mold design, and verified the results by performing simulations.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.137-138
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• 2012

박막태양전지의 경우 기판재와 태양전지를 구성하는 반도체 층간의 열팽창 거동 차이가 태양전지의 변형을 야기한다. 이러한 열변형은 태양전지의 효율에 영향을 주는 것으로 알려져 있다. 그러므로 태양전지를 구성하는 반도체 층과 열팽창 거동이 유사한 기판재의 적용이 필요하다. 본 연구에서는 연성 CIGS 태양전지를 구성하는 기판과 박막층의 두께변화가 열공정 중 발생하는 잔류응력에 미치는 영향을 전산해석 하고자 하였다. 전산해석 결과 Fe-52wt%Ni 기판재의 두께가 증가함에 따라 CIGS 박막층 내부의 잔류응력은 감소하였다. SiO2 절연층의 두께가 증가하면 CIGS 박막층의 잔류응력이 증가하였다. Mo 후면전극층이 얇아지면 잔류응력이 감소하였으나 CIGS층의 두께변화는 CIGS층의 잔류응력에 큰 영향을 미치지 않았다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.21-26
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• 2003

In this research, the change of coefficient of thermal expansion (CTE) of graphite/epoxy composite laminate under space environment was measured using fiber optic sensors. Two fiber Bragg grating (FBG) sensors have been adopted for the simultaneous measurement of thermal strain and temperature. Low Earth Orbit (LEO) conditions with high vacuum, ultraviolet and thermal cycling environments were simulated in a thermal vacuum chamber. As a pre-test, a FBG temperature sensor was calibrated and a FBG strain sensor was verified through the comparison with the electric strain gauge (ESG) attached on an aluminun specimen at high and low temperature respectively. The change of the CTE in a composite laminate exposed to space environment was measured for intervals of aging cycles in real time. As a whole, there was no abrupt change of the CTE after 1000 aging cycles. After aging, however, the CTE decreased a Little all over the test temperature range. These changes are caused by outgassing, moisture desorption, matrix cracking etc.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1049-1056
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• 2014

Microelectronics components contain various materials with different coefficients of thermal expansion (CTE). Although a large amount of published data on the CTE of standard materials is available, it occasionally becomes necessary to measure this property for a specific actual material over a particular temperature range. A change in the temperature of a material causes a corresponding change in the output of the strain gage installed on the specimen because of not only the mechanical load but also the temperature change. In this paper, a detailed technique for CTE measurement based on these thermal characteristics of strain gages is proposed and its reliability is evaluated. A steel specimen, aluminum specimen, and copper specimen, whose CTE values are well known, were used in this evaluation. The proposed technique was successfully applied to the measurement of the CTE of a coreless package substrate composing of electronics packages.

• Composites Research
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• v.34 no.6
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• pp.426-433
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• 2021

The carbon fiber reinforced plastic manufacturing process has a problem in that a dimensional error occurs due to thermal deformation such as residual stress, spring-in, and warpage. The main causes of thermal deformation are various, including the shape of the product, the chemical shrinkage, thermal expansion of the resin, and the mold effect according to the material and surface condition of the mold. In this study, a viscoelastic model was applied to the plate model to predict the thermal deformation. The effects of chemical shrinkage and thermal expansion of the resin, which are the main causes of thermal deformation, were analyzed, and the analysis technique of the 3-D viscoelastic model with and without mold was also studied. Then, the L-shaped mold effect was analyzed using the verified 3D viscoelastic model analysis technique. The results show that different residual deformation occurs depending on the surface condition even when the same mold is used.

• Journal of Welding and Joining
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• v.22 no.2
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• pp.1-2
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• 2004

강구조물 제작시 용접프로세스에 의해 용접부 근방에서는 용접열원에 의해 급속가열ㆍ급속냉각의 열 사이클을 받으며, 열원의 이동과 함께 온도장이 변화하므로 용접부에 불균일한 온도분포가 발생된다. 이러한 불균일한 온도분포에 의한 용접부 근방의 열팽창ㆍ수축을 용접부로부터 떨어져 있는 저온상태의 부재가 이를 구속하여 결과적으로 용접변형과 잔류응력이 발생한다.(중략)