• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.90-95
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• 2001

Thermo-mechanical and flexural behavior of a wire-bond plastic ball grid array (WB-PBGA) are characterized by high sensitive $moir{\acute{e}}$ interferometry. $Moir{\acute{e}}$ fringe patterns are recorded and analyzed at several various bending loads and temperature steps. At the temperature higher that $100^{\circ}C$, the inelastic deformation in solder balls became more dominant. As a result the bending of the molding compound decreased while temperature increased. The strain results show that the solder ball located at the edge of the chip has largest shear strain by the thermal load while the maximum average shear strain by the bending moment occurs in the end solder. The results also show that $moir{\acute{e}}$ interferometry is a powerful and effective tool in experimental studies of electronic packaging.

• Elastomers and Composites
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• 제42권4호
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• pp.217-223
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• 2007

결정성을 갖는 에틸렌프로필렌디엔 고무($Nordel^{(R)}$ IP)를 과산화물로 가교시키고 열적, 기계적특성과 형상기억거동을 조사하였다. 겔함량 측정결과 가교도는 DCP 함량에 따라 증가되었으며, DSC 분석결과 가교된 고무는 결정상이 존재하고 있음을 알 수 있었다. 인장시험 결과가교도가 증가함에 따라 고무의 모듈러스는 증가되며 파단신율은 감소되었다. 이와 같이 가교구조 내에 결정상을 함유하는 고무는 우수한 형상기억 특성을 나타내었다. 즉, 이러한 고무는 결정상의 용융온도 이상에서 쉽게 원하는 형태로 변형되고, 변형된 상태에서 냉각시키면 변형된 형태로 잘 고정되었으며, 또한 이렇게 변형된 형상의 시료를 용융온도 이상으로 가열하면 원래의 모양으로 신속히 되돌아오는 것을 관찰할 수 있었다.

• 한국지반공학회논문집
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• 제40권1호
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• pp.55-63
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• 2024

본 연구에서는 에너지 슬래브의 안정성을 검토하기 위해 열-역학적 수치해석 모델을 개발하였다. 먼저, 주거용 건물 지하주차장에 벽체형 에너지 슬래브를 설치한 뒤 현장 열성능 평가시험(Thermal performance test, TPT)을 수행하였다. 이를 기반으로 현장 열성능 평가시험의 열-수리학적 거동을 정교하게 모사할 수 있는 에너지 슬래브의 열-수리학적 수치해석 모델을 개발하였다. 마지막으로, 열-수리학적 모델을 통해 도출된 시간-온도 데이터를 기반으로 에너지 슬래브의 열-역학적 수치해석 모델을 개발하였다. 개발된 모델을 기반으로 에너지 슬래브의 운용에 따른 열응력을 산정한 결과 최대 5,300kPa의 열응력이 발생하였으며, 이는 에너지 슬래브의 안정적인 운용을 위해 충분한 인장강도가 확보된 시멘트 몰탈 활용이 필요하다는 것을 시사한다.

• Advances in aircraft and spacecraft science
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• 제10권1호
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• pp.83-106
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• 2023

In this work, the static behavior of FGM macro and nano-plates under thermomechanical loading. Equilibrium equations are determined by using virtual work principle and local and non-local theory. The novelty of the current model is using a new displacement field with four variables and a warping function considering the effect of shear. Through this analysis, the considered sandwich FGM macro and nanoplates are a homogeneous core and P-FGM faces, homogeneous faces and an E-FGM core and finally P-FGM faces and an E-FGM core. The analytical solution is obtained by using Navier method. The model is verified with previous published works by other models and very close results are obtained within maximum 1% deviation. The numerical results are performed to present the influence of the various parameters such as, geometric ratios, material index as well as the scale parameters are investigated. The present model can be applicable for sandwich FG plates used in nuclear, aero-space, marine, civil and mechanical applications.

• Tribology and Lubricants
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• 제18권3호
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• pp.219-227
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• 2002

A linear elastic fracture mechanics analysis of double subsurface cracks propagation in a half-space subjected to moving thermomechanical surface traction was performed using the finite element method. The effect of frictional heat at the sliding surface on the crack growth behavior is analyzed in terms of the thermal load and peclet number. The crack propagation direction is predicted in light of the magnitudes of the maximum shear and tensile stress intensity factor ranges. When moving thermomechanical surface traction exists, subsurface horizontal cracks are propagation in-plane crack growth rate at the beginning but they are propagation out-of-plane crack growth rate by the frictional heat which is occurrence by the repeated sliding contact.

• Structural Engineering and Mechanics
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• 제56권1호
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• pp.85-106
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• 2015

Postbuckling of thick plates made of functionally graded material (FGM) subjected to in-plane compressive, thermal and thermomechanical loads is investigated in this work. It is assumed that the plate is in contact with a Pasternak-type elastic foundation during deformation. Thermomechanical non-homogeneous properties are considered to be temperature independent, and graded smoothly by the distribution of power law across the thickness in the thickness in terms of the volume fractions of constituents. By employing the higher order shear deformation plate theory together the non-linear von-Karman strain-displacement relations, the equilibrium and compatibility equations of imperfect FGM plates are derived. The Galerkin technique is used to determine the buckling loads and postbuckling equilibrium paths for simply supported plates. Numerical examples are presented to show the influences of power law index, foundation stiffness and imperfection on the buckling and postbuckling loading capacity of the plates.

• 한국세라믹학회지
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• 제32권9호
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• pp.977-988
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• 1995

Several oxide (ZrO2, Al2TiO5, reactive Al2O3) and nonoxide (SiC, Si3N4, "ALON" (5AlN.9Al2O3)) additives were used as a microfiller for alumina based LCC (Low-Cement-Castable). High temperature prooperties (HMOR, softening under load) and the phase changes of developed LCC on various sintering temperatures were examined. In addition, thermal shock test and corrosion test were accomplished. Based on these data the effects of each microfiller on the properties of LCC were established comparing to those of the commercial LCC with amorphous silica as a microfiller. The castables, containing reactive alumina, ZrO2 and "ALON" (5AlN.9Al2O3) as a first portion, exhibited considerably higher HMOR-values over 100$0^{\circ}C$, better creep behavior, and thermal shock resistance than those of castables with amorphous silica. The LCC with 5% Al2TiO5 showed no corrosion against molten aluminum.nst molten aluminum.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.50-58
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• 2000

A linear elastic fracture mechanics analysis of multiful subsurface cracks propagation in a half-space subjected to moving thermomechanical surface traction was peformed using the finite element method. The effect of frictional heat at the sliding surface on the crack growth behavior is analyzed in terms of the thermal load and peclet number. The crack propagation direction is predicted in light of the magnitudes of the maximum shear and tensile stress intensity factor ranges. When moving thermomechanical surface traction exists, subsurface horizontal cracks are propagation in-plane crack growth rate at the beginning but they are propagation out-of-plane crack growth rate by the frictional heat which is occurrence by the repeated sliding contact.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1436-1441
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• 2006

Each type of optical sheets in a LCD module experiences a characteristic behavior for thermal loading and unloading. During thermal cycling, a polymeric behavior is reversible and recyclable, depending on a material stiffness critically affected by temperature and time. Some critical issues on temperature- and time-dependent themomechanical deformation of the polymeric sheet are addressed by finite-element thermal results, followed by structural simulation results in this study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1407-1412
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• 2003

In MEMS devices, packaging induced stress or stress induced structure deformation become increasing concerns since it directly affects the performance of the device. In this paper, deformation behavior of MEMS gyroscope package subjected to temparature change is investigated using high-sensitivity $Moir{\acute{e}}$ interferometry. Using the real-time $Moir{\acute{e}}$ setup, fringe patterns are recorded and analyzed at several temperatures. Temperature dependent analyses of warpages and extensions/contractions of the package are presented. Linear elastic behavior is documented in the temperature region of room temperature to $125^{\circ}C$. Analysis of the package reveals that global bending occurs due to the mismatch of thermal expansion coefficient between the chip, the molding compond and the PCB.