• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1992년도 춘계학술대회 논문집 92
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• pp.115-130
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• 1992

The analysis of thermoplastic automotive bumpers needs not only characterizations of the thermomechanical properties of thermoplastic materials but also the finite element method which can solve the problems with a large deflection, an elastic-inelastic deformation, and a change of a contact state. This paper describes the modeling techniques in the finite element analysis in order to get a good prediction of thermoplastic bumper behaviors. Simplification effects of a complex geometry of thermoplastic bumpers are studied by comparing the results from static loading tests and the finite element analysis.

• Steel and Composite Structures
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• 제41권6호
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• pp.787-803
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• 2021

The size-dependent nonlinear thermomechanical vibration analysis of pre- and post-buckled tapered two-directional functionally graded (2D-FG) microbeams is presented in this study. In the context of the modified couple stress theory, the formulations are derived based on the parabolic shear deformation beam theory and von Karman nonlinear strains. Different thermomechanical material properties are assumed to be temperature-dependent and smoothly vary in both length and thickness directions using the power law and the physical neutral axis concept is employed. The nonlinear governing equations are derived using the Hamilton principle and the resulting variable coefficient equations of motion are solved using the differential quadrature method (DQM) and iterative Newton's method for clamped-clamped and simply supported boundary conditions. Comparison studies are presented to validate the derived model and solution procedure. The impacts of induced thermal moments, temperature power index, two gradient indices, nonuniform cross-section, and microstructure length scale parameter on the frequency-temperature configurations are explored for both clamped and simply supported microbeams.

• 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.

• 한국분말재료학회지
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• 제4권2호
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• pp.83-89
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• 1997

A finite element analysis to solve the coupled thermomechanical problem in the plane strain upsetting of the porous metals was performed. The analysis was formulated using the yield function advanced by Lee and kim and developed using the thermo-elasto-plastic time integration procedure. The density and temperature dependent thermal and mechanical properties of porous metals were considered. The internal heat generation by the plastic deformation and the changing thermal boundary conditions corresponding to the geometry were incorporated in the program. The distributions of the stress, strain, pressure, density and temperature were predicted during the free resting period, deformation period and dwelling period of the forging process.

• 펄프종이기술
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• 제47권5호
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• pp.33-42
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• 2015

Pitches contained in thermomechanical pulp negatively influence paper qaulity and pulp and papermaking process. Without controlling TMP pitches suitably, it is hard to make a certain quality of paper. In order to control pitches in TMP, they must be quantitatively recognized by proper tools. One of the most widely used way to detecting TMP pitches is a staining method using a hydrophobic dye such as Sudan IV. Sudan IV could be used with three different protocols including different application of its dissolution, washing, dyeing time, etc. The dyeing protocols were classified into three categories including Stain I, Stain II, and Stain III. In dyeing time, Stain I required more than 24 hours to dye pitches. On the other hand, Stain III could stain TMP pitches with the most brief way. The images of red-stained pitches could be captured by a stereomicroscope with ${\times}35$ and ${\times}45$ magnifications, and then quantitatively analysed measuring their numbers and areas by Carl Zeiss AxioVision (ver. 4.8.2) program. Among three protocols, both Stain I and Stain III were the most ideal methods to detect TMP pitches because they detected more pitches and bigger pitch areas compared to Stain II against the same specimen. In particular, it was recognized that Stain III could be used as the most useful tool to detect TMP pitches accurately within several minutes.

• Steel and Composite Structures
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• 제19권1호
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• pp.93-110
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• 2015

The thermomechanical bending response of anti-symmetric cross-ply composite plates is investigated by the use of the simple four variable sinusoidal plate theory. The theory accounts for sinusoidal distribution of transverse shear stress, and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations for the present theory is reduced, significantly facilitating engineering analysis. The validity of the present theory is demonstrated by comparison with solutions available in the literature. Numerical results are presented to demonstrate the behavior of the system. The influences of aspect ratio, side-to-thickness ratio, thermal expansion coefficients ratio and stacking sequence on the thermally induced response are studied. The present study is relevant to aerospace, chemical process and nuclear engineering structures which may be subjected to intense thermal loads.

• 한국항공우주학회지
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• 제39권8호
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• pp.711-718
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• 2011

본 논문에서는 열화학적 분해 및 열기계학적 변형이 고려된 구성 방정식을 사용하여 다공성 탄소/페놀릭 복합재료의 열탄성 거동을 예측하였다. 다공성 복합재료의 온도 의존성 및 열화학적 분해 과정에서의 기공도, 분해 가스에 의한 기공 압력, 재료의 수축을 고려하였다. 기공도와 기공 압력이 고려된 대표 체적 요소 모델의 유한요소 해석을 통해 산출된 거시적 기공 탄성 계수를 구성 방정식에 적용하였다. 간단한 수치 실험을 통해 기공탄성 계수가 다공성 재료의 열탄성 거동에 미치는 영향을 분석하였으며, 재료 내부에 형성된 기공과 기공 압력에 의한 응력 구배 및 변형을 확인하였다.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4504-4517
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• 2023

After a loss of coolant accident (LOCA) in the prestressed concrete containment vessels (PCCVs) of nuclear power plants, the coupling of temperature and pressure can significantly affect the mechanical properties of the PCCVs. However, there is no consensus on how this coupling affects the failure mechanism of PCCVs. In this paper, a simplified finite element modeling method is proposed to study the effect of temperature and pressure coupling on PCCVs. The experiment results of a 1:4 scale PCCV model tested at Sandia National Laboratory (SNL) are compared with the results obtained from the proposed modeling approach. Seven working conditions are set up by varying the internal and external temperatures to investigate the failure mechanism of the PCCV model under the coupling effect of temperature and pressure. The results of this paper demonstrate that the finite element model established by the simplified finite element method proposed in this paper is highly consistent with the experimental results. Furthermore, the stress-displacement curve of the PCCV during loading can be divided into four stages, each of which corresponds to the damage to the concrete, steel liner, steel rebar, and prestressing tendon. Finally, the failure mechanism of the PCCV is significantly affected by temperature.

• 폴리머
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• 제34권5호
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• pp.480-484
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• 2010

무수산인 4,4'-(4,4'-isopropylidene-diphenoxy)bis(phthalic anhydride)(BPADA)와 아민계인 2,2'-bis(trifluoromethyl)benzidine(TFB), bis(3-aminophenyl)sulfone(APS), 4,4'-methylene-bis-(2-methylcyclohexylamine)(MMCA), bis[4-(3-aminophenoxy)phenyl]sulfone(BAPS)에 melamine을 각각 5 몰%로 반응시켜 N,N'-dimethylacetamide(DMAc) 용매 속에서 폴리아믹산(poly(amic acid), PAA)들을 얻었다. 용액 상태의 PAA를 캐스팅하여 각각 다른 반응 온도에서 열처리를 통해 무색 투명한 폴리이미드(PI) 필름을 얻었다. PI의 열적 성질, 광학적 특성을 다양한 아민 구조의 변화에 따라 조사하였으며, 열적 성질은 differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), thermomechanical analysis(TMA)를 이용해 측정하였고, 광학적 투명도는 색차계(spectrophotometry)를 이용하였다. 제조된 모든 필름의 열 팽창계수는 $48.53-64.24ppm/^{\circ}C$ 사이의 값을 얻었으며, 모든 필름 시료의 노란색 지수(yellow index, YI)는 3 이하를 나타내었다.

• 폴리머
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• 제36권1호
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• pp.9-15
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• 2012

용융법을 이용해서 말단에 가교 반응이 가능한 메틸 말레이미드(methyl maleimide)기를 가진 전방향족 에스터 결합의 액정(liquid crystal, LC)을 합성하였고, 합성된 LC를 이용해서 적당한 열처리 과정을 통해 열경화성 액정(liquid crystalline thermoset, LCT) 필름을 제조하였다. 합성된 LC 및 LCT 필름은 FTIR(Fourier transform infrared) 분광기, WAXD(wide angle X-ray diffraction), DSC(differential scanning calorimetry), TGA(thermogravimetric analysis), TMA(thermomechanical analysis), 그리고 가열판이 장착된 편광 현미경으로 특성 분석을 하였다. 유리전이온도($T_g$)와 열팽창 계수는 주사슬 구조의 메소겐에 의해 강한 영향을 받는 것으로 확인되었고, $para$-로 치환된 비페닐구조를 가진 LCT 필름이 가장 좋은 열적 성질을 보여 주었다.