• 한국안전학회지
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• 제7권1호
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• pp.20-29
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• 1992

Effects of strain hardening exponents on the retardation behavior of fatigue crack propagation are experimentally investigated. The retardation of fatigue crack propagation seems to be induced by the crack closure at crack tip. The phenomenon of crack closure becomes remarkable with the increment of strain hardening exponent and magnitude of percent peak load. The ratio of crack growth increment(a$\_$d//w$\_$d/) is influenced by a single overloading (a$\_$d/) and estimated plastic zone size (W$\_$d/=2r$\_$y/) is increased according with the increasing of strain ha.dening exponents. The number of retarded crack growth cycles were (N$\_$d/) decreased as the baseline stress intensity factor .ange( K$\_$b/) was increased. Within the limitation of these experimental results obtained under the single overload, an empirical relation between crack retardation ratio (Nd/N＊), strain hardening exponent (n) and percent peak load (％PL) has been proposed as; Nd/N＊＝ exp [PL $.$ PL$.$A(n)＋B(n) ] where, A(n)＝${\alpha}$n＋${\beta}$, B(n)＝${\gamma}$n＋$\delta$, PL＝％PL/100 and ${\alpha}$＝0.78, ${\beta}$＝0.54, ${\gamma}$＝0.58 and $\delta$＝-0.01, It is interesting to note that all these constants are identical for materials such as aluminum(A3203), steel(S4SC), steel(SS41) and stainless steel(SUS316) used in this experimental study.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1614-1616
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• 2000

The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulating the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. We can design the thermoelectric modules having the good properties of thermoelectric generation. Resistivity of thermoelectric module for thermoelectric generation consisting of 62 cells was $0.15{\sim}0.4{\Omega}$. The maximum power of thermoelectric generator using thermoelectric generating modules can be defined as temperature function, and in this case it can be analogized the linear relation between current and voltage characteristics as function of temperature. The thermoelectric generator using 128 generating modules was assembled with 4 parallel connected modules sets composed with 32 directly connected modules.

• Structural Engineering and Mechanics
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• 제25권4호
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• pp.365-382
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• 2007

A pilot study has been conducted to guide the development of a finite element modeling formulation for the analysis of architectural glass curtain walls under in-plane lateral load simulating earthquake effects. This pilot study is one aspect of ongoing efforts to develop a general prediction model for glass cracking and glass fallout for architectural glass storefront and curtain wall systems during seismic loading. For this study, the ANSYS finite element analysis program was used to develop a model and obtain the stress distribution within an architectural glass panel after presumed seismic movements cause glass-to-frame contact. The analysis was limited to static loading of a dry-glazed glass curtain wall panel. A mock-up of the glass curtain wall considered in the analysis with strain gages mounted at select locations on the glass and the aluminum framing was subjected to static loading. A comparison is made between the finite element analysis predicted strain and the experimentally measured strain at each strain gage location.

• 동력기계공학회지
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• 제17권4호
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• pp.86-93
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• 2013

This paper deals with the effects of driving force and material properties on statistical distribution of fatigue crack growth rate (FCGR) for the friction stir welded joints of Al 7075-T651 aluminum plate. In this work, the statistical probability distribution of fatigue crack growth rate was analyzed by using our previous constant stress intensity factor range controlled fatigue crack growth test data. As far as this study are concerned, the statistical probability distribution of fatigue crack growth rate for the friction stir welded (FSWed) joints was found to evaluate the variability of fatigue crack growth rate for base metal (BM), heat affected zone (HAZ) and weld metal (WM) specimens. The probability distribution of fatigue crack growth rate for FSWed joints was found to follow well log-normal distribution. The shape parameter of BM and HAZ was decreased with increasing the driving force, however, the shape parameter of WM was decreased and increased with increasing the driving force. The scale parameter of BM, HAZ and WM was increased with the driving force.

• 한국정밀공학회지
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• 제16권9호
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• pp.123-134
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• 1999

A new forming technology has been developed to fabricate near-net shape components by using aluminum alloys with globular microstructure. The estimations of filling characteristic in the forging simulation with arbitrarily shaped dies of SSM are calculated by finite element method with proposed algorithm. The proposed model and various boundary conditions for arbitrarily shaped die are investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation processes with arbitrarily shaped dies are performed on the isothermal conditions and axisymmetric problems. To analyze the forging process simulation with SSM, new stress-strain relationship for semi-solid behaviour is described, and forging the liquid flow. Furthermore, For the purpose of getting net shape of SSM, it is important to be obtain a solid fraction in forging process with arbitrarily shaped dies. To produce a automotive part which have good mechanical properties, the filling pattern in accordance with die velocity and solid fraction distribution has to be estimated for arbitrarily shaped die.

• 대한금속재료학회지
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• 제49권8호
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• pp.664-670
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• 2011

3-ply Mg/Al/STS clad-metal was fabricated by the roll bonding process. An interfacial reaction layer was formed at the Mg/Al interface at and above $300^{\circ}C$ whereas no interfacial reaction layer was observed up to $400^{\circ}C$. The effect of the interfacial reaction layer on the mechanical and fracture properties in clad metals after heat treatments were investigated The chemical compositions were analyzed at the Mg/Al interface by an Energy dispersive X-ray analysis (EDX). A tension test was performed to examine the interfacial cracking properties. The Mg layer fractured first, causing a sudden drop of the stress and Al/STS layer continued to deform until the final fracture. Periodic cracks and crack propagation was observed at the reaction layer between Mg and Al.

• 항공우주시스템공학회지
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• 제12권1호
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• pp.42-46
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• 2018

본 연구는 소형 엔진 추력 시험 장비에 대한 구조의 안전성 해석에 관한 연구이다. 본 연구에서 소형 엔진 시험 장치를 위한 철강 및 알루미늄 합금 적용 구조의 설계 및 해석을 수행하였다. 1차적으로 엔진 시험 장치의 구조 설계 요구 조건이 분석되었다. 구조 설계 이후 유한 요소 해석 기법을 활용하여 엔진 시험 장치의 구조 해석이 수행되었다. 적용 하중 조건에서 응력 및 변위 해석이 수행되었다. 최종 구조 해석을 통해 설계된 엔진 시험 장치 구조는 안전한 것으로 확인되었다.

• 소성∙가공
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• 제30권4호
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• pp.165-171
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• 2021

This study was conducted on the manufacturing method of high-strength aluminum bolts. We obtained the displacement-load information by tensile test of the Al 6056 raw material and the T6 heat-treated material and calculated the precise flow stress and fracture limit using repetitive finite element analysis for before and after heat treatment. We designed a multi-stage forging process for T6 heat-treated material, and calculated that the accumulated damage value does not exceed fracture limits by finite element method. We produced the prototype forgings without any harmful defects such as cracks and folding occurring. Bolts made of T6 heat treated material show 9.6%higher tensile strength than T6 heat treated material after wire drawing.

• Structural Engineering and Mechanics
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• 제91권6호
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• pp.627-642
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• 2024

In the present work, the deformation and stresses induced in a functionally graded disk have been reported for different loading conditions. The governing differential equation is solved using the classical method namely Navier's method by considering thermal and mechanical boundary conditions at the surface of the disk. To simplify solving the second-order differential equation, a plane stress condition was assumed. Following validation using a one-dimensional steady-state heat condition problem, temperature variations were computed for constant heat generation and varying conductivity. The research aims to investigate both the individual and combined effects of rotation, gravity, and temperature with constant heat generation on a hollow disk operating under complex loading conditions. The results demonstrated a high degree of accuracy when compared with those in existing literature. Material properties, such as Young's modulus, density, conductivity, and thermal expansion coefficient, were modeled using a power law variation along the disk's radius by considering aluminum as a base material. The proposed analytical method is straightforward, providing valuable insights into the behavior of disks under various loading conditions. This method is particularly useful for researchers and industries in selecting appropriate loading conditions and grading parameters for engineering applications, including aerospace components, energy systems, and rotary machinery parts.

• 한국작물학회지
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• 제52권2호
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• pp.213-219
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• 2007

본 연구는 알루미늄 스트레스가 녹두에 미치는 영향을 보기 위해 뿌리의 생장, 알루미늄 함량, 뿌리 표면의 pH 변화, 원형질막의 $H^+-ATPase$ 활성과 단백질 양의 변화를 조사하여 분석하였다. 1. 처리된 알루미늄의 농도는 10, 25, 50, $100{\mu}M$이었으며, 알루미늄에 의한 뿌리생장의 억제는 $25{\mu}M$ 이상의 농도 처리구에서 12시간부터 현저히 나타났고, 50과 $100{\mu}M$ 처리구에서는 뿌리의 생장이 거의 중단되었다. 2. 0.2% Hematoxlin으로 염색 시 알루미늄이 처리된 근단부에서 주로 염색되었으며, $50{\mu}M$ 농도로 처리된 뿌리의 경우 12시간째보다는 24시간째에 근단부 전체가 염색되어 그 피해가 심각함을 보여 주었다. 또 근단 부위가 대조구와 비교하여 어두운 갈색을 나타내고, 표면이 가로 쪽으로 갈라졌다. 3. 처리 농도별 근단부(1 cm)와 근단부를 제외한 부위의 뿌리로 나누어 24시간 처리를 한 후 알루미늄 함량을 측정한 결과, $10{\mu}M$ 처리구에서는 차이가 없었다. 그러나 알루미늄 처리 농도가 높을수록 즉, $25{\mu}M$ 이상 알루미늄 처리구에서는 근단부에서 2.5배 이상 높았다. 4. pH 지시약과 agarose plate technique를 이용하여 뿌리표면의 $H^+-flux$의 차이를 본 결과 녹두의 근단부 표면의 알카리화가 대조구에서는 12시간 정도부터 노란색(pH 4.5)에서 보라색(pH 6.0 이상)으로 변하는 것을 관찰하였으나 알루미늄 처리구에서는 색깔의 변화를 볼 수 없었다. 5. 24시간 동안 $50{\mu}M$ 알루미늄을 처리한 뿌리 원형질막 $H^+-ATPase$ 활성은 대조구에 비해 56%가 억제 되었다. $H^+-ATPase$ 단백질의 발현을 조사한 Western blotting 결과는 효소 활성의 감소와 유사하게 알루미늄이 처리된 뿌리에서 현저하게 줄어들었음을 확인할 수 있었다.