• Steel and Composite Structures
• /
• 제51권3호
• /
• pp.243-260
• /
• 2024

Thirteen self-compacting recycled concrete filled aluminium tubular (SCRCFAT) columns were tested under concentric compression loads. The effects of the replacement ratio of the recycled concrete aggregate (RCA) and steel fibre (SF) reinforcement on the structural performance of the SCRCFAT columns were studied. A control specimen (C000) was cast with normal concrete without SF to be reference for comparison. Twelve columns were cast using RCA, six columns were cast using concrete incorporating 2% SF while the rest of columns were cast without SF. Failure mode, ductility, ultimate load capacity, axial deformation, ultimate strains, stress-strain response, and stiffness of the SCRCFAT columns were studied. The results showed that, the peak load of tested SCRCFAT columns incorporating 5-100 % RCA without SF reduced by 2.33-11.28 % compared to that of C000. Conversely, the peak load of tested SCRCFAT columns incorporating 5-100% RCA in addition to 2% SF increased by 21.1-40.25%, compared to C000. Consequently, the ultimate axial deformation (Δ) of column C100 (RCA=100% and SF 0%) increased by about 118.9 % compared to C000. The addition of 2% SF to the concrete mix decreased the axial deformation of SCRCFAT columns compared to those cast with 0% SF. Moreover, the stiffness of the columns cast without SF decreased as the RCA % increased. In contrast, the columns stiffness cast with 2% SF increased by 26.28-89.7 % over that of C000. Finally, a theoretical model was proposed to predict the ultimate loads tested SCRCFAT columns and the obtained theoretical results agreed well with the experimental results.

• 한국생산제조학회지
• /
• 제19권1호
• /
• pp.108-113
• /
• 2010

Decreasing products lifecycles and increasing consumers desires for quality and design make the automotive industries try to reduce time for developing new designs. In order to reduce developing time, I have designed head lamps, which are really important to have an effect on brand identities and images, using layers concept that is one of the international automotive design trends by alias and photoshop, and produced prototype by RP. To assemble the produced prototype to the body and manufacture the frame to exterior modelling efficiently, I have studied on joining dissimilar materials of aluminum alloy that can make the prototype lighter and stainless steel, which is good for corrosion resistance by using laser beam. These materials were welded for finding the optimum joining condition and evaluating the soundness of joining zone. The joining was performed under the condition of laser power 500, 550, 575, 600W and 11~14Hz. In this study, the suitable joining condition between aluminum alloy (Al 2024) and stainless steel (STS 304) can be obtained at the laser power 575W and frequency 12Hz.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.74-77
• /
• 2001

The impact response and damage of CLAS panel was investigated experimentally. The facesheet material used was RO4003 woven-glass hydrocarbon/ceramic and the core material was Nomex honeycomb with a cell size of 3.2mm and a density of 96 kg/$\textrm{m}^{3}$. The shield plane used was RO4003 and 2024-T3 aluminum. Static indentation and impact test was conducted to characterize the type and extent of the damage observed in two CLAS panels, and the performance of antenna used in a wireless LAN system. Correlation of peak contact force, residual indentation and the delamination area shows impact damage of the panel with an aluminum shield plane is larger than that of the panel with RO4003 shield plane, although tile former is more penetration resistant. The damage was observed by naked eye, ultrasonic inspection and cross sectioning. The shape and size of delamination was estimated by ultrasonic inspection, and the area of delamination linearly increases as impact energy increases. The performance of impact damaged antenna was estimated by measuring return loss and radiation pattern.

• 한국항공운항학회지
• /
• 제27권3호
• /
• pp.24-29
• /
• 2019

The paste-type adhesive can be stored for a certain period of time and can be cured at room temperature. So it is mainly used for crack patching repair of aircraft airframe structures. This study analysed the influence of environmental factors and evaluated the adherence strength characteristics according to the adherence delay time of the paste-type adhesive. The test specimens were made of aluminum alloy(AL 2024-T3) with reference to ASTM D1002 which is generally performed to measure the adherence strength of the adhesive used for metal bonding. As a result of analysing the influence of temperature and humidity, it was found that the optimal temperature range is $24.5{\pm}0.5^{\circ}C$ and the optimal humidity range is $71{\pm}1%$ for maintenance work of the aircraft using EA-9320 adhesive. In addition, the adherence strength did not decrease with the inherent application time of the EA-9320, but it was found that the adherence strength dropped rapidly when the applied time exceeded the inherent application time of it.

• 비파괴검사학회지
• /
• 제22권2호
• /
• pp.155-169
• /
• 2002

피로균열 진전시 균열 열림 및 닫힘에 따른 음향방출 특성을 규명하고자 구조용 알루미늄 2024-T4 와 6061-T6 재료에 대해 소형인장 시편에서의 피로균열 진전시 발생되는 AE 특성을 관찰하였으며, 기존의 AE파라미터 분석은 물론 재료의 파단면 분석을 통해 재료특성에 따른 AE 발생거동 사이의 관계를 논의하였다. 대부분의 음향방출 신호는 균열이 열리기 시작하는 위상과 균열이 완전히 닫히는 위상에서 많이 발생되었으며 하중을 최대로 받는 균열 완전 열림에서는 전반적으로 적게 발생됨을 알 수 있었다. 또한 재료에 따라서 균열 완전 열렴 부분에서 발생하는 음향방출 특성은 달라졌으나 각 피로 사이클 주파수 변화 (0.1, 0.2, 1.0Hz)에 따른 결과에서는 통일 재료일 경우 피로 사이클 주파수가 변화하더라도 각 사이클에서의 AE hit 발생 경향용 비슷하게 나타났다. 이와 같은 결과로부터 균열 열림 및 닫힘시 재료 의 미세조직과 기계적 특성인 연장강도와 항복강도에 따라 AE 특성이 달라질 수 있음을 알 수 있었다.

• 한국지반환경공학회 논문집
• /
• 제25권5호
• /
• pp.39-47
• /
• 2024

본 연구에서는 재활용 시 도로용이나 지반 보강재로 사용되는 전기로 제강슬래그의 입경별 중금속 용출 실험과 제강슬래그와 점토를 혼합한 혼합비별 공시체의 이온 용출을 실험하여 환경적 특성을 분석하였다. 폐기물 공정시험결과 시료 시험항목에서 중금속은 검출되지 않은 것으로 나타났으며, 물과 접하지 않은 제강슬래그의 경우 용출이 일어나지 않는 것을 알 수 있었으나, 제강슬래그의 중금속 용출 실험을 진행하여 ICP-OES 분석한 결과 일부 중금속이 검출되었다. 제강슬래그가 물과 반응하면 제강슬래그 내에 존재하는 Free CaO와 화학반응이 일어나 용출이 되는 것을 알 수 있었다. 제강슬래그의 입경별 용출 실험을 진행한 결과 가장 많은 용출이 일어난 알루미늄의 경우 입경이 작을수록 커지는 것으로 나타났으며, 제강슬래그와 점토를 혼합한 혼합토의 경우 제강슬래그의 함량이 증가할수록 알루미늄의 용출량은 증가하였다. 그러나 제강슬래그만을 사용했을 때보다 제강슬래그와 점토의 혼합토에서 용출되는 알루미늄의 양이 현저히 낮아졌으며, 다른 중금속들도 용출되는 양이 기준치 이하로 나타났다. 그러므로 제강슬래그와 점토의 혼합토를 재활용하여 도로용이나 성토용 재료로 사용 시 중금속의 용출에 대한 우려는 매우 낮아질 것으로 사료된다. 이러한 결과는 순수 제강슬래그만을 사용하는 것보다 제강슬래그와 점토를 혼합한 재료가 친환경적으로 지속가능하고 안전한 대안이 될 수 있다고 판단된다.

• 한국응용과학기술학회지
• /
• 제41권1호
• /
• pp.58-68
• /
• 2024

본 연구의 목적은 알츠하이머질환(Alzheimer's disease: AD) 동물 모델을 대상으로 트레드밀 운동(Treadmill exercise: TE)과 환경강화(environmental enrichment: EE) 처치가 인지기능, 근 기능, 및 밀착연접 단백질 발현에 미치는 영향을 확인하는데 있다. AD 동물 모델을 제작하기 위해 aluminum chloride(AlCl₃)를 90일간(40mg/kg/하루) 투여 하였으며 동시에 TE(10-12m/min, 40-60min/day) 혹은 EE에 노출시켰다. 그 결과 AlCl₃ 투여에 의한 인지기능 저하와 근 기능 감소가 TE와 EE에 의해 완화된 것으로 나타났다. 또한, TE와 EE는 AD 질환에서 나타나는 β-amyloid(Aβ), alpha-synuclein 및 tumor necrosis factor-α(TNF-α) 단백질의 발현 증가를 감소시킨 것으로 나타났다. 게다가 TE와 EE는 AlCl₃ 투여에 의해 감소된 밀착연접 단백질(Occludin, Claudin-5 및 ZO-1)의 발현을 통계적으로 유의하게 증가시킨 것으로 나타났다. 마지막으로 Aβ 단백질과 밀착연접 단백질과의 상관분석을 실시한 결과 부적 상관관계(Occludin: r=-0.853, p=0.001; Claudin-5 : r=-0.352, p=0.915; ZO-1 : r=-0.424, p=0.0390)로 나타났다. 따라서 이를 종합해 보면 TE 혹은 EE 처치는 AD에 나타나는 병리학적 특징들을 일부 완화시켜 인지기능과 근 기능을 일부 개선 시킬 수 있는 효과적인 운동 방법이라고 생각된다.

• Corrosion Science and Technology
• /
• 제6권4호
• /
• pp.206-210
• /
• 2007

Aerospace aluminum alloys such as Al alloy 2024-T3 and 7075-T6 are subject to localized corrosion due the existence of intermetallics containing Cu, Mg or Zn. Chromate is currently widely used in the aerospace industry as the corrosion inhibitor for these alloys. However, chromate needs to be replaced due to its strong carcinogenicity. In this study, an extensive pigment screening has been performed to find replacements for chromates. Different categories of inhibitors were evaluated by immersion tests, DC polarization tests and other methods. Phosphates, zinc salts, cerium salts, vanadates and benzotriazole were found to be effective inhibitors for AA7075. Among those inhibitors, zinc phosphate was found to be the most effective in our novel, silane-based, one-step aqueous primer system. The performance of this primer is comparable to that of currently used chromate primers in accelerated corrosion tests, while it is completely chromate-free and its VOC is about 80% less than that of current primers. Studies by SEM/EDS showed that the unique structure of the superprimer accounts for the strong anti-corrosion performance of the zinc phosphate pigment. The self-assembled stratified double-layer structure of the superprimer is characterized by a less-penetrable hydrophobic layer at the top and a hydrophilic layer accommodating the inhibitors underneath. The top layer functions as the physical barrier against water ingress, while the lower layer functions as a reservoirfor the inhibitor, which is leached out only if the coating is damaged by a scratch or scribe. The presence of a silane in the primer further improves the adhesion and anti-corrosion performance of the primer.

• International Journal of Ocean System Engineering
• /
• 제2권2호
• /
• pp.106-115
• /
• 2012

In the present study, TiN and CrN films were coated by arc ion plating equipment onto aluminum alloy substrate, A2024. The film thickness was about 4.65 ${\mu}m$. TiN and CrN films were analyzed by X-ray diffraction and energy dispersive X-ray equipments. The Young's modulus and the micro-Vickers hardness of aluminum substrate were modified by the ceramic film coatings. The difference in Young's modulus between substrate and coating film would affect on the wear resistance. The critical load, Lc, was 75.8 N for TiN and 85.5 N for CrN. It indicated from the observation of optical micrographs for TiN and CrN films that lots of cracks widely propagated toward the both sides of scratch track in the early stage of MODE I. TiN film began to delaminate completely at MODE II stage. The substrate was finally glittered at MODE III stage. For CrN film, a few crack can be observed at MODE I stage. The delamination of film was not still occurred at MODE II and then was happened at MODE III. This agrees with critical load measurement which the adhesive strength was greater for CrN film than for TiN film. Consequently, it was difficult for CrN to delaminate because the adhesive strength was excellent against Al substrate. The wear process, which the film adheres and the ball transfers, could be enhanced because of the increase in loading. The wear weight of ball was less for CrN than for TiN. This means that the wear damage of ball was greater for TiN than for CrN film. It is also obvious that it was difficult to delaminate because the CrN coating film has high toughness. The coefficient of friction was less for CrN coating film than for TiN film.

• Structural Engineering and Mechanics
• /
• 제83권5호
• /
• pp.693-707
• /
• 2022

Bonded joints have proven their performance against conventional joining processes such as welding, riveting and bolting. The single-lap joint is the most widely used to characterize adhesive joints in tensile-shear loadings. However, the high stress concentrations in the adhesive joint due to the non-linearity of the applied loads generate a bending moment in the joint, resulting in high stresses at the adhesive edges. Geometric optimization of the bonded joint to reduce this high stress concentration prompted various researchers to perform geometric modifications of the adhesive and adherends at their free edges. Modifying both edges of the adhesive (spew) and the adherends (bevel) has proven to be an effective solution to reduce stresses at both edges and improve stress transfer at the inner part of the adhesive layer. The majority of research aimed at improving the geometry of the plate and adhesive edges has not considered the effect of temperature and water absorption in evaluating the strength of the joint. The objective of this work is to analyze, by the finite element method, the stress distribution in an adhesive joint between two 2024-T3 aluminum plates. The effects of the adhesive fillet and adherend bevel on the bonded joint stresses were taken into account. On the other hand, degradation of the mechanical properties of the adhesive following its exposure to moisture and temperature was found. The results clearly showed that the modification of the edges of the adhesive and of the bonding agent have an important role in the durability of the bond. Although the modification of the adhesive and bonding edges significantly improves the joint strength, the simultaneous exposure of the joint to temperature and moisture generates high stress concentrations in the adhesive joint that, in most cases, can easily reach the failure point of the material even at low applied stresses.