• 소성∙가공
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• 제21권5호
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• pp.305-311
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• 2012

One of the main methods of building LNG tankers uses the Moss spherical tank design since it can be precisely analyzed with respect to reliability and safety of construction by stress analysis. Aluminum alloy 5083 is generally used in the Moss spherical tank design for the wall in constructing the LNG tanker. This aluminum alloy does not have low temperature brittleness, but has good corrosion resistance, good weldability, and excellent material properties for the application. The Moss spherical tank is constructed with several sections of A5083 thick plate with curved surfaces, which are welded together. It is essential to predict the amount of springback for the deformed thick plates in design to insure a reliable construction because the structure needs to be assembled into a perfect sphere. Unless the initial construction meets the design, there are additional processing costs for reworking to meet the specifications as well as a cost penalty paid to a consumer. In this paper, FE analyses were conducted to predict the amount of springback for various forming conditions and forming processes. The various forming processes were evaluated with respect to reducing springback and compared with the conventional forming process used for curved surfaces of thick Al plate.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.371-376
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• 1997

A 100*100.mu.m$^{2}$ aluminum micro mirror is designed and fabricated using a thick photoresist as a sacrificial layer andas a mold for nickel electroplating. The micro mirror is composed of aluminum mirror plate, two nickel support posts, two aluminum hinges, two address eletrodes, and two landing electrodes. The aluminum mirror plate,which is supported by two nickel support posts, is overhung about 10.mu.m from the silicon substrate. THe aluminum mirror plate is actuated like a seesaw by electrostatic force generated by electic potential difference applied between the mirror plate and the address electrode. This paper presents some methods to measure the optical and the dynamic characteristics of the fabricated micro mirror.

• 소성∙가공
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• 제20권4호
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• pp.316-323
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• 2011

The hot curvature-forming of large aluminum thick plate using a grid-typed hybrid die is a process for the production of a spherical LNG tank. Many variables such as the initial die surface quality, grid size, grid thickness, size of blank plate and cooling line design, control the success of the process. In addition, the plate used in this process is generally larger than $10{\times}10m$ in size. Thus, it is very difficult to predict the surface characteristics of the plate during forming and to measure the different parameters due to the high cost of the experiments. In order to optimize the process design for the grid-type die, the development of an analytical method to predict the surface characteristics of the final product in hot curvature-forming is needed. This paper described the development of the method and procedures for FE simulations of the hot curvature-forming process, including hot forming, air flow, cooling, and thermal deformation analyses. An experiment for a small scale model of the process was conducted to check the validity of the numerical method. The results showed that the curvature of the plate in the analysis agrees well with that of the experiment within 0.037 and 0.016% tolerance margins for its side and corner, respectively.

• 한국해양공학회지
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• 제15권3호
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• pp.81-86
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• 2001

Ultrasonic travel-times obtained with the LCR ultrasonic technique have shown an ability to distinguish among three aluminum plates. The 244$\times$150mm thick, but differ in heat treatment. One is fully annealed, the second is quenched and then tempered, and the third is heat-treated to T651 plate, as received plate. Travel-times were obtained at four locations on each side of all plates. The data for both sides of each plate clearly are in very close agreement except location 1 of each plate. In order to show travel-time variation throughout the plate areas, the average travel-time for both sides of each plate were calculated. For Plate 1, the travel-time data were the highest and the data of Plate, the travel-time data were the highest and the data of Plate 2 were upper than Plate 3. Finally, the residual stresses for each plate were measured by X-ray diffraction method. The results showed a good relation. These preliminary results indicate that the LCR Ultrasonic Technique may be not only further developed for use in quality control in the manufacture of rolled aluminum plates but also industry.

• 한국표면공학회지
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• 제53권5호
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• pp.227-231
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• 2020

This article investigated the effects of stainless steel plate-patterns bonded to aluminum frypan on the thermal distortion and surface temperature of the frypan during gas or induction heating. Two different stainless steel plate-patterns were employed: type A contains only circular holes and type B has not only circular holes but also vacant spaces of 0.5 mm thick and 40 mm long straight line crossing 60 mm long curved line. The bottom of the frypan was distorted during heating when type A stainless steel plate-bonded frypan while no significant thermal distortion was observed for type B stainless steel plate-bonded frypan during heating. Temperature of the frypan surface showed the same trend during gas heating, irrespective of stainless steel plate-patterns. During induction heating, however, the frypan with type B stainless steel plate-pattern showed lower surface temperature than the frypan with type A stainless steel plate-pattern. It is concluded that Type B stainless steel plate-pattern with circular holes and vacant spaces of lines is very effective for minimizing a thermal distortion and lowering the surface temperature of an aluminum frypan during induction heating.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.47-51
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• 2002

ECT(eddy currentign testing) is very effective technique to detect a flaw within a conductor. Co-based amorphous wire was used as a sensor head. The wire has almost 0 magneto-striction and high permeability. An uniform magnetic field was applied to 1mm thick copper plate and $25{\mu}m$ thick aluminum sheet conductor using spiral typed coil The size of the coil has $40mm{\times}40mm$ outer width and $8mm{\times}8mm$ inner width. The copper plate and aluminum sheet has 0.5mm and 0.1mm wide gap, respectively. The frequency range of applied field was 100kHz-600kHz. The induced voltage difference of 2.5mV was obtained in the maximum voltage and minimum one measured across the gap of the 1mm thick conductor. In the case of aluminum sheet, 0.4mV was obtained. From this results, the effectiveness of Co-based amorphous wire was confirmed in the ECT technique.

• 한국자동차공학회논문집
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• 제20권1호
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• pp.141-146
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• 2012

Aluminum alloys have been used with various thicknesses suitable for light weight of structure. It is known that the thickness effect of material is an important factor affecting fatigue crack propagation under constant fatigue stress condition. In this work, we presented the behavior of fatigue crack propagation in thin plate compared to thick plate Al 2024-T3 alloy with referred thickness effect in a correlative equation determined by the shape factor and the loading factor. We chose two factors that are used in the correlative equation with considering that the experiments were carried out under a constant fatigue stress condition. The thickness ratio of thin plate compared to thick plate and the equivalent effective stress intensity factor ratio depending on thickness were chosen as shape and loading factors. A correlative equation is utilized to determine the equivalent effective stress intensity factor range of thin plate and identify the degree of increasing phenomenon of fatigue life in thin plate compared to thick plate.

• 한국전산구조공학회논문집
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• 제16권2호
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• pp.133-140
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• 2003

샌드위치 판은 질량에 비해 높은 강성과 강도를 갖고 있으므로 매우 효율적인 구조재로서 폭넓게 쓰이고 있다. 알루미늄 압출 샌드위치 판의 적절한 설계를 위하여는 역학적 거동 해석이 선행되어야 하나, 아직 이에 대한 연구는 미비한 상태이다. 코어가 채워져 있지 않은 중공 단면(hollow section)인 샌드위치 판의 역학적 거동 해석에는 일반적으로 상세 유한 요소 해석을 하게되나, 이는 모델링과 해석에 많은 시간이 소요된다. 본 논문에서는 트러스(truss) 형상의 심재를 갖는 샌드위치 구조 압출재를 이방성의 판으로 치환하여 해석하는 방법을 제시하였다 적절한 이방성 후판으로의 치환을 위해 등가의 강성을 평가하는 방법을 제안하였으며, 이 등가의 강성을 판 이론에 적용하여 균일 분포 하중을 받는 사변 단순지지 조건의 알루미늄 압출재에 대한 처짐과 응력에 대해 간이 해석식을 개발하였다. 아울러 상용 유한 요소 프로그램을 이용하여 계산한 결과와 비교한 결과 제시한 간이식의 높은 정도와 효율성이 입증되었다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.110-114
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• 2000

This paper shows the possibility of performing the friction stir welding and the development of optimizing tools for FSW with 2mm thick plate of aluminum alloys using milling machine. This research can be reported on achieving above 90% of the tensile strength in 1050 aluminum alloys friction stir welded in the room temperature. This welding process is very simple and does not require filler metal eliminates straightening of the workpiece. It is currently attracting interest from different industries working with aluminum alloys.

• Journal of Welding and Joining
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• 제31권1호
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• pp.21-25
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• 2013

Aluminum alloy, Al5083-O, is one of candidate materials for the LNG storage tank, because of its excellent weldability, cryogenic characteristics, and corrosion resistance. The good weldability of Al5083-O is very important in LNG storage tank manufacturing. In this study, high current metal inert gas(MIG) welding process was used to get one pass welding of thick plate aluminum alloy. Bead on plate(BOP) welding was performed to evaluate the effect of welding conditions on the height of bead and depth of penetration. The optimum welding conditions were derived to get one pass welding of the thickness of 14.5mm. The mechanical properties of the welded joint were evaluated. The cross-sectional macro test, tensile test, and bending test satisfied the class rule.