• 한국항공우주학회지
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• 제48권12호
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• pp.1005-1012
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• 2020

PCI-Express 버스를 적용하는 항공전자 시스템은 CPU와 입출력 장치를 하나의 채널만을 사용하여 연결하기 때문에, 불행하게도 그 채널에 고장이 발생하면 적어도 하나의 입출력 장치를 사용할 수 없게 되는 문제가 있다. 본 논문은 항공전자 시스템을 위한 PCI-Express 버스의 결함감내 구조를 제시하기 위해서, PCI-Express 채널을 이중화하여 하나의 채널에 고장이 발생하여도 고장이 발생하지 않은 다른 채널을 통해 여전히 정상적으로 기능하는 버스 구조를 제시한다. 논문에서 제시하는 버스 구조는 두 개의 CPU port에서 출력된 이중적 PCI-Express 버스 신호를 각각의 switch 회로에 입력되게 하고, 이 회로가 각 입출력 장치에 결함을 감내하도록 선택된 독립된 버스 채널을 제공하게 한다. 본 논문에서는 제시하는 버스 구조를 구현 및 실험하여 하나의 PCI-Express 버스에 고장이 발생하면, 그 고장 상황을 실시간으로 감지되고, 고장이 발생하지 않은 다른 버스로 채널을 전환되어 정상적으로 통신이 수행되는 것을 보인다.

• 산업경영시스템학회지
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• 제44권4호
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• pp.208-219
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• 2021

In the era of the 4th industrial revolution driven by the convergence of ICT(information and communication technology) and manufacturing, research on smart factories is being actively conducted. In particular, the manufacturing industry prefers smart factories that autonomously connect and analyze data. For the efficient implementation of smart factories, it is essential to have an integrated production system that vertically integrates separately operated production equipment and heterogeneous S/W systems such as ERP, MES. In addition, it is necessary to double-verify production data by using automatic data collection technology so that the production process can be traced transparently. In this study, we want to show a case of data-centered integration of a large aircraft parts processing factory that requires high precision, takes a long time, and has the characteristics of processing large raw materials. For this, the components of the data-oriented integrated production system were identified and the connection structure between them was explained. And we would like to share the experience gained through the design and implementation case. The integrated production system proposed in this study integrates internal components based on data, which is expected to serve as a basis for SMEs to develop into an advanced stage, and traces materials with RFID technology.

• 한국항공우주학회지
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• 제50권3호
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• pp.157-164
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• 2022

본 논문에서는 무인기의 경로 계획을 위한 산악 지형, 레이더 그리고 방공망 등을 3차원 환경으로 구현하고, Sampling 기반의 경로 계획 알고리즘인 PRM 알고리즘을 사용하여 경로 계획 및 재계획을 수행하는 방안에 대해 서술한다. 기존의 PRM 알고리즘의 경우 생성된 노드 사이에 장애물 존재 여부를 확인하기 위한 계산이 노드 간 1:1로 이루어지고 연속적으로 수행되어 노드 수나 노드를 연결하는 거리에 계산량이 크게 영향을 받는다. 이러한 부분을 개선하기 위해 제안하는 LineGridMask 기법을 통해 장애물 존재 여부 확인 방식을 단순화하고, 병렬화를 통해 경로 계획의 계산 시간을 감소시킨다. 마지막으로 기존 PRM 알고리즘과의 성능을 비교한 결과, 경로 계획에서는 최대 88%, 재계획의 경우 최대 94%까지 계산 시간이 감소하였음을 확인하였다.

• 한국분말재료학회지
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• 제29권5호
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• pp.363-369
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• 2022

AlSi10Mg alloys are being actively studied through additive manufacturing for application in the automobile and aerospace industries because of their excellent mechanical properties. To obtain a consistently high quality product through additive manufacturing, studying the flowability and spreadability of the metal powder is necessary. AlSi10Mg powder easily forms an oxide film on the powder surface and has hydrophilic properties, making it vulnerable to moisture. Therefore, in this study, AlSi10Mg powder was hydrophobically modified through silane surface treatment to improve the flowability and spreadability by reducing the effects of moisture. The improved flowability according to the number of silane surface treatments was confirmed using a Carney flowmeter. In addition, to confirm the effects of improved spreadability, the powder prior to surface treatment and that subjected to surface treatment four times were measured and compared using s self-designed recoating tester. The results of this study confirmed the improved flowability and spreadability based on the modified metal powder from hydrophilic to hydrophobic for obtaining a high-quality additive manufacturing product.

• 열처리공학회지
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• 제36권2호
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• pp.61-68
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• 2023

Ti and Ti alloys are used in the automobile and aerospace industries due to their high specific strength and excellent corrosion resistance. However their application is limited due to poor formability at room temperature and high unit cost. In order to overcome these issues, dissimilarly jointed materials, such as cladding materials, are widely investigated to utilize them in each industrial field because of an enhanced plasticity and relatively low cost. Among various dissimilar bonding processes, the rolled cladding process is widely used in Ti alloys, but has a disadvantage of low bonding strength. Although this problem can be solved through post-heat treatment, the mechanical properties at the bonded interface are deteriorated due to residual stress generated during post-heat treatment. Therefore, in this study, the microstructure change and residual stress trends at the interfaces of Ti/Al cladding materials were studied with increasing post-heat treatment temperature. As a result, compared to the as-rolled specimens, no difference in microstructure was observed in the specimens after postheat treatment at 300, 400, and 500℃. However, a new intermetallic compound layer was formed between Ti and Al when post-heat treatment was performed at a temperature of 600℃ or higher. Then, it was also confirmed that compressive residual stress with a large deviation was formed in Ti due to the difference in thermal expansion coefficient and modulus of elasticity between Ti Grade II and Al 1050.

• Advances in materials Research
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• 제11권4호
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• pp.375-390
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• 2022

Carbon Fiber Reinforced Polymer (CFRP) composite provides outstanding mechanical capabilities and is therefore popular in the automotive and aerospace industries. Drilling is a common final production technique for composite laminates however, drilling high-strength composite laminates is extremely complex and challenging. The delamination of composites during the drilling at the entry and exit of the hole has a severe impact on the results of the holes surface and the material properties. The major goal of this research is to investigate contemporary industry solutions for drilling CFRP composites: enhanced edge geometries of cutting tools. This study examined the occurrence of delamination at the entry and exit of the hole during the drilling. For each of the 80°, 90°, and 118°point angle uncoated Brad point, Dagger, and Twist solid carbide drills, Taguchi design of experiments were undertaken. Cutting parameters included three variable cutting speeds (100-125-150 m/min) and feed rates (0.1-0.2-0.3 mm/rev). Brad point drills induced less delamination than dagger and twist drills, according to the research, and the best cutting parameters were found to be a combination of maximum cutting speed, minimum feed rate, and low drill point angle (V:150 m/min, f: 0.1 mm/rev, θ: 80°). The feed rate was determined to be the most efficient factor in preventing hole entry and exit delamination using analysis of variance (ANOVA). Regression analysis was used to create first-degree mathematical models for each cutting tool's entrance and exit delamination components. The results of optimization, mathematical modelling, and experimental tests are thought to be reasonably coherent based on the information obtained.

• 한국분말재료학회지
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• 제30권3호
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• pp.203-209
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• 2023

Aluminum alloy-based additive manufacturing (AM) has emerged as a popular manufacturing process for the fabrication of complex parts in the automotive and aerospace industries. The addition of an inoculant to aluminum alloy powder has been demonstrated to effectively reduce cracking by promoting the formation of equiaxed grains. However, the optimization of the AM process parameters remains challenging owing to their variability. In this study, the response surface methodology (RSM) was used to predict the crack density of AM-processed Al alloy samples. RSM was performed by setting the process parameters and equiaxed grain ratio, which influence crack propagation, as independent variables and designating crack density as a response variable. The RSM-based quadratic polynomial models for crack-density prediction were found to be highly accurate. The relationship among the process parameters, crack density, and equiaxed grain fraction was also investigated using RSM. The findings of this study highlight the efficacy of RSM as a reliable approach for optimizing the properties of AM-processed parts with limited experimental data. These results can contribute to the development of robust AM processing strategies for the fabrication of high-quality Al alloy components for various applications.

• 한국표면공학회지
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• 제56권6호
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• pp.401-411
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• 2023

This study investigates the synthesis, characterization, and application of zinc oxide (ZnO) nanoparticles for corrosion resistance and stress corrosion cracking (SCC) mitigation in high-temperature and high-pressure environments. The ZnO nanoparticles are synthesized using plasma discharge in water, resulting in rod-shaped particles with a hexagonal crystal structure. The ZnO nanoparticles are applied to Alloy 600 tubes in simulated nuclear power plant atmospheres to evaluate their effectiveness. X-ray diffraction and X-ray photoelectron spectroscopy analysis reveals the formation of thermodynamically stable ZnCr₂O₄and ZnFe₂O₄ spinel phases with a depth of approximately 35 nm on the surface after 240 hours of treatment. Stress corrosion cracking (SCC) mitigation experiments reveal that ZnO treatment enhances thermal and mechanical stability. The ZnO-treated specimens exhibit increased maximum temperature tolerance up to 310 ℃ and higher-pressure resistance up to 60 bar compared to non-treated ZnO samples. Measurements of crack length indicate reduced crack propagation in ZnO-treated specimens. The formation of thermodynamically stable Zn spinel structures on the surface of Alloy 600 and the subsequent improvements in surface properties contribute to the enhanced durability and performance of the material in challenging high-temperature and high-pressure environments. These findings have significant implications for the development of corrosion-resistant materials and the mitigation of stress corrosion cracking in various industries.

• 한국분말재료학회지
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• 제31권1호
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• pp.30-36
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• 2024

The aerospace and power generation industries have an increasing demand for high-temperature, high-strength materials. However, conventional materials typically lack sufficient fracture toughness and oxidation resistance at high temperatures. This study aims to enhance the high-temperature properties of Nb-Si-Ti alloys through ball milling. To analyze the effects of milling time, the progression of alloying is evaluated on the basis of XRD patterns and the microstructure of alloy powders. Spark plasma sintering (SPS) is employed to produce compacts, with thermodynamic modeling assisting in predicting phase fractions and sintering temperature ranges. The changes in the microstructure and variation in the mechanical properties due to the adjustment of the sintering temperature provide insights into the influence of Nb solid solution, Nb5Si3, and crystallite size within the compacts. By investigating the changes in the mechanical properties through strengthening mechanisms, such as precipitation strengthening, solid solution strengthening, and crystallite refinement, this study aims to verify the applicability of Nb-Si-Ti alloys in advanced material systems.

• 품질경영학회지
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• 제52권2호
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• pp.275-286
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• 2024

Purpose: The spare part cost is one of the most important cost factors with which construct Life Cycle Cost. The LCSP(Life Cycle Sustainment Plan) Guidebook issued by Korea Ministry of Defense, however, suggests a simple equation to estimate the spare part cost using maintenance task frequencies and each part cost. Therefore, following the cost estimation method in the LCSP Guidebook may lead to an improper cost estimation result since both the hierarchical structure of the weapon system and the part discard rate are not considered. The purpose of this study is to develop a new life cycle cost estimation method for spare parts of weapon system during its life cycle. Methods: In this study, the detailed cost structure of spare parts is provided. Also a new spare part cost estimation methods for the each cost element are proposed, considering the hierarchical structure of weapon system and the part discard rate. And the proposed spare cost estimation methods are applied to K system for a case study. Results: Based on the case study of K system, the spare part cost estimation method, proposed by this study, shows that it can complement the estimation method suggested by the LCSP Guidebook. It also shows that it is applicable to the weapon systems for Korea armed forces. Conclusion: The proposed life cycle cost estimation method for spare parts has an advantage of estimating the spare part cost more accurately. It is expected to be useful in analyzing the procurement alternatives objectively and making up the Korea armed forces budget effectively.