피마자 기반 수성 폴리우레탄(CPUD)을 얻기 위해 무 변성 피마자유 (CO) 와 투명 필름을 얻기 위해 이소포론 디이소시아네이트(IPDI)를 사용했다. 유연성을 증가시키기 위해 폴리프로필렌글리콜 (PPG)의 혼합 효과를 분석하였다. 또한, 사슬연장제로 에틸렌다이아민(EDA)을 사용했다. 각각 피마자유 함유에 따른 변화와 사슬연장제 변화에 따른 인장강도, 연신율 내마모성을 측정했다. 피마자유 함유가 많은 시료의 인장강도가 1.112kgf/㎟, 연신율 88%로 나타났으며, 사슬연장제 함유가 많은 시료의 인장 강도가 3.33kgf/㎟, 연신율 99%로 측정되었다. 표면강도는 SEM을 통해 육안으로 확인하였다.
Powder flowability is critical in additive manufacturing processes, especially for laser powder bed fusion. Many powder features, such as powder size distribution, particle shape, surface roughness, and chemical composition, simultaneously affect the flow properties of a powder; however, the individual effect of each factor on powder flowability has not been comprehensively evaluated. In this study, the impact of particle shape (sphericity) on the rheological properties of Ti-6Al-4V powder is quantified using an FT4 powder rheometer. Dynamic image analysis is conducted on plasma-atomized (PA) and gas-atomized (GA) powders to evaluate their particle sphericity. PA and GA powders exhibit negligible differences in compressibility and permeability tests, but GA powder shows more cohesive behavior, especially in a dynamic state, because lower particle sphericity facilitates interaction between particles during the powder flow. These results provide guidelines for the manufacturing of advanced metal powders with excellent powder flowability for laser powder bed fusion.
This paper presents the torque ripple reduction control to apply an SRM to the X-by-wire drive systems which replaces the mechanical control method with “by-wire” to secure the flexibility of design and modification. However, torque ripples generated from the SRM can affect the performance and stability of the system. The proposed torque ripple control schemes are compared with the previously studied methods by dynamic simulation in regards to torque distribution functions and instant torque controller.
In this paper, 1kW prototype PCS for tidal power generation system, which is attracting attention as the next-generation renewable energy, is studied. Tidal power generation is a method of producing energy using the difference between the tides. The advantage of tidal generators is that, unlike other renewable energies such as wave power, wind power, and solar power, they are relatively less affected by the weather changes and are regularly produced at regular intervals.
Due to stricter environmental regulations of the International Maritime Organization (IMO), the number of ships fueled by Liquefied Natural Gas (LNG) is rapidly increasing. The International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) limits the material of tanks that can store cryogenic substances such as LNG. Among the materials listed in the IGC Code, ASTM A553M-17 has been recently adopted as a material for LNG fuel tank projects because of its excellent mechanical properties at cryogenic temperatures. In shipyards, this material is being used to build tanks through Flux Cored Arc Welding (FCAW). However, there is a problem that magnetization occurs during welding and there is a big difference in welding quality depending on the welding position. In order to overcome this problem, this study intends to conduct basic research to apply laser welding to ASTM A553M-17 material. As a result of analyzing the bead shape according to laser BOP speed and Energy density performed in this study, it was confirmed that the penetration and energy density are proportional but the penetration and BOP speed are inverse proportional to some extent. In addition, a range of suitable welding speed and energy density were proposed for the 6.1mm thickness material performed in this study.
Due to stricter environmental regulations of the International Maritime Organization (IMO), the number of ships fueled by Liquefied Natural Gas (LNG) is rapidly increasing. The International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code) limits the material of tanks that can store cryogenic substances such as LNG. Among the materials listed in the IGC Code, ASTM A553M-17 has been recently adopted as a material for LNG fuel tank projects because of its excellent mechanical properties at cryogenic temperatures. In shipyards, this material is being used to build tanks through Flux Cored Arc Welding (FCAW). However, there is a problem that magnetization occurs during welding and there is a big difference in welding quality depending on the welding position. In order to overcome this problem, this study intends to conduct basic research to apply laser welding to ASTM A553M-17 material. In Part I, the bead shape according to the welding output was analyzed and in PART II, the penetration phenomenon according to the welding speed was analyzed after Bead on Plate (BOP) test. As a result of analyzing the bead shape according to laser power performed in this study, it was confirmed that the laser power and penetration depth are proportional to some extent. In addition, a range of suitable welding power was proposed for the 6.1mm thickness material performed in this study.
To cope with automobile exhaust gas regulations, ISG and charging control systems are applied to HEV vehicles for the purpose of improving fuel economy. These systems require quick charge-discharge performance of high current. Therefore, a Module of the AGM battery with high energy density and EDLC(Electric Double Layer Capacitor) with high power density are constructed to study the charging and discharging behavior. In CCA, which evaluates the starting performance at -18 oC & 30 oC with high current, EDLC contributed for about 8 sec at the beginning. At 0 oC CA (Charge Acceptance), the initial Charging current of the AGM/EDLC Module, is twice that of the AGM lead acid battery. To play the role of EDLC during high-current rapid charging and discharging, the condition of the AGM lead-acid battery is optimally maintained. As a result of a Standard of Battery Association of Japan (SBA) S0101 test, the service life of the Module of the AGM Lead Acid Battery/EDLC is found to improve by 2 times compared to that of the AGM Lead Acid Battery.
Conductive polymer composites with high electrical and mechanical properties are in demand for bipolar plates of phosphoric acid fuel cells (PAFC). In this study, composites based on natural graphite/fluorinated ethylene propylene (FEP) and different ratios of carbon black are mixed and hot formed into bars. The overall content of natural graphite is replaced by carbon black (0.2 wt% to 3.0 wt%). It is found that the addition of carbon black reduces electrical resistivity and density. The density of composite materials added with carbon black 3.0 wt% is 2.168 g/cm3, which is 0.017 g/cm3 less than that of non-additive composites. In-plane electrical resistivity is 7.68 μΩm and through-plane electrical resistivity is 27.66 μΩm. Compared with non-additive composites, in-plane electrical resistivity decreases by 95.7 % and through-plane decreases by 95.9 %. Also, the bending strength is about 30 % improved when carbon black is added at 2.0 wt% compared to non-additive cases. The decrease of electrical resistivity of composites is estimated to stem from the carbon black, which is a conductive material located between melted FEP and acts a path for electrons; the increasing mechanical properties are estimated to result from carbon black filling up pores in the composites.
This study has related to lightweight automobiles due to global warming with the reduction of fossil fuel reserves are rapidly progressing around the automobile industry.
This study has revealed the relationship for the mechanical properties via the analyzed microstructure, precipitated phase variation of the wheel hub of a commercial vehicle manufactured using molten forging technology using A356 and A357 alloys, which are high-strength Al-Si-Mg base cast aluminum alloys. Differential scanning calorimetry has performed to analyze the precipitation amount of each alloy that influences the mechanical properties of aluminum alloy. The XRD analysis has measured for the microstructure's crystal phase on A356 and A357 alloys.
In this paper has evaluated to compare the properties of the A356 alloy and the A357 alloy for the mechanical properties. The A356 alloy has confirmed that a microstructure is finer than A357 alloy, and a quantity of precipitated material is more than A357 alloy. Therefore, this study confirmed that the A356 alloy has better mechanical properties than the A357 alloy.
The objective of this study is to optimize the diameter of tubular shaft yoke and solid shaft yoke, which are the core components of Al IMS for xEV. The processes of both products were designed totally 6 steps to manufactured the shaft part and the yoke part. The diameter of solid shaft yoke and tubular shaft yoke were changed from 20mm to 25mm and from 30mm to 35mm, respectively. Al 6082 was applied to the material of both products. The friction condition between die and material was employed Oil_Cold (Aluminum) with reference to the library in the program. The results were analyzed and compared in terms of effective stress, effective strain, and nodal velocity characteristics. The effective strain value for manufacturing the yoke part was higher than the shaft part because its part has a complex geometry. The value of nodal velocity was also higher with high effective strain region. However, in 6 stage process of tubular shaft yoke, although it had the high effective strain value, the nodal velocity value was the lowest due to the piercing process. The effect of shaft part diameter on effective stress in the tubular shaft was difficult to observe, however, in the solid shaft yoke, when the shaft part of one increased, the effective stress value was increased due to the larger yoke size.
The purpose of this study is to analyze the temperature and heat resistance distribution, which is a criterion for evaluating the cooling performance, by using computer simulation of the cooling system combined with the CPU of the individual highest heat generation section, and use it as important data for the heat sink design. Using a single material of Al 6063-T5, which is an integral part of the desktop, fan and heat sink, fins and base, the analysis was carried out with various fin numbers, thicknesses, pitches and shapes of heat sinks. Ambient temperature, 25°C, heat source, 130W and cooling fan speed, 2500 rpm (50CFM) were used as boundary conditions, and heat transfer characteristics regarding temperature distribution and heat resistance were investigated using ANSYS Icepak. As a result, it has been found that as the number of fins of heat sink increases, the heat dissipation area increases to decrease heat resistance, and as the distance between each fin decreases, the ventilation resistance increases to decrease the flow intensity of the cooling air in contact with the heat dissipation area. The sunburst array also exhibits better heat transfer characteristics by obtaining a lower distribution of heat resistance with a cooling effect of about 10°C than the one-way basic array.
용천요는 중국 요업사 상 가장 중요한 요장 중 하나로 근 천년에 걸쳐 생산된 중국 고대 청자의 최전성기 전형으로 꼽힌다. 그 문화가 풍부하고 생산 규모가 커 남북요업의 문화교류와 융합의 본보기이자 중국 청자 공예발전의 역사의 집성이다. 용천요는 국내에서 널리 사용이 이루어졌는데, 궁정귀족에게 사랑을 받은 것은 물론 서민에게도 널리 쓰였다. 이 뿐만 아니라 수출용으로 대량 소비되어 세계 문명에 매우 큰 영향을 끼쳤다. 근 백 년 동안 용천요의 고고학적 조사와 발굴, 특히 신세기 들어 수많은 고고학적 작업이 진행되면서 충분한 데 이터가 축적되어 용천요의 발생․발전․쇠락의 전 과정을 알 수 있다.