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Study of the Constant Current Fuzzy Control System Design using CRS Algorithm during Inverter DC Resistance Spot Welding Process (인버터 DC 저항점용접 공정에서 CRS 알고리즘을 이용한 정전류 퍼지 제어시스템 설계에 관한 연구)

  • Park, Hyoung-Jin;Park, Pyeong-Won;Yu, Ji-Young;Kim, Dong-Cheol;Kang, Mun-Jin;Rhee, Se-Hun
    • Journal of Welding and Joining
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    • v.28 no.6
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    • pp.76-83
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    • 2010
  • The purpose of this study is to propose a method to decide near-optimal settings of the constant current fuzzy control parameters using a controlled random search. This method tries to find the near-optimal settings of the constant current fuzzy control parameters through experiments. It has an advantage of being able to carry out searches in the search domain which includes some irregular points. The method suggested in this study was used to determine the fuzzy control parameters by which the desired welding current were formed during inverter DC resistance spot welding. The output variable was the ITAE (integral of time multiplied by the absolute error). This output variable was determined according to the input variables, which are the GE, GDE, and GDU. This study described how to obtained near-optimal welding current condition over a wide search space conducting a relatively small number of experiments.

A Study on the Heat Transfer Enhancement of Miniature loop Heat Pipes by Using the Cu Nanofluids

  • Kim, Young-Sik;Jeong, Hyo-Min;Chung, Han-Shik;Tanshen, Md.Riyad;Lee, Dae-Chul;Ji, Myoung-Kuk;Bae, Kang-Youl
    • Journal of Power System Engineering
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    • v.17 no.2
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    • pp.70-77
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    • 2013
  • An experimental study was carried out to understand the heat transfer performance of a miniature loop heat pipes using water-based copper nanoparticles suspensions as the working fluid. The suspensions consisted of deionized water and copper nanoparticles with an average diameter of 80 nm. Effects of the cupper mass concentration and the operation pressure on the average evaporation and condensation heat transfer coefficients, the critical heat flux and the total heat resistance of the mLHPs were investigated and discussed. The pressure frequency also depends upon the evaporator temperature which has been maintained from 60C to 90C. The Investigation shows 60% filling ratio gives the highest inside pressure magnitude of highest number pressure frequency at any of setting of evaporator temperature and 5wt% results the lowest heat flow resistance.

Wear Characterization of Al/Al2O3 Composites Reinforced with Hybrid of Carbon Fibers and SiC Whiskers (탄소섬유와 SiC 휘스커를 혼합한 Al/Al2O3 복합재료의 마멸특성)

  • 봉하동;송정일;한경섭
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.7
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    • pp.1619-1629
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    • 1995
  • The Al/Al2O3 SiC and Al/Al2O3/C hybrid metal matrix composites (MMCs) were fabricated by squeeze infiltration method. Uniform distribution of reinforcements were found in the microstructure of metal matrix composites. Mechanical tests were carried out under various test conditions to clearly identify mechanical behavior of MMCs, and the wear mechanism of Al/Al2O3/(SiC or C) hybrid metal matrix composites were investigated. The tensile strength and hardness of hybrid composites was resulted in increasing compared with those of the unreinforced matrix alloy. Wear resistance was strongly dependent upon kinds of fiber, volume fraction and sliding speed. The wear resistance of metal matrix composites was remarkably improved by the addition of reinforcements. Especially, the wear resistance of the hybrid composites of carbon fibers was more effective than in the composites reinforced with alumina and SiC whiskers of reinforcements. This was due to the effect of carbon fiber on the solid lubrication. Wear mechanisms of hybrid composites were suggested from wear surface analyses. The major wear mechanism of hybrid composites was the abrasive wear at low to intermediate sliding speed, and the melting wear at intermediate to high sliding speed.

Investigation of rolling resistance and surface damage of rolling elements (구름계의 구름저항 및 표면파손현상의 실험적 고찰)

  • Cha, Kum-Hwan;Kim, Dae-Eun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.12
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    • pp.2019-2028
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    • 1997
  • It has been well established that resistant force and wear that occur during rolling motion depend on several factors such as material type, hardness, subsurface microstructure, applied load, and speed. The purpose of this work is to investigate the effect of microstructure and the state of deformed layer on the rolling contact characteristics in dry and lubricated rolling contacts. The results of this work show that the rolling resistance behavior depends on the state of the deformed layer. Also, lubrication can reduce the plastic flow at the surface but may still have an effect on the subsurface strain. The cross-sectional view of the microstructure shows that surface traction has a difinite effect on the morphology of the surface region. That is, significant slip seems to have taken place between the ball than those of the dry rolling case. The surface generation effects were significantly less compared to the case of dry rolling contact.

Improvement of Joining Strength of Mechanical Joining Process of a Sheet Metal Pair (박판페어의 기계적 접합장치의 결합강도 개선에 관한 연구)

  • 윤희주;김태정;양동열;권순용;신철수
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2002.05a
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    • pp.29-32
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    • 2002
  • The mechanical joining process of a sheet metal pair has been developed in order to replace the resistance spot welding process in case that joining of mechanically unweldable materials and coated sheet metals with different thickness are needed. Form-joining or clinching, a kind of mechanical joining process, is defined as joining process of a sheet metal pair by geometric constraint imposed by plastic deformation of workpieces without any additive part. It has been reported that the joining strength by commercial form-joining apparatus is 50∼70 percent of that by resistance spot welding. Therefore, a two-step form-joining process with a secondary punch is proposed. The device is designed to improve the joining strength by increasing the geometric constraint of the deformed shape by combining a primary punch, a secondary punch and a female die. In order to verify the improved joining strength by the designed process, the tensile-shear strength, the peel-tension strength and the asymmetric peel-tension strength are compared with those by the TOX process and resistance spot welding.

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Effects of Environmental Factors such as Temperature and Ozone Concentration on the Properties of BR/Crystalline Rubber Blend (BR고무/결정성고무 블렌드의 물성에 미치는 온도 및 오존농도 등의 환경인자의 영향)

  • Park, Chan-Young;Lee, Won-Kee;Min, Seong-Kee
    • Elastomers and Composites
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    • v.45 no.1
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    • pp.44-50
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    • 2010
  • The butadiene rubber(BR) blends with chloroprene rubber(CR) were prepared by mechanical mixing method. Cure characteristics, mechanical properties, ozone resistance properties and dynamic mechanical properties were subsequently examined. The properties of ozone resistance of pure BR was significantly improved through blending with 50 wt% CR. Dynamic characteristics determined from a Rheovibron generally showed two glass transition(Tg) for the entire blends, tanδ peak monotonically shifted toward the higher temperature with the increasing content of CR. Optimum cure time of compound was significantly lengthened with loading of CR.

Effects of Soil Texture and Bulk Density on the Least-Limiting Water Range (토성(土性)과 용적밀도(容積密度)가 최소생육제한수분범위(最小生育制限水分範圍)에 미치는 영향(影響))

  • Jo, In-Sang;Hyun, Byung-Keun;Cho, Hyun-Jun;Jang, Yong-Seon;Shin, Jae-Sung
    • Korean Journal of Soil Science and Fertilizer
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    • v.30 no.1
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    • pp.51-55
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    • 1997
  • Three soils, sandy loam, loam and silty clay loam, were selected and three inches soil cores with 4 bulk density(BD) levels were made by compressing the soils wetted with 3 levels water. Mechanical and water characteristics were measured and analyzed the mechanical resistance limiting water, available water and least-limiting water range. Mechanical resistance limiting water(MRLW) were appeared at higher bulk density than 1.6Mg/m3 in sandy loam, and 1.4Mg/m3 in loam and silty clay loam. The least-limiting water ranges were sharply decreased at the bulk density 1.6Mg/m3 in sandy loam and loam, 1.4Mg/m3 in silty clay loam. There were big deferences between available water contents and least limiting water ranges in finer texture and higher bulk density soils.

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Effect of silica fume and polyepoxide-based polymer on electrical resistivity, mechanical properties, and ultrasonic response of SCLC

  • Mazloom, Moosa;Allahabadi, Ali;Karamloo, Mohammad
    • Advances in concrete construction
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    • v.5 no.6
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    • pp.587-611
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    • 2017
  • This study focused on the influences regarding the use of polyepoxide-based polymer and silica fume (SF) on the fresh and hardened state properties of self-compacting lightweight concrete (SCLC) along with their impacts on electrical resistance and ultrasonic pulse velocity (UPV). To do so, two series of compositions each of which consists of twelve mixes, with water to binder (W/B) ratios of 0.35 and 0.4 were cast. Three different silica fume/binder ratios of 0, 5%, and 10% were considered along with four different polymer/binder ratios of 0, 5%, 10%, and 15%. Afterwards, the rupture modulus, tensile strength, 14-day, 28-day, and 90-day compressive strength, the UPV and the electrical resistance of the mixes were tested. The results indicated that although the use of polymer could enhance the passing and filling abilities, it could lead to a decrease of segregation resistance. In addition, the interaction of the SF and the polymeric contents enhanced the workability. However, the impacts regarding the use of polymeric contents on fresh state properties of SCLC were more prevalent than those regarding the use of SF. Besides the fresh state properties, the durability and mechanical properties of the mixes were affected due to the use of polymeric and SF contents. In other words, the use of the SF and the polymer enhanced the durability and mechanical properties of SCLC specimens.

Quality assurance algorithm using fuzzy reasoning for resistance spot weldings (퍼지추론을 이용한 저항 점용접부위의 품질평가 알고리듬)

  • Kim, Joo-Seok;Lee, Jae-Ik;Lee, Sang-ryong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.3
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    • pp.644-653
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    • 1998
  • In resistance spot weld, the assurance of weld quality has been a long-standing problem. Since the weld nuggets if resustance spot welding form between the workpieces, visual detection of defects in usually impossible. Welding quality of resistance spot welding can be verified by non destructive and destructive inspections such as X-Ray inspection and testing of weld strength. But these tests, in addition to being time-consuming and costly, can entail risks due to sampling basis. The purpose of this study is the development of the monitoring system based on fuzzy inference, aimed at diagonosis of quality in resistance spot welding. The fuzzy inference system consists of fuzzy input variables, fuzzy membership functions and fuzzy rules. For inferring the welding quality(strength), the experimental data of the spot welding were acquired in various welding conditions with the monitoring system designed. Some fuzzy input variables-maximum, slop and difference values of electrode movement signals-were extracted from the experimental data. It was confirmed that the fuzzy inference values of strength have a .±5% error in comparison with actual values for the selected welding conditions(9-10.5KA, 10-14 cycle, 250-300 kgf). This monitoring system can be useful in improving the quality assurance and reliability of the resistance spot welding process.

Development of an Efficient Mechanical Inoculation Technique to Screen Barley Genotypes for Resistance to Barley mild mosaic virus Disease and its Comparison to Natural Infection

  • Jonson, Gilda;Park, Jong-Chul;Noh, Tae-Hwan;Kim, Mi-Jung;Hyun, Jong-Nae;Kim, Jong-Gon
    • The Plant Pathology Journal
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    • v.22 no.4
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    • pp.348-352
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    • 2006
  • Barley mild mosaic virus(BaMMV) is a soilborne Bymovirus vectored by root-infecting fungus, Polymyxa graminis. Mechanism of cultivar's resistance to BaMMV in field tests are difficult to assess since resistance could be either due to the virus or to P. graminis, or both. Whereas, available mechanical inoculation methods for BaMMV and other related viruses are labor intensive, give inconsistent results and generally result in low infection rates. Inoculation method using stick with gauze(SWG) was developed for BaMMV. The improved method proved to be simple, efficient, and reliable. The infected leaf tissues were preserved by drying in a frozen state under high vaccum(freeze dried barley infected leaves) to circumvent reduction of virus infectivity during storage. Five Korean barley cultivars were mechanically inoculated with BaMMV-infected sap by the improved method. Infection rates obtained were compared with natural infection. Cultivar Naehanssalbori showed resistance to BaMMV in the field trials but was found highly susceptible in the greenhouse tests by mechanical inoculation, indicating that the field resistance may be possibly due to resistance to P. graminis.