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Virtual Mold Technique in Thermal Stress Analysis during Casting Process

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Journal of Materials Science & Technology 2008年第3期24卷 359-363页

作者： Si-Young Kwak Jae-Wook Baek jeong-Ho Nam jeong-kil choi E-Design Center Korea Institute of Industrial Technology Department of Virtual Engineering Korea University of Science & Technology

It is important to analyse the casting product and the mold at the same time considering thermal contraction of the casting and thermal expansion of the mold. The analysis considering contact of the casting and the mold induces the precise prediction of stress distribution and the defect such as hot tearing. But it is difficult to generate FEM mesh for the interface of the casting and the mold. Moreover the mesh for the mold domain spends lots of computational time and memory for the analysis due to a number of meshes. Consequently we proposed the virtual mold technique which only uses mesh of the casting part for thermal stress analysis in casting process. The spring bar element in virtual mold technique is used to consider the contact of the casting and the mold. In general, a volume of the mold is much bigger than that of casting part, so the proposed technique decreases the number of mesh and saves the computational memory and time greatly. In this study, the proposed technique was verified by the comparison with the traditional contact technique on a specimen. And the proposed technique gave satisfactory results.

关键词： Casting process Thermal stress analysis Virtual mold

Heat Transfer between Casting and Die during High Pressure Die Casting Process of AM50 Alloy-Modeling and Experimental Results

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Journal of Materials Science & Technology 2008年第1期24卷 131-135页

作者： Zhipeng GUO Shoumei XIONG Sang-Hyun Cho jeong-kil choi Key Laboratory for Advanced Manufacturing by Materials Processing Technology Department of Mechanical Engineering Tsinghua University Beijing 100084 China Advanced Material R＆D Center Korean Institute of Industrial Technology 994-32 Dongchun-Dong Yonsu-Ku Inchon Korea

A method based on die casting experiments and mathematic modeling is presented for the determination of the heat flow density （HFD） and interfacial heat transfer coefficient （IHTC） during the high pressure die casting （HPDC） *** were carried out using step shape casting and a commercial magnesium alloy,*** profiles were measured and recorded using thermocouples embedded inside the die. Based on these temperature readings,the HFD and IHTC were successfully determined and the calculation results show that the HFD and IHTC at the metal-die interface increases sharply right after the fast phase injection process until approaching their maximum values,after which their values decrease to a much lower level until the dies are *** patterns of heat transfer behavior were found between the die and the casting at different *** thinner the casting was,the more quickly the HFD and IHTC reached their steady ***,the values for both the HFD and IHTC values were different between die and casting at different thicknesses.

关键词： : Interfacial heat transfer coefficient High pressure die casting process AM50 Magnesium alloy

Application of Integrated Database to the Casting Design

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Journal of Materials Science & Technology 2008年第3期24卷 351-355页

作者： In-Sung Cho Seung-Mok Yoo Chae-Ho Lim jeong-kil choi KITECH 7-47 Songdo-dongYeonsu-gu

Construction of integrated database including casting shapes with their casting design, technical knowledge, and thermophysical properties of the casting alloys were introduced in the present study. Recognition tech- nique for casting design by industrial computer tomography was used for the construction of shape database. Technical knowledge of the casting processes such as ferrous and non-ferrous alloys and their manufacturing process of the castings were accumulated and the search engine for the knowledge was developed. Database of thermophysical properties of the casting alloys were obtained via the experimental study, and the properties were used for the in-house computer simulation of casting process. The databases were linked with intelligent casting expert system developed in center for e-design, KITECH. It is expected that the databases can help non casting experts to devise the casting and its process. Various examples of the application by using the databases were shown in the present study.

关键词： Integrated database Casting design Shape recognition

Development of high performance casting analysis software by coupled parallel computation

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China Foundry 2007年第3期4卷 215-219页

作者： Sang Hyun CHO jeong kil choi Center For e-Design Korea Institute of Industrial Technology994-32Dongchun-DongYeonsu-GuIncheon406-800Korea

Up to now,so much casting analysis software has been continuing to develop the new access way to real casting processes. Those include the melt flow analysis,heat transfer analysis for solidification calculation,mechanical property predictions and microstructure predictions. These trials were successful to obtain the ideal results comparing with real situations,so that CAE technologies became inevitable to design or develop new casting processes. But for manufacturing fields,CAE technologies are not so frequently being used because of their difficulties in using the software or insufficient computing performances. To introduce CAE technologies to manufacturing field,the high performance analysis is essential to shorten the gap between product designing time and prototyping time. The software code optimization can be helpful,but it is not enough,because the codes developed by software experts are already optimized enough. As an alternative proposal for high performance computations,the parallel computation technologies are eagerly being applied to CAE technologies to make the analysis time shorter. In this research,SMP (Shared Memory Processing) and MPI (Message Passing Interface) (1) methods for parallelization were applied to commercial software "Z-Cast" to calculate the casting processes. In the code parallelizing processes,the network stabilization,core optimization were also carried out under Microsoft Windows platform and their performances and results were compared with those of normal linear analysis codes.

关键词： parallel computation message passing interface casting analysis SMP performance improvement

Impact analysis of casting parts considering shrinkage cavity defect

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China Foundry 2011年第1期8卷 112-116页

作者： Si-Young Kwak Jie Cheng jeong-kil choi Center for e-Design Korea Institute of lndustrial Technology Incheon 406-800 Korea Department of Virtual Engineering School of Engineering Korea University of Science ＆ Technology Daejeon Korea

Shrinkage cavity may be detrimental to mechanical performances of casting *** a consequence,design engineers often use overly large safety factors in many designs due to insufficient understanding of quantitative effects of shrinkage cavity *** this paper,process of Al alloy wheel impact test was computationally analyzed for both the wheel models with and without shrinkage cavity *** on shrinkage cavity data obtained from industrial CT (Computerized Tomography),the shrinkage cavity defects were modeled with SSM (Shape Simplification Method),which reconstructs shrinkage cavity defects to hollow spheroid *** the impact simulation was conducted,the results show that under impact test condition,the wheel considering shrinkage cavity defects may fracture while the sound-assumed wheel may not.

关键词： casting shrinkage cavity defect impact computational analysis Al alloy wheel

Critical cooling rate on carbide precipitation during quenching of austenitic manganese steel

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China Foundry 2010年第2期7卷 178-182页

作者： Youn-Soo Ham jeong-Tae Kim Si-Young Kwak jeong-kil choi Woo-Young Yoon Daeyang R-Tech.Co. Ltd290-28Daehwa-DongDaeduk-GuDaejeonKorea e-Design Center KITECH7-47Songdo-DongYeonsu-GuIncheon 406-800Korea Department of Materials Science and Engineering Korea UniversityAnam-DongSeongbuk-GuSeoul 136-701Korea

Critical cooling rate to avoid carbide precipitation during quenching of austenitic manganese steel was investigated by means of optical microscopy,image analyzer and numerical *** efficient heat treatment analysis program including temperature-dependent material properties was developed for the prediction of cooling rate and probability of carbide precipitation during quenching by finite difference ***-dependent heat transfer coefficient was adopted to achieve more precise *** ratio of carbide precipitation was measured by image analyzer to determine the critical point of carbide ***-dependent critical cooling rate at that point was calculated by the developed numerical ***,the probability of carbide precipitation on the whole area of specimen can be predicted by the proposed numerical program and the numerical result of a specimen was compared with the experimental result.

关键词： austenitic manganese steel carbide precipitation quenching critical cooling rate

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具有缩孔缺陷铸件的冲击分析

铸造 2011年第4期60卷 414-418页

作者： Si-Young Kwak Jie Cheng jeong-kil choi Cyber Design Center KITECH 7-47 Songdo-Dong Yeonsu-Gu Incheon Korea School of Engineering Korea University of Science ＆ Technology Daejeon Korea

缩孔对铸件的力学性能是有害的。由于未能充分掌握缩孔缺陷的定量结果,因此设计工程师往往在很多设计中使用较大的安全系数。文中针对Al合金轮的冲击测试进行了计算分析,包括含有缩孔缺陷的和不含缩孔缺陷的轮体模型。根据工业计算机X... 详细信息

缩孔对铸件的力学性能是有害的。由于未能充分掌握缩孔缺陷的定量结果,因此设计工程师往往在很多设计中使用较大的安全系数。文中针对Al合金轮的冲击测试进行了计算分析,包括含有缩孔缺陷的和不含缩孔缺陷的轮体模型。根据工业计算机X射线断层扫描技术获得的缩孔数据,用形状简化法建立了缩孔缺陷模型,将缩孔缺陷重构成简单的中空椭球形,进行了冲击模拟。结果表明:在冲击测试条件下,含有缩孔缺陷的铝轮会发生破坏,而假设不含缺陷的完好铝轮则不会发生破坏。

关键词：铸件缩孔缺陷冲击计算分析铝合金轮

Therapeutic potential of exercise-hormone irisin in Alzheimer's disease

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Neural Regeneration Research 2025年第6期20卷 1555-1564页

作者： Eunhee Kim Rudolph ETanzi Se Hoon choi Genetics and Aging Research Unit MassGeneral Institute for Neurodegenerative DiseaseDepartment of NeurologyMassachusetts General HospitalHarvard Medical SchoolCharlestownMAUSA McCance Center for Brain Health Massachusetts General HospitalBostonMAUSA

Irisin is a myokine that is generated by cleavage of the membrane protein fibronectin type Ⅲ domain-containing protein 5(FNDC5) in response to physical exercise. Studies reveal that irisin/FNDC5 has neuroprotective functions against Alzheimer's disease, the most common form of dementia in the elderly, by improving cognitive function and reducing amyloid-β and tau pathologies as well as neuroinflammation in cell culture or animal models of Alzheimer's disease. Although current and ongoing studies on irisin/FNDC5 show promising results, further mechanistic studies are required to clarify its potential as a meaningful therapeutic target for alleviating Alzheimer's disease. We recently found that irisin treatment reduces amyloid-β pathology by increasing the activity/levels of amyloid-β-degrading enzyme neprilysin secreted from astrocytes. Herein, we present an overview of irisin/FNDC5's protective roles and mechanisms against Alzheimer's disease.

关键词： Alzheimer's disease exercise fibronectin typeⅢdomain-containing protein 5(FNDC5) irisin

Apolipoprotein A-I binding protein-mediated neuroprotection in glaucomatous neuroinflammation and neurodegeneration

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Neural Regeneration Research 2025年第5期20卷 1414-1415页

作者： Sinwoo Hwang Seunghwan choi Soo-Ho choi Keun-Young Kim Yury I.Miller Won-Kyu Ju Hamilton Glaucoma Center and Shiley Eye Institute The Viterbi Family Department of OphthalmologyUniversity of California San DiegoLa JollaCAUSA Department of Medicine University of California San DiegoLa JollaCAUSA National Center for Microscopy and Imaging Research Department of NeurosciencesUniversity of California San DiegoLa JollaCAUSA

Glaucoma is a multifactorial eye disorder that can cause vision loss and irreversible blindness,affecting individ uals aged 40 to 80 yea rs *** to the aging population,it is expected that the number of people affected by glaucoma will surpass 111 million by 2040 as the disease becomes more *** primarily contributes to optic nerve axon loss and the progressive degeneration of retinal ganglion cells (RGCs),subsequently leading to vision impairment.

关键词： irreversible pass primarily