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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

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

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

Black esophagus with concomitant candidiasis developed after diabetic ketoacidosis

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World Journal of Gastroenterology 2007年第42期13卷 5662-5663页

作者： Yong Hwan Kim si young Choi Department of Thoracic and Cardiovascular Surgery Uijeongbu St. Mary's Hospital The Catholic University of Korea College of Medicine Seoul 480-821 Korea Department of Thoracic and Cardiovascular Surgery Uijeongbu St. Mary’s Hospital The Catholic University of Korea College of Medicine Seoul 480-821 Korea

Black esophagus is a very rare disease and its pathogenesis has been *** esophagus developed concomitantly with candidiasis after diabetic ketoacidosis has not been reported *** report a case who developed esophageal stricture after the treatment of black esophagus and thus balloon dilatation was performed several times but failed,hence,surgical treatment was performed.

关键词： Esophagus Candidiasis Diabetic ketoacidosis Surgery

Evaluation the Properties of Titanium Matrix Composites by Melting Route Synthesis

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Journal of Materials Science & Technology 2008年第1期24卷 105-109页

作者： Bong-Jae Choi si-young Sung Myoung-Gyun Kim young-Jig Kim Department of Advanced Materials Engineering Sungkyunkwan University SuwonKorea Department of Advanced Materials Engineering Sungkyunkwan University SuwonKorea Materials & Processing Engineering CenterR&D DivisionKorea Automotive Technology InstituteChonanChungnamKorea Research Institute of Industrial Science and Technology Pohang Korea

The main purpose of this study is an in-situ synthesis of （TiB＋TiC） hybrid titanium matrix composites （TMCs） by vacuum induction melting method and to verify its mechanical *** melting route was adopted to synthesize the commercial pure titanium （cp Ti） and granular boron carbide （B-4C）.The reinforcements,the fraction of 10 ***,were formed by adding 1.88 wt pct B-4C to cp *** in-situ synthesis of TMCs,electron probe micro-analysis elemental mapping was carried out to confirm the distribution and shape of *** cone-on-disk type sliding wear test was also done for the identification of *** is concluded that （TiB＋TiC） hybrid TMCs can be in-situ synthesized and has better wear properties than H13.

关键词： Titanium matrix composites H13 In-situ Wear

Microstructure of porous Cu fabricated by freeze-drying process of CuO/camphene slurry

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中国有色金属学会会刊：英文版 2012年第S3期22卷 688-691页

作者： Sung-tag OH si-young CHANG Myung-jin SUK Department of Materials Science and Engineering Seoul National University of Science and Technology Department of Materials Engineering Korea Aerospace University Department of Materials and Metallurgical Engineering Kangwon National University

Porous Cu with macroscopically aligned channels was synthesized using a freeze-drying ***-based CuO slurry was prepared by milling at 60 °C with a small amount of *** of a slurry was done at 25 °C while unidirectionally controlling the growth direction of the *** were generated subsequently by sublimation of the camphene during *** green body was hydrogen-reduced at 300 °C for 30 min,and sintered in the furnace at 700 °C for 1 h under a hydrogen *** observation reveals that all of the sintered samples are composed of only Cu phase and show macroscopic open pores with an average size of 100 μm which are aligned along its macroscopic growth *** internal wall of the macroscopic aligned pore shows relatively small pores due to the traces of the camphene left between the concentrated Cu particles on the internal *** in the porosity and pore size with increasing camphene content was explained by the change of the growth behavior of the camphene crystals.

关键词： porous Cu CuO-camphene slurry freeze-drying hydrogen reduction sintering

Evaluation of Alpha-case in Titanium Castings

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Journal of Materials Science & Technology 2008年第1期24卷 70-74页

作者： si-young Sung Bong-Jae Choi Beom-Suck Han Han-dun Oh young-Jig Kim Materials & Processing Engineering Center R&D Division Korea Automotive Technology InstituteChonanChungnamKorea Department of Advanced Materials Engineering Sungkyunkwan University SuwonKorea Department of Materials Science Hanseo University Seosan 352-820Korea

The alpha-case formation reactions between Ti and investment molds （Al-2O-3,ZrsiO-4,ZrO-2,CaO stabilized ZrO-2） were evaluated in a plasma arc melting *** of thermodynamic approaches,there were distinct alpha-case *** reaction products were characterized by electron probe micro-analysis and transmission electron ***α-case generation between Ti and Al-2O-3 mold was not able to be explained by the conventionalα-case formation mechanism,which is known to be formed by the interstitials,especially oxygen dissolved from mold ***,from our experimental results and thermodynamic calculations,it was confirmed that theα-case is formed not only by an interstitial element but also by substitutional metallic elements dissolved from mold *** newly establishedα-case formation mechanism will surely lead to a variety of significant applications of theα-case controlled Ti casting.

关键词： Titanium Casting Alpha-case Net-shape

Materials property mapping from atomic scale imaging via machine learning based sub-pixel processing

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npj Computational Materials 2022年第1期8卷 1868-1876页

作者： Junghun Han Kyoung-June Go Jinhyuk Jang Sejung Yang si-young Choi Department of Biomedical Engineering Yonsei UniversityWonju26493Republic of Korea Department of Materials Science and Engineering Pohang University of Science and TechnologyPohang37673Republic of Korea

Direct visualization of the atomic structure in scanning transmission electron microscopy has led to a comprehensive understanding of the structure-property ***,a reliable characterization of the structural transition on a picometric scale is still challenging because of the limited spatial resolution and ***,we demonstrate that the primary segmentation of atomic signals from background,succeeded by a denoising process,enables structural analysis in a sub-pixel *** noise is eliminated using the block matching and three-dimensional filtering with Anscombe transformation,and remnant noise is removed via morphological filtering,which results in an increase of peak signal-to-noise ratio from 7 to 11 *** the centroids of atomic columns segmented via K-means clustering,an unsupervised method for robust thresholding,achieves an average error of less than 0.7 pixel,which corresponds to 4.6 *** study will contribute to a profound understanding of the local structural dynamics in crystal structures.

关键词： property filtering removed