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Directional solidification of metal-gas eutectic and fabrication of regular porous metals
LIU Yuan, LI Yanxiang, WAN Jiang
《机械工程前沿(英文)》 2007年 第2卷 第2期 页码 180-183 doi: 10.1007/s11465-007-0030-x
关键词: orientation solid-gas eutectic research solidifying porosity
Novel casting processes for single-crystal turbine blades of superalloys
Dexin MA
《机械工程前沿(英文)》 2018年 第13卷 第1期 页码 3-16 doi: 10.1007/s11465-018-0475-0
This paper presents a brief review of the current casting techniques for single-crystal (SC) blades, as well as an analysis of the solidification process in complex turbine blades. A series of novel casting methods based on the Bridgman process were presented to illustrate the development in the production of SC blades from superalloys. The grain continuator and the heat conductor techniques were developed to remove geometry-related grain defects. In these techniques, the heat barrier that hinders lateral SC growth from the blade airfoil into the extremities of the platform is minimized. The parallel heating and cooling system was developed to achieve symmetric thermal conditions for SC solidification in blade clusters, thus considerably decreasing the negative shadow effect and its related defects in the current Bridgman process. The dipping and heaving technique, in which thin-shell molds are utilized, was developed to enable the establishment of a high temperature gradient for SC growth and the freckle-free solidification of superalloy castings. Moreover, by applying the targeted cooling and heating technique, a novel concept for the three-dimensional and precise control of SC growth, a proper thermal arrangement may be dynamically established for the microscopic control of SC growth in the critical areas of large industrial gas turbine blades.
关键词: superalloy investment casting Bridgman process directional solidification single crystal turbine blade
Premature melt solidification during mold filling and its influence on the as-cast structure
M. WU, M. AHMADEIN, A. LUDWIG
《机械工程前沿(英文)》 2018年 第13卷 第1期 页码 53-65 doi: 10.1007/s11465-017-0437-y
Premature melt solidification is the solidification of a melt during mold filling. In this study, a numerical model is used to analyze the influence of the pouring process on the premature solidification. The numerical model considers three phases, namely, air, melt, and equiaxed crystals. The crystals are assumed to have originated from the heterogeneous nucleation in the undercooled melt resulting from the first contact of the melt with the cold mold during pouring. The transport of the crystals by the melt flow, in accordance with the so-called “big bang” theory, is considered. The crystals are assumed globular in morphology and capable of growing according to the local constitutional undercooling. These crystals can also be remelted by mixing with the superheated melt. As the modeling results, the evolutionary trends of the number density of the crystals and the volume fraction of the solid crystals in the melt during pouring are presented. The calculated number density of the crystals and the volume fraction of the solid crystals in the melt at the end of pouring are used as the initial conditions for the subsequent solidification simulation of the evolution of the as-cast structure. A five-phase volume-average model for mixed columnar-equiaxed solidification is used for the solidification simulation. An improved agreement between the simulation and experimental results is achieved by considering the effect of premature melt solidification during mold filling. Finally, the influences of pouring parameters, namely, pouring temperature, initial mold temperature, and pouring rate, on the premature melt solidification are discussed.
关键词: premature solidification mold filling as-cast structure modeling
Improved directional-distance filter
JIN Lianghai, LI Dehua
《机械工程前沿(英文)》 2008年 第3卷 第2期 页码 205-211 doi: 10.1007/s11465-008-0025-2
关键词: information distance-weighted directional-distance ADWDDF traditional DDF spatial-distance weighting
《能源前沿(英文)》 2021年 第15卷 第4期 页码 959-973 doi: 10.1007/s11708-021-0753-0
关键词: molten metal spreading solidification particle method severe accident fuel debris decommissioning
A Bayesian modeling approach to bi-directional pedestrian flows in carnival events
S. Q. XIE, S. C. WONG, William H. K. LAM
《工程管理前沿(英文)》 2017年 第4卷 第4期 页码 483-489 doi: 10.15302/J-FEM-2017023
关键词: pedestrian flow model bi-directional interactions empirical studies Bayesian inference
Acoustic characteristics of bi-directional turbines for thermoacoustic generators
Dongdong LIU, Yanyan CHEN, Wei DAI, Ercang LUO
《能源前沿(英文)》 2022年 第16卷 第6期 页码 1027-1036 doi: 10.1007/s11708-020-0702-3
关键词: thermoacoustic power generator acoustic characteristics bi-directional impulse turbine energy conversion
Novel technologies for the lost foam casting process
Wenming JIANG, Zitian FAN
《机械工程前沿(英文)》 2018年 第13卷 第1期 页码 37-47 doi: 10.1007/s11465-018-0473-2
Lost foam casting (LFC) is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the Al and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting techno- logy; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thin-wall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the Al/Mg and Al/Al bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.
关键词: LFC under vacuum and low pressure vibration solidification pressure solidification expendable shell casting bimetallic castings
Cement-based solidification/stabilization of contaminated soils by nitrobenzene
Jianguo LIU, Xiaoqin NIE, Xianwei ZENG, Zhaoji SU
《环境科学与工程前沿(英文)》 2012年 第6卷 第3期 页码 437-443 doi: 10.1007/s11783-012-0406-y
关键词: solidification/stabilization nitrobenzene contaminated soils powder activated carbon
Improvement of solidification model and analysis of 3D channel blockage with MPS method
《能源前沿(英文)》 2021年 第15卷 第4期 页码 946-958 doi: 10.1007/s11708-021-0754-z
关键词: boiling water reactor (BWR) severe accident channel blockage moving particle semi-implicit (MPS) method solidification
介万奇
《中国工程科学》 2002年 第4卷 第6期 页码 1-4
从对材料成形加工技术进步的分析入手,论述了凝固技术在材料先进成形加工技术中的应用及其重要性。结合对几种凝固新技术的实例的分析指出,不论是传统材料加工过程“控形—控性(控制组织)—控制成本—控制污染”一体化新技术,还是作为新材料研制手段,凝固技术的重要性均是非常突出的。进而分析了近年来受到广泛重视的凝固过程研究的新课题及其由此可能带来的技术进步。
朱鸣芳,于金,洪俊杓
《中国工程科学》 2004年 第6卷 第5期 页码 8-16
应用计算机数值模拟技术研究金属凝固显微组织的形成规律是材料科学发展的重要前沿领域之一。文章对该领域的最新研究进展作了简要评述;重点介绍了作者发展的一个改进的MCA(modified cellular automaton)模型的特点以及应用该模型在合金凝固组织 数值模拟方面的一些主要工作。
关键词: 凝固 显微组织 计算机模拟 cellular automaton模型
Hefu Pu, Aamir Khan Mastoi, Xunlong Chen, Dingbao Song, Jinwei Qiu, Peng Yang
《环境科学与工程前沿(英文)》 2021年 第15卷 第4期 doi: 10.1007/s11783-020-1359-1
关键词: Dredged contaminated sediment Dewatering Solidification/stabilization Vacuum preloading Prefabricated horizontal drain Heavy metal
null
《医学前沿(英文)》 2016年 第10卷 第3期 页码 286-296 doi: 10.1007/s11684-016-0456-9
Exogenic electric fields can effectively accelerate bone healing and remodeling through the enhanced migration of bone marrow mesenchymal stem cells (BMSCs) toward the injured area. This study aimed to determine the following: (1) the direction of rat BMSC (rBMSC) migration upon exposure to a direct current electric field (DCEF), (2) the optimal DCEF intensity and duration, and (3) the possible regulatory role of SDF-1/CXCR4 axis in rBMSC migration as induced by DCEF. Results showed that rBMSCs migrated to the positive electrode of the DCEF, and that the DCEF of 200 mV/mm for 4 h was found to be optimal in enhancing rBMSC migration. This DCEF strength and duration also upregulated the expression of osteoblastic genes, including ALP and OCN, and upregulated the expression of ALP and Runx2 proteins. Moreover, when CXCR4 was inhibited, rBMSC migration due to DCEF was partially blocked. These findings indicated that DCEF can effectively induce rBMSC migration. A DCEF of 200 mV/mm for 4 h was recommended because of its ability to promote rBMSC migration, proliferation, and osteogenic differentiation. The SDF-1/CXCR4 signaling pathway may play an important role in regulating the DCEF-induced migration of rBMSCs.
关键词: DCEF migration osteogenesis differentiation rBMSCs SDF-1/CXCR-4
标题 作者 时间 类型 操作
Directional solidification of metal-gas eutectic and fabrication of regular porous metals
LIU Yuan, LI Yanxiang, WAN Jiang
期刊论文
Premature melt solidification during mold filling and its influence on the as-cast structure
M. WU, M. AHMADEIN, A. LUDWIG
期刊论文
Analysis of molten metal spreading and solidification behaviors utilizing moving particle full-implicit
期刊论文
A Bayesian modeling approach to bi-directional pedestrian flows in carnival events
S. Q. XIE, S. C. WONG, William H. K. LAM
期刊论文
Acoustic characteristics of bi-directional turbines for thermoacoustic generators
Dongdong LIU, Yanyan CHEN, Wei DAI, Ercang LUO
期刊论文
Cement-based solidification/stabilization of contaminated soils by nitrobenzene
Jianguo LIU, Xiaoqin NIE, Xianwei ZENG, Zhaoji SU
期刊论文
An integrated method for the rapid dewatering and solidification/stabilization of dredged contaminated
Hefu Pu, Aamir Khan Mastoi, Xunlong Chen, Dingbao Song, Jinwei Qiu, Peng Yang
期刊论文