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Optimization of casting Process for heat and Abrasion Resistant Large Gray Iron castings

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Tsinghua Science and Technology 2008年第2期13卷 152-156页

作者： S. M. Yoo Y. S. cho c. c. lee j. h. Kim c. h. Kim j. K. choi center for E-Design Korea Institute of Industrial Technology Kwanghee casting Mfg. co. R&D center Doosan Engine Co. Ltd.

Numerical simulations were used to optimize the casting design and conditions for large cast iron castings for marine engines, Simulations of the mold filling and solidification sequences were used to analyze the problems of previous casting conditions with marked improvements for large cylinder liner parts, The amount and positions of chills were optimized to improve the mechanical properties and to minimize the shrinkage and micro porosity in the castings. Ultra sonic testing, penetration testing, and mechanical property testing show no defects in the castings with the productivity significantly increased.

关键词： gray cast iron numerical simulation marine engine cylinder liner chill casting design optimization

The Kirkendall effect on erosion resistance of chrome-coated 25cr3Mo2WNiV and 30SiMn2MoV gun barrel steels

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journal of Materials Science & Technology 2024年第10期177卷 246-255页

作者： c.h.Dou P.F.jin c.Z.Wang j.j.Li c.Zhang j.F.huang c.Zhang Key Laboratory for Advanced Materials Processing State State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology BeijingBeijing 100083China National joint Engineering Research center for Abrasion control and Molding of Metal Materials School of Materials Science and EngineeringHenan University of Science and TechnologyLuoyang 471003China

This study aimed to investigate the erosion behavior and mechanism of a newly developed 25cr3Mo2WNiV steel with a chrome coating using promoted ignition combustion *** erosion threshold pressure and temperature of the chrome-coated 25cr3Mo2WNiV steel were determined to be 0.2 MPa and 254.3 K higher than those of traditional chrome-coated 30SiMn2MoV ***,Kirkendall voids and inter-diffusion between the cr coating and matrix were first observed before *** improved erosion resistance of the chrome-coated 25cr3Mo2WNiV steel was attributed to the suppression of the Kirkendall effect,which minimized heat generation at the cr/matrix interface by pre-venting oxygen diffusion and reducing oxygen affinity.

关键词： Erosion resistance Kirkendall effect cr coating Gun steel

A numerical study on the influence of grain boundary oxides on dwell fatigue crack growth of a nickel-based superalloy

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journal of Materials Science & Technology 2022年第9期104卷 224-235页

作者： c.Z.Fang h.c.Basoalto M.j.Anderson h.Y.Li S.j.Williams P.Bowen Department of Materials Science and Engineering University of SheffieldMappin StSheffield S13JDUK School of Metallurgy and Materials University of BirminghamEdgbastonBirmingham B152TTUK Institute of Structural Materials Swansea UniversitySwansea SA18ENUK

A theoretical treatment on the oxide-controlled dwell fatigue crack growth of aγ'strengthened nickelbased superalloys is *** particular,this study investigates the influence of an externally applied load and variations in theγ'dispersion on the grain boundary oxide growth kinetics.A dislocation-based viscoplastic constitutive description for high temperature deformation is used to simulate the stress state evolution in the vicinity of a crack at elevated *** viscoplastic model explicitly accounts for multimodalγ'particle size distributions.A multicomponent mass transport formulation is used to simulate the formation/evolution of an oxide wedge ahead of the crack tip,where stress-assisted vacancy diffusion is assumed to *** resulting set of constitutive and mass transport equations have been implemented within a finite element *** of predicted compositional fields across the matrix/oxide interface are compared with experiments and shown to be in good *** indicate that the presence of a fineγ'size distribution has a strong influence on the predicted ow stress of the material and consequently on the relaxation in the vicinity of the crack-tip/oxide *** is shown that a unimodal dispersion leads to reduced oxide growth rates(parabolic behavior)when compared to a bimodal *** conditions for oxide formation are investigated and is associated with the prediction of compressive stresses within the oxide layer just ahead of the crack tip,which become progressively negative as the oxide wedge ***,mechanical equilibrium requirements induce tensile stresses at the tip of the oxide wedge,where failure of the oxide is *** time taken to reach this critical stress for oxide failure has been calculated,from which dwell crack growth rates are computationally *** predicted rates are shown to be in good agreement with available experimental data.

关键词： Nickel based superalloy Dwell crack growth Gamma prime creep Oxidation Dislocation-based modeling Multicomponent diffusion Finite element method

Flow of a micropolar fluid in a micro-channel under the action of an alternating electric field: Estimates of flow in bio-fluidic devices

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journal of hydrodynamics 2015年第3期27卷 350-358页

作者： MISRA j.c. chANDRA S. hERWIG h. centre for healthcare Science and Technology Indian Institute of Engineering Science and Technology Department of Physics Sabang S. K. Mahavidyalaya Vidyasagar University Institute of Thermo-Fluid Dynamics Technische Universitat Hamburg-Harburg

The paper is devoted to a study of the electro-osmotic flow of a micropolar bio-fluid, when the flow takes place between two plates that are in a state of periodic vibrations. considering blood as a micropolar fluid, it is found that the amplitude of oscillation of the microparticles of blood increases when the micropolar effect is pronounced more and more and that a rise in Debyehtickel parameter enhances both the velocity and microrotation gradient. The results provide guidelines for the improvement of design of bio-sensing and micro-fluidic devices. The study leads to the conclusion that electrical double layers formed in the vicinity of the wall can significantly alter the flow dynamics of physiological fluids in micro-bio-fluidic devices.

关键词： microrotation Electro-osmotic flow Debye-hiickel parameter micropolar fluid

Design of small-area multi-bit antifuse-type 1 kbit OTP memory

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journal of central South University 2009年第3期16卷 467-473页

作者：李龙镇 lee j h KIM T h jIN K h PARK M h hA P B KIM Y h Department of Electronic Engineering Changwon National University Department of computer Science and Technology Yanbian University

A multi-bit antifuse-type one-time programmable （OTP） memory is designed, which has a smaller area and a shorter programming time compared with the conventional single-bit antifuse-type OTP memory. While the conventional antifuse-type OTP memory can store a bit per cell, a proposed OTP memory can store two consecutive bits per cell through a data compression technique. The 1 kbit OTP memory designed with Magnachip 0.18 μm cMOS （complementary metal-oxide semiconductor） process is 34% smaller than the conventional single-bit antifuse-type OTP memory since the sizes of cell array and row decoder are reduced. And the programming time of the proposed OTP memory is nearly 50% smaller than that of the conventional counterpart since two consecutive bytes can be compressed and programmed into eight OTP cells at once. The layout area is 214 μm× 327 μ,, and the read current is simulated to be 30.4 μA.

关键词： multi-bit OTP programming time antifuse memory data compression

Preparation of Pure copper Powder from Acidic copper chloride Waste Etchant

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journal of Materials Science & Technology 2008年第1期24卷 141-142页

作者： h.S.hong M.S.Kong j.K.Ghu j.K.lee h.G.Suk Plant Engineering center.Institute for Advanced Engineering Yongin 449-863 Korea Dept. of Advanced Mater. Eng. Korea Polytechnic University Shihung 429-793 Korea Nano-surface Treat. Tech. Team Korea Inst. of Industrial Technology Incheon 463-130 Korea Dept. of Mater. and Met. Eng. Kangwon National University Samcheok 245-711 Korea

The method for the recycling of copper from copper chloride solution was developed. This process consists of extraction of copper, purification and particle size reduction. In the first step, reductive metal scraps were added to acidic copper chloride waste enchants produced in the PcB industry to obtain copper powder. composition analysis showed that this powder contained impurities such as Fe, Ni, and water. So, drying and purification were carried out by using microwave and a centrifugal separator. Thereby the copper powder had a purity of higher than 99% and spherical form in morphology. The copper powder size was decreased by ball milling.

关键词： copper chloride liquid waste Printed circuit board (PcB), Liquid waste highpurity copper powder

A novel twice-interpolation finite element method for solid mechanics problems

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Acta Mechanica Sinica 2010年第2期26卷 265-278页

作者： c. Zheng S. c. Wu X. h. Tang j. h. Zhang State Key Laboratory of hydraulics and Mountain River Engineering Sichuan University 610065 Chengdu China State Key Laboratory of Digital Manufacturing and Equipment Technology Huazhong University of Science and Technology 430074 Wuhan China Department of Mechanical Engineering Centre for Advanced Computations in Engineering Science (ACES)National University of Singapore Singapore 117576 Singapore

Formulation and numerical evaluation of a novel twice-interpolation finite element method （TFEM） is presented for solid mechanics problems. In this method, the trial function for Galerkin weak form is constructed through two stages of consecutive interpolation. The primary interpolation follows exactly the same procedure of standard FEM and is further reproduced according to both nodal values and averaged nodal gradients obtained from primary interpolation. The trial functions thus constructed have continuous nodal gradients and contain higher order polynomial without increasing total freedoms. Several benchmark examples and a real dam problem are used to examine the TFEM in terms of accuracy and convergence. compared with standard FEM, TFEM can achieve significantly better accuracy and higher convergence rate, and the continuous nodal stress can be obtained without any smoothing operation. It is also found that TFEM is insensitive to the quality of the elemental mesh. In addition, the present TFEM can treat the incompressible material without any modification.

关键词： Twice-interpolation finite element method·Stress smoothing Volumetric locking Mesh distortion

A novel mesh-free poly-cell Galerkin method

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Acta Mechanica Sinica 2009年第4期25卷 517-527页

作者： c. Zheng X. h. Tang j. h. Zhang S. c. Wu State Key Laboratory of hydraulics and Mountain River Engineering Sichuan University State Key Laboratory of Digital Manufacturing and Equipment Technology Huazhong University of Science and Technology centre for Advanced computations in Engineering Science (AcES) Department of Mechanical EngineeringNational University of Singapore

A novel numerical method is explored and named as mesh-free poly-cell Galerkin method. An improved moving least-square （MLS） scheme is presented, which can avoid the matrix inversion in standard MLS and can be used to construct shape functions possessing delta Kronecher property. A new type of local support is introduced to ensure the alignment of integral domains with the cells of the back-ground mesh, which will reduce the difficult in integration. An intensive numerical study is conducted to test the accuracy of the present method. It is observed that solutions with good accuracy can be obtained with the present method.

关键词： MPG cO-MSL Mesh-free Meshless Voronoi diagram

hot cracking in AZ31 and AZ61 Magnesium Alloy

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journal of Materials Science & Technology 2011年第7期27卷 633-640页

作者： c.j. huang c.M. cheng c.P. chou F.h. chen Department of Mechanical Engineering National Chiao Tung University Hsinchu 300 Taiwan China Department of Industrial Education National Taiwan Normal University Taipei 106 Taiwan China

This paper examined the impact of the number of thermal cycles and augmented strain on hot cracking in AZ31 and AZ61 magnesium alloy. Statistical analyses were performed. Following observation using a scanning electron microscope （SEM）, an energy dispersive spectrometer （EDS） was used for component analysis. Results showed that Al content in magnesium alloy has an effect on hot cracking susceptibility. In addition, the nonequilibrium solidification process produced segregation in Al content, causing higher liquid Mg-alloy rich Al content at grain boundaries, and resulting into liquefied grain boundaries of partially melted zone （PMZ）. In summary, under multiple thermal cycles AZ61 produced serious liquation cracking. AZ61 has higher （6 wt%） Al content and produced much liquefied Mg17Al12 at grain boundaries under multiple thermal cycles. The liquefied Mg17Al12 were pulled apart and hot cracks formed at weld metal hAZ due to the augmented strain. Since AZ31 had half the Al content of AZ61, its hot-cracking susceptibility was lower than AZ61. In addition, AZ61 showed longer total crack length （TcL） in one thermal cycle compared to that in three thermal cycles. This phenomenon was possibly due to high-temperature gasification of Al during the welding process, which resulted in lower overall Al content. consequently, shorter hot cracks exhibited in three thermal cycles. It was found the Al content of AZ31 and AZ61 can be used to assess the hot-cracking susceptibility.

关键词： Varestraint test Thermal cycles hot-cracking susceptibility Gas tungsten arc welding (GTAW) AZ31 AZ61