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Experimental and numerical investigations of bonding interface behavior in stationary shoulder friction stir lap welding

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Journal of Materials Science & Technology 2019年第1期35卷 192-200页

作者： Q.Wen W.Y.Li W.B.wang f.f.wang Y.J.Gao V.Patel State key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University China fSW Center China Academy of Launch Vehicle Technology Beijing Institute of Astronautical Systems Engineering Capital Aerospace Machinery Company Pandit Deendayal Petroleum University

Stationary shoulder friction stir lap welding(SSfSLW) was employed to weld 2024 aluminum alloy. A coupled Eulerian-Lagrangian(CEL) model was developed to investigate the lap interface behavior during SSfSLW. Numerical results of material movement and equivalent plastic strain were in good agreement with the experimental work. With increasing welding speed, the distances from the hook tip to the top surface of the upper workpiece on the retreating side(RS) and the advancing side(AS) increase, while the distance between two wave-shaped alclads decreases. A symmetric interface bending is observed on the AS and the RS during plunging, while the interface bending on the AS is bigger than that on the RS during welding. The peak temperature of the interface on the AS is higher than that on the RS. The equivalent plastic strain gradually increases as the distance to the weld center decreases, and its peak value is obtained near the bottom of the weld.

关键词： Stationary shoulder friction stir lap welding Coupled Eulerian-Lagrangian Temperature field Material distribution Equivalent plastic strain

Recent Progress in Exploiting Small Molecule Peptides as Supramolecular Hydrogelators

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Chinese Journal of Polymer Science 2017年第10期35卷 1194-1211页

作者： Hao Su Yuzhu wang Caleb f.Anderson Jin Mo koo Han wang Honggang Cui Department of Chemical and Biomolecular Engineering The Johns Hopkins University Baltimore Maryland 21218 USA Institute for NanoBio Technology The Johns Hopkins University Baltimore Maryland 21218 USA Department of Oncology and Sidney kimmel Comprehensive Cancer Center Johns Hopkins University School of Medicine Baltimore MD 21205 USA Center for Nanomedicine The Wilmer Eye Institute Johns Hopkins University School of Medicine 400 North Broadway Baltimore MD 21231 USA

Small molecule peptides and their derivatives are an emerging class of supramolecular hydrogelators that have attracted rapidly growing interest in the fields of drug delivery and regenerative medicine due to their inherent biodegradability and biocompatibility, as well as versatility in molecular design and ease of synthesis. Built upon the directional, intermolecular interactions such as hydrogen bonding and π-π stacking, peptide-based molecular units can associate in aqueous solution into filamentous assemblies of various sizes and shapes. Under appropriate conditions, these filamentous assemblies can percolate into a 3D network with materials properties tailorable for specific biomedical applications. In this review, we survey the literature published over the past three years in the development of peptide-based hydrogelators for biomedical applications. We highlight several representative examples and center our discussion on the fundamentals of molecular design, assembly, and gelation conditions.

关键词： PNIPAM spheres reversible assembled colloidal Highly ordered assembly leaving anhydride

Unsteady magnetohydrodynamic stagnation point flow — closed-form analytical solutions

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Applied Mathematics and Mechanics(English Edition) 2019年第4期40卷 449-464页

作者： T.G.fANG f.J.wang Bo GAO Mechanical and Aerospace Engineering Department North Carolina State University School of Energy & Power Engineering Jiangsu University

This paper investigates the unsteady stagnation point flow and heat transfer of magnetohydrodynamic(MHD) fluids over a moving permeable flat surface. The unsteady Navier-Stokes(NS) equations are transformed into a similarity nonlinear ordinary differential equation, and a closed form solution is obtained for the unsteadiness parameter of 2. The boundary layer energy equation is transformed into a similarity equation,and is solved for a constant wall temperature and a time-dependent uniform wall heat flux case. The solution domain, velocity, and temperature profiles are calculated for different combinations of parameters including the Prandtl number, mass transfer parameter, wall moving parameter, and magnetic parameter. Two solution branches are obtained for certain combinations of the controlling parameters, and a stability analysis demonstrates that the lower solution branch is not stable. The present solutions provide an exact solution to the entire unsteady MHD NS equations, which can be used for validating the numerical code of computational fluid dynamics.

关键词： unsteady stagnation point flow stretching/shrinking sheet magnetohy-drodynamic(MHD) Navier-Stokes(NS)equation

Rare earth monosilicates as oxidation resistant interphase for SiCf/SiC CMC:Investigation of SiC_(f)/Yb_(2)SiO_(5)model composites

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Journal of Advanced Ceramics 2022年第5期11卷 702-711页

作者： Xirui LV Mengkun YUE Xue fENG Xiaoyan LI Yumin wang Jiemin wang Jie ZHANG Jingyang wang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China AML Department of Engineering MechanicsTsinghua UniversityBeijing 100084China Center for Mechanics and Materials Tsinghua UniversityBeijing 100084China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

Model composites consisting of SiC fiber and Yb_(2)SiO_(5)were processed by the spark plasma sintering(SPS)*** mechanical compatibility and chemical stability between Yb_(2)SiO_(5)and SiC fiber were studied to evaluate the potential application of Yb monosilicate as the interphase of silicon carbide fiber reinforced silicon carbide ceramic matrix composite(SiC_(f)/SiC CMC).Two kinds of interfaces,namely mechanical and chemical bonding interfaces,were achieved by adjusting sintering ***_(f)/Yb_(2)SiO_(5)interfaces prepared at 1450 and 1500℃exhibit high interface strength and debond energy,which do not satisfy the crack deflection criteria based on He-Hutchison *** spectrum analyzation indicates that the thermal expansion mismatch between Yb_(2)SiO_(5)and SiC contributes to high compressive thermal stress at interface,and leads to high interfacial *** layer at interface in model composite sintered at 1550℃is related to the diffusion promoted by high temperature and DC electric filed during *** is inspired that the interfacial parameters could be adjusted by introducing Yb_(2)Si_(2)O_(7)-Yb_(2)SiO_(5)interphase with controlled composition to optimize the mechanical fuse mechanism in SiC_(f)/SiC CMC.

关键词： silicon carbide fiber reinforced silicon carbide ceramic matrix composite(SiCf/SiC CMC) interphase rare earth(RE)silicates interfacial parameters

Recovery of rare and precious metals from urban mines —— A review

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frontiers of Environmental Science & Engineering 2017年第5期11卷 3-19页

作者： Mengmeng wang Quanyin Tan Joseph f. Chiang Jinhui Li key Laboratory for Solid Waste Management and Environment Safety (Tsinghua University) Ministry of Education of China School of Environment Tsinghua University Beijing 100084 China Department of Chemistry and Biochemistry State University of New York College at Oneonta Oneonta NY 13820 USA

Urban mining is essential for continued natural resource extraction. The recovery of rare and precious metals （RPMs） from urban mines has attracted increasing attention from both academic and industrial sectors, because of the broad application and high price of RPMs, and their low content in natural ores. This study summarizes the distribution characteristics of various RPMs in urban mines, and the advantages and shortcomings of various technologies for RPM recovery from urban mines, including both conventional （pyrometallurgical, hydrometallurgical, and biometallurgical processing）, and emerging （electrochemical, supereritieal fluid, mechanochemical, and ionic liquids processing） technologies. Mechanical/physical technologies are commonly employed to separate RPMs from nonmetallic components in a pre-treatment process. A pyrometallurgical process is often used tbr RPM recovery, although the expensive equipment required has limited its use in small and medium-sized enterprises. Hydrometallurgical processing is effective and easy to operate, with high selectivity of target metals and high recovery efficiency of RPMs, compared to pyrometallurgy. Biometallurgy, though, has shown the most promise for leaching RPMs from urban mines, because of its low cost and environmental friendliness. Newly developed technologies electrochemical, supercritical fluid, ionic liquid, and mechanochemical have offered new choices and achieved some success in laboratory experiments, especially as efficient and environmentally friendly methods of recycling RPMs. With continuing advances in science and technology, more technologies will no doubt be developed in this field, and be able to contribute to the sustainability of RPM mining.

关键词： Rare and precious metals (RPMs) Distribution characteristics Recycling technology Emerging technology Supercritical fluid

Magnetic interaction in the metamaterial/magnet system

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Chinese Physics B 2014年第8期23卷 537-539页

作者： M.k.Alqadi f.Y.Alzoubi Department of Physics Jordan University of Science and Technology

The stability of the magnetic dipole and the metamaterial with negative permeability are investigated. Analytical expressions of the interaction force and stiffness of the magnetic line and metamaterial with negative permeability are derived. The repulsive force between the magnetic line and the metamaterial exceeds the value of the maximum force in the magnet-superconductor system.

关键词： metamaterial interaction energy negative permeability

A crystal plasticity based approach to establish role of grain size and crystallographic texture in the Tension–Compression yield asymmetry and strain hardening behavior of a Magnesium–Silver–Rare Earth alloy

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Journal of Magnesium and Alloys 2022年第9期10卷 2546-2562页

作者： Sourav Mishra f.khan S.k.Panigrahi Department of Mechanical Engineering Indian Institute of Technology MadrasChennai 600036Tamil NaduIndia Applied Magnesium Research Group Centre for Materials and Manufacturing for Futuristic MobilityIndian Institute of Technology MadrasChennai 600036Tamil NaduIndia School of Mechanical Engineering Vellore Institute of TechnologyVellore 632014Tamil NaduIndia

Existence of tension–compression yield asymmetry is a serious limitation to the load bearing capablities of Magnesium alloys in a number of light weight structural *** present work is aimed at nullifying the tension to compression asymmetry problem and strain hardening anomalies in a Magnesium–Silver–Rare Earth alloy by engineering different levels of microstructural conditions via friction stir processing and post process *** existence and extent of yield asymmetry ratio in the range of microstructural conditions was experimentally obtained through quasistatic tensile and compression *** yield asymmetry problem was profoundly present in specimens of coarse grained microstructures when compared to their fine grained and ultra fine grained *** impact of the microstructure and associated mechanisms of plasticity on the macroscopic strain hardening behavior was established by kock–Mecking’s *** plasticity simulations using Viscoplastic Self Consistency approach revealed the consequential role of extension twinning mechanism for the existence of yield asymmetry and anomalies in strain hardening *** was especially dominant with coarsening of grain *** Microscopy and characterization were conducted thoroughly in partially deformed specimens to confirm the predictions of the above *** role of crystallographic texture for inducing the polarity to Tension–Compression yield asymmetry was corroborated.A critical grain size in Magnesium–Silver–Rare earth alloy was hereby established which could nullify influences of extension twinning in yield asymmetry ratio.

关键词： Magnesium silver rare earth alloy friction stir processing Ultrafine-grained microstructure Tension to compression yield strength asymmetry Crystallographic texture Strain hardening kock mecking plots Visco plastic self consistency

A new thermodynamically stable Nb_(2)Ni intermetallic compound phase revealed by peritectoid transition within binary Nb-Ni alloy system

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Journal of Materials Science & Technology 2022年第5期100卷 246-253页

作者： J.f.Zhao H.P.wang B.Wei School of Physical Science and Technology Northwestern Polytechnical UniversityXi’an 710072China

A new intermetallic compound of thermodynamically stable Nb_(2)Ni phase is discovered within Nb-Ni binary system,refreshing the current situation that there are only three stable intermediate phases of Nb_(7)Ni_(6),NbNi_(3) and NbNi_(8).The new stable phase is generated from the peritectoid transition:(Nb)+Nb_(7)Ni_(6)→Nb_(2)Ni,and the transformation temperature is 1533 *** refreshes the current equilibrium Nb-Ni binary phase *** is confirmed by transmission electron microscopy and the annealing experiments,which is determined to be the fCC structure(Pearson:cf96,space grope:fd-3m O2,a=11.888A).furthermore,the equilibrium properties of Nb_(2)Ni phase are produced by density functional theory,including the formation energy,cohesive energy,bulk modulus and lattice constant.

关键词： Intermetallic compound Peritectoid transition Transmission electron microscopy Density functional theory Nb alloy

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