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journal of Magnesium and Alloys 2023年第10期11卷 3829-3839页

作者： y.j.Hu j.y.Wang W.Zhai B.Wei School of Physical Science and Technology Northwestern Polytechnical UniversityXi’an 710072China

One dimensional(1D) and three dimensional(3D) ultrasound sources were applied to the solidification process of Mg_(71.5)Zn_(26.1)y_(2.4) *** acoustic spectra were in-situ measured, based on which the cavitation intensities and dynamic solidification mechanism were further investigated. With the increase of ultrasonic dimension and amplitude, the primary Mg_(3)Zn_(6)y phase was significantly refined from petals to nearly pentagonal shape. The sound field measurements showed that the transient cavitation played a decisive role in generating a high local undercooling, which facilitated the formation of icosahedral clusters and promoted the nucleation of primary Mg_(3)Zn_(6)y phase. The morphological transition of(α-Mg+Mg_(3)Zn_(6)y) eutectic from lamellar to anomalous structure occurred under 3D ultrasonic condition. The stable cavitation took the main responsibility because the high pressure excited by nonlinearly oscillating bubbles induced the preferential nucleation of α-Mg phase rather than Mg_(3)Zn_(6)y phase. As compared with its static values, the tensile strength and compression plasticity of this alloy were increased by the factors of 1.9 and 2.1, and its corrosion resistance was also improved with the corrosion current density decreased by one order of magnitude.

关键词： Three dimensional ultrasounds Quasicrystalline Mg_(3)Zn_(6)y phase Anomalous eutectic Mechanical performances Corrosion resistance

Mathematical modelling of axonal microtubule bundles under dynamic torsion

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Applied Mathematics and Mechanics(English Edition) 2018年第6期39卷 829-844页

作者： j.y.WU Hong yUAN L.y.LI MOE Key Laboratory of Disaster Forecast and Control in Engineering Institute of Applied MechanicsJinan University School of Engineering University of Plymouth

Owing to its viscoelastic nature, axon exhibits a stress rate-dependent me- chanical behavior. An extended tension-shear chain model with Kelvin-Voigt viscoelas- ticity is developed to illustrate the micromechanical behavior of the axon under dynamic torsional conditions. Theoretical closed-form expressions are derived to predict the de- formation, stress transfer, and failure mechanism between microtubule （MT） and tau protein while the axon is sheared dynamically. The results obtained from the present an- alytical solutions demonstrate how the MT-tau interface length, spacing between the tau proteins, and loading rate affect the mechanical properties of axon. Moreover, it is found that the MTs are more prone to rupture due to the contributions from the viscoelastic effects. Under the torsional force, the MTs are so long that the stress concentrates at the loaded end where axonal MTs will break. This MT-tau protein dynamics model can help to understand the underlying pathology and molecular mechanisms of axonal injury. Additionally, the emphasis of this paper is on the micromechanical behavior of axon, whereas this theoretical model can be equally applicable to other soft or hard tissues, owning the similar fibrous structure.

关键词： torsion biocomposite diffuse axonal injury (DAI) Kelvin-Voigt viscoelas-tic model dynamic response tension-shear chain model

A modified multi-objective particle swarm optimization approach and its application to the design of a deepwater composite riser

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Acta Mechanica Sinica 2018年第2期34卷 275-284页

作者： y.Zheng j.Chen Department of Mechanics Huazhong University of Science and TechnologyWuhan 430074China Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment Wuhan 430074China

A modified multi-objective particle swarm optimization method is proposed for obtaining Pareto-optimal solutions effectively. Different from traditional multiobjective particle swarm optimization methods, Kriging meta-models and the trapezoid index are introduced and integrated with the traditional one. Kriging meta-models are built to match expensive or black-box functions. By applying Kriging meta-models, function evaluation numbers are decreased and the boundary Pareto-optimal solutions are identified rapidly. For bi-objective optimization problems, the trapezoid index is calculated as the sum of the trapezoid’s area formed by the Pareto-optimal solutions and one objective axis. It can serve as a measure whether the Pareto-optimal solutions converge to the Pareto front. Illustrative examples indicate that to obtain Paretooptimal solutions, the method proposed needs fewer function evaluations than the traditional multi-objective particle swarm optimization method and the non-dominated sorting genetic algorithm II method, and both the accuracy and the computational efficiency are improved. The proposed method is also applied to the design of a deepwater composite riser example in which the structural performances are calculated by numerical analysis. The design aim was to enhance the tension strength and minimize the cost. Under the buckling constraint, the optimal trade-off of tensile strength and material volume is obtained. The results demonstrated that the proposed method can effec tively deal with multi-objective optimizations with black-box functions.

关键词： Multi-objective particle swarm optimization Kriging meta-model Trapezoid index Deepwater composite riser

Statistical moment-based structural damage detection method in time domain

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Earthquake Engineering and Engineering Vibration 2013年第1期12卷 13-23页

作者： j.Zhang y.L.Xu j.Li y.Xia j.C.Li Department of Civil and Environmental Engineering The Hong Kong Polytechnic University Department of Building Engineering Tongji University Faculty of Engineering University of Technology Sydney

A novel structural damage detection method with a new damage index,i.e.,the statistical moment-based damage detection（SMBDD） method in the frequency domain,has been recently *** aim of this study is to extend the SMBDD method in the frequency domain to the time domain for building structures subjected to non-Gaussian and non-stationary *** applicability and effectiveness of the SMBDD method in the time domainis verified both numerically and *** buildings with various damage scenarios are first numerically investigated in the time domain taking into account the effect of measurement *** applicability of the proposed method in the time domain to building structures subjected to non-Gaussian and non-stationary excitations is then experimentally investigated through a series of shaking table tests,in which two three-story shear building models with four damage scenarios *** identified damage locations and severities are then compared with the preset *** comparative results are found to be satisfactory,and the SMBDD method is shown to be feasible and effective for building structures subjected to non-Gaussian and non-stationary excitations.

关键词： damage detection statistical moment time domain non-Gaussian non-stationary experimental investigation

Mechanism of soft x-ray continuum radiation from low-energy pinch discharges of hydrogen and ultra-low field ignition of solid fuels

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Plasma Science and Technology 2017年第9期19卷 7-34页

作者： R MILLS j LOTOSKI y LU Brilliant Light Power Inc.493 Old Trenton RoadCranburyNJ 08512United States of America

EUV continuum radiation（10–30 nm） arising only from very low energy pulsed pinch gas discharges comprising some hydrogen was first observed at Black Light Power, Inc. and reproduced at the Harvard Center for Astrophysics（Cf A）. The source was determined to be due to the transition of H to the lower-energy hydrogen or hydrino state H（1/4） whose emission matches that observed wherein alternative sources were eliminated. The identity of the catalyst that accepts 3 · 27.2 eV from the H to cause the H to H（1/4） transition was determined to HOH versus 3H. The mechanism was elucidated using different oxide-coated electrodes that were selective in forming HOH versus plasma forming metal atoms as well as from the intensity profile that was a mismatch for the multi-body reaction required during 3H catalysis. The HOH catalyst was further shown to give EUV radiation of the same nature by igniting a solid fuel comprising a source of H and HOH catalyst by passing a low voltage, high current through the fuel to produce explosive plasma. No chemical reaction can release such high-energy light. No high field existed to form highly ionized ions that could give radiation in this EUV region that persisted even without power input. This plasma source serves as strong evidence for the existence of the transition of H to hydrino H（1/4） by HOH as the catalyst and a corresponding new power source wherein initial extraordinarily brilliant light-emitting prototypes are already producing photovoltaic generated electrical power. The hydrino product of a catalyst reaction of atomic hydrogen was analyzed by multiple spectroscopic techniques. Moreover, the m H catalyst was identified to be active in astronomical sources such as the Sun, stars and interstellar medium wherein the characteristics of hydrino match those of the dark matter of the Universe.

关键词： ignition continuum brilliant catalysis matches elucidated reproduced spectroscopic figure helium

Microstructure and tensile properties of magnesium nanocomposites fabricated using magnesium chips and carbon black

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journal of Magnesium and Alloys 2020年第3期8卷 860-872页

作者： T.j.Lee W.j.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

In this study,carbon black(0,0.01,0.03 and 0.08 wt%)and AZ31(Mg-3Al-lZn)magnesium chips were used to fabricate carbon black-reinforced magnesium matrix composites with extrusion or a combination of extrusion and high-ratio differential speed *** hot pressing at 693 K and extrusion at 623 K with an extrusion ratio of 22,the magnesium chips coated with carbon black were soundly bonded into a bulk composite *** grain sizes of the extruded materials were similar with a size of 48.2-51.5|im despite the difference in the amount of carbon *** yield strength and ultimate tensile strength increased from 177 to 191 MPa and from 240 to 265 MPa,respectively,as a result of the addition of 0.01%carbon black;however,a further increase in the strength was marginal with additional carbon *** same trend was observed in the strain hardening *** tensile elongation increased by to the addition of 0.01%carbon black(from 15.8%to 17.4%)due to the increased work hardening effect,but decreased with additional carbon black due to its agglomeration and poor dispersion at higher *** high-ratio differential speed rolling(HRDSR)on the extruded materials and subsequent annealing,the AZ31 and AZ31 composites had a similar fine grain size of 16.3-17.9 *** annealed HRDSR composites showed the best mechanical properties at a higher content of carbon black(0.03%)compared to that(0.01%)for the extruded *** resulted from the enhanced dispersion effect of the carbon black due to the high shear flow induced during the HRDSR *** extruded composites exhibited the three distinct hardening stages(stage II,stage III and stage IV),while the annealed HRDSR composites mainly displayed the stage III *** addition of carbon black increased the strain hardening rate at all the strain hardening stages in both of the extruded and annealed HRDSR *** the initial hardening stage,the strain hardening rates of the extruded comp

关键词： Recycling Magnesium alloys chips Carbon black Nanocomposites Extrusion Differential speed rolling

Numerical analysis of thermal plasma scrubber for CF4 decomposition

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Plasma Science and Technology 2019年第6期21卷 9-14页

作者： j KO T H kim S CHOI Department of Nuclear and Energy Engineering Jeju National University Jeju 63243 Republic of Korea Institute for Nuclear Science and Technology Jeju National University Jeju 63243 Republic of Korea

CF4 gas emitted in the semiconductor and display manufacturing process is a very harmful greenhouse *** must be removed or converted safely due to its extreme *** a CF4 decomposition system using a thermal plasma scrubber was commercialized,its removal efficiency is *** this work,a numerical analysis of CF4 decomposition in the thermal plasma scrubber was carried out in order to propose an efficient decomposition *** decomposition and recombination temperatures of CF4 were analyzed using thermodynamic equilibrium *** chemical reaction of CF4 decomposition into carbon and fluorine gas was considered in this numerical *** injection position and angle of the CF4 were controlled in order to enhance the decomposition *** vertical injection of CF4 near the torch exit improved the mixing of the CF4 with the thermal plasma *** addition,it was confirmed that the high temperature region expanded due to a vortex generated by strong turbulence in the bottleneck-shaped *** a result,it is revealed that the CF4 injection location and the reactor configuration are the most important factors in improving the decomposition rate.

关键词： numerical simulation decomposition CF4 thermal plasma scrubber

Effects of Alumina on Cristobalite Crystallization and Properties of Silica-Based Ceramic Cores

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journal of Materials Science & Technology 2017年第2期33卷 204-209页

作者： j.j.Liang Q.H.Lin X.Zhang T.jin y.Z.Zhou X.F.Sun B.G.Choi I.S.kim j.H.Do C.y.jo Institute of Metal Research Chinese Academy of SciencesShenyang 110016China Korea Institute of Materials Science Changwon 642-831Republic of Korea

In this work, the influences of alumina addition on cristobalite crystallization and properties of injec- tion molded silica-based ceramic cores were investigated. X-ray diffraction （XRD） was used to characterize phase transformations in the samples, and the XRD result indicated that the addition of alumina pro- moted crystallization of fused silica during sintering at 1180-1220 ℃ and thus increases the amount of cristobalite. The increased amount of cristobalite as well as alumina addition led to much more thermal dilation due to their higher coefficients of thermal expansion than that of fused silica. The flexural strengths at room temperature and 1500 ~C were tested, and it was shown that alumina addition could not affect room temperature strength, but decreased the flexural strength at 1500 ℃. In addition, deflection resis- tance during heating to high temperatures was investigated, and the result indicated that alumina addition speeded up high temperature softening of the samples. XRD and scanning electron microscopy equipped with energy dispersive spectrometry （SEMjEDS） analysis suggested that this softening behavior was related with viscous flow sintering which could be accelerated by the reaction of alumina and silica with a product of mullite.

关键词： Silica-based ceramic cores Alumina Cristobalite crystallization Properties

Effect of roll speed ratio on the texture and microstructural evolution of an FCC high-entropy alloy during differential speed rolling

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journal of Materials Science & Technology 2022年第16期111卷 152-166页

作者： H.T.jeong W.j.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

A very coarse-grained(335μm)Fe_(41)Mn_(25)Ni_(24)Co_(8)Cr_(2)high-entropy alloy with a single FCC phase was cold rolling to a 80%reduction in thickness using the differential speed rolling technique with various speed ratios(SRs)ranging between 1 and *** the SR was increased,the volume fraction of the region of high-density micro-shear bands increased to accommodate the higher shear *** SR=4,the entire thickness of the sheet was covered with micro-shear bands,and ultrafine(sub)grains with a size of1.4μm were uniformly formed along the shear bands.A continuous dynamic recrystallization(CDRX)mechanism occurred during rolling,and a higher SR accelerated the CDRX *** conventional rolling(at SR=1),a brass{110}orientation texture with minor components of S{123}and Cu{112}orientations *** higher SRs,shear texture developed as the main type,while the development of rolling texture was *** microstructure at SR=4 obtained after annealing at973 K showed a fully recrystallized microstructure composed of a five times smaller grain size(4μm)with a higher intensity ofγfiber texture compared with that prepared by conventional *** samples processed with high SRs exhibited better tensile properties compared with the conventionally rolled sample in terms of strength and ductility after *** current results demonstrate that by using differential speed rolling with a high SR,one can achieve a significantly finer and more homogeneous microstructure,stronger shear texture,and superior tensile mechanical properties for an FCC high-entropy alloy compared to that obtained by conventional *** strength of the as-rolled and annealed samples was quantitatively explained by considering the contribution of grain size and dislocation density to strengthening.

关键词： High entropy alloys Differential speed rolling Texture Grain refinement Strength Severe plastic deformation

Grain size and temperature effect on the tensile behavior and deformation mechanisms of non-equiatomic Fe(41)Mn(25)Ni(24)Co8Cr2high entropy alloy

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journal of Materials Science & Technology 2020年第7期42卷 190-202页

作者： H.T.jeong W.j.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

The effect of the grain size on the tensile properties and deformation mechanisms of a nonequiatomic Fe(41)Mn(25)Ni(24)Co8 Cr2 high-entropy alloy was studied in the temperature range between 298 and 1173 K by preparing the samples with three different grain sizes through severe plastic deformation and subsequent annealing:ultrafine(sub)grain size(≤0.5μm),8.1μm and 590.2μ*** the temperature between 298 and773 K,the material with the large grain size of 590.2μm exhibited the largest tensile ductility(57%-82%)due to its high strain hardening associated with mechanical twinning,but it exhibited the lowest strength due to its large grain *** material with the ultrafine(sub)grain size exhibited the lowest tensile ductility(3%-7%)due to a greatly reduced strain hardening ability after severe plastic deformation,but it exhibited the highest strength due to the dislocation strengthening and grain refinement *** tensile testing at temperatures above 973 K,recrystallization occurred in the material with the ultrafine(sub)grains during the sample heating and holding stage,leading to the formation of fine and equiaxed grains with the sizes of 6.8-13.5μ*** deformation behavior of the Fe(41)Mn(25)Ni(24)Co8 Cr2 with different grain sizes in the high temperature range between 973 and 1173 K,where pseudosteady-state flow was attained in the stress-strain curves,could be explained by considering the simultaneous contribution of grain boundary sliding and dislocation-climb creep to total plastic *** activation energies for plastic flow for the materials with different grain sizes were similar as^199 kj/*** predicting the deformation mechanism,it was important to consider the change in grain size by rapid grain growth or recrystallization during the sample heating and holding stage because grain boundary sliding is a grain-size-dependent deformation *** sample with the ultrafine(sub)grains exhibited the large tensile elongations of 30%-85%due to it

关键词： High entropy alloys Grain size High temperature deformation mechanism Tensile behavior Grain boundary sliding