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Compressive property and energy absorption characteristic of interconnected porous Mg-Zn-Y alloys with adjusting Y addition

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journal of Magnesium and Alloys 2024年第1期12卷 171-185页

作者： j.A.Liu S.j.Liu b.wang w.b.Sun X.j.Liu Z.w.Han College of Materials Science and Engineering Key Laboratory of Automobile Materials(Ministry of Education)Jilin UniversityChangchun 130022PR China Key Laboratory of bionic Engineering(Ministry of Education) College of Biological and Agricultural EngineeringJilin UniversityChangchun130022PR China weihai Institute for bionics-jilin University Weihai 264205PR China

In this study,interconnected porous Mg-2Zn-xY alloys with different phase compositions were prepared by various Y additions(x=0.4,3,and 6 wt.%)to adjust the compressive properties and energy absorption *** characterization methods were then applied to identify the microstructure of the porous Mg-Zn-Y and describe the details of the second *** tests were performed at room temperature(RT),200℃,and 300℃to study the impact of the Y addition and testing temperature on the compressive properties of the porous *** experimental results showed that a high Y content promotes a microstructure refinement and increases the volume fraction of the second *** the Y content increases,different Mg-Zn-Y ternary phases appear:I-phase(Mg_(3)Zn_(6)Y),w-phase(Mg_(3)Zn_(3)Y_(2)),and LPSO phase(Mg_(12)ZnY).when the Y content ranges between 0.4%and 6%,the compressive strength increases from 6.30MPa to 9.23 MPa,and the energy absorption capacity increases from 7.33 Mj/m^(3)to 10.97 Mj/m^(3)at RT,which is mainly attributed to the phase composition and volume fraction of the second ***,the average energy absorption efficiency is independent of the Y *** addition,the compressive deformation behaviors of the porous Mg-Zn-Y are altered by the testing *** compressive strength and energy absorption capacity of the porous Mg-Zn-Y decrease due to the softening effect of the high temperature on the *** deformation behaviors at different temperatures are finally observed to reflect the failure mechanisms of the struts.

关键词： Porous magnesium Rare earth elements Microstructure Compressive behavior Energy absorption characteristic

A Normal Mode Stability Analysis of Numerical Interface Conditions for Fluid/Structure Interaction

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Communications in Computational Physics 2011年第7期10卷 279-304页

作者： j.w.banks b.Sjogreen Center for Applied Scientific Computing Lawrence Livermore National LaboratoryLivermoreCA 94551USA

In multi physics computations where a compressible fluid is coupled with a linearly elastic solid,it is standard to enforce continuity of the normal velocities and of the normal stresses at the interface between the fluid and the *** a numerical scheme,there are many ways that velocity-and stress-continuity can be enforced in the discrete *** paper performs a normal mode stability analysis of the linearized problem to investigate the stability of different numerical interface conditions for a model problem approximated by upwind type finite difference *** analysis shows that depending on the ratio of densities between the solid and the fluid,some numerical interface conditions are stable up to the maximal CFL-limit,while other numerical interface conditions suffer from a severe reduction of the stable *** paper also presents a new interface condition,obtained as a simplified characteristic boundary condition,that is proved to not suffer from any reduction of the stable *** experiments in one space dimension show that the new interface condition is stable also for computations with the non-linear Euler equations of compressible fluid flow coupled with a linearly elastic solid.

关键词： Finite difference method normal mode analysis fluid/structure interaction compressible fluid interface condition

Low Temperature Plasma Nitriding of H13 Steel for Improved Surface Hardness

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稀有金属材料与工程 2012年第S1期41卷 69-73页

作者： j Pongsopa P Visuttipitukul w bhanthumnavin b Paosawatyanyong Nanoscience and Technology Program Graduate SchoolChulalongkorn UniversityBangkok 10330Thailand Department of Metallurgical Engineering Faculty of EngineeringChulalongkorn UniversityBangkok 10330Thailand Faculty of Science Chulalongkorn UniversityBangkok 10330Thailand ThEP Center Commission on Higher EducationBangkok 10330Thailand

AISI H13 steel samples were plasma nitrided to improve their surface hardness using a locally developed combined ***-ionized RFICP plasma was employed in combination with DC glow discharge and thermal emission source to achieve the nitride precipitates in iron-matrix under low sample *** nitride layers over 150 microns could be realized with low RF power of 100 w under the processing time between 1-20 h and low sample temperature of 300℃.The gas mixtures of H2 and N2 were utilized while the processing pressure and the DC bias to the sample were maintained at 0.5 torr and 300 V,*** electron microscope(SEM),energy dispersive X-ray spectroscopy(EDS),glancing incident angle X-ray diffractometer(GIXD)and Vickers hardness test were employed to characterize the properties of sample *** increases of surface hardness to over 1,000 HV were observed after treatment.

关键词： H13 tool steel plasma nitriding surface hardness

Mechanisms of Organelle Inheritance in Dividing Plant Cells

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journal of Integrative Plant biology 2007年第8期49卷 1208-1218页

作者： Michael b Sheahan Ray j Rose David w McCurdy School of Environmental and Life Sciences The University of NewcastleCallaghan NSW 2308Australia Australian Research Council Centre of Excellence for Integrative Legume ResearchSchool of Environmental and Life SciencesThe University of NewcastleCallaghan NSW 2308Australia School of Environmental and Life Sciences The University of NewcastleCallaghan NSW 2308Australia

Organelles form essential compartments of all eukaryotic cells. Mechanisms that ensure the unbiased inheritance of organelles during cell division are therefore necessary to maintain the viability of future cell generations. Although inheritance of organelles represents a fundamental component of the cell cycle, surprisingly little is known about the underlying mechanisms that facilitate unbiased organelle inheritance. Evidence from a select number of studies, however, indicates that ordered organelle inheritance strategies exist in dividing cells of higher plants. The basic requirement for unbiased organelle inheritance is the duplication of organelle volume and distribution of the resulting organelle populations in a manner that facilitates unbiased partitioning of the organelle population to each daughter cell. Often, partitioning strategies are specific to the organelle, being influenced by the functional requirements of the organelle and whether the cells are mitotically active or re-entering into the cell cycle. Organelle partitioning mechanisms frequently depend on interactions with either the actin or microtubule cytoskeleton. In this focused review, we attempt to summarize key findings regarding organelle partitioning strategies in dividing cells of higher plants. we particularly concentrate on the role of the cytoskeleton in mediating unbiased organelle partitioning.

关键词： Actin cytoskeleton cell division green fluorescent protein-fimbrin AbD2 organelle partitioning protoplast

A Model of Tangential Contact Damping Considering Asperity Interaction and Lateral Contact

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Acta Mechanica Solida Sinica 2018年第6期31卷 758-774页

作者： w.P.Fu Z.Q.Gao w.wang j.b.wu School of Mechanical and Precision Instrument Engineering Xi'an University of TechnologyXi'an 710048 China

A precise tangential contact damping model is proposed,which includes the lateral contact of the upper-lower asperities and the interaction of adjacent *** effects of the normal static preload,frequency,and amplitude of tangential displacement on the tangential contact damping were analyzed by simulation,***,the results of simulation are verified by *** tangential contact damping of considering the interaction and lateral contact of asperity is very close to the experimental results.

关键词： Asperity Lateral contact Interaction Tangential contact damping

Ultrasonic solidification mechanism and optimized application performances of ternary Mg_(71.5)Zn_(26.1)Y_(2.4) alloy

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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

Microstructure and mechanical optimization of probeless friction stir spot welded joint of an Al-Li alloy

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journal of Materials Science & Technology 2018年第10期34卷 1739-1746页

作者： Q. Chu w.Y. Li X.w. Yang j.j. Shen A. Vairis w.Y. Feng w.b. wang State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University Xi'an710072 China Helmholtz-Zentrum Geesthacht Institute of Materials Research Materials Mechanics Geesthacht 21502 Germany Mechanical Engineering Department TEl of Crete Heraklion Crete 71004 Greece China PSw Center Beijing 100024 China

In this work, a third generation AI-Li alloy has been successfully spot welded with probeless friction stir spot welding （P-FSSw）, which is a variant of conventional friction stir welding. The box-behnken exper-imental design in response surface methodology （RSM） was applied to optimize the P-FSSw parameters to attain maximum tensile/shear strength of the spot joints. Results show that an optimal failure load of 7.83 kN was obtained under a dwell time of 7.2 s, rotation speed of 950 rpm and plunge rate of 30 mm/rain. Sufficient dwell time is essential for heat conduction, material flow and expansion of the stir zone to form a sound joint. Two fracture modes were observed, which were significantly affected by hook defect. In addition to mechanical testing, electron backscattering diffraction （EbSD） and differential scanning calorimetry （DSC） were used for microstructure evolution and property analysis. The precipitation of GP zone and AI3Li as well as the ultrafine grains were responsible for the high microhardness in the stir zone.

关键词： Probeless friction stir spot welding Precipitation Mechanical property Fracture mechanism

EFFECTS OF THERMAL CYCLE ON MECHANICAL PROPERTIES AND FRACTOGRAPHY IN HAZ OF HQ130 STEEL

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 274-278页

作者： b. Liu j.X.Qu w.j.Sun Department of Mechanical Engineering Changsha University Changsha 410003 China Department of Materials Sci. & Eng. China Univ. of Mining and Technology Beijing 100083 ChinaDepartment of Materials Sci. & Eng. China Univ. of Mining and Technology Beijing 100083 ChinaDepartment of Materials Sci. & Eng. China Univ. of Mining and Technology Beijing 100083 China

The effect of different peak temperature T_P) and cooling time (t_(8/5)) on hardness,impact toughness and fracture morphology in the heat--affected zone (HAZ) of HQ130steel was studied by using welding thermo--simulation test. Experimental results showthat the impact toughness and hardness decrease with the decrease of T_P or increase oft_(8/5) under the condition of a single thermal cycle. There is a brittle zone in the vicinityof T_P=800℃, where the impact toughness is considerebly low. There is softened zonein vicinity of T_P=700℃, where the harkness decreases but the toughness increases. Inthe practical application of multi--layer and multi--pass welding, the welding heat inputshould be strictly limited (t_(8/5)≤20s) so as to reduce the softness and brittleness in theHAZ of HQ130 steel.

关键词： high strength steel welding thermal cycle heat-affected zone impact toughness

Palaeolake and palaeoenvironment between 42 and 18 kabP in Tengger Desert,Nw China

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Chinese Science bulletin 2002年第23期47卷 1946-1956页

作者： H.j.Pachur b.wünnemann National Laboratory of western China’s Environmental Systems MOE Lanzhou University Lanzhou China Nanjing Institute of Geology and Paleontology Academia Sinica Nanjing China Geolaboratory Institute of Geographical Sciences Free University of Berlin Berlin Germany

Comprehensive field investigations and laboratory analyses show that palaeolakes, including fresh-mesohaline water Megalake Tengger and other semi-connected, isolated water bodies, during late Pleistocene covered an area of more than 20000 km2, which is more than half of the Tengger Desert in Nw China. Stratigraphic correlation and chronological evidence indicate that before ca. 42000 abP the area was more arid. The palaeolakes started to develop around 40000 uncal. 14C abP but until 37000 14C abP their scope was limited. High water levels established from 35000 14C abP lasted until 22000 14C abP. Lake levels regressed between 22000 and 20000 14C abP but transgressed from 20000 to 18600 14C abP. Subsequently, water level declined further and the Megalake Tengger finally desiccated at around 18000 14C abP. Megalake Tengger possessed a fresh-mesohaline water property, implying that the regional precipitation increased significantly. During the period of Megalake Tengger, the climate was warmer-humid

关键词： Tengger Desert palaeolake palaeoenvironment Nw China.