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Effect of EcAP temperature on microstructure and mechanical properties of Al–Zn–Mg–cu alloy

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Progress in Natural science:Materials International 2016年第2期26卷 182-191页

作者： M.h.shaeri M.shaeri M.Ebrahimi M.T.salehi s.h seyyedein Department of Metallurgy and Materials Engineering Engineering Faculty Imam Khomeini International University Department of Materials science and Engineering Sharif University of Technology Department of Mechanical Engineering University of Maragheh Department of Metallurgy and Materials Engineering Iran University of Science and Technology

The effect of equal channel angular pressing(EcAP) at different temperatures(room temperature, 120,150 and 180 °c) on microstructure and mechanical properties of Al-7075 solid solution alloy was investigated. microstructure of the specimens was examined using orientation imaging microscopy,transmission electron microscopy as well as X-ray diffractometer, and mechanical properties were measured by Vickers microhardness and tensile tests. microstructural investigations showed that after3 or 4 passes of EcAP, fi ne grains with average grain sizes in range of 300–1000 nm could be obtained at different EcAP temperatures. Increasing EcAP temperature from 120 to 180 °c caused a decrease in mechanical properties as a result of increasing grains and precipitates sizes, decreasing fraction of high angle boundaries and also transformation of η′ into η phase, while increasing EcAP temperature from RT to 120 °c leads to an increase in mechanical properties due to the formation of small η′ precipitates. so it can be concluded that EcAP process at 120 °c is the optimum process for attaining maximum mechanical properties. Quantitative estimates of various strengthening mechanisms revealed that the improvement of mechanical properties was mainly attributed to grain re fi nement strengthening, precipitation strengthening and dislocation strengthening.

关键词： Equal channel angular pressing microstructure strengthening mechanisms Mechanical properties

TENsILE cREEP DEFORMATION AND DAMAGE BEhAVIOR IN A NIcKEL-BAsE sUPERALLOY AT 900℃

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Acta Metallurgica sinica(English Letters) 2004年第4期17卷 606-611页

作者： h.c.Yu s.s.Xie h.c.Yang Beijing Institute of Aeronautical Materials Beijing 100095 ChinaR & D Center Baosteel Co. Ltd. Shanghai 201900 ChinaCollege of Materials and Metallurgy Northeastern University Shenyang 110004 China

The tensile creep deformation and damage evolution in a Ni-base superalloy at 900℃/170MPa were investigated. At the first creep stage, abnormal creep occured due to the resolution of fine particles, and the deformation initiated from grain boundary areas. It is evident that nearly all of the dislocations were in γ matrix channels in form of dislocation pairs and the dislocations were impeded at γ/γ' interfaces, thus the dislocation networks developed deformation. At the steady creep stage, impeded dislocations atγ/γ' interfaces climbed over γ' phases by diffusion-dominant mechanism. At the last creep stage, voids were formed around carbides at grain boundary which leaded to accumulated damage and caused creep rate accelerated. With the dislocation networks being broken, the voids connected and grew into micro-cracks gradually. Finally the cracks propagated along grain boundary area and resulted in failure.

关键词： creep deformation and damage dislocation microstructure su-peralloy

Temperature and Thermal stress Distribution for Metal Mold in squeeze casting Process

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Journal of Materials science & Technology 2008年第3期24卷 347-350页

作者： c.h.Lee s.h.Lee Institute of Technology and science Chung-Ang University

In the squeeze casting process, loaded high pressure （over approximately 200 MPa） and high temperature influence the thermo-mechanical behavior and performance of the used metal mold. Therefore, to safely maintain the metal molds, the thermo-mechanical characteristics （temperature and thermal stress） of metal mold in the squeeze casting must be investigated. In this paper, temperature and thermal stress distribution of steel mold in squeeze casting process were investigated by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic-plastic analysis considering temperature-dependent thermophysical and mechanical properties of the steel mold.

关键词： squeeze casting steel mold Thermal stress Thermo-Mechanical analysis

Optimal design of V-type ultrasonic motor

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Journal of central south University 2010年第6期17卷 1247-1250页

作者： JEONG s s PARK c h PARK T G s.hool of Mechatronics Changwon National UniversityChangwon 641773Korea

V-type ultrasonic linear motor fabricated using a simple punching technique was proposed to utilize as an actuator of small precision *** stator of the motor is composed of a thin elastic body and four ceramics attached to the upper and bottom areas of the *** ceramics.have each direction of *** two harmonic voltages with a 90° phase difference are applied to the ceramics,symmetric and anti-symmetric displacements will generate at the tip to produce an elliptical motion.A finite element analysis(ATILA) was conducted to simulate the motion pattern for the contact tip of the *** develop a model that generates the maximum displacement at contact tip,the FEM program was used for various *** addition,an optimal model was chosen by considering the magnitude and shape of the displacement according to changes in *** maximum elliptical displacement is shown by W2L11 model,which has a ratio of ceramic width to length of 1:***,the displacement of the contact tip is reduced by the bucking phenomenon if the ratio is larger than 1:6.

关键词： ultrasonic motor piezo-actuator finite element method optimal design elliptical motion

Roles of soil-structure interaction and damping in base-isolated structures built on numerous soil layers overlying a half-space

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Earthquake Engineering and Engineering Vibration 2016年第2期15卷 387-400页

作者： c.s.Tsai c.I.hsueh h.c.su Department of civil Engineering Feng Chia University Graduate Institute of civil & hydraulic Engineering Feng Chia University Department of Water Resources Engineering and conservation Feng Chia University

This study examines the roles of soil-structure interaction （ssI）, higher modes, and damping in a base-isolated structure built on multiple layers of soil overlying a half space. closed-form solutions for the entire system, including a superstructure, seismic isolator, and numerous soil layers overlying a half-space, were obtained. The formulations obtained in this study simply in terms of well-known frequencies and mechanical impedance ratios can explicitly interpret the dynamic behavior of a base-isolated structure interacting with multiple soil layers overlying a half-space. The key factors influencing the performance of the isolation system are the damping ratio of the isolator and the ratio of the natural frequency of the fixed-base structure to that of the isolated structure by assuming that the superstructure moves as a rigid body. This study reveals that higher damping in the base isolator is unfavorable to higher mode responses that usually dominate the responses of the superstructure and that the damping mechanism plays an important role in transmitting energy in addition to absorbing energy. It is also concluded that it is possible to design a soft soil layer as an isolation system for isolating vibration energy.

关键词： base isolation seismic isolation soil-structure interaction closed- form solution higher-mode effects soilstratum passive control damping effects

Equivalent series system to model a multiple friction pendulum system with numerous sliding interfaces for seismic analyses

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Earthquake Engineering and Engineering Vibration 2014年第1期13卷 85-99页

作者： c.s.Tsai h.c.su T.c.chiang Department of civil Engineering Feng Chia University Department of Water Resources Engineering and conservation Feng Chia University Earthquake Proof systems Inc.

current structural analysis software programs offer few if any applicable device-specifi c hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system(MFPs) with numerous sliding *** on the concept of subsystems,an equivalent series system that adopts existing nonlinear elements with parameters systematically calculated and mathematically proven through rigorous derivations is *** aim is to simulate the characteristics of sliding motions for an MFPs isolation system with numerous concave sliding interfaces without prior knowledge of detailed information on the mobilized forces at various sliding *** MFPs with numerous concave sliding interfaces and one articulated or rigid slider located between these interfaces is divided into two subsystems: the fi rst represents the concave sliding interfaces above the slider,and the second represents those below the *** equivalent series system for the entire system is then obtained by connecting those for each subsystem in *** equivalent series system is validated by comparing numerical results for an MFPs with four sliding interfaces obtained from the proposed method with those from a previous study by Fenz and ***,these numerical results demonstrate that an MFPs isolator with numerous concave sliding interfaces,which may have any number of sliding interfaces,is a good isolation device to protect structures from earthquake damage through appropriate designs with controllable mechanisms.

关键词： seismic isolation base isolation earthquake engineering multiple friction pendulum system structural control mathematical modeling equivalent series system

synthesis of highly ordered Large size Mesoporous silica and Effect of stabilization as Enzyme supports in Organic solvent

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chemical Research in chinese Universities 2002年第2期18卷 200-205页

作者： LI Bo Inagaki s miyazaki c Takahashi h Toyota central R&D Labs. Inc.411YokomichiNagakute choAichi 4801192Japan

FsM 16, McM 41 and sBA 15 types of hexagonal mesoporous silica with a highly ordered 2 dimensional structure were synthesized by using different silicon sources and surfactants. In the 2 dimensional silicate framework, pore size can be uniformly controlled by the combined use of the surfactants.having different alkyl chain lengths and the swelling agents(triisopropyl benzene). The pore diameter of FsM 16 and McM 41 can be expanded to be 10 nm, sBA 15 to be 15 nm. The crystal regularity was decreased with the increase of the pore diameter. In FsM 16 derived from kanemite(silicon source) and McM 41 from water glass, their anionic characteristics on the pore wall may be stronger than those of sBA 15 derived from oligomeric tetramethoxysilane(TMOs). We have successfully used FsM 16 and McM 41 to immobilize the enzyme having cationic residues below isoelectric point. The level of adsorption of enzymes in FsM 16 and McM 41 was relatively high, but was low in sBA 15 support. The mechanism of enzyme to be adsorbed in mesoporous silica was suggested to be the ionic interactions. In aqueous solutions, horseradish peroxidase(hTP) was immobilized in FsM 16 with 8.9 nm mesopores and the highest loading amount(183 mg/mg FsM) was obtained, but for the FsM 16 of pore diameter 30 nm only an amount of 28 mg/mg FsM was obtained. The catalytic activity in the organic solvent was.high when hRP was immobilized in FsM 16 and McM 41, but it was low in case of sBA 15.

关键词： Mesoporous silica surfactant swelling agent Enzyme Activity

Model-based adaptive locomotion and clustering control of microparticles through ultrasonic topological charge modulation

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Applied Mathematics and Mechanics(English Edition) 2023年第4期44卷 623-640页

作者： h.s.LEE h.X.cAO D.Jung c.s.KIM s.hool of Mechanical Engineering Chonnam National UniversityGwangju 61186South Korea Korea Institute of Medical microrobotics Gwangju 61011South Korea

We present a novel motion control technique for microrobot clusters to exploit the characteristics of the ultrasonic *** method comprises two steps,i.e.,introducing an ultrasonic actuation(UA)linear model for three-dimensional(3D)locomotion and controlling the topological charge(Tc)in the ultrasonic vortex for microrobot ***,the Tc is a controllable parameter for the expansion and contraction of the pressure null space inside the *** present a Tc control method to cluster sporadically distributed microrobots in a specific *** validate the concept,a UA system composed of 30 ultrasonic transducers with 1 Mhz frequency is fabricated,and the characteristics of the generated acoustic pressure field are analyzed through ***,the performances of the adaptive controller for precise 3D locomotion and the Tc control method for clustering are ***,the UA technology,which performs both clustering and locomotion in a complex manner,is validated with a gelatin phantom in an in-vitro environment.

关键词： ultrasonic actuation(UA) topological charge(Tc) adaptive control particle manipulation

high-cycle Fatigue Life Extension of Glass Fiber/Polymer composites with carbon Nanotubes

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Journal of Wuhan University of Technology(Materials science) 2009年第2期24卷 167-173页

作者： christopher s Grimmer c K h Dharan Berkeley composites Laboratory University of California 5135 Etcheverry Hall Berkeley CA94720-1740 USA

The present work shows that the addition of small volume fractions of multi-walled carbon nanotubes （cNTs） to the matrix results in a significant increase in the high-cycle fatigue life. It is proposed that carbon nanotubes tend to inhibit the formation of large cracks by nucleating nano-scale damage zones. In addition, the contribution to energy absorption from the fracture of nanotubes bridging across nano-scale cracks and from nanotube pull-out from the matrix are mechanisms that can improve the fatigue life. An energy-based model was proposed to estimate the additional strain energy absorbed in fatigue. The distributed nanotubes in the matrix appear to both distribute damage as well as inhibit damage propagation resulting in an overall improvement in the fatigue strength of glass fiber composites.

关键词： glass fiber composites carbon nanotubes fatigue strain energy