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Analysis for twinning and slip in face-centered cubic crystals under axisymmetric co-deformation

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science china(Technological sciences) 2006年第5期49卷 521-536页

作者： CHEN Zhiyong1,2, CAI Hongnian1, ZHANG Xinming2, WANG Fuchi1 & TAN Chengwen1,3 1. school of Material science and engineering, beijing Institute of Technology, beijing 100081, china 2. school of Material science and engineering, Central South university, Changsha 410083, china 3. school of Material science and engineering, beijing university of aeronautics and astronautics, beijing 100083, china 1. school of Material science and engineering Beijing Institute of Technology Beijing 100081 China 2. school of Material science and engineering Central South University Changsha 410083 China 3. school of Material science and engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals (f.c.c.) for twinning on {111} 112 and slip on {111} 110 systems. The influence of ξ , the ratio of critical re- solved shear stress for twinning to slip, on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically. The Taylor factors and the anisotropy of yield strength for three important orientations [100], [110] and [111] in orientation space were analyzed. It is found that the yield strength asymmetry for the case of axisymmetric de- formation of tension and compression can be explained based on the microscopic theory of crystal plasticity. The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation. The deformation texture formation and development of f.c.c. crystals with low stacking fault energy for axisymmetric tension can be explained qualita- tively on the basis of analyzed results.

关键词： twinning slip face-centered cubic crystals axisymmetric co-deformation Bishop-Hill maximum work principle yield strength anisotropy

Application of output feedback sliding mode control to active flutter suppression of two-dimensional airfoil

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science china(Technological sciences) 2010年第5期53卷 1338-1348页

作者： YANG Chao,SONG Chen,WU ZhiGang & XIE ChangChuan school of Aeronautic science and engineering,beijing university of aeronautics & astronautics,beijing 100191,china 1. school of Aeronautic science and engineering Beijing University of Aeronautics & Astronautics Beijing 100191 China

The effectiveness of the sliding mode control(SMC) method for active flutter suppression(AFS) and the issues concerning control system discretization and control input constraints were studied using a typical two-dimensional *** airfoil has a trailing-edge flap for flutter *** aeroelastic system involves a two-degrees-of-freedom motion(pitch and plunge),and the equations were constructed by utilizing quasi-steady aerodynamic *** control system,designed by the output feedback SMC method,was incorporated to suppress the pitch-plunge ***,the system discretization and the flap deflection constraints were ***,a classical Runge-Kutta(RK) algorithm was utilized for numerical *** results indicated that the close-loop system with the SMC system could be stable at a speed above the flutter ***,when the flap deflection limits are reached,the close-loop system with the simple discretized control system loses ***,control compensation developed by theoretical analysis was proposed to make the system stable *** parameter perturbations and the time delay effects were also discussed in this paper.

关键词： aeroelasticity flutter airfoil sliding mode control output feedback control

Effects of Na/K ratio on the phase structure and electrical properties of Na_xK_(1-x)NbO_3 lead-free piezoelectric ceramics

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Rare Metals 2010年第2期29卷 220-225页

作者： ZHANG Qian, ZHANG Boping, Li Haitao, and SHANG Pengpeng school of Materials science and engineering, university of science and Technology beijing, beijing 100083, china school of Materials science and engineering University of Science and Technology Beijing

Lead-free piezoelectric NaxK1-xNbO3（x = 0.3-0.8）（NKN） ceramics were fabricated by normal sintering at 1060°C for 2 *** and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na *** grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary（MPB） in NaxK1-xNbO3 *** MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703, respectively for the Na0.7K0.3NbO3 *** temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively.

关键词： lead-free piezoelectric ceramics NKN sintering morphotropic phase boundary(MPB)

Effects of heat treatment on magnetic properties of Co-Fe-plated hollow ceramic microspheres

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Progress in Natural science:Materials International 2011年第5期21卷 392-400页

作者： Xiang LI,Yue-xin DUAN,Yan ZHAO,Lei ZHU school of Materials science and engineering,beijing university of aeronautics and astronautics, beijing 100191,china school of Materials science and engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

Functional hollow ceramic microspheres plated with Co-Fe were obtained through electroless plating technique for the application of lightweight microwave *** were treated at different temperatures by vacuum annealing *** surface-coated hollow microspheres were characterized by scanning electron microscopy(SEM) and X-ray diffraction analysis (XRD).The microwave electromagnetic loss and absorbing properties of hollow microspheres plated with Co-Fe were tested by network vector *** magnetic properties were tested by vibrating sample magnetometer(VSM).The results show that the annealing treatment changed the crystal phase of Co from HCP to FCC,simultaneously increased the crystallinity and crystal size of Co and Fe in coating ***,after annealing at 800℃or 1 000℃,the microwave absorbing properties and soft magnetic properties of hollow microspheres plated with Co-Fe were further improved.

关键词： electroless plating hollow ceramic microspheres magnetic properties heat treatment Co-Fe

The effect of diffusion on the permanence of Smith population model in a polluted patch

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Communications in Nonlinear science and Numerical Simulation 2001年第4期6卷 217-221页

作者： Zhuoqin YANG, Qishao LU and Zaizhong YANG school of science, beijing university of aeronautics and astronautics, beijing 100083, china Department of Mathematics, Inner Mongolia university, Inner Mongolia 010021, china school of science Beijing Univ. of Aero. and Astronautics Beijing 100083 China Department of Mathematics Inner Mongolia University Inner Mongolia 010021 China

The effect of diffusion on the permanence of population in a polluted patch is studied by setting up a single-population diffusive system in two patches. The analysis focuses on the case that the toxicant input in the polluted patch has a limit value. It is shown that when there is no diffusion and the limit value exceeds a certain value, the population in the polluted patch goes extinct; when the diffusion exists and population diffusive coefficients between the two patches satisfy some conditions, the population of the system goes either permanent or extinct.

关键词： population diffusion system pollution permanence extinction

Surface characteristics of rapidly solidified nickel-based superalloy pow-ders prepared by PREP

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Rare Metals 2003年第4期22卷 309-314页

作者： CHEN Huanming , HU Benfu , and LI Huiying1) school of Materials science and engineering, university of science and Technology beijing, beijing 100083, china2) school of Physics and electrical Information engineering, Ningxia university, Yinchuan 750021, china school of Materials science and engineering University of Science and Technology Beijing Beijing 100083 Chins

The surface microstructure and the surface segregation of FGH 95 nickel-basedsuperalloy powders prepared through plasma rotating electrode processing (PREP) have beeninvestigated by using SEM and AES. The results indicate that the surface microstructure of powderschanges from dendrite into cellular stricture as the particle size of powders decrease, and thepredominant precipitates solidified on the particle surfaces were identified as MC' type carbidesenriched with Nb and Ti. It was also indicated that along with the depth of particle surfaces, thesegregation layer of S, C and O elements are thick, and that of Ti, Cr elements are thin for largesire powders while they are in reverse for median size particles.

关键词： FGH 95 nickel-based superalloy powders surface characteristics microstructure plasma rotating electrode processing

Formation control for networked spacecraft in deep space:with or without communication delays and with switching topology

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science china(Information sciences) 2011年第3期54卷 469-481页

作者： WANG Nan 1,2, ZHANG TianWu 2 & XU JieQiong 1 1 school of Aeronautic science and engineering, beijing university of aeronautics and astronautics, beijing 100191, china 2 Department of Computer science and engineering, Henan Institute of engineering, Zhengzhou 451191, china 1. school of Aeronautic science and engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China2. Department of Computer Science and Engineering Henan Institute of Engineering Zhengzhou 451191 China

In this paper, several formation controllers are developed with constant and variable connected communication topology for six-degree-of-freedom (6-DOF) networked spacecraft flying in deep space with constant and time-varying communication delays considered. In the control algorithm, any explicit leader does not exist in the formation team and it is required that each spacecraft communicate only with its neighbors and therefore the required communication loads of the whole formation is greatly reduced. The proposed control strategies allow that each spacecraft can track its desired position and attitude and simultaneously the whole group moves to the desired formation and obtain its desired relative attitudes with its neighbors. Simulation results demonstrate the effectiveness of the proposed controllers.

关键词： deep space graph theory formation control communication topology delays

Bonded Terfenol-D composites with low eddy current loss and high magnetostriction

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Rare Metals 2010年第6期29卷 579-582页

作者： TIAN Jianjun,ZUO Zhijun,PAN De’an,and ZHANG Shengen school of Materials science and engineering,university of science and Technology beijing,beijing 100083,china school of Materials science and engineering University of Science and Technology Beijing Beijing China

Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high ***,the nonmagnetic binder impairs the magnetostriction of the *** achieve high magnetostriction and low eddy current loss,the mixture of the alloy powder and binder was compressed at low pressure in an oriented magnetic *** this,the aligned samples were recompressed by cold isostatic pressing（CIP）.Besides,the effect of particle size on the magnetostriction of the bonded Terfenol-D composites was also *** results showed that the bonded Terfenol-D composites had excellent magnetostriction when the particle size was 50-80 μ*** oriented magnetic field and CIP could improve the magnetostriction of the bonded composites,which reaches 1020×*** bonded Terfenol-D composites had good compact structure and high density（7.24 g/cm3）.The magnetic loss of the bonded Terfenol-D composites was 192 mW/cm3 at a frequency of 100 kHz in a magnetic field of 960 A/m,which was about one third of that of casting Terfenol-D alloys.

关键词： composites Terfenol-D magnetostriction eddy current losses density

Application of Tandem Cascade to Design of Fan Stator with Supersonic Inflow

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Chinese Journal of aeronautics 2010年第1期23卷 9-14页

作者： Li Qiushi,Wu Hong,Zhou Sheng school of Jet Propulsion,beijing university of aeronautics and astronautics,beijing 100191,china [a] school of Jet Propulsion Beijing University of Aeronautics astronautics Beijing 100191 China

This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to reduce the shock wave intensity turning the flow into subsonic,while the rear cascade adopts a subsonic profile with a large camber offering the flow a large turning angle. It is disclosed that the losses would be minimized if the leading edge of the rear cas- cade lies close to the pressure side of the front cascade at a distance of 20% pitch in pitch-wise direction without either axial spacing or overlapping in axial direction. The 2D numerical test results show that,with the inflow Mach number of 1.25 and the turning angle of 52° ,the total pressure loss coefficient of the tandem cascade reaches 0. 106 ,and the diffusion factor 0. 745. Finally,this article has designed and simulated a high-loaded fan stage with the proposed tandem stator,which has the pressure ratio of 3.15 and the efficiency of 86.32% at the rotor tip speed of 495.32 m/s.

关键词： fan/compressor tandem cascade stator supersonic inflow