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Surface investigation on Upilex-S polymide film iradiated by vacuum ultraviolet radiation

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Rare Metals 2007年第S1期26卷 168-174页

作者： LIU Yuyan1),GONG Xianyun2.,WAN Zhimin3),and DU Xingwen4)1) Department of Applied Chemistry,harbin institute of {2.,harbin 150001,china 2. Department of Life Science and Chemistry,harbin University,harbin 150001,china 3) Analysis and measurement center,harbin institute of {2.,harbin 150001,china 4) center for Composite Materials,harbin institute of {2.,harbin 150001,china harbin Inst Technol Dept Appl Chem Harbin 150001 Peoples R China harbin Univ Dept Life Sci & Chem Harbin 150001 Peoples R China harbin Inst Technol Ctr Anal & Measurement Harbin 150001 Peoples R China harbin Inst Technol Ctr Composite Mat Harbin 150001 Peoples R China

Vacuum ultraviolet radiation of Upilex-S polyimide film 2. μm thick was performed using a gas jet type of vacuum ultraviolet simulator which gives unfixed wavelength from 5 nm to 2.0 *** redeposited on the films were observed and the nanoparticles formed on the surface consist mainly of carbon *** in the composition and the chemical characteristics of film surface after radiation were identified by X-ray photoelectron spectroscopy(XPS).Relative O content in the radiated area was found to be higher,while N content was lower than in the pristine *** indicates that Upilex-S polyimide film releases N atoms as volatile *** the C1s,O1s envelopes were fitted using Multipak Spectrum *** surface morphologies on iradiated area were examined by Atomic Force Microscope(AFM).Pieces of radiant products protrude from the eradiated surface,leading to considerable roughness for the iradiated *** the surface transmittance of Upilex-S film after radiation reduces.

关键词： vacuum ultraviolet radiation Upilex-S polyimide film

Mesh-dependence of Material with Softening Behavior

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Chinese Journal of Aeronautics 2010年第1期23卷 46-53页

作者： Fu Li,Du Xingwen center for Composite Materials,harbin {2. of technology,harbin 150001,china [a] center for Composite Materials Harbin Institute of Technology Harbin 150001 China

The issue of mesh-dependence emerges when the conventional continuum damage model is applied to handling the softening behavior. In order to circumvent the mesh-dependence, the non-local theory is introduced into the conventional damage model and the finite element formulas are derived for two-dimensional gradient-enhanced damage model. A new element is proposed in which the basic unknown quantities are displacement, non-local equivalent strain and the gradient of non-local equivalent strain. The element and constitutive equation proposed in this article are added to the finite element software ABAQUS through user subroutine UEL. Numerical results show that the gradient-enhanced damage model can eliminate the mesh-dependence and is effective for dealing with the issue of softening behavior.

关键词： non-local theory gradient dependence softening behavior mesh-dependence Hermitian element finite element method

Pseudo-beam method for compressive buckling characteristics analysis of space inflatable load-carrying structures

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Acta Mechanica Sinica 2009年第5期25卷 659-668页

作者： Changguo Wang Huifeng Tan Xingwen Du center for Composite Materials,harbin {2. of technology, 150001 harbin, china center for Composite Materials Harbin Institute of Technology 150001 Harbin China

This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a prestressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko＇s beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our proposed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the loadcarrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.

关键词： Inflatable structure - Pseudo-beam method Inflatable beam theory Nonlinear buckling finite element

The nonlocal theory solution of a Mode-I crack in functionally graded materials

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Science china(Technological Sciences) 2009年第4期52卷 1101-1111页

作者： LIANG Jun center for Composite Materials and Structures, harbin institute of technology,{2., china 1. center for Composite Materials and Structures Harbin Institute of Technology Harbin 150001 China

The behavior of a Mode-I finite crack in functionally graded materials is investigated using the non-local theory. To make the analysis tractable, it is assumed that the shear modulus varies exponentially with coordinate vertical to the crack. The problem in this paper can be solved through the Fourier transform with the help of two pairs of dual integral equations, in which the unknown variables are jumps of dis- placements across crack surfaces. To solve dual integral equations, the jumps of displacements across crack surfaces are directly expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solu- tions yield a finite stress at crack tips, thus allowing us to use the maximum stress as a fracture crite- rion. Numerical examples are provided to show the effects of the crack length, the parameter describ- ing the functionally graded materials, the lattice parameter of materials and the materials constants upon the stress fields near crack tips.

关键词： crack functionally graded materials the non-local theory mechanics of solids

Effects of binders on the performance of electric double-layer capacitors of carbon nanotube electrodes

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Progress in Natural Science:Materials International 2005年第5期15卷 453-457页

作者： LI Chensha1*, WANG Dazhi1, ZHANG Baoyou2. WANG Xiaofeng1, CAO Maosheng3 and LIANG Ji1(1. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, china 2. center for Analysis and {2., harbin institute of technology, harbin 150001, china 3. School of Material Science and Engineering, Tsinghua University, Beijing 100084, china) Department of Mechanical Engineering Tsinghua University Beijing 100084 China center for Analysis and measurement Harbin Institute of Technology Harbin 150001 China School of Material Science and Engineering Tsinghua University Beijing 100084 China

Polarizable electrodes of electric double layer capacitor (EDLCs) were made from carbon nanotubes. Effects of different binders, which are phenolic resin (PF) and polytetrafluoroethylene (PTFE), on the properties of polarizable electrodes are studied. Results indicate that the microstructure, pore size distribution and specific capacitance of the electrodes with PTFE binder are superior to those electrodes with PF binder after carbonization. The suitable binder (PTFE) for carbon nanotubes electrodes is proposed.

关键词： carbon nanotubes electric double-layer capacitors phenolic resin polytetrafluoroethylene.

Spinning Deformation Criteria of Thin-walled Tubular Part with Longitudinal Inner Ribs

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Journal of Wuhan University of technology(Materials Science) 2006年第4期21卷 169-172页

作者：江树勇 Engineering Training center Harbin Engineering University Harbin 150001China

As a successive and local plastic deformation process, backward ball spinning was applied for the purpose of prodacing thin-walled tubular parts with longitudinal inner ribs. According to the local plastic deformation theoo,, the application of yield criterion to the spinning process and the influence of the radial spinning force component on the formability of inner ribs were analyzed. Based on yield criterion and plastic mechanics, the stable flow rule of metal material and forming criteria of the inner ribs were obtained aad conformed to the experimental results so as to contribute greatly to improving the ball spinning process and optimizing the process variables, such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank, which have a significant influenee on the formability of the inner ribs. The knowledge of the influence of the process variables such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank on the spinning process is essential to preventing the quality defects of the spun parts and obtaining the desired spun parts.

关键词： ball spinning power spinning spinning force criterion

The nonlocal solution of two parallel cracks in functionally graded materials subjected to harmonic anti-plane shear waves

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Acta Mechanica Sinica 2007年第4期23卷 427-435页

作者： Jun Liang Shiping Wu Shanyi Du center for Composite Materials and Structure,harbin {2. of technology,harbin 150001,china center for Composite Materials and Structure Harbin Institute of Technology Harbin 150001 China

In this paper, the dynamic interaction of two parallel cracks in functionally graded materials （FGMs） is investigated by means of the non-local theory. To make the analysis tractable, the shear modulus and the material density are assumed to vary exponentially with the coordinate vertical to the crack. To reduce mathematical difficulties, a one-dimensional non-local kernel is used instead of a twodimensional one for the dynamic problem to obtain stress fields near the crack tips. By use of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations, in which the unknown variables are the jumps of displacements across the crack surfaces. To solve the dual integral equations, the jumps of displacements across the crack surfaces are expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularity is present at the crack tips. The non-local elastic solutions yield a finite hoop stress at the crack tips. The present result provides theoretical references helpful for evaluating relevant strength and preventing material failure of FGMs with initial cracks. The magnitude of the finite stress field depends on relevant parameters, such as the crack length, the distance between two parallel cracks, the parameter describing the FGMs, the frequency of the incident waves and the lattice parameter of materials.

关键词： Crack The non-local theory Stress waves Functionally graded materials

Uniqueness and stability in an inverse problem for a Poisson's equation

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Science china Mathematics 2007年第7期50卷 967-976页

作者： Li-xin FENG~(1+) Yan-cheng QU~2.1 School of Mathematical Sciences,Heilongjiang University,harbin 150080,china 2.Research {2. of Control and Inertial technology,harbin institute of technology,harbin 150001,china 1. School of Mathematical Sciences Heilongjiang University Harbin 150080 China 2. Research center of Control and Inertial technology Harbin Institute of Technology Harbin 150001 China

Consider the Poisson’s equation Ψ″ (x) = ?e v?Ψ + e Ψ?v ? N(x) with the Dirichlet boundary data, and we mainly investigate the inverse problem of determining the unknown function N(x) from a parameter function fa... 详细信息

关键词： Poisson’s equation well-posedness inverse problem 65N30 35R30

Experimental Study of Monitoring and Controlling of Composite Cure Process in Autoclave Featured with Fiber Optic Sensor

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Journal of Materials Science & technology 2001年第4期17卷 449-452页

作者： Boming ZHANG, Zhanjun WU , Dianfu WANG and Shanyi DU center for composite, harbin institute of technology{2., china harbin Inst Technol Ctr Composite Harbin 150001 Peoples R China

With the aid of the latest fiber optic sensing technology parameters in the cure process of ther- mosetting resin-matrix composite, such as temperature, viscosity,void and residual stress, can be monitored entirely and *** this paper, experiment results of viscosity measurement in composite cure process in autoclave using fiber optic sensors are presented. Based on the sensed information, a computer program is utilized to control the cure process. With this technology, the cure process becomes more apparent and controllable, which will greatly improve the cured products and reduce the cost.

关键词： Experimental Study of Monitoring and Controlling of Composite Cure Process in Autoclave Featured with Fiber Optic Sensor