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CALCULATION FOR PATH-DOMAIN INDEPENDENT J INTEGRAL WITH ELASTO-VISCOPLASTIC CONSISTENT TANGENT OPERATOR CONCEPT-BASED BOUNDARY ELEMENT METHODS

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Acta Mechanica Sinica 1999年第2期15卷 164-175页

作者：刘勇洪起超梁利华 dept. of Mech. eng. Zhejiang Univ. of Tech. Hangzhou China 310014

This paper presents an elasto-viscoplastic consistent tangent operator (CTO) based boundary element formulation, and application for calculation of path-domain independentJ integrals (extension of the classicalJ integrals) in nonlinear crack analysis. When viscoplastic deformation happens, the effective stresses around the crack tip in the nonlinear region is allowed to exceed the loading surface, and the pure plastic theory is not suitable for this situation. The concept of consistency employed in the solution of increment viscoplastic problem, plays a crucial role in preserving the quadratic rate asymptotic convergence of iteractive schemes based on Newton's method. Therefore, this paper investigates the viscoplastic crack problem, and presents an implicit viscoplastic algorithm using the CTO concept in a boundary element framework for path-domain independentJ integrals. Applications are presented with two numerical examples for viscoplastic crack problems andJ integrals.

关键词： boundary element method (BEM) consistent tangent operator (CTO) elasto-viscoplasticity path-domain independentJ integral fracture mechanics

Effect of Heat Treatment on High Temperature Stress Rupture Streng.h of Brazing Seam for Nickel-base Superalloy

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Journal of University of Science and Technology Beijing 2001年第2期8卷 123-125页

作者： Junying Zhang, Zhongtai Zhang, Jisheng.Sun, Xiaofang Liu, Wei Tian (State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and eng.neering, Tsinghua University, Beijing 100084, China) (Beijing Institute of Aeronautical SKLNCFP Dept. of Materials Sci. and Eng. Tsinghua University Beijing 100084 China

In order to enhance the high-temperature stress rupture streng.h of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam especially morphology of gamma ' phase and boride was observed and the streng.h of brazing seam was measured in this process. The results show that heat treatment can enhance high-temperature stress rupture streng.h by improving the microstructure of brazing seam. The streng.h of brazing seam after solution heat treatment decreases in comparison with that only after diffusion treatment while aging treatment after solution heat treatment increases the streng.h of brazing seam.

关键词： wide-gap brazing high temperature stress rupture streng.h microstructure nickel-base superalloy

Use of a Laser/TIG Combination for Surface Modification of Ti-6Al-4V Alloy

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Journal of Materials Science & Technology 2001年第2期17卷 237-239页

作者： M.Labudovic and R.Kovacevic Southern Methodist University, dept. of Mechanical eng.neering, Dallas, Texas, U.S.A. dept. of Mech. eng. Southern Methodist Univ. Dallas United States

The surface modification of materials such as Ti-6Al-4V is necessary to improve their wear resistant properties for use in tribological applications. In this paper it is shown that a laser with low power and tungsten inert gas (TIG) can be combined together for surface modification of Ti-6Al-4V alloy, and when performed in a controlled atmosphere of pure nitrogen or a mixture of nitrogen and argon, can produce a wear-resistant surface alloy. Compared with laser processing, a cheaper surface modification process has been developed involving a shorter processing time, which is free of stringent requirements such as a vacuum system.

关键词： Ti TIG Use of a Laser/TIG Combination for Surface Modification of Ti-6Al-4V Alloy Al

Stress Field Analyses of Functionally Gradient Ceramic Tool by FEM

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Journal of Materials Science & Technology 2001年第4期17卷 466-468页

作者： Ning FAN , Xing AI and Jun ZHAO Department of Mechanical eng.neering, Shandong University,Jinan 250061, China dept. of Mech. eng. Shandong Univ. Ji'nan 250061 China

The cutting properties of the functionally gradient ceramic cutting tools relate closely to the gradient distribution. A cutting model of the functionally gradient ceramic tool is firstly designed in the present paper... 详细信息

关键词： Stress Field Analyses of Functionally Gradient Ceramic Tool by FEM Tool

Microstructure in the Weld Metal of Austenitic-Pearlitic Dissimilar Steels and Diffusion of Element in the Fusion Zone

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Journal of Materials Science & Technology 2001年第3期17卷 338-342页

作者： Yajiang LI, Zeng.a ZOU and Bing ZHOU Department of Materials eng.neering, Shandong University, Jinan 250061, China E-mail: yajli@*** dept. of Mat. eng. Shandong Univ. Ji'nan 250061 China

Microstructure and alloy element distribution in the welded joint between austenitic stainless steel (1Cr18Ni9Ti) and pearlitic heat-resistant steel (1Cr5Mo) were researched by means of light microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Microstructure, divisions of the fusion zone and elemental diffusion distributions in the welded joints were investigated. Furthermore, solidification microstructure and S-ferrite distribution in the weld metal of these steels are also discussed.

关键词： Microstructure in the Weld Metal of Austenitic-Pearlitic Dissimilar Steels and Diffusion of Element in the Fusion Zone

PERTURBATION SOLUTION OF SECONDARY FLOW OF POWER-LAW FLUID IN HELICAL PIPES WITH CIRCULAR CROSS-SECTION

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Journal of Hydrodynamics 2001年第4期13卷 72-78页

作者： Cui Hai-qing, Wang Ke-liang Department of Petroleum eng.neering, Daqing Petroleum Institute, Anda 151400, China Wu Fu-bing Department of Navy and Ocean eng.neering, Harbin eng.neering University, Harbin 150001, China Zheng.Xiao-song Department of Pet dept. of Petroleum eng. Daqing Petroleum Inst. Anda 151400 China

In terms of tensor analysis technique, the Navier-Stokes equations in helical coordinate system were derived. A steady incompressible flow of power-law fluid in helical pipes at low Reynolds number was investigated by the perturbation method. A second order solution of secondary flow was worked out. The secondary flow characteristics in helical pipes are analyzed. The effects of the number Dn, curvature and torsion on the secondary flow at different flow parameters were discussed. The results show that the secondary flow pattern changes from a single vortex to two vortices as the number Dn increases at a given curvature and a given torsion. Because of the effect of torsion, the secondary flow pattern changes from two almost symmetrical vortices to a single vortex as the torsion of the helical pipe increases while the Reynolds number and curvature hold constant. The secondary flow pattern cannot be affected by the curvature of the helical pipe at a given Dn number.

关键词： helical pipe secondary flow power-law fluid perturbation method

COMPLEX FUNDAMENTAL SOLUTIONS FOR SEMI-INFINITEPLANE AND INFINITE PLANE WITH HOLE UNDER VARIOUS BOUNDARY CONDITIONS

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Applied Mathematics and Mechanics(eng.ish Edition) 1998年第4期19卷 335-344页

作者：唐寿高曹志远 dept. of eng. Mechanics and Technol. Tongji University Shanghai 200092 China

A general method of finding the complex fundamental solutions for semi-infinite plane and infinite plane with hole under various boundary conditions has be established by using Riemann-Schwarz symmetric principle and ... 详细信息

关键词： fundamental solution Riemann-Schwarz symmetric principle superposition principle

COMPOSITE MODELING APPROACH AND EXPERIMENTAL STUDY FOR SUBSURFACE TRANSPORT OF CONTAMINANTS FROM LAND-DISPOSAL SITES

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Journal of Hydrodynamics 2003年第4期15卷 1-9页

作者： Wang Chao, Wang Pei-fang, Li Yong Department of Environmental eng.neering, Hohai University, Nanjing 210098, China dept. of Environ. eng. Hohai Univ. Nanjing 210098 China

A composite modeling approach was presented for simulating thethree-dimensional (3-D) subsurface transport of dissolved contaminants with transformation *** approach was based on vertical infiltration and contaminant transport in the unsaturated zoneand 3-D groundwater flow and contaminant migration in the saturated zone. Moisture movement andgroundwater flow were considered to be steady, but contaminant transport was treated as continuousand transient. The transformed unsaturated zone and saturated zone transport equations were solvednumerically with different techniques. The model contains a 3-D solution to flow and transport inthe saturated zone, as well as two-dimensional solutions to vertical cross-sectional and arealscenarios. In order to verify the composite modeling, extensive experiments were conducted in twolarge-scale variable-slope soil tanks of 1200cm in leng.h, 150cm in width and 150cm in height. Sandsoil was filled in the tank as the porous media. The solutions of KBr or NH_4C1 were introduced intoeach soil tank from 80 X 37cm^2 area sources located on the top of the porous medium. Results fromnumerical simulations were compared with the data from tests. Predicted results are in goodagreement with the experimental data.

关键词： composite modeling groundater flow finite element model experiment

Transmitting boundary and radiation conditions at infinity

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Science China(Technological Sciences) 2001年第2期44卷 177-186页

作者：廖振鹏 dept. of Shipbldg. and Ocean eng. University of Engineering Harbin 150001 China

Relationship between the radiation conditions at infinity and the transmitting boundary for numerical simulation of the near-field wave motion has been studied in this paper. The conclusion is that the transmitting boundary is approximately equivalent to the radiation conditions at infinity for a large class of infinite media. And the errors of the approximation are of the same order of magnitude as those of the finite elements or finite differences in numerical simulation of wave motion. This result provides a sound theoretical basis for the transmitting boundary used in the numerical simulation of the near-field wave motion and gives a complete explanation for the major experiences accumulated in applications of the transmitting boundary to the numerical simulation.

关键词： numerical simulation of wave motion radiation conditions at infinity local artificial boundary condition multi-transmitting formula