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10 August 2004, Volume 26 Issue 4
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    Education Study
    2004, 26(4):  0-0.  doi:10.6052/1000-0879-2003-030
    Abstract ( 1178 )   PDF (214KB) ( 520 )  
    Based on the magnetic field state and fluid velocity distribution, a dynamic model of paramagnetic particles to be captured by ferromagnetic matrix is proposed. The phenomenological interpretation of paramagnetic particle's trajectory different from diamagnetic particle's is valuable on calculating the capture zone. From the observation on coal concentration and de-sulphurization by the High Gradient Magnetic Separation (i.e. HGMS), the magnetic field is not axisymmetrical so that the concept of capture radius is not very accurate. According to the Static Equilibrium Buildup Model (i.e. SEBM) proposed by J.E. Nesset and J.A. Finch, the notion of capture zone is proposed, the boundary curve separating the capture zone and expel zone is found to be a single hyperbolic curve, and thus the new formula for calculating the area of capture zone is obtained.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-064
    Abstract ( 1107 )   PDF (499KB) ( 582 )  
    Plastic unstability induced by localized necking in sheet metal forming process and forming limit analysis are reviewed. Some applications of plastic unstability criteria on forming limit analysis and related computer simulations are discussed. Plastic unstability-failure, as an interaction between plastic work-hardening and damage-softening is presented and the advances of Continuum Damage Mechanics related to this project are also reviewed in this paper.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-083
    Abstract ( 1162 )   PDF (256KB) ( 410 )  
    Two serious defects of GB8167-87 are found by analyzing the testing. Two new sets of testing methods of dynamic compression for package cushioning materials are proposed, as an improvement over GB8167-87.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-104
    Abstract ( 1195 )   PDF (228KB) ( 590 )  
    This paper presents the limit analysis of thick wall spherical shell of linear hardening material with different yield strength in tension and compression based on the Mohr's yield criterion. The analytic expressions of stress distribution in the elastic and plastic deformation area are obtained. The analytic expression of the limiting pressure with respect to the parameter αis also obtained by the analysis. The theoretical analysis shows that the different yield strength of the material in tension and compression will influence the limited pressure of thick walled spherical shell.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-122
    Abstract ( 1018 )   PDF (339KB) ( 539 )  
    The limit equilibrium equation for the analysis of earth slope stability is derived from the system energy by the use of the stress softening model and the instability is analyzed by the catastrophe theory. It is indicated that the catastrophic instability sliding arises accompanying an abrupt increment of the sliding-displacement when the slope parameter reaches the critical value. The limit equilibrium stability theory of a rigid body can not explain the catastrophe of instability of the stress softening earth slope.
    Application study
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-125
    Abstract ( 1251 )   PDF (420KB) ( 492 )  
    Hill's yield criterion for plastically orthotropic solids is used to predict the yield stresses of single crystal Nickel-based superalloys DD3, but the correlation to experiments at 760℃ is poor. Taking into account the fact that the components of tension stresses are coupled with components of torsion stresses when off-axis loads are applied for an orthotropic material, Hill's yield criterion for plastically orthotropic solids is modified by adding an invariant which is composed of the quadratic product item of components of deviatoric stress tensor, and a new yield criterion is put forward in term of the characteristics of cubic single crystal material. The coefficients in the new criterion can be determined from uniaxial tension tests and the method of determining those coefficients is given in the paper. Equivalent stress and equivalent strain for the new criterion are defined. The new criterion, new equivalent stress and equivalent strain will be reduced to the von Mises's for isotropic material. The correlation to experiments is very good while the new criterion is used to predict the yield stresses of single crystal Nickel-based superalloys DD3, and it gives more accurate results than that of Hill's at 760℃.
    Education Study
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-166
    Abstract ( 1112 )   PDF (273KB) ( 478 )  
    In order to guarantee the precision of the cable tension of a cable-stayed bridge measured by vibration method, in one large-span bridge as an example, the effect of cable parameters on the cable tension determination is studied by nonlinear FEM. The results can explain the cable tension difference measured in the same bridge by two different groups.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-168
    Abstract ( 1145 )   PDF (348KB) ( 377 )  
    The well repairing by drawing casing and changing is a new technology for restoring a well of casing failure and is very effective. During the well repairing, the diameter of the milled sleeve is large and the clearance is small, so that the sticking of the milled sleeve becomes very serious. It often increases the repairing period and repairing cost. In this paper, the theoretical model of preventing milled sleeve from sticking is established by a mechanical analysis. It takes account of both pressure difference and sticking effect on the milled sleeve. On the basis of the model, the longest time for the milled sleeve stopped in the well is calculated, so that it can be prevented from sticking. The main factors of sticking milled sleeve are analyzed.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-191
    Abstract ( 1568 )   PDF (429KB) ( 509 )  
    Based on probabilistic fracture mechanics and Monte Carlo simulation, a reliability analysis method for fatigue life of autofrettaged gun barrel is proposed. The residual stress solution of the autofrettaged gun barrel is suitable for the gun barrel made of steel with strain hardening and Bauschinger effect. The stress intensity factors of the gun barrel are calculated using the weight function method. The analysis of an example shows that a lognormal distribution is the best fit for fatigue life. And the fatigue life of the gun barrel on the condition of different reliabilities and confidences is obtained. The influence of the initial crack depth and fracture toughness of material on the fatigue life of the gun barrel is also discussed.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-218
    Abstract ( 1072 )   PDF (376KB) ( 545 )  
    The experimental equipment is established for simulating water distribution in landslide with reservoir table changed. The laboratory model is made based on the shape, geometric characters and soil-rock ratio of Maoping slide. The water distributions in the simulated slide are simulated with water table at the half height of the soared interface and the height of the first platform. When the reservoir table drops down in the experiment, a part of the slide fails. The results show that wetting lagging is the main factor of slide failure during the reservoir table drop-down.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-232
    Abstract ( 953 )   PDF (323KB) ( 410 )  
    Vehicle bump at the bridge-head is a common disease from differential settlement between bridge structure and approach fill in a super highway. In engineering, there is no ideal remedy for it, because the common bridge abutment fill cannot be compacted effectively. In recent years, a new type abutment -- flexible abutment was applied in engineering, which may prevent differential settlement radically. But its reinforced interval value was determined blindly. In this article, 4 groups of model tests were carried out for comparative analysis. The tests indicated that the best reinforced interval value was between 30cm and 50cm.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-238
    Abstract ( 1117 )   PDF (277KB) ( 424 )  
    The driving system is an essential part of the modern bundling machine. 3D contact nonlinear finite element analysis on the driving wheel system of the bundling machine is made by using the finite element analysis software ANSYS. The contact stress distribution is obtained. It is found that the maximal contact stresses are in agreement with the simplified calculation using the conventional method.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-252
    Abstract ( 1160 )   PDF (184KB) ( 507 )  
    A dynamical equation is established based on a simplified mechanics model for the collision between tennis racket and the ball within very short time, and the relationships between the string tension of the racket and the velocity of the tennis ball, separate time, and separate distance are analyzed. It is concluded that the ball would gain higher velocity if the string tension is weaker. Correspondingly, the separate time and the separate distance will increase.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-272
    Abstract ( 1042 )   PDF (299KB) ( 564 )  
    Based on the numerical method of die swell for viscoelastic fluid, proposed by the authors, simulations of 4:1 axisymmetric contraction flow for IUPAC-LDPE melt are presented in this paper. The relative vortex intensity and the entrance correction obtained here agree with the results reported in the literatures, and the flow fields are also reasonable. The results in the paper indicate that the method used by the authors is suitable for calculating the entry flow in contraction for viscoelastic polymer melt described by the integral-type PSM constitutive equation.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-309
    Abstract ( 1044 )   PDF (273KB) ( 500 )  
    With wood being considered as an orthogonal anisotropic material, its fracture toughness KIC, denoting wood resistance against crack extension is one of wood basic mechanical properties, with obvious anisotropy. The test results indicate that LT specimen fracture toughness is obviously higher than that of TL, TR specimen; those of TL and TR specimen are close. Regardless of specimen types, crack propagation all occurs at the crack tip. TL and TR specimen crack extension direction is consistent with the original crack direction, while LT specimen crack grows nearly parallel to the fiber direction, The influence tendency of moisture content on each wood direction fracture toughness is about the same.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-315
    Abstract ( 1017 )   PDF (373KB) ( 411 )  
    Under the dynamical load, the interaction between the structure and its interior equipment is evident. In this interacting system, the structure is considered as the main-structure, and the interior equipment is regarded as a sub-structure. Its mechanism and influencing factor of reducing vibration are studied by means of frequency domain analysis. The result of study indicates that the mechanism is that the sub-structure provides an inertial dynamic load, and the load can reduce the vibration of the interacting system.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-405
    Abstract ( 1308 )   PDF (292KB) ( 516 )  
    When a fly is in contact with a hard and smooth surface, the process involves the adhesion between the surface and the cilium of the fly legs. In this article, the contact problem is formulated under the JKR theory. An expression of the adhesion force is derived with respect to the surface energy. The bounds for the scales of the cilium that enable the fly to adhere and to detach from a hard surface are estimated. These bounds are consistent with the SEM observation.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2003-471
    Abstract ( 1191 )   PDF (350KB) ( 402 )  
    For the elastic supported continuous beam and frame, its internal forces are related not only to the stiffness of each member, but also to the stiffness of the supported structure. With a different tension and compression modulus, the flexural rigidity of each member is not constant any more (as is different from that of classic mechanics), but is a function of the internal force, that is, the calculation for the internal force is a nonlinear problem. In this paper, the formulas of neutral axis and internal force for the elastic supported continuous beam and frame are derived by using the phased integration method, and an iterative program for nonlinear internal force is developed, an example is calculated and analyzed. In the end, the author proposes a suggestion for the calculation of structure, and concludes that the structure can be optimized by using the different modulus theory.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2002-140
    Abstract ( 1040 )  
    The differential equations of variable section framed-tube structures are derived based on a mathematical model of an equivalent continuum and the energy variational principle. Every storey with a same section is taken as a calculation element. The element matrix, section matrix and transfer matrix of every element are derived by the differential equations. Then the variable section framed-tube structure is anlyzed by the transfer matrix method. Finally, a mumerical example is given.
    2004, 26(4):  0-0.  doi:10.6052/1000-0992-2004-196
    Abstract ( 1355 )   PDF (664KB) ( 513 )  
    By using the fluid stratification technique in experimental fluid dynamics, the neutral atmosphere, in which the atmospheric potential temperature is constant with respect to height, is simulated with uniform water in a water channel. Then the density of salt water is stratified to simulate the stable atmosphere, in which the potential temperature increases with height. The similarity theory and experimental method of atmospheric simulation by using water as the medium are introduced in the present paper. The influences of the terrain in Beijing area on the urban atmospheric environment are studied to illustrate the problems which should be solved in the treatment of the capital urban air pollution. The water channel experiments combined with the field observation and numerical computation are successfully used to study the influences of terrain on the atmospheric transport and diffusion of the radioactive airborne effluents released from a nuclear power plant in operation, in Fujian Province.