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10 October 2006, Volume 28 Issue 5
Education Study
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-265
Abstract ( 1158 )   PDF (469KB) ( 551 )
By using the tensor analysis, the paper proves that the three theories for describing the nonlinear constitutive relation of incompressible viscoelastical materials, including BKZ theory, Lianis theory and Chirstensen theory, have a same representation when they are used for the uniaxial tension of isotropic materials. And we also show that the three theories amount the same in explaining the nonlinear constitutive relation.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-286
Abstract ( 1099 )   PDF (424KB) ( 379 )
An analytical study is conducted on energy losses of a fully developed convective heat transfer inside tubes. With the assumption of a fully developed inside tube flow subjected to constant wall heat flux or constant wall temperature, approximate expressions for dimensionless energy losses describing effects of heating, pumping power and the variation of viscosity are obtained. The present model is applicable for the energy analysis on fully developed laminar and turbulent flows inside tubes of a variety of cross-sectional shape.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-321
Abstract ( 1274 )   PDF (693KB) ( 536 )
In this paper, based on the reological theory of rock, and the principle of seepage, considering the effect of the pore pressure and porosity on deformation of rock, analytical solutions are obtained by using the the Laplace transform (corresponding principle). In certain conditions, the creep curve under pore pressure is obtained by using the principle of effective stress (the equation of effective stress of Terzaghi) and H-K model as the constitutive equation. Comparing this curve with that without pore pressure, we can see that our results agree better with the actual situation.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-329
Abstract ( 1384 )   PDF (601KB) ( 570 )
In this paper, a program for feedback automation control in the ANSYS's PSD(power spectrum density) analysis is developed in the powerful APDL(ANSYS Parametric Design Language) language. Multi-table is used to store the base importing spectrum, which has lifted the limit that the base importing spectrum can only be described by less than 50 data points. So the base importing spectrum can be identified via a feedback. The computing efficiency and precision are improved greatly.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-331
Abstract ( 1393 )   PDF (648KB) ( 602 )
The implicit LU-SGS scheme based on unstructured meshes is employed to solve three-dimensional Euler equations. The flow field of a hollow projectile is numerically simulated for different Mach number and different attack angle. Complicated flow structure and its lift and drag characteristics are discussed. The numerical results indicate that the drag coefficient of a hollow projectile is smaller by about 30 percent than that of a common projectile with the same diameter, and the correlations between the drag and the lift coefficients of the hollow projectile and the attack angle are in agreement with those of the common projectile. The results are relevant to engineering designs.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-341
Abstract ( 1108 )   PDF (745KB) ( 538 )
The engineering background and technical reality about calibrating the clamping parameters of a cupping testing machine is introduced. A solution method of using a cross cantilever sensor to calibrate the clamping parameters is presented, with the mathematical model for calculating the clamping parameters. The problems such as stress distribution, manufacture of the sensor and calibration, non-linearity error correction, data processing for the device are discussed, and a technique basis for calibrating the clamping parameters of a cupping testing machine is provided.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-348
Abstract ( 1299 )   PDF (764KB) ( 590 )
Wave function expansion method is used to study the scattering of steady incident plane SH-wave by circular arc elastic lining at the corner point of a rectangular plane. The total wave solutions inside and outside the lining are constructed, which satisfy the free stress conditions of the two rectangular boundaries; all unknown coefficients in the scattering solutions and the refraction wave solutions are determined by solving the linear equations with the conditions of displacement/stress at the boundaries of the circular lining. An example is given to illustrate the variations of DTSCF(dynamic tangential stress concentration factor) and amplitude ratio of the points at the interior boundary of the circular lining vs dimensionless wave numbers and incident angles. The results of the example show that the DTSCF and the amplitude ratio are magnified to some extent.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-349
Abstract ( 1143 )   PDF (483KB) ( 440 )
The prediction ability of the simplified Acierno-type constitutive equation is examined in the present paper. The thixotropy-loop tests of an LDPE(Q200) melt are predicted by the simplified Acierno equation, and the differences between the model and the variant Huang model in the descriptions and the predictions of the thixotropy-loop tests are compared. It is shown that the deviations of the predictions by the simplified Acierno equation from the experiments are smaller than those obtained by the variant Huang model under the same calculation conditions, although only partial descriptions of the thixotropy-loop tests of the melt by the simplified Acierno model agree with the experiments. The constitution of the simplified Acierno equation is more reasonable than that of the variant Huang model.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-365
Abstract ( 1081 )   PDF (605KB) ( 452 )
Based on the theory of mechanics, a structure model is built for wobble-plate engines. By analyzing the linkage's response to shaking force, the whole system was divided two parts, a multiplex open chain linkage and a circular linkage with N pistons. Then the complete force balance of the two parts is studied separately. The results show that the wobble-plate engine will attain a complete force balance by adding only a counterweight on the principal axis. The method is simpler and more convenient than that of analyzing single loop spatial RRSSC linkage, so it can be used for special environments.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-436
Abstract ( 1085 )   PDF (572KB) ( 440 )
By using the method of quasi-shells, the nonlinear dynamical equations are established for three-dimensional shallow spherical shells with circular bottom based on the nonlinear dynamical equations for circular reticulated structures with three-dimensional grids. The foundational equations and the boundary conditions are simplified by introducing dimensionless quantities, and a nonlinear differential equation of the third order is derived under the boundary conditions of fixed edges by using Galerkin method. In order to obtain the Melnikov function, the free oscillation equation of a kind of nonlinear dynamics system is solved, and then the exact solution to the problem is obtained. The stability is discussed on the condition of no external excitation. The conditions for chaotic motion are given by solving for the Melnikov function under external excitations. Existence of the chaotic motion is proved by numerical simulation and the phase planes are plotted.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-447
Abstract ( 1494 )   PDF (473KB) ( 768 )
The mean fatigue life curves of a material can be obtained from damage mechanics. The material parameters that affect the $S$-$N$ curve and the relationship between them are obtained. The mean fatigue life curves, namely, the material parameters corresponding to $K_t=1.0$, are obtained by using the up-down method and the group fatigue test. One needs only to use the up-down fatigue test to get the fatigue limit under any coefficient of stress concentration $K_t$, then, we can get the mean fatigue life curves corresponding to the stress concentration.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-458
Abstract ( 1288 )   PDF (686KB) ( 483 )
The single-layer lattice dome geometry model is established by using beam elements in the FE software------MSC. Patran. The dome is analyzed for three different sections and different number of constraints. According the results, the sensitivity of the dimension of the section to the stress and deformation is calculated, the static characteristics of the dome and its influence factors are obtained. %The results are very valuable for designing and optimizing the similar structure domes.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2005-470
Abstract ( 1253 )   PDF (646KB) ( 588 )
The buckling of an axially compressive strut constrained by a flexible sleeve is studied for the cases of a single point contact and a curved line contact between the strut and the sleeve. Under the small deflection assumption, the second order differential equilibrium equations of the strut and the sleeve satisfying deformation compatibility conditions are obtained. The deflection, the axial displacement, and the contact reactions of the strut are then obtained. The length of the line contact is uniquely determined by the axially compressive force. Two examples indicate that the axial displacement of the strut caused by bending is large when the stiffness of the sleeve is small, and vice versa, which is in good agreement with the large deflection solution. It is confirmed that the small deflection assumption is valid here.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2006-110
Abstract ( 1158 )   PDF (994KB) ( 428 )
A two dimensional numerical simulation of natural convection in a differentially heated cavity is performed. The evolution of the horizontal hot intrusion is observed and its physical properties are described. The numerical results show that, after the hot intrusion reaches the cold wall, some accumulates in the cold top corner, since the cold boundary layer flow cannot entrain all of the hot intrusion. Due to the hot fluid accumulation and the buoyancy effect, a reverse flow (opposing the cold boundary layer flow) first arises in the cold top corner, and then forms a clockwise local circulation. This circulation may move back to the hot wall, and ultimately a cavity-scale oscillation (i.e. internal gravity wave) is resulted between the hot and cold walls underneath the ceiling of the cavity. Such oscillation significantly decays with the passage of time, and almost disappears after two periods.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2006-192
Abstract ( 1238 )   PDF (1514KB) ( 556 )
Well cementing is an important operation in the construction of any oil well. After a section of the steel casing is inserted into the hole, a sequence of cement slurry is pumped down the inside of the tubing and coming back up through the annular gap, and then allowed to settle in the annulus. Several fluid mechanics problems are discussed in the present paper, such as, how to determine the mechanical models for describing rheological behavior of cementing slurry at high temperature and high pressure, the influences of eccentricities on slurry flow, and the stability of the interface between slurry and spacer. This paper briefly reviews the latest investigations on fluid mechanics problems, and some important directions for future researches are pointed out.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2006-197
Abstract ( 6158 )   PDF (653KB) ( 1106 )
Lissajous figures can be used to detect the phase shift of two signals with a same frequency. This paper introduces a analysis method for determining dynamic characteristics of a second order acceleration measurement system with inertial mass, spring and damping, where the Lissajous figures are used to detect the dynamic characteristics of the force balance acceleration sensor, i.e. amplitude response and phase response. The natural frequency $\omega _{n}$ and damping ratio $\xi$ of the sensor are determined in order to assess the overall performance of the sensor.
2006, 28(5):  0-0.  doi:10.6052/1000-0992-2006-252
Abstract ( 1333 )   PDF (1798KB) ( 521 )
Some important research progresses of high temperature gas-dynamics related to hypersonic sciences and technologies are reviewed. Several fundamental research topics are discussed for future research, which include the advanced hypersonic test facilities; modeling aero-thermo-chemistry; stagnation flow region prediction; hypersonic boundary layer transition and shock waves/viscous interactions. The physical flow phenomena in such situations are thought to be closely related to real gas effects and strong shock wave interactions. It is believed that future improvements of hypersonic critical techniques depend on better understanding of those phenomena.