2014 Vol. 35, No. 7

Display Method:
Plastic Constitutive Relation and Plastic Constitutive Theory for Engineering Materials
ZHENG Ying-ren, KONG Liang, LIU Yuan-xue
2014, 35(7): 713-722. doi: 10.3879/j.issn.1000-0887.2014.07.001
Abstract(1562) PDF(1616)
Abstract:
Based on deep analysis of the plastic constitutive theory for engineering materials, a more rigorous and general plastic constitutive equation was proposed, which could work as the theoretical basis for constitutive modeling of engineering materials. Then the constitutive relation was applied to 3 kinds of engineering materials, i.e. geotechnical friction materials, metal crystal materials and strength control problems. According to the material properties and requirements of engineering calculation, the constitutive relation could be simplified for the geotechnical friction materials and metal materials respectively. For the strength control engineering problems, the related material could be deemed as perfectly plastic on condition of sufficient plastic deformation, and the yield condition with the limit analysis condition was used to determine the safety factor or ultimate bearing capacity through traditional or numerical limit analysis.
Calibration of Analytical Fragility Curves Based on Empirical Data of Bridges
WU Zi-yan, JIA Zhao-ping, LIU Xiao-xiao
2014, 35(7): 723-736. doi: 10.3879/j.issn.1000-0887.2014.07.002
Abstract(1331) PDF(934)
Abstract:
Most previous studies of analytical fragility curves based on bridge damage states defined through theoretical computations or experimental investigations couldn’t fully include the influences of bridge configuration (geometric properties, material properties, etc.), ground motion, site condition and so on. In view of this, the empirical fragility curves of the 2-parameter lognormal distribution were firstly constructed on the basis of the bridge damage data from the 1994 Northridge earthquake. Meanwhile, the analytical fragility curves of a multispan bridge model under four different damage states were obtained with definition of the bent column rotational ductility thresholds. Lastly, the analytical fragility curves were calibrated with the empirical fragility curves of the 90% confidence interval. The results show that the calibrated analytical fragility curves of the bridge model are fairly consistent with the empirical ones, and the threshold values of the 3 damage states are also calibrated with the SRSS optimization formula. With the progress of the structural damage knowledge, the calibrated analytical fragility curves can be updated again. The improved fragility curves are promising in the seismic risk assessment of a highway network containing as many as thousands of bridges that may be affected by a major earthquake nearby or far away.
Study and Application of a 4-DOF 1/2 Vehicle-Road Coupling Dynamic Model
LUO Hong, LIANG Bo, WU Zhi-hua, SHI Shi-rong
2014, 35(7): 737-749. doi: 10.3879/j.issn.1000-0887.2014.07.003
Abstract(1102) PDF(1220)
Abstract:
In the case of a vehicle running on a road, coupling vibration of the vehicle-road system will be induced because of the road unevenness. To simplify the analysis, the vehicle-road system was first divided into a vehicle subsystem above and a road subsystem below, then the 2 subsystems coupled with each other to form a complete system. The vehicle-road dynamic model consisted of a 4-DOF 1/2 vehicle model and an elastic multi-layer finite element road model, and they coupled through the displacement compatibility between the tires and the pavement. The dynamic equilibrium equations for the system were formulated and the decoupling method for the equations was discussed. Several theoretical indices reflecting the road design parameters and the vehicle operation quality were proposed, which provided theoretical basis and solving rationale for the systematic study of relationship between the vehicle operation quality and road design parameters. Furthermore, numerical results of the examples give comparative evaluation of the traveling quality indices of the 2 typical pavement structures of asphalt concrete and cement concrete, making a useful reference for the design and analysis of different pavement structures.
Analytic Method for Shear Lag Effect of Box Girders Under Concentrated Bending Moments
LIN Peng-zhen, YANG Zi-jiang, SUN Li-xiang>, JI Wei
2014, 35(7): 750-758. doi: 10.3879/j.issn.1000-0887.2014.07.004
Abstract(1004) PDF(1087)
Abstract:
For simply supported box girders under concentrated bending moments, general analytic solutions to shear lag effect were presented based on the energy variational principle. Formulae for shear lag effect were given for several typical cases of one bending moment acting on the girder span interior, one end, or both ends. For an example box girder, shear lag effect was calculated respectively in the 3 cases of concentrated bending moment applied. The analytic results were compared with those of the finite shell element method. It’s shown that the presented analytic method has high accuracy in the calculation of box girder shear lag effect in comparison with the finite element method. Where there exists a concentrated bending moment applied on a simply supported box girder, there occurs sharp shear lag effect.
Blasting Process Simulation and Stability Study of an Open Mine Slope Based on PFC3D
CUI Tie-jun, MA Yun-dong>, WANG Lai-gui
2014, 35(7): 759-767. doi: 10.3879/j.issn.1000-0887.2014.07.005
Abstract(1136) PDF(1401)
Abstract:
To study the blasting process in an open mine slope, based on the theory of energy conservation, it was assumed that all the chemical energy released during explosion was transmitted to the surrounding rock body within a certain range and partially converted to kinetic energy, then the explosion energy was transferred and absorbed in the fractured and damping rock until the ultimate balance at the end of this dynamic process. The PFC3D simulation platform was employed to calcaulate the singlehole blasting processes with different heights, buried depths and charge amounts in the open mine slope, and the slope stability after blasting was discussed. The simulation results show that: the blasting process can be divided into 3 phases. In the first phase, the explosion impact plays a leading role, accompanied by the reverberation of the velocity vectors. In the second phase, gravity is the dominant factor for the collapse of the overburden rock. In the third phase, some particles roll or slip down and end in balance. The time length of the following phase is bigger than that of the preceding one by almost 1 order of magnitude. In general, the upper sandstone is stable after all sorts of blasting, i.e. the slope top is stable. The lower sandstone and sandy mudstone are subject to a certain degree of damage but still in control.
Study on the Stress-Strain Relationship of Gas-Bearing Coal Rock Under Variable Confining Pressure-Pore Pressure Conditions
FANG Ping-liang, SHAO Li-ming>, ZENG Zhi-guo, LI Ning
2014, 35(7): 768-776. doi: 10.3879/j.issn.1000-0887.2014.07.006
Abstract(1026) PDF(736)
Abstract:
Under different confining pressure-pore pressure conditions, the numerical method was used to simulate the failure process and the stress-strain relationship of gas-bearing coal rock. A micro-heterogeneous elastic-brittle model based on elasticity theory and failure theory was constructed with the influences of confining pressure and pore pressure considered. An FEM program was developed partially out of the FEPG software, to simulate the deformation and failure behaviors of the gas-bearing coal rock under variable confining pressure-pore pressure conditions. The results show that the coal rock becomes ductile with increase of the confining pressure, and the carrying capacity is enhanced, while the influence of the pore pressure is just opposite. The simulation results quantitatively agree well with the experimental results, which, to a certain extent, proves accuracy of the proposed constitutional model and effectiveness of the FEM program.
Analytical and Numerical Investigation of the Variable Coefficient Burgers Equation Under Cauchy Condition With the Exponential Homotopy Method
ZOU Li, WANG Zhen, ZONG Zhi, WANG Xi-jun, ZHANG Shuo
2014, 35(7): 777-789. doi: 10.3879/j.issn.1000-0887.2014.07.007
Abstract(1138) PDF(875)
Abstract:
The variable coefficient Burgers equation was studied with an approximate analytical method under the given initial and boundary conditions. A new-form homotopy was introduced to overcome the problem brought by the variable coefficient, this new-form homotopy enhanced the computational efficiency in comparison with the traditional forms, and gave a consistent analytical solution expression in time domain. Analytical solutions to the variable coefficient Burgers equation in finite space domain were determined respectively, and shock wave formation in finite space domain was also discussed. Convergence of the presented analytical solution was explored in the sense of norm. Based on the Lie transformtion group theory, symmetry of the variable coefficient Burgers equation was studied with its infinitesimal generators, conservation law and group invariant solution obtained. The presented solution was directly deduced from the nonlinear partial differential equation without travelling wave transformation. Convergence of the approximate analytical solution was discussed with the so-called‘h-curve’criteria. Direct numerical simulation with the finite difference method proves accuracy and effectiveness of the proposed exponential homotopy method.
A Family of High Accuracy Implicit Difference Schemes for Solving Parabolic Equations
ZHAN Yong-qiang, ZHANG Chuan-lin
2014, 35(7): 790-797. doi: 10.3879/j.issn.1000-0887.2014.07.008
Abstract(1570) PDF(861)
Abstract:
A family of implicit difference schemes with high accuracy for solving 1-dimensional parabolic equations were given. First, a difference approximation expression of the first order partial derivative of the solution to the parabolic equation was deduced at the special nodes; then this difference approximation expression and the second order central difference quotient approximation were used to construct a family of implicit difference schemes by the method of undetermined coefficients, and appropriate parameters were chosen to endow the schemes with high order truncation errors. In turn, the new difference schemes were proved to be stable as long as r was more than 1/6 with the Fourier analysis method. Finally, a numerical experiment was conduted on comparison of accuracy between the exact solutions, results of the new difference schemes and those of the other schemes with the same order truncation errors, as well as comparison of computational efficiency between the new schemes and the classical implicit difference schemes. The results demonstrate the high accuracy and efficiency of the presented difference schemes.
Inverse Limit and Lauwerier Attractor(Ⅱ)
GUO Feng, LI Deng-hui
2014, 35(7): 798-804. doi: 10.3879/j.issn.1000-0887.2014.07.009
Abstract(879) PDF(795)
Abstract:
The quadratic mapping had an attracting periodic orbit of which the attraction set was dense in a unit closed interval for an appropriate parameter. According to that property, an upper semi-continuous decomposition of the Lauwerier mapping was defined, with respect to which there existed a separable quotient space. The 2D Lauwerier mapping was reduced to a 1D quadratic mapping through projection. The dynamic properties of the Lauwerier mapping was studied with the shift map on the inverse limit space of the quadratic mapping. First, the quadratic mapping was nearly Markov partitioned, then each partition interval was expanded to a corresponding small rectangular region, in turn the Lauwerier mapping was nearly Markov partitioned again. It is proved that the Lauwerier mapping is topologically semi-conjugate to the shift map on the inverse limit space of the quadratic mapping when the parameter is under 4.
Riemann’s Boundary Value Problem of K-Analytic Functions
ZHANG Jian-yuan, ZHAO Shu-fen, HAN Yan
2014, 35(7): 805-814. doi: 10.3879/j.issn.1000-0887.2014.07.010
Abstract(1103) PDF(828)
Abstract:
First, the concepts of the (piecewise) K-analytic function and the Cauchy type K-integral were introduced, and some properties of the Cauchy type K-integral were studied through K-symmetry transformation. Then, with the function index of the curve and the properties of the Cauchy type K-integral, the solvable conditions and the solution expressions for the Riemann’s boundary value problem of the K-analytic function as well as the relationship between the solutions and the index were obtained. Since both the analytic functions and the conjugate analytic functions are special cases of the K-analytic functions, the present conclusions generalize many known related results of them.
Numerical Simulation of Monolayer Coolant-Side Heat Transfer Characteristics for Plate-Fin Oil Coolers With Different Structures
LIU Ya-ping, ZENG Zhong, XU Xiao-long, ZHANG Zhen, QU Jing-jing
2014, 35(7): 815-822. doi: 10.3879/j.issn.1000-0887.2014.07.011
Abstract(896) PDF(687)
Abstract:
Based on the porous medium model, the monolayer coolant-side flow and heat transfer in the plate-fin oil coolers with 5 kinds of structures were numerically simulated by means of the finite volume method. The results indicate that the distribution of pressure and temperature is more even and the temperature difference is larger when the inlet and outlet are diagonally positioned than they are positioned on the same side, with the fins’layouts in the same direction. Given the same outlet positions, the distribution of pressure and temperature in the case of transverse arrangement of fins is more even, and the pressure difference is larger than those in the case of vertical arrangement, while similar temperature differences occur in both cases. The plate-fin oil cooler with clapboards has the biggest temperature difference as well as pressure difference 1 order of magnitude higher than that of other structures.
Study of Self-Adaptive Ant Colony Optimization for Heat Source Search in Inverse Heat Conduction Problems
ZHANG Tao, LU Mei, LI Bo-han, TAO Liang
2014, 35(7): 823-830. doi: 10.3879/j.issn.1000-0887.2014.07.012
Abstract(1088) PDF(672)
Abstract:
A model based on ant colony optimization (ACO) was presented for the solution of two-dimensional stable inverse heat conduction problems (IHCP). According to comparison between the measured information at boundary points and the calculated temperature at those points, the IHCP was transformed to an optimization problem. By means of different path construction methods the ACO was improved as a self-adaptive algorithm to inversely calculate the heat-source intensity and location with high precision. The results show that the present self-adaptive ACO with the path construction methods for different inversion parameters is robust and accurate for the search of location and intensity of the heat source.