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08 December 2008, Volume 30 Issue 6
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Application study
2008, 30(6):  64-67.  doi:10.6052/1000-0992-2007-284
Abstract ( 1149 )   PDF (4387KB) ( 840 )
To study the failure laws of surrounding rocks for the roadway in deep rock mass, in view of the heterogeneity of rock, we use a constitutive model based on damage mechanics and statistical theory and the RFPA$^{\rm 2D}$, to analyze the deformation and nonlinear gradual failure characteristics of circular roadway in deep rock mass as well as the displacement and the stress variations in the key positions in the periphery of the roadway, and also the mechanism of loose rock zone in the surrounding rock of the circular roadway. The study indicates that the stress concentration occurs in the periphery of the roadway after evacuation and plastic deformation zone is engendered under the persisting stress of the surrounding rock, then the cracks appears and extends continuously, the loose fraction zone (loose rock zone) appears at last and the intensity of the stress concentration decreases as well as the stress field shifts beyond.
2008, 30(6):  68-72.  doi:10.6052/1000-0992-2007-330
Abstract ( 1451 )   PDF (791KB) ( 615 )
The area under resistance-deflection ($R$-$y$) curve of reinforced concrete (RC) slab gives the energy which a RC slab can absorb when subjected to the blast loads. For the RC simple supported one-way slab under blast loads, a bilinear model is used to simulate the $R$-$y$ curve in the analysis of blast dynamic response. After comparing the areas under the $R$-$y$ curves of RC slabs with different reinforcement ratios, the reinforcement ratio responding to the biggest area can be defined as the optimal reinforcement ratio. Because the effects of nonlinearity of the material and the strain rate on the reinforced concrete and reinforcing steel should be considered, a layered method is used to determine the $R$-$y$ curves and the dynamic response of slabs. The derived results can be used to optimiz design of RC simply supported one-way slabs.
2008, 30(6):  73-76.  doi:10.6052/1000-0992-2007-409
Abstract ( 1400 )   PDF (758KB) ( 743 )
Based on the principle of Bayes discriminant analysis, a Bayes discriminant model for evaluating expansive soil is established. Five indexes, including the liquid limit, the overall rate of expansion and contraction, plastic index, moisture content, free expansion rate, are selected as the factors for synthetic evaluation of expansive soil. The shrink and expansion is divided into four grades as four normal populations in Bayes discriminant analysis. Bayes discriminant functions obtained through training a set of expansive soil samples are used to compute the Bayes function values of the evaluating samples, and the maximal function value is used to judge which population the evaluating sample belongs to. The usefulness of the proposed model is verified by Jackknife method. The study shows that the average prediction accuracy is 13.3%
2008, 30(6):  35-38.  doi:10.6052/1000-0879-2007-411
Abstract ( 1771 )   PDF (729KB) ( 687 )
A new method for reliability evaluation is proposed, in which Space Mapping technique is combined with Response Surface Methodology. In the new approach, the limit state function is only fitted once in the first iteration; in other iterations, Space Mapping technique is applied to map the original limit state function to the new ones. The new approach does not require experimental design, model evaluation and response surface fitting of the limit state function repetitively, which amounts to a great reduction of computational effort involved.
Review
2008, 30(6):  11-17.  doi:10.6052/1000-0992-2007-441
Abstract ( 1377 )   PDF (2574KB) ( 857 )
Various kinds of intelligent composite material have widely been applied in engineering and technology. This paper reviews the basic concepts, main types and sensing and actuating mechanisms of intelligent materials and intelligent composite materials, focusing on art-of-state applications of intelligent composite materials. The multi-physics coupling behavior of intelligent composite materials is emphasized in the present paper.
Application study
2008, 30(6):  60-63.  doi:10.6052/1000-0992-2007-481
Abstract ( 1356 )   PDF (565KB) ( 692 )
On the basis of flexibility matrix in a single pile, a formula for calculating the settlement of a pile group of varying rigidity is derived to complement Technical Code for Building Pile foundations''. Comparing with the results for uniform piles, it is shown that piles of varying rigidity can reduce differential settlement. The method can be used for reference in drawing new code.
2008, 30(6):  51-55.  doi:10.6052/1000-0992-2007-496
Abstract ( 1534 )   PDF (920KB) ( 711 )
Based on the basic theory of structural dynamics, the determination of damping coefficients of pavement materials and its influence on the dynamic deflection of asphalt pavement were studied. The results demonstrate that the damping coefficients determined from the natural frequencies of the first and second principal vibration modes do not suffer from the error of the conventional calculation method. The viscous damping coefficient has little influence on the pavement deflection and can be neglected in the dynamic analysis of pavement structure. Compared with the other materials, the damping feature of the subgrade is a main factor affecting the pavement deflection. The analysis provides a reference for the calculation and determination of material damping coefficients in dynamic analysis of pavement structure.
2008, 30(6):  56-59.  doi:10.6052/1000-0992-2007-516
Abstract ( 1600 )   PDF (2060KB) ( 735 )
The stress-strain field of interface crack tip in orthotropic bi-materials is determined by photoelastic coating in this paper, and the fracture mechanics parameters for interface crack are derived. Orthotropic bi-materials panel is made into a tension specimen, and metallic-aluminum coating is plated in the surface of unilateral polycarbonate coating to enhance the reflectivity of polycarbonate coating. Then the load along the interface prefabricated cracks of bi-materials is gradually increased, a series of clear equi-difference lines can be observed. Stress intensity factor can be calculated by using stress component expressions for interface crack in orthotropic bi-materials. The testing-result indicates that photoelastic coating can effectively analyze the problem for interface crack in orthotropic bi-materials.
2008, 30(6):  77-80.  doi:10.6052/1000-0992-2007-536
Abstract ( 1136 )   PDF (1263KB) ( 553 )
The mechanical properties of hydroxyapatites under the influence of subcutaneous tissues are tested using digital image correlation technique (DIC). Two groups of samples are tested. They are made of hydroxyapatite and hydroxyapatite implanted in rat subcutaneous for 20 days. The stress strain curves, without treatment of the all samples of the two groups are obtained. Both the Young's moduli and Poisson ratios are measured by DIC, and ultimate compressive stresses are also measured. The test results show that all samples of the two group give a linear stress strain relationship. The results also show that subcutaneous tissues increase Young's modului and compressive strength of hydroxyaptite by 29.06{\%} and 28.71{\%}, respectively.
2008, 30(6):  22-27.  doi:10.6052/1000-0992-2007-556
Abstract ( 1118 )   PDF (942KB) ( 540 )
An intelligent generation and analysis system of trusses is built. It can complete the process of layout, topological generation and calculation for truss structures automatically. The layout design of trusses include joints setting and selective bar connecting. The structure is formed automatically by use of the topological variation method. The basic internal force matrix is adopted to analyze the structure. Examples show that this proposed system enjoys a good performance and is easy to operate. The system is characterized with intelligent and self-adaptive abilities. It can help to realize the topology and layout optimization design of structures.
2008, 30(6):  28-30.  doi:10.6052/1000-0992-2007-559
Abstract ( 1418 )   PDF (429KB) ( 637 )
The convolution-type Galerkin method is proposed to calculate a beam with arbitrary boundary conditions by using a series function in time domain and the mode shape function of the beam in space domain. The example of the beam with its both ends cramped is calculated and it is shown that highly accurate results can be obtained. The approach is worth further investigation and extension.
2008, 30(6):  18-21.  doi:10.6052/1000-0879-2007-571
Abstract ( 1295 )   PDF (1059KB) ( 635 )
The YONGLE big bell and the wood-rack for suspending the big bell are valuable antique relics. Their safety and reliability have attracted much attention of scientists and engineers. In the present paper a preliminary study on stability of the trapezoidal wood-rack is carried out. Based on a simplified bending constitutive model of the mortise and tenon joint (in Chinese it is called MAO-SUN'') between beams and pillars of the rack, the influence of the side-angle of the pillars on the stability of the rack is analyzed. The energy method of stability theory of elastic structures and the comparison method are used. The formulas for the critical load are derived for the reduced two dimensional trapezoidal rack structures. The critical loads are computed for the wood-rack with different side-angles, as well as for that without side-angle. The results are compared with each other for different racks with different side-angles. It is concluded that the wood-rack with side-angle has better stability as compared to that without side-angle. The wood rack design with inclined pillars is a typical design of wooden architectures in ancient China and shows the wisdom of designers and craftsmen.
2008, 30(6):  81-83.  doi:10.6052/1000-0879-2007-578
Abstract ( 1084 )   PDF (2176KB) ( 973 )
The vibration characteristics of photography tripod are studied based on its mathematical partial differential equation. The displacement of tripod vibration caused by the impact due to camera shutter release is analyzed. Applications in engineering are described and examples are given. The results are useful for both tripod users and manufacturers.
2008, 30(6):  43-46.  doi:10.6052/1000-0879-2007-580
Abstract ( 1311 )   PDF (752KB) ( 659 )
The paper discusses the development of an ultrasonic symmetric bending fatigue system on the basis of the three-point bending method, including the design of ultrasonic symmetric bending samples and the influence of processing errors. The $S$-$N$ curve of 50$^{\# }$ axle steel is determined by the ultrasonic symmetric bending fatigue system (20\,KHz).The results show that the $S$-$N$ curve of 50$^{\#}$ axle steel is a continuously declining curve. Compared to the $S$-$N$ curve of 50$^{\#}$ axle steel under the symmetric tension and compression loading, it is shown that in the high-cycle stage, the loading method has a significant effect on fatigue properties, and in the ultra-high-cycle stage, the loading method has no significant impact on fatigue properties.
2008, 30(6):  39-42.  doi:10.6052/1000-0879-2008-007
Abstract ( 1298 )   PDF (622KB) ( 555 )
Based on the energy variational principle, the governing differential equations and the boundary conditions of a beam-and-slab structure under axial loads are derived, with shear lag effect being taken into account. The initial-value solutions of the equations under a uniformly distributed load are obtained. The field matrix and point matrix are derived, by which the inner force, stress and displacement can be recursively calculated. A transfer matrix method for shear lag analysis of a beam-and-slab structure is put forward. The computation example shows that the method proposed in the paper is valid and effective.
2008, 30(6):  31-34.  doi:10.6052/1000-0879-2008-008
Abstract ( 1129 )   PDF (799KB) ( 875 )
A new model reduction method based on deformation modification is presented for dynamic analysis. Complex structures can be divided into several displacement synchronous parts by analyzing the finite element models based on a synchronistic assumption. The displacement can be approached by an appropriate mode, and the transformation relationship between global displacement and local displacement can be obtained by minimizing Global Strain Energy. The results of examples show the validity of the method.
2008, 30(6):  47-50.  doi:10.6052/1000-0879-2008-009
Abstract ( 6333 )   PDF (703KB) ( 673 )
In order to study the steady thermal stresses in ceramic-metal three-layered composite plate with an interlayer of FGM under EFBF mechanical boundary conditions, the analytical model for the steady thermal stresses in the composite plate was established, from heat conduction law and calculation formulas of thermal stresses. When $T_{a}=500$\,K and $T_{b}=1\,800$\,K, the steady thermal stress distribution of the composite plate was analyzed by the FEM and the Simpson method, and results were compared with that of nongraded two-layered plate. The paper gives the effects of thickness and composition and porosity in FGM gradient layer on thermal stresses of the composite EFBF plate, and it is shown that the thermal stress in graded three-layered plate is not significant and the maximum tensile stress reduces by 29.18{\%}. The results provide a reference for the design and applications of the composite plate.
Review
2008, 30(6):  1-10.  doi:10.6052/1000-0879-2008-189
Abstract ( 1302 )   PDF (5582KB) ( 862 )
This paper reviews the new developments in experiments of biomembrane nanotubes, focusing on the problems of symmetry and topological invariability in biomembrane nanotube networks at (stable) equilibriums. Two origins for the symmetric topology of biomembrane nanotube networks at (stable) equilibriums are disclosed: One is the symmetric integral theorems in differential geometry, and another is the stationary energy principle and Steiner (minimal) tree. The importance and applications of the (stable) equilibrium law for biomembrane nanotube networks are discussed.
Around the mechanics
2008, 30(6):  99-101.  doi:10.6052/1000-0879-2008-244
Abstract ( 1542 )   PDF (471KB) ( 1799 )
Education Study
2008, 30(6):  97-98.  doi:10.6052/1000-0879-2008-359
Abstract ( 1239 )   PDF (405KB) ( 537 )
Terms
2008, 30(6):  120-123.  doi:10.6052/1000-0879-2008-481
Abstract ( 1513 )   PDF (888KB) ( 833 )