Advanced Materials Research Vols. 261-263

Abstract: Normal transformation technique is often used in practical probabilistic analysis in structural or civil engineering especially when multivariate random variables with the probabilistic characteristics expressed using only statistical moments are involved. In this paper, a modified high-order moment method(MHOM) is given based on the polynomial coefficients of a third-order normal transformation polynomial (NTP) using the first four central moments of random variables having unknown distributions. The present high-order moment method is introduced into several typical test problems having unknown distributions are available. Since it needs neither the computation of derivatives nor iteration, and since it is unnecessary to know the probability distribution of the basic random variables, the present method should be practical in actual reliability problems. Applications to several typical examples have helped to elucidate the successful working of the present MHOM.

Abstract: By using the critical point theory of variational method and Lax-Milgram theorem, we obtain the new results for the solution existence of the fourth-order impulsive partial differential equations with periodic boundary value problems.

Abstract: Nonlinear vibration computational problem of isotropic thin plates in large amplitude was investigated here. We applied the Von Kármán’s theory of thin plates to derive the governing equations of nonlinear free vibration of isotropic thin plates, and solved the governing equations by direct integration method combined with power series expansion method. We obtained the power series solution of the nonlinear vibration frequency of the rectangular thin plates with four edges simply supported. Finally, the paper gave the computational example and compared the two results from the large amplitude theory and the small one, respectively. Results obtained from this paper provide a new analytical computational approach for calculating the frequency of nonlinear free vibration of isotropic thin plates in large amplitude, and provide more accurate theoretical basis for the vibration control and dynamic design of plate structures.

Abstract: In calculating the internal force and deformation of a thin-walled member, the influence of the free torsion rigidity must be considered and it makes the study complicated. Actually, from the analogy relations between the equilibrium equation in the constraint torsion theory of a thin-walled member and that in the plane bending theory of a tension-bending solid bar, the action of the free torsion rigidity can be regarded as a tension effect on a thin-walled member with torsion, i.e. the action can be described as a second-order effect like the tension action in the plane bending theory. Taking cantilever bars for example, the simple calculation method of the internal force and deformation of thin-walled members are deduced by the Taylor series in mathematics, and then verified by ANSYS.

Abstract: In this paper mixed variable method is generalized to solve the problem of bending of the triangular plate with three sides clamped under the action of a concentrated load. Gives the surface deflection equation and a chart, the chart can be directly applied to engineering practice.

Abstract: This paper presents a fundamental research in the mechanical properties of the regular jagged discontinuity under various normal stresses in the shear test. The mechanical properties of the regular jagged discontinuity under shear stress and their principal regularities are described. The strength and roughness of discontinuity under shear stress are investigated by the analysis of the data obtained. The calculation of shear stiffness of discontinuity and an empirical formula between the slope angle and roughness coefficient of discontinuity are proposed. The changing regularity of the parameters of the shear strength of discontinuity under shear stress is investigated, and an empirical formula is established to evaluate the shear strength of discontinuity.

Abstract: To more exactly predict the chloride diffusivity of cement paste, it is essential to determine the two-point probability function of capillary pores. The intention of the paper is to present a computer simulation method for evaluating the two-point probability function of capillary pores. By introducing three physical quantities to quantify the mutual interference between neighboring cement particles, the microstructure evolution of cement paste is simulated. Based on the simulated microstructure of cement paste, a numerical method is developed for evaluating the two-point probability function of capillary pores. After verifying the numerical method with the experimental results obtained from the literature, the effect of the hydration time and water/cement ratio on the two-point probability function is assessed in a quantitative manner. It is found that the two-point probability function decreases with the increase of the hydration time for a given water/cement ratio, but increases with an increase in water/cement ratio for a given hydration time.

Abstract: Carbon nanotube is the one-dimensional carbon nano-materials. The synthesis of carbon nanotubes from pyrolysis flame is a new method. Variety of carbon nanotubes with special structure can be seen from pyrolysis flame due to the influence of key factors such as the concentration of reactants and catalyst particle size. The morphology and structural of carbon nanotubes were characterized by scanning electron microscope and transmission electron microscopy respectively. Carbon nanotubes with special structure such as bamboo-like, pod-like and coil-like can be seen in the experiment. The bamboo-like carbon nanotube has a bamboo-like structure clearly. The shape of pod-like carbon nanotube is very similar with the peasecod. The coil-like carbon nanotube is similar to carbon nanofiber in structure. It was discussed and analyzed that the formation mechanism of bamboo-like, pod-like and coil-like carbon nanotubes from the V-type pyrolysis flame.

Abstract: This paper presents a deep research on 2-DOF planar parallel mechanism during developing a new type of hybrid machine tool. The composition of this planar parallel mechanism is introduced, its direct and inverse kinematics solution equations as well as the solution equations for the speed and the acceleration are deduced, meanwhile, the jacobian matrix is obtained. The statics problems of the parallel mechanism are modeled and analyzed based on principle of virtual work, and the balancing driving force solution equation of the driving part is given. Through the solving process we can see that the direct and inverse solution equations of this mechanism have explicit expressions and convenient to realize real-time control. It forms a solid basis for the design and development of this mechanism.

Abstract: The fields of applications and design for piezoelectric effect grew rapidly in recent years, and these materials play an important role in countless areas of modern life. By means of two-scale method and based on the two-scale asymptotic expansions for the displacement and the potential for structure of composites with small periodic configuration under piezoelectric condition, the coupled relation between the displacement field and the electric field within periodic cell is built, and the approximate errors of the displacement and the potential are presented. As a result, one new method of higher order for computing approximate solutions of the displacement and the potential in periodic structure under condition of piezoelectricity is given.