Advanced Materials Research Vols. 243-249

Abstract: Bi-stable structure can be stable in both its extended and coiled forms. As a novel deployable structure, it shows a broad application prospect in the field of aeronautics and civil engineering, etc. Considered two cylindrical shells having the same flattening configurations, they can be closely bound together by applying external forces. And the corresponding double-layered cylindrical shell model is proposed. Expressions for the bending and stretching strain energies of the cylindrical shells are presented. Calculations show that total strain energy has two local minimal values, which reveals that the double-layered cylindrical shell has its bi-stability. The corresponding rolled-up radii are thus determined.

Abstract: The numerical simulation of two-phase oil-water flows in a low permeability reservoir was carried out by means of an increment-dimension precise integration method (IDPIM). First of all, state equations denoted with pore fluid pressures at mesh nodes were built up according to finite difference method (FDM). Secondly, the recurrence formulae of the pore fluid pressures at mesh nodes were set up based on IDPIM. Finally, the numerical simulations of two-phase oil water seepages for a typical five point injection-production reservoir as an example were conducted by means of IDPIM and IMPES respectively. Calculation results by IDPIM are in good accordance with those by IMPES, and then IDPIM is quite reliable. At the same time, the effect rule of the startup pressure gradients on recovery degree, liquid production rate and oil production rate has been investigated. The start-up pressure gradients have an outstanding effect on recovery degree, liquid production rate and oil production rate, and the existence of the startup pressure gradients will enhance development difficulty and cost.

Abstract: The cracks-tip field on ModeⅡperiodic cracks of infinite orthotropic fiber reinforcement composite plate subjected to the concentrated force was studied. With the introduction of the Westergaard stress function and application of complex function theory and undetermined coefficients method, mechanical problem is changed into partial differential boundary value problem. Owing to the distribution of periodic cracks, stress intensity factor(SIF) depends on the shape factor, which is greatly influenced by the crack spacing and the crack length. The results show that interaction happens between the periodic cracks, and that scale effect of the stress intensity factor in cracks-tip is obvious.

Abstract: According to the bending equation and boundary conditions of skew plate in the oblique coordinates system parallel to the edge of the plate, expanding deflection and load into form of Fourier series, the paper derives and obtains unified solution of bending problem for the four-edge-supported skew plate under arbitrary load. Programmed and calculated by mathematica language, the paper also comes with deflections and moments under the condition of any oblique angles, ratios of side length and Poisson ratios. The results of the paper is compared with those by the finite element method in the example, and they’re in good agreement with each other. The paper extends the bending theory of rectangular plate to the skew plate of any angle. The theory being reliable and the result being accurate, the research of the paper can provide reference for engineering design.

Abstract: This paper shows that different materials have different quadratic functions, tensor function theory can make the function of history to represent the plastic strain, which can be a sheet metal pressing does uniaxial tensile test show that the plane of sheet metal, sheet metal specimen axis and the angle between the rolling direction changes, to the metal plastic strain ratio (R) along with the changes. To explain this phenomenon, the introduction of a quadratic yield function to describe the experimental results of some of the metal sheet. This paper shows that different materials have different quadratic functions, tensor function theory can make the function of history to represent the plastic strain, which can be a sheet metal pressing does not depend on the value of history.

Abstract: The hybrid radial boundary node method is applied to solve the biharmonic problems. Based on modified variational principle, the variational formula of the biharmonic problems is established. The radial basis point interpolation is employed to approximate the boundary variables, while the domain variables are interpolated by a combination of the fundamental solution of the laplace equation and the biharmonic equation. Compared to the regular hybrid boundary node method, as the shape function has the delta function property, the boundary conditions of the original problem can be easily implemented, and the fictitious source points are not involved. Numerical examples show that this method is efficient for solving the biharmonic equation.

Abstract: With regard to viscoelasticity, we can’t use elastic-viscoelastic corresponding principle in quasi-static situation in view of dynamic response. In allusion to compressible materials, basis equations were applied, and constitutive equations were applied in convolution form, we derived the equations with which displacement function was satisfied, the displacement solution and stress expression in image space were derived by Laplace transforms. We discussed boundary value problems on the condition of the given displacement on the inner surface of the spherical shell, and the solutions were verified in calculating example.

Abstract: An inverse analysis algorithm is proposed to identify the material parameters of functional graded materials (FGMs). The inverse analysis of the material parameters is formulated as the problem of minimizing the objective function defined as a square sum of differences between the measured displacement and the computed displacement by a finite element model. Levenberg-Marquardt method is used to solve the minimization problem. The sensitivities of displacements with respect to the material parameters are based on the finite difference approximation method. A numerical example is given to demonstrate the effectiveness of the proposed algorithm.

Abstract: In this paper, the anti-calculated method for the static pressure associated with the silo structure is developed and the strain sensitivity is derived based on the formulations of the finite element method. In the proposed approach, the Taylor expansion technique at the initial guess strain is used to evaluate the hoop strain at adjacent points and the least square method are employed to match the numerical results and the known test results. Finally, the developed algorithm is verified by solving the silo with internal wall.

Abstract: The objective of this study is to develop a finite element analysis model that simulates the temperature profile in concrete-filled steel tubular structures during welding procedure in which several metal plates are fixed on the outer surface of steel tube to increase the strength and stiffness of it. In the present model, the thermal property such as thermal conductivity of the steel phase is assumed to be functions of temperature variable. Spatial and temporal distributions of temperature are illustrated under extreme weld heating conditions to investigate the behaviors of the structure at every time step. Simulation results indicate that the maximum value of temperature on the interface of steel and concrete caused by the weld heat source doesn’t damage the mechanical properties of concrete and steel.