Applied Mechanics and Materials Vol. 392

Abstract: In this paper we present a robust, high order method for numerical solution of compressible Euler Equations of the gas dynamics. Euler equations are hyperbolic in nature. Our scheme is based on Nodal Discontinuous Galerkin Finite Element Method (NDG-FEM). This method combines mainly two key ideas which are based on the finite volume and finite element methods. In this method, we employ Discontinuous Galerkin (DG) technique for finite element space discretization by discontinuous approximations. Whereas, for temporal discretization, we used explicit Runge-Kutta (ERK) method. In order to compute fluxes at element interfaces, we have used Roe Approximate scheme. We used filter to remove spurious oscillations near the shock waves. Numerical predictions for Shock tube problem (SOD) are presented and compared with exact solution at different polynomial order and mesh sizes. Results show the suitability of DG method for modeling gas dynamics equations and effectiveness of high order approximations.

Abstract: with the BP algorithm, this paper sets up the High angle of attack unsteady aerodynamic neural network model. By using the large-amplitude pitch oscillation dynamic test data of some slender model in high-speed wind tunnel, this paper trains and verifies the BP neural network model and discusses elements which may influence the arithmetic speed and prediction accuracy of the neural network model. Test results show that the established BP neural network model matches the wind tunnel test results nicely and has relatively good capacity to predict the High angle of attack unsteady aerodynamics.

Abstract: At this paper attempts have been made to determine the effects of internal pressure on the reinforced composite pressure vessel. Finite element analysis (FEA) along with the Tsai-Wu failure criterion was utilized to predict the failure pressure of the vessel and the optimum fiber angle orientation. Six layers of E-glass/Epoxy and Graphite/Epoxyfibers have been selected to reinforce the aluminium vessel. Fibers were oriented with six different winding angles of 30⁰, 45⁰, 55⁰, 60⁰, 75⁰ and 90⁰ at asymmetric fiber orientation. The commercial code ABAQUS CAE was employed to simulate the model and analyse the structure. Results were revealed that Graphite/Epoxy has higher strength in comparison with E-glass/Epoxy fiber. Also it was observed that for both composite materials 55⁰fiber angle is the optimum winding angle. Results were compared to the experimental ones and there was a good agreement between them.

Abstract: We consider a variational inequalities of the second kind with cocoercive operator and a non-differentiable proper convex functional. Such inequalities arise in the mathematical modeling of the problem of finding the boundaries of ultimately-stable pillars of residual viscous-plastic oil. To solve the variational inequalities we suggest the iterative process and its convergence investigated. The numerical results confirm the efficiency of the proposed method.

Abstract: We consider a spatial equilibrium problem of a soft network shell in the presence of several external point loads concentrated at some pairwise distinct points. A generalized statement of the problem is formulated in the form of integral identity. Then we introduce an auxiliary problem with the right-hand side given by the delta function. For the auxiliary problem we are able to find the solution in an explicit form. Due to this, the generalized statement of the problem under consideration is reduced to finding the solution of the operator equation. We establish the properties of the operator of this equation (boundedness, continuity, monotonicity, and coercitivity), which makes it possible to apply known general results from the theory of monotone operatorsfor the proof of the existence theorem. It is proved that the set of solutions of the generalized problem is non-empty, convex, and closed.

Abstract: The safe operation of industrial gas turbines is dependent on the structural integrity of the critical geometrical features such as blade-disc attachments. Knowledge of stress distribution in this region is the principal necessity for damage tolerance analysis and lifetime estimations. The finite element analysis which includes contact between two deformable bodies is complicated and takes extensive computational costs. A simplified FE model is needed which could predict the stress distribution without modeling the exact contact features. The main objective of this study is to present and compare two simplified FE models which can predict stress distribution at blade disc interface. Fir-tree region in a gas turbine disc assembly is modeled and comprehensive 2D and 3D non-linear finite element analysis is carried out. FE results are verified using photo elasticity method.

Abstract: Extended parametric models of transition tube structures were implemented based on authors previous work [11] on constant cross section area assumption along arbitrary central routes like straight, circular and oblique curves on CATIA platform. It is aimed at that these structures can provide more flexible geometric configuration options and modifications to tube channel transitions for multi phase flow systems and pipeline junctions. Details of parameterized modeling process were exhibited on CATIA Generative Shape Design module with the help of Parameters and Relations functions. The tube surface models are all in circular cross sections and constrained in many ways along arbitrary coplanar or cylindrical sub-central routes three dimensionally for various layouts. Future work is emphasized on numerical simulation and experimental investigation with these geometric structures in multi phase flow systems and pipeline application.

Abstract: This paper presents an application of computer technologyin the virtual prototyping of thermal management systems. The main advantages of this virtual prototyping approach include the search of standard thermoelectric cooling (TEC) components, as well as comparison of the thermal performances and costs of the resulting system prototypes. The framework and implementation are discussed in the paper.

Abstract: This paper mainly discusses the use of virtual reality technology to make the complex steel production environment into direct, simple virtual interface. The model of square steel and the model of cylindrical steel have been founded through object-oriented method and powerful 3D image edit function provided by OpenGL which is employed in this system. Simulation system framework and friendly man-machine interaction are founded using 3-tier application for interactive control. The establishment and maintenance of the steel template, the real-time processing of the temperature in the steel production.

Abstract: For solving the problem of manually dividing section of main girder into grillages, a program is developed using VBA tool in AutoCAD environment, which can automatically search the divided position of grillage for section of single box with several rooms, and obtain characteristics of section of each grillage. Meanwhile calculational data can be stored as a text file, which is convenient to be directly called by commercial structural software. By comparing with the finite element software ANSYS, the reliability of the program and the accuracy of calculational results are verified. The program is ease to be amplified and transplanted owing to using the modularizational idea, and it greatly improves efficiency of setting up grillage model.