Advances in Engineering Software (1978)最新文献

This paper discusses computationally efficient methods for evaluating engineering properties of objects on computers. These methods use existing solid modeling techniques that lend themselves to mass property evaluations. An overall review of the quasidisjoint representation methods used for the approximate evaluation of integral properties of solid models is given. These methods of representation are typically used by analysis packages in the calculation of volume, surface area, center of gravity, mass, moment of inertia, etc. The methods are identical to approximate solid modeling techniques whose implementation involves the subdivision of space into subdomains. Finally, the method of cell decomposition is used for the determination of integral properties of solids modeled by a Constructive Solid Geometry (CSG) technique. The method suggested is very practical for microcomputer implementation. Sample numerical results are finally shown to compare the approximated results with the exact values.

For a calendered polymer sheet, it is desirable that all types of shape defects, especially nonuniform gauge and improper layflatness, can be avoided. In general, shape defects arise mostly from inappropriate control of the bending behavior of the calendering rolls. To assist in control of the roll bending behavior, an analytical on-line model that simulates the face contour of the bent roll with or without roll bending systems has been developed. The roll bending system adjusts the roll profile by applying an external bending moment to both ends of the roll. The roll deflection is calculated using a modified beam theory for the bending and shear components as well as the Poisson effect. The polymeric flow pressure developed in the bite region is estimated based on the classical lubrication approximation utilizing the power law constitutive relationship. Analytical solutions are obtained to speed up the computation. The analytical model, therefore, is compact enough to be implemented on a personal- or micro-computer and also fast enough for on-line simulation or control. Good agreement has been found when the present solution is compared with other published results and on-line measurements.

Sparse storage technique used in surveying computation is reviewed. Main points and defects of Banker's algorithm are presented. An improved Banker's algorithm has been developed and its superiority is shown by examples.

A Structal Design Language (SDL) has been developed in INTERLISP environment for building coupled knowledge-based expert systems for integrated design of a class of structures. The integrated design includes the preliminary design, structural analysis, design of members, design of connections, and computer-aided drafting of the final design. The complex body of knowledge needed for detailed design of a structure is fractionated into smaller and more manageable knowledge sources which are organized into a hierarchy of cooperating conceptual specialists. SDL provides a multiwindow graphics interface capable of displaying both the orthographic and isometric views of the frame structure and beam-column connections. A three-dimensional face frame representation sentation is used for the graphic display of the beam-column connections. SDL has been used to develop a prototype knowledge-based system for integrated design of steel building structures consisting of moment-resisting frames.

This paper describes an interactive environment for dynamic response optimization problems. It is shown that with proper interactive facilities and designer intervention, the optimal design process can be more flexible, efficient and effective in solving practical design problems. The process can be initiated with a rough design model for the problem. As the iterations progress and insight is gained into the problem, the model can be interactively refined, without stopping the process, to obtain the final solution. Two example problems — a system dynamics problem and a control problem — are used to study and show advantages of the designer interaction. It is concluded that interactive optimum design capabilities offer more opportunities to the designer to obtain better designs.

Advanced models of the thermodynamic processes in internal combustion engines require the exact estimation of the thermodynamic and transport properties of combustion reactants and products. Although many works have been reported on the properties of air, fuel vapour and combustion products, a study on the properties of the fuel liquid phase seems to be lacking in the open literature. These properties are very important for simulating the fuel droplet evaporation process, which plays an important role on diesel engine combustion and emitted pollutant modelling. In the present work the values of the thermodynamic and transport properties of liquid diesel fuel are computed, as a function of pressure and temperature, by polynomial fitting against available experimental data. This is accomplished in a fraction of a second when using a personal computer with a very small error. N-Dodecane is treated in the present study, which forms a representative fuel of the diesel fuel in most diesel engine cycle simulations. The relevant computer program subroutines are given in an educational form, in FORTRAN-77 language.