Browsing by Author "Zheng, Zhijun"

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    The analytical force prediction and dynamic response analysis of the Bristol H25A compressor
    Zheng, Zhijun (Virginia Tech, 1995)
    The objective of this research is to perform an in-depth study of the force components within the H25A compressor along with a computer simulation program and the dynamic response analysis of the compressor internals using the finite element method. The model tor force prediction was created based on the assumption that the frame of the shell structure is rigid and the subassemblies within the shell behave as one lumped mass. Springs are the connections between the shell and the subassemblies. Various parameters of the model were entered through the preprocessor of the simulation program which provides a series of data entry forms. The processor part of the program contains several modules for performing different tasks, such as the eigenanalysis, kinematic force computation. displacement/velocity/acceleration prediction, spring-end force calculation and variable-speed motor simulation. The simulation program also features post-processor functions in order to display the results of the analysis in plots, tables or with animation. Further research was focused on the correlation of the predicted force and orbit with the observations. With a finite element model of the full compressor. the spring-end forces due to the excitation at mass center were obtained from the dynamic response analysis and compared to the force gauge measurements. The excitations included the enforced displacement at the mass center which was regenerated from the accelerometer measurements. and the superposition of the kinematic forces and equivalent valve impact forces at the mass center.
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    A preprocessor for the analysis of space frames in the Microsoft Windows environment
    Zheng, Zhijun (Virginia Tech, 1993)
    A preprocessor for the analysis of space frame structures is developed. The preprocessor is designed to run in the Microsoft Windows graphical environment which is widely available on personal computers. The program is written in the Visual Basic programming language. Visual Basic is an object-oriented programming language that provides a powerful way to create applications for the Windows environment. It is an ideal programming language for developing small or medium size Windows applications. The basic features of the preprocessor include the ability to read and write data files, entry and review of structural data, and a context-sensitive online help system. In addition, the program provides a user-friendly interface and adopts standard Windows user interface guidelines. A sophisticated automatic data checking mechanism reduces data entry errors to a minimum. The preprocessor also features three-dimensional graphics which can display the structural geometry and applied loads.