Nonlinear dynamic finite element analysis of rate sensitive materials using object-oriented programming.

摘要

Existing commercial nonlinear finite element codes suffer from a number of difficulties, including: inefficient and outdated code formulations, convergence problems, inflexibility and lack in abstraction. In view of their inflexibility and extensive file requirements for data processing, they are unsuitable for use in interactive design environments. It is with this in mind we conduct the current investigation.This thesis is devoted to the development of an efficient, accurate and flexible finite element software to evaluate the dynamic response of elasto-plastic solids under dynamic loading. The finite element formulations not only account for material and geometric nonlinearities, but also high strain rate effects. In these formulations, the large deformation is accounted for by the use of an updated Lagrangian method and the temporal analysis is conducted using an explicit solver. The material non-linearity was accounted for by the use of a viscoplastic model of the power law type. The developed code is supported by two-dimensional solid and axisymmetric shell elements. Unlike most existing finite element analysis packages, these elements can accommodate geometric and material nonlinearities under high rates of strain.To provide an efficient and flexible software with different levels of abstraction, the software was designed and implemented using a high-level programming language (C++) which is characterized by the object-oriented paradigm. In this concern, encapsulation of data structure and operations within the different modules ensured the correct and efficient treatment of data.To establish the validity of the current code, a number of test cases are examined and compared with existing analytical, finite element (scANSYS) and experimental results. Furthermore, the study was extended to treat the crashworthiness of a novel shock absorber for a new generation of an electrically powered vehicle. Two aspects of the novel design of the absorber were examined. The first is concerned with the verification with earlier results for the quasi-static case, while the second is concerned with the prediction of the collapse loads and the level of energy absorbed under high rates of strain.