Research And Application Of Structural Dynamic Reanalysis Algorithm

With the rapid development of space, shipbuilding, automotive industry and civil engineering in China, the structural design is becoming more and more complex. The analysis and optimization of complex structures can not be solved by the traditional design method any more. The generation of CAE technology has made up this contribution. CAE is becoming a necessary process and step in structural design, and it is becoming more and more useful and common. With the structural model growing, the cost of the CAE computations is increasing. In order to improve the computational efficiency, some researchers devote themselves to the development of the HPC (High Performance Computer), while others are researching into the improved algorithm for fast computations.This thesis is supported by National Natural Science Foundation of China"Fast Optimization of Cross-Sectional Parameters for Simplified Car Body Multi-Elements Frame Structure Based on Reanalysis Theory"(No.50975121), Specialized Research Fund for the Doctoral Program of Higher Education"The Research of Adaptive Reanalysis Algorithm of the Defective Vibration System"(No.20090061110022) and FAW Group Science and Technology Innovation Project"The Multi-Optimization Platform for Car-Body Performance"(No.0837and093715). The structural dynamic reanalysis algorithm is generated, and the applications of the reanalysis method in structural dynamic modifications and structural optimizations have been discussed in this thesis.The Frequency-Shift Combined Approximations (FSCA) reanalysis method is first developed for structural vibration, and is compared with the Combined Approximations (CA) method and the Modified Combined Approximations (MCA) method. The FSCA method treats the modal reanalysis with frequency-shift factor and Epsilon algorithm, which have reduced the high mode calculation errors in CA method successfully. Compared to the MCA method, the cost of computations in FSCA method is reduced obviously.Based on the Preconditioning Lanczos algorithm for static reanalysis, a method for dynamic response reanalysis is developed using immediate integration method. The Preconditioning Lanczos method is used for solving the equivalent static equations in the immediate integration. Based on the Central Difference method, Houbolt method, Wilson-θmethod and Newmark method, the dynamic response reanalysis algorithms are developed, respectively. A truck-body dynamic response reanalysis example is demonstrated for the accuracy of algorithms.Based on the FSCA modal reanalysis, a dynamic response reanlysis method is developed using modal superposition method. The truck-body dynamic response reanalysis example is demonstrated for the accuracy.Based on the research of reanalysis method, effective procedures for repeated sensitivity analysis of static problems, vibration problems and dynamic problems in structural modifications are developed. With the sensitivity information, the first order and second order Taylor expansions are used for solving the inverse problems of structural dynamic modification. Equations and examples are given to demonstrate the effect for the modal modifications.Based on the Solid Isotropic Material with Penalization model (SIMP) method for topology optimization and the Optimization Criterion(OC) method, static stiffness problems of car-body joints are solved by using shell and solid finite elements, and schemes for the reinforcing plate are given for the joints structure, respectively. A truck-body size optimization is brought out using the experimental design, structural reanalysis method, least square regression and penalty function. The stiffness, modal frequency and dynamic parameters are calculated with the reanalysis method. Different penalty factors are introduced for testing the optimization process.