Research On Modeling And Optimization Method Of Electronic Devices Dynamic Properties

Electronic devices are indispensable to modern industry, agriculture as well as our daily life. Along with the development of electronic devices towards integration, specialization and high accuracy, requirements on their structural dynamic properties have been continuously increasing. Thus the related analysis and optimization based on finite element method (FEM) are now playing more and more important roles in the evaluation and improvement of the structural performance of electronic devices. According to the problems in structural analysis and optimization of electronic devices, this thesis focuses on the researches shown as follows.1) Study of substructure modeling method in structural analysis of electronic devicesFirstly, a parametric substructure method is presented, which enables convenient modeling and analysis for homogeneous structures while significantly reduces its human labors. Secondly, the causes of the error in static condensation substructure method are deduced based on Numman series and matrix perturbation theory. Additionally, comparisons among some strategies for selection of master degree of freedom (MDOF) in plate-like structure are also made in the thesis, which shows good consistency with the theoretical conclusions.2) Study of equivalent method for modeling of printed circuit board (PCB) dynamic propertiesFirstly, an equivalent method for modeling of PCB dynamic properties based on FEM is presented. In the method, equivalent dimensions are obtained from the main dimension of a real PCB, while equivalent density is calculated by the principle of mass equality, and the equivalent stiffness formula is derived based on vibration theory and FEM, respectively. The effects of size, location and layout of components on equivalent stiffness are discussed. For the complex PCB of which FEM modeling is too difficult, an equivalent modeling method based on experiment data about PCB dynamic properties is also presented, in which equivalent stiffness is derived based on vibration theory and FEM. Additionally, the influence of the support condition on equivalent stiffness is discussed as well.3) Study of maximization of PCB natural frequency by optimization of supporting layoutBased on the structural characters of PCB, a topology optimization method of PCB structure is established. In this method the supporting part is simulated by elastic material with no mass, and the PCB component part is refined by condensation of degree of freedom to reduce computation amount. The sensitivity coefficient for element removal is derived by evolutionary structural optimization (ESO) algorithm. And then, an ANSYS-based computational method is presented. Meanwhile, the influence of stiffness of support material on the maximal frequency of structure is discussed. In the end, optimization examples demonstrate that this method is reasonable and effective in engineering projects.4) Study of PCB dynamical property optimization methodFirstly, by using freedom condensing technology and modal synthesis method, a new component layout optimization method is presented for PCB dynamic properties. By using a modified genetic algorithm, the layout optimization problem for multiple components can be solved. And then, a new support layout optimization method for PCB structure is built up. Additionally, by using the genetic algorithm and second-develop technique, a solving software developed.5) Study of software development method for structural analysis and optimization of electric devicesTo resolve the problems of complexity and ineffectiveness in FEM modeling, an object oriented secondary development method is presented. By taking full advantage of the resource of FEM software, the method avoids development of fundamental FEM algorithm, and thus leads to a high development efficiency as well as good reliability. Besides, by using the object-oriented theory, the program design thought is much clearer and the debugging is much easier.The originalities in this thesis can be summarized as follows:1) An equivalent method for modeling of PCB dynamic properties based on FEM model is presentedIn the method, the equivalent dimension is obtained from the main dimension of real PCB, the equivalent density is calculated by the principle of mass equality, and the equivalent stiffness formula is derived based on the theory of vibration and finite element method. Additionally, the influences of the size, the location and the layout of part on equivalent stiffness are studied.2) An equivalent method for modeling of PCB dynamic properties based on experimental data is proposedFinite-element modeling of PCB is often very difficulty due to the structural complexity, so an equivalent modeling method of PCB based on experimental data for dynamic property analysis is presented. In the method, the equivalent dimension is obtained from main dimension of real PCB structure, the equivalent density is calculated by the principle of mass equality, and the equivalent stiffness formula is derived based on the theory of vibration and finite element method. Additionally, the influences of joint constrain on equivalent stiffness are studied.3) A PCB dynamical property layout optimization method is built upSupport layout will affect the stiffness distribution of PCB, and then affect the modal frequency. The method of maximization of PCB natural frequency with optimal support layout is built up. Using condensation method of degree of freedom for reduce computation amount. And the sensitivity number for element removal is derived by using evolutionary structural optimization algorithm and the implementation method by using ANSYS is built up. In the end, the influences of support material stiffness on the maximal frequency of structure are discussed. Application examples show the optimization method is effective and efficient in engineering projects.