Evolutionary Optimization Study On Structural Dynamic Design

Evolutionary structural optimization, known as ESO, is a new structure optimization method, which provides optimal structure in FEA. The heart of ESO is to judge the importance degree for all the elements and determine the removal or retention the elements according to some specific criterion. The structure will be more efficient by deleting the unnecessary or less important material in accordance with the proper judging criterion. ESO method is feasible and versatile in engineering application. The application of ESO can be combined with the finite element software easily.In this paper, multi-constraint and multi-objective optimization of the structure dynamics based on ESO and the use of ESO with structural damage localization have been researched intensively.(1) Structure dynamic optimization without damping is studied under multi-constraints. The sensitivity of mode shape nodal lines position and frequency with regard to structure parameters has been investigated. Thereafter, the element deletion criterion with frequency and mode shape nodal lines position constraints is proposed. Then on the base above, the fit path of topology optimization is provided with the constraints of frequency and the mode shape nodal lines position. It can be easily integrated into the complex structures topology optimization to overcome the difficulty of the modal shape constraints.(2) Structure dynamic optimization with constrained layer damping under multi-constraints is studied. The modal damping ratio weighting function is defined according to the character of dynamic and the fit path for the optimization is afforded. The distribution of constrained layer damping with multi-constraints is optimized in this paper.(3) Optimization of structures with constrained layer damping by BESO is studied. Since too many iterations needed to optimize the complicated structure or structure with too many elements by ESO, BESO is introduced into the damping structure optimization. The fit path of BESO for damping structure is given. The optimization of the distribution of the constrained damping layer under the condition of maximizing the specified stage modal damping of the structure with given mass of materials is achieved.(4) Fuzzy theory is introduced to evolutionary structural optimization. Hierarchical evolutionary method for fuzzy optimization is built. The nonlinear membership function is selected and the evolutionary structural optimization with fuzzy multi-objective hierarchical method is established to research the objectives of minimizing compliance and maximizing fundamental eigenvalue. (5) The feasibility of using ESO for damage localization with resonant frequencies and anti-resonant frequencies is investigated. The key of this approach is that, due to the character of topology optimization, a search for defects is performed globally over the entire structure. The sensitivity of anti-resonant frequency is afforded, the formulation for damage localization is built, and the damage approximation method is given for the slightly damaged structures. Several illustrations are given for the damaged structures with varying degrees.(6) The experiment is carried out for hoist structure modal testing and the damping affection of the structure with constraint damping layer. By the vibration testing, the acceleration and strain response of the structure with constraint damping layer is afford. Then, the comparison between the theoretical simulation and the testing result of the acceleration and strain response is given.