Dynamic Design Optimization Of Skin-Stringer Structures Based On Equivalent Static Loads

As the key components of aircraft and launch vehicle,skin-stringer structures face multiple operating conditions,multiple targets,multiple performances,light weight,and high reliability.It needs to be optimized for dynamic response,so that it can meet the dynamic performance requirements while further reducing weight and improving reliability.However,the process of dynamic response calculation and optimization is too complex,time-consuming and the optimization is difficult to converge,which leads to the difficulty of structural dynamic response optimization.The design optimization of the skin-stringer structures based on equivalent static loads can transform the dynamic optimization problem into a static optimization problem,which can be effectively solved and improve the optimization efficiency.But,at present,there are many problems,such as the long calculation time of design optimization due to the complexity of structure,the design variables contain both discrete variables and continuous variables,and the equivalent static transformation of dynamic load is not accurate.In order to solve the above problems,the present thesis carried out related research on the dynamic design optimization of skin-stringer structure based on equivalent static loads through the method of theoretical derivation and comparison of simulation results.By considering the displacement constraints on the key space points,as well as the constraints on the maximum stress of the structure and the total strain energy of the structure,with the goal of minimizing the average displacement error at the key space points under dynamic and static loads,a new static equivalent model of dynamic load is developed.Taking a compartment structure of launch vehicle as an example,the skin-stringer structure is parametrically modeled.This model can be used for dynamic analysis and design optimization.According to the characteristics of the model,the structural weight is taken as the target,and the skin and beam strength are used as constraints to construct the optimization model.The experimental design method is used to extract the sample points and a surrogate model of optimization model is constructed.By combining the genetic algorithm,the optimal design of the skin-stringer structure based on the equivalent static load was obtained.The results show that,compared with the design optimization based on transient dynamic analysis,the design optimization based on equivalent static load is better in terms of optimization efficiency and optimization objective.By comparing the optimization time and optimization results,it is shown that the dynamic design optimization of the skin-stringer structures based on the new equivalent static load is feasible and effective.