Study On The Evolutionary Structural Optimization Method Considering Service Safety

With the development of society and the progress of science and technology,there have been many studies on topology optimization methods considering strength,trying to solve the strength failure problem in engineering structures.On the other hand,the fail-safe issue in engineering structure makes the robustness of the design structure concerned.Due to the lack of redundant load paths,the structures designed by traditional topology optimization methods are sensitive to partial damage.Therefore,fail-safe issue has recently been introduced in continuum topology optimization by some scholars.In this work,Bi-directional Evolutionary Structural Optimization(BESO)method considering service safety is studied from two perspectives of strength and fail safety.The main research contents are as follows:Firstly,an evolutionary structural optimization method considering stress constraints is developed.This method provides a solution to the optimization problem where the overall compliance of the structure is minimized and the maximum stress of the structure and the amount of material are constrained.The global stress measure of P-norm condensation is used to approximate the maximum stress of the structure,and the global stress measure is coupled to the optimization objective by the Lagrange multiplier method to address the multiconstraints optimization problem.In order to improve the adaptability and optimization efficiency of the method,an efficient and universal adaptive scheme is adopted to determine the Lagrange multiplier instead of the original empirical scheme.The reliability of the proposed method is verified by a series of numerical examples.The results show that the efficiency can be greatly improved and better design can be obtained using the method in this paper rather than the original one.Secondly,a fail-safe evolutionary structural optimization was proposed for continuum.Aiming to the optimization problem of material consumption as the minimized objective,and a variety of nodal displacements for all damaged structures as constraints,the method adopts the P-norm condensation measure to approximate the maximum displacement in all the damage scenarios.Then,derive the sensitivity calculation format and determine the update scheme of target volume fraction for each iteration step.Through a series of numerical examples,the reliability of the proposed method is verified and the design results are compared with the ones in previous research works.The results show that the structure designed by the method in this paper can still maintain good bearing capacity after partial damage.Finally,based on the traditional BESO method and the above improved stress-constrained BESO method,an evolutionary topology optimization platform is established with the combination of ANSYS and MATLAB.MATLAB and ANSYS complete the optimization calculation and model analysis process respectively,and the parameter transmission process for topology optimization is automatically realized between the two software platforms using parameterization language.A typical aero-engine bracket under multiple loading conditions is re-designed using the above topology optimization platform.The stress-constrained design is re-constructed using basic CAD primitives.The result shows that,the stiffness and strength performance of the re-designed lightweight bracket are significantly improved using stressconstrained BESO method improved in this work.