Constant geometric method-based composite thin-walled structure inherent frequency design method

Abstract

The invention discloses a constant geometric method-based composite thin-walled structure inherent frequency design method. The method comprises the following steps of: describing a curved surface shape of each sub-structure of an initial thin-walled composite structure through NURBS, and classifying sub-curved surfaces into a design domain and a non-design domain, changing the shape of the designdomain through movements of control points, and setting positions of the control points as design variables; carrying out grid partition on the structure by adoption of a constant geometric Kirchhoffshell unit, calculating quality and rigidity matrixes of the sub-structures, and carrying out modal analysis; respectively constructing reduction models of the sub-structures by utilizing the first several orders of feature values and feature vectors, forming a reduction model of the composite structure through an immobile interface modal synthesis method, and solving the reduction model to obtain a fixed frequency; and carrying out design sensitivity analysis on the structure to obtain an analysis sensitivity, for a shape design variable, of the fixed frequency, and finally solving a designproblem through a gradient-based optimization algorithm. According to the method, the grid generation process is simplified and the optimization efficiency is improved at the same time.

Description

technical field [0001] The invention relates to the field of optimization design of thin-walled structures, in particular to a natural frequency design method of combined thin-walled structures based on an isogeometric method, which overcomes the problems of cumbersome grid generation and low optimization efficiency in the optimization design of thin-walled combined structures with finite elements. Background technique [0002] Thin-wall composite structures are widely used in aerospace, automobile manufacturing and other industries, and their natural frequency is closely related to the shape of the structure. The natural frequency of a thin-wall composite structure reflects the dynamic characteristics of the structure and determines its response to dynamic loads. [0003] Thin-wall composite structures in the aerospace and automotive industries often require shape adjustments to change their natural frequencies for relevant purposes. For example, by changing the natural fr...

AI Technical Summary

Problems solved by technology

In this process, the automatic and high-quality generation of finite element meshes takes a long time. For actual structural analysis, this part takes about 80% of the time spent in the entire analysis, which is very cumbersome and inefficient.

The design sensitivity is generally approximated by difference, that is, the sensitivity of a design variable at a certain point is obtained through two or three calculations, which takes a long time and has low precision, which slows down the optimization speed.

In addition, what needs to be optimized in practice is often a certain part of the combined structure, but the above process meshes the overall structure, resulting in a larger analysis model, which also reduces the analysis efficiency and slows down the speed of optimization design.

Images