结构有限元模型的综合修正方法

INTEGRATED FEM UPDATING APPROACH

本文的方法是针对像卫星这样的大型复杂结构而提出的。它既包含了对物理参数的修正又包含了对矩阵元素的修正。除了可以修正刚度矩阵[K]和质量矩阵[M]外,它还可以修正阻尼矩阵[C]。该方法最大限度地利用了实验数据,包括固有频率、模态和频响函数。在对许多模态和固有频率进行修正的基础上,首先保证了前几阶固有频率的修正精度。本文的计算方法不需要实验频响函数是满秩的,只需要在做实验时得到频响函数的一行或一列、几行或几列,而且避免了对阻抗矩阵求逆。本文提出的方法可以进行较大误差的修正。

Obtaining highly accurate finite element models(FEM) is necessary for computation of dynamic behavior and design of active and/or passive control. Trail data can be used to update finite element models. This task is known as FEM updating or experimental/computational models correlation. Aiming at large - scale complex structures, such as satellites, we bring forward the Integrated FEM Updating Approach in this paper. This approach can correct both elements in matrices of FEM and design parameters-physical and geometrical parameters. It can not only update mass matrix [M]and stiffness matrix [K] but also modify damping matrix [C] .This approach furthest utilizes trail data, including trial natural frequencies, trail mode shapes, and trail frequency response functions. While many frequencies and mode shapes of FEM are modified to approximately match the trail data,the updating precision of the first several important frequencies of FEM is ensured. The computational method in this paper does not need that trail frequency response functions matrices are fully gained. It just needs one row of one column or several rows or several columns of the trail frequency response functions. The method is available when some big errors exist. This approach needs to utilize certain existing FE program, such as MSC/NASTRAN. By u-tilizing the existing FE program, stiffness sensitivities, mass sensitivities and damping sensitivities are gained. The mode shapes that are used to produce one kind of dynamic reduction matrix are also gained throughout the existing FE program. The approach finally exchanges the FEM updating problem to an optimization problem, which includes both a set of equations and a set of inequations. It is important to find out a good method of optimization for preferable results of FEM updating .