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本文给出了结构动态应变/应力分析的模态分析原理和方法。其基本思想是:结构在承受动态载荷的作用时,其应变场可用所谓“固有的模态应变场”按某种比例的叠加来表达。固有模态应变场(简称应变模态)对应于结构的固有振动位移模态,并取决于结构的动特性。根据这一思路导得的应变响应预测模型以及固有应变模态和相应的模态参数识别方法,我们称之谓应变模态分析。按本文发展的方法,可以通过电阻应变计直接测量应变频响函数,然后用曲线拟合法求取应变模态及模态参数。给出的实例说明,应变模态对于结构的局部变化较为敏感。
In this paper, the principles and methods of modal analysis of structural dynamic strain / stress analysis are given. The basic idea is: the structure in the role of dynamic load, the strain field can be so-called “inherent modal strain field” by a certain percentage of superposition to express. The inherent modal strain field (referred to as strain mode) corresponds to the natural vibration displacement mode of the structure and depends on the dynamic characteristics of the structure. Based on the strain response prediction model derived from this idea, as well as the inherent strain modes and corresponding modal parameter identification methods, we call them strain mode analysis. According to the method developed in this paper, the strain-frequency response function can be directly measured by the resistance strain gauge, and then the strain mode and modal parameters can be obtained by the curve fitting method. The examples given illustrate that strain modes are more sensitive to local changes in structure.