基于振动测试的非线性参数识别方法

A novel method for nonlinear parametric identification based on vibration tests

研究了利用特殊的正弦扫频技术识别非线性参数的方法。该方法利用目前线性系统成熟的模态分析技术,并结合等效线性化理论,通过振动测试识别结构的非线性参数,可建立一个更加准确的模型来反映非线性结构的动力学特性,从而提高模型的预测精度。该方法包括常位移测试识别非线性刚度与常速度测试识别非线性阻尼。常位移测试是在一次正弦扫频过程中,通过调整各频率下的激励力幅值使得位移响应的幅值为常数,获得一组频响函数,再进行模态分析获得等效刚度;改变位移响应的幅值进行多次测试,获得多组等效刚度;对获得的一系列恒定位移响应下的等效刚度进行曲线拟合,即可获得所有线性和非线性刚度参数。常速度测试与其类似。以三自由度非线性系统为例,进行了常位移测试和常速度测试的数值仿真,并用随机激励进行验证,表明了该方法的有效性。

A novel method for parametric identification of structural nonlinearity was developed. Ires memou rook advantage of modal test and analysis, and could construct a more accurate model to represent the nonlinear dynamic behavior of a structure. The method consisted of two dynamic tests of constant-amplitude displacement test and constant- amplitude velocity one. The two tests all used special sinusoidal force excitations. The constant-amplitude displacement test was used to identify nonlinear stiffness terms from the measured frequency response functions （FRFs） of the structure subjected to sinusoidal force excitations ensuring the amplitudes of displacement were constant through adjusting the amplitudes of the force over its frequency range. The constant-amplitude velocity test was similar to the constant-amplitude displacement one and used to identify nonlinear damping terms. A simulated 3-DOF lumped-mass system with a weak nonlinear stiffness and damping behavior was used to verify the effectiveness of the proposed method using sinusoidal and random excitations.