数值计算结合试验测定模态阻尼法  

A method based on numeral calculation and experiment for determination of modal damping

作　　者：唐宇航[1] 陈志坚[1] 梅志远[1] 孙建连 

机构地区：[1]海军工程大学舰船工程系,武汉430033 [2]国网蚌埠供电公司,安徽蚌埠233000

出　　处：《振动与冲击》2017年第4期32-40,共9页Journal of Vibration and Shock

基　　金：国家自然科学基金(51479205)

摘　　要：任一种分布的激励必将引起多个模态的响应,试验中要激出单一模态振动是很难的,传统阻尼比估算方法所采用的信号处理手段不能有效分离叠加模态,以致测试阻尼比往往误差较大。从多自由度叠加法动响应分析入手,指出模态混叠现象是制约精确阻尼比测试的重要因素,在阻尼较大、刚度较低时模态更密集、叠加效应更显著,提出通过数值计算进行模态截断以实现"纯模态"提取的方案,推导了共振激励下试验与数值仿真结果中频响峰值谱线表达式,找出二者间的关系,用纯模态计算结果修正测试阻尼比。通过对4块不同板单元进行前8阶试验模态分析与数值计算参数修正,结合频响函数验证了修正阻尼比的数据可靠性,得出了不同结构、材料间阻尼比差异的部分规律。结果表明,模型试验对复合材料板的阻尼比识别准确性要低于钢板,其阻尼性能往往被低估且修正幅度较大,该方法为模态参数识别的进一步研究提供了思路。Any distribution of incentives lead to multiple modes of response, it is thus very difficult to stimulate single mode of vibration in experiments. The limitation of current signal processing techniques implies that traditional methods used to estimate the damping ratio cannot effectively separate the superposition modes, which leads to larger error in obtained damping ratio. Starting with modal superposition method theory in dealing with multiple-degrees-of-freedom system dynamic response, it was pointed out that mode confusion problem is one important limitation in precise damping ratio test. Modes are more crowded and the superimposed effect is more significant when system damping is larger and stiffness is lower. One program was proposed to achieve “pure mode” extraction by applying modal truncation in numeral calculation. The formula expressions of frequency-response spectrum peak line in both of resonance excitation experiment and numeral calculation were derived. The relationship between them was investigated. “Pure mode” calculation results were used to correct experimental damping ratio. Through four different board units, eight pre-order experimental modal analysis and numerical calculation parameter correction, combining frequency response function to verify data reliability of the correction damping ratio, some laws of damping ratio between different structures or materials were obtained. The results show that: the identification accuracy of composite plate's modal damping ratio is lower than steel's by model experiment calculation, and its damping performance is often underestimated and large amplitude correction are also often needed. The method provides a guideline for further study of modal parameter identification. © 2017, Editorial Office of Journal of Vibration and Shock. All right reserved.

关 键 词：数值计算 模态阻尼比识别 频响曲线 模态截断 模态叠加 

分 类 号：TH212[机械工程—机械制造及自动化] TH213.3