基于自由振动衰减信号包络线法辨识硬涂层复合结构的阻尼特性

Estimating system damping for a hard coating composite structure based on envelope of a free damped vibration signal

硬涂层阻尼减振是一种新兴的振动被动控制方法,而测试出硬涂层复合结构的阻尼特性参数是阻尼减振研究的基础。由于硬涂层阻尼机理的复杂性,目前还没有通用而有效的方法辨识涂层复合结构的阻尼。本文主要研究基于自由振动衰减信号包络线法辨识硬涂层-薄板复合结构阻尼特性的方法。首先,用实验说明了锤击激励、半功率带宽法拾振对于测试薄板结构阻尼特性的局限性。接着,推导了自由振动衰减信号包络线法辨识阻尼特性的原理性公式,提出了具体的测试复合结构模态阻尼比的流程,并在此基础上,搭建了相应的振动测试实验系统。最后,以涂敷NiCrAlY的钛板为对象,对其涂层前后的阻尼特性进行了测试,测试结果表明,本文所提出的方法具有较好的可重复性,从而确保具有较高的测试精度。同时,还讨论拾振传感器的类型以及激振力幅等对薄板结构阻尼测试结果的影响。

Vibration reduction with hard coating is an important passive vibration control method and identifying damping of a hard coating composite structure is a basis for vibration reduction study. Because of complex damping mechanism of a hard coating, there is not a universal and effective method to identify its damping. Here, estimating system damping with envelope of a free damped vibration signal was studied for a hard coating-thin plate composite structure. Firstly, a test was done to illustrate that the hammering test and the half-power bandwidth method have a limitation for measuring the damping feature of a hard coating composite structure. Then, the principle formulas of the envelope method were derived, the procedure of measuring modal damping ratios of a composite structure was proposed and the corresponding measuring test system was set up. At last, a thin plate coated with NiCrA1~ hard coating was taken as a study object, the damping feature was measured for un-coating and coating cases. The test results showed that the proposed method has good repeatability, the higher accuracy of identifying damping can be ensured. Furthermore, the influences of the pick-up sensor types and the exciting force amplitude on damping identification were also discussed.