應用壓電晶片感應器於簡支板之實驗模態分析

The Use of PZT Ceramics as Sensors for the Experimental Modal Analysis of a Simply Supported Plate

王柏村(Bor-Tsuen Wang) ； 陳榮亮(Rong-Liang Chen)

《中華民國振動與噪音工程學會論文集》 1997 (1997/05) Pp. 385-394

https://doi.org/10.30028/CSSVANNUAL.199705.0385

摘要

本文主要是將壓電晶片黏貼在結構表面上作爲感應器，並配合衝擊鎚作爲驅動器從事簡支板之實驗模態分析。首先由理論分析推導出結構受點力激振及壓電片感測之頻率響應函數通式，其中點力激振器與壓電片感測器之特徵函數可分別定義爲位移振型及壓電片兩端斜率差振型，針對簡支板而言，此壓電片兩端之斜率差振型可證明與位移振型具有比例之關係。本文之實驗是利用雙頻道訊號分析儀作分析，其實驗方式爲移動衝擊鎚而固定壓電片，因此經由實驗可求得頻率響應函數矩陣中一列之頻率響應函數，再將此一系列頻率響應函數經由曲線嵌合軟體可求出結構之模態參數，包括簡支板之自然頻率、振型及阻尼比等。最後其結果顯示，實驗與理論之頻率響應函數相吻合，而且實驗所得之模態參數可以與理論分析之物理意義相符。因此本文證明用壓電片感應器結合衝擊鎚從事實驗模態分析之可行性，並且以可以應用在其他結構。

關鍵字

壓電晶片 ； 簡支板 ； 實驗模態分析 ； 位移振型 ； 斜率差振型 ； 模態參數。

並列摘要

This work presents the use of a rectangular shape of PZT ceramics adhered onto the surface of a simply supported plate and uses it as the sensor, while the impact hammer is applied as the actuator for the structural modal testing. This work first formulates the frequency response function (FRF) based on the point force excitation and PZT sensing. The point force actuator eigenfunction and the PZT sensor eigenfunction can be identified as the displacement mode shape and the mode shape of slope difference between PZT edges respectively. In particular, the mode shape of slope difference between PZT edges for the simply supported plate can be shown to be proportional to the displacement mode shape. The experiments are then performed on a dual-channel FFT analyzer. A column of FRF matrix can be obtained by roving the impact hammer with the fixed PZT sensor. A curve-fitting software, LMS CADA-PC, is used to extract the modal parameters, including natural frequencies, mode shapes and modal dumpings of the plate. The frequency response functions are shown to be agreed well between theoretical and experimental results. Results also show that modal parameters can be properly obtained and physically interpreted with theoretical solutions. This work, therefore, demonstrates the feasibility of using PZT sensor in conjunction with the impact hammer for structural modal testing and can also be extended to other structures.

並列關鍵字

PZT ceramics ； simply supported plate ； modal testing ； displacement mode shape ； mode shape of slope difference ； modal parameters