激振系統與測力規效應對振動量測影響

Effects of Excitation systems and Load cells on Vibration Testing

呂明憲(Ming-Hsien Lu)

指導教授 ： 楊大中

元智大學/工程學院/機械工程學系/碩士(2004年)

摘要

使用激振器做振動量測時通常會在結構上貼測力規量測待測結構的受力，同時在測力規與激振器之間加上推桿以減少非軸向力的干擾。當待測結構連接這些激振裝置與感測器後，結構的動態特性也會改變。因此實驗結果也與真實結構的頻率響應函數不同。測力規的質量對待測結構產生質量效應，激振系統產生推桿效應與激振器的效應。測力規直接貼在待測結構上一起運動，所以測力規得到的訊號也受到測力規內部質量與待測結構的影響，造成干擾。一般模擬激振系統對振動量測的影響未考量測力規的結構，因此本文考慮測力規結構之影響，模擬結果可以說明測力規的質量效應與構造使頻率響應函數測量產生差異。同時也以不同激振方式與不同長度推桿的實驗結果比較，來說明測力規與推桿對振動測試的影響。

關鍵字

測力規 ； 推桿 ； 子結構合成 ； 量測

並列摘要

Load cells and stingers are frequently used in the vibration testing using shakers to measure the excitation force and to reduce the non-axial excitation respectively. These devices, however, alter the dynamic characteristics of tested structures and result in measured frequency response functions different from the true frequency response functions of the structures. The exciter (shaker) and stinger will have their individual effects on the response of the tested structures, while the mass of load cells will cause the inertia effect and the response signals will also depend on the internal structure of the load cell. The effects of the load cell structure are generally not considered in the simulation of the excitation system. This effect is investigated in this paper and simulation results show that both the inertia and structure of load cells may cause discrepancy in the measurement. Experiment with different methods of excitation and various lengths of stingers are conducted to demonstrate the influence of load cells and stingers.

並列關鍵字

load cell ； stinger ； substructure synthesis ； measurement

參考文獻

2. Keinholtz, D. A., “A Suspension System for Simulating Unconstrained Boundary Conditions,” Proceedings of the 7th International Modal Analysis Conference, 1989, pp. 1251

3. Foss, G. C., “A Low Stiffness Suspension System for Free-Free Modal Testing,” Proceedings of the 6th International Modal Analysis Conference, 1988, pp. 1402

4. Hu, X., McConnell, K., G., “An Advanced Model for Stinger Force, Motion and Energy Transmissibility,” International Journal Analytical and Experimental Modal Analysis, Vol. 7(4), Oct, 1992, pp. 271-281

5. Hieber, G. M., “Non-Toxic Stingers,” Proceedings of the 6th International Modal Analysis Conference, 1988, pp. 1371-1379

10. Tomlinson, G. R., “Force Distortion in Resonance Testing of Structures with Electrodynamic Vibration Exciters,” Journal of Sound and Vibration, Vol. 63, No3, 1979, pp. 337-350