Journal of Computational & Applied Research in Mechanical Engineering (JCARME)

Document Type : Research Paper

Authors

Ali Nouri ¹
Sajad Hajirezaee ²

¹ Department of Aerospace Engineering, Shahid Sattari Aeronautical University of Science and Technology, Tehran, Tehran, 1384673411, Iran

² Department of Aerospace Engineering, Sharif University of Technology, Tehran, Tehran, 1458889694, Iran

https://doi.org/10.22061/jcarme.2017.1552.1128

Abstract

In this research, the modal parameters of a beam in free-free condition are extracted by performing different experiments in laboratory. For this purpose, two different techniques are employed. The first methodology is considered as a time domain method in Operational Modal Analysis. While the other one is frequency domain impact hammer test which is categorized as an Experimental Modal Analysis method and can be regarded as the most common method in modal analysis. Checking the results obtained by the two methods, one can notice a distinct inconsistency in modal damping ratios extracted by each method. However, based on recent publications on the subject, it can be inferred that the time domain methods have better accuracy in identifying damping ratios of structures. In order to confirm the findings, the effect of excitation is examined for each method by altering the excitation tool. For the operational method, it is concluded that changing the excitation tool will not have a noticeable influence on the identified damping ratios, whilst for the Experimental Modal Analysis method changing the hammer tip leads to inconsistent results for damping ratios. This study exemplifies the deficiency of Experimental Modal Analysis methods in their dependency on excitation techniques.

Graphical Abstract

Keywords

dor

20.1001.1.22287922.2018.8.1.2.3

Main Subjects

Vibration

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