جستجوی مقالات مرتبط با کلیدواژه "آنالیز مودال کارکردی" در نشریات گروه "مکانیک"

It is impossible to measure the random excitation loads of structures during transportation under road excitations or satellite carriers thrown under environmental excitations in order to identify modal parameters; thus in this research, our challenge and purpose is to determine the modal properties of structures without having the input excitation load and, but only by having the response. In the studies have been performed so far in the field of modal analysis, less attention has been paid to comparing time and frequency methods, especially in the determination of damping. In addition, no sensitivity analysis between different excitations of white noise, sinusoidal sweep and the effect of these excitations on time and frequency domain methods of modal functional analysis have been performed so far. At first, these methods are implemented and validated on a 5-DOF discrete model (mass, spring, and damper), and finally they are industrially implemented on an actual structure. This paper shows that the decomposition methods are capable to extract the modal parameters of the primary modes of an actual sample. At the end, a comparison is made between the results and the effectiveness of each method is evaluated.

In the present research, performance of harmonic components identification and elimination techniques in practical operational modal data is investigated. Firstly, classical modal testing has been carried out on a cantilever steel beam and modal data are extracted. Four bending modes were available in the frequency band of interest. Afterwards, the same structure underwent operational modal tests with simultaneous random and harmonic excitation forces. In OMA, measurement data obtained from the operational responses are used to estimate the parameters of models that describe the system behavior. Extracted modal parameters from these data compared with baseline parameters. Extraction of modal parameters from operational data was fulfilled through different common OMA techniques. Each set of obtained results was evaluated in comparison with reference results. Accuracy and capability of each method in eliminating spurious modes caused by harmonic input components have been studied. For data analysis, in addition to developed MATLAB codes, commercial software of PULSE has been utilized in parallel as a tool for verification. The results of this survey demonstrate that the accuracy of the Stochastic Subspace Identification method is higher compared to Frequency Domain Decomposition and Enhanced Frequency Domain Decomposition methods. However, when the system has low modal damping, Frequency Domain Decomposition methods provide better estimates.