Journal of Theoretical
and Applied Mechanics
56, 4, pp. 1069-1081, Warsaw 2018
DOI: 10.15632/jtam-pl.56.4.1069

Free vibrational analysis of rectangular ducts with different joint conditions

Nagaraja Jade, B. Venkatesham
Rectangular ducts are fabricated using thin sheets of a metal with different joint conditions.
Due to the presence of these joints, ducts deviate from their assumptive ideal shapes. The
objective of the present work is to study the effect of different joint conditions and wall
thickness on dynamic characteristics of the ducts. Experimental Modal Analysis (EMA)
is performed on three rectangular ducts of different joint types. Numerical Modal Analysis
(NMA) is also performed by considering that the ducts are of ideal rectangular shape
(without joint condition). Correlation analysis is performed between EMA and NMA in
terms of Modal Assurance Criteria (MAC), Relative Frequency Difference (RFD) plots and
auto-MAC. It is observed that natural frequencies are in good agreement but there is a
discrepancy in mode shapes.
Keywords: rectangular duct, duct joint, experimental modal analysis, modal assurance criteria

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