The performance characteristics of misaligned bidirectional dynamic vibration absorbers

Bidirectional dynamic vibration absorbers (DVAs) can simultaneously reduce the resonant response of two perpendicular modes of lightly damped structures. The performance of the DVA is affected if its directions of motion are not aligned with the structural modes. When the DVA is misaligned, the 2D structure–DVA system is represented as a coupled 4‐degree‐of‐freedom system. The efficacy of a DVA is often quantified using the concept of added effective damping. Novel formulae are derived that relate the added effective damping for each structural mode to the response covariance of the structure and DVA. It is shown experimentally and numerically that these expressions can be used to determine the added effective damping of a DVA using the responses of the structure and DVA. These expressions can be used to verify the in situ performance of a DVA, which has previously been challenging to do. Lastly, contour plots are created to investigate the performance characteristics of a 2D structure–DVA system for various DVA orientation angles, structural frequency ratios, and excitation amplitudes. The influence of these parameters on the added effective damping, reduction of the resultant root mean square structural response, and correlation between the two structural responses are considered. The trends shown in these contour plots enable the possible influence of DVA misalignment to be rapidly assessed.