Frequency intermittency and energy pumping by linear attachments

• Targeted energy pumping employing a linear system.
• A linear, master, oscillator is coupled in parallel to numerous linear resonators.
• Comparative analysis with a nonlinear energy sink.
• The special architecture of the linear system allows a very effective energy pumping.
• The instantaneous frequency of the master is characterized by intermittency.

The present paper considers the problem of realizing an effective targeted energy pumping from a linear oscillator to a set of ungrounded linear resonators attached to it. Theoretical as well as numerical results demonstrate the efficacy of using a complex attachment as a passive absorber of broadband energy injected into the primary structure. The paper unveils also the existence of an instantaneous frequency associated with the master response characterized by intermittency: a rather surprising result for a linear autonomous system. Comparison with nonlinear energy sinks demonstrates that the two systems have some analogies in this respect and that the linear complex attachment is a very efficient energy trap.