Coherent Super Decay by Membrane-type Tuned Mass Dampers

Coherent Super Decay (CSD) is a phenomenon observed that the first part of linear sum of displacement decays much faster with the use of a set of damped oscillators than any of the individual oscillators. Under an impulse excitation, the decay of the first resonance mode at 100 Hz of a free hanging steel plate (400 mm x 400 mm x 5 mm, 6.4 kg) with a Q-factor over 3000 is measured. With the carefully engineered membrane-type tuned mass dampers (MTMD) with a total added mass of only 0.2% of the primary structure (the steel plate), 97% of the vibrational energy is dissipated within 100 ms, i.e., the decay is almost completed in 10 periods of oscillation. The damping ratio is 4.6 %, and the corresponding Q-factor is 11. MTMD provides an easily tunable, light weight, and miniaturized devices for the experiments. Our finite element numerical simulations can reproduce the experimental CSD very well. The numerical investigations show a group of slow decay response function can approximate the response function of a fast decay resonator. The process is called the response function decomposition (RFD). Most important, the response functions can be converted into complex functions respectively but with different singularity points.