Forced response of cylindrical shells coupled with nonlinear shape-memory-alloy (SMA) actuators regulated by sinusoidal and saw-tooth temperature profiles

Abstract

Dynamic responses of cylindrical shells coupled with shape-memory alloy (SMA) ring segments placed at critical locations are investigated. Since the SMA actuators are highly nonlinear and governed by the temperatedependent stiffness and martensite/austenite fraction, input shaping and phase shift of temperature profiles are incorporated to control the shell vibrations. Open-loop equations of an elastic cylindrical shell panel are defined first and then used with assumed mode-shape functions satisfying specified boundary conditions in the free-vibration analysis. Modal-analysis data are used to determine spatial strain distributions of natural modes. Distributed modal-signal characteristics suggest optimal placements of SMA actuator segment(s) for each given mnth mode. Based on the modal-expansion method, the open-loop control force induced by the SMA ring segments applied to a simply supported cylindrical shell panel is formulated. This formulation indicates that only the odd modes in the circumferential direction can be controlled. Longitudinal modes are controlled via placing specific number, depending on the mode, of actuator segments along the panel length. To predict control effects of the nonlinear SMA ring segments, the modal participation factor response is determined for an external harmonic excitation applied to the shell along with induced SMA control forces, via sinusoidal and saw-tooth temperature profiles to generate desirable control forces and to eliminate the unwanted effects. Analysis results suggest that with proper choice of temperature waveform function to the SMA ring segments and minor modifications to frequency and phase, the SMA ring segments can attenuate unwanted external vibrations of cylindrical shells.

Responses of rings with light-activated shape memory polymers regulated by neural network and phase shift

“…Compared with the modal response without LaSMP control (Figure 7), the steady-state peak-to-peak magnitude of n = 2 modal response is reduced by 47.7%. To further enhance the effectiveness of LaSMP actuation, a phase-shift technique (DeHaven and Tzou, 2008;Li et al, 2013) and the neural network controller are applied in the independent modal control.…”

Experimental investigation on the vibration tuning of a shell with a shape memory alloy ring

“…The vibration tuning mechanism of the SMA smart ring can be described as reinforced constraining layer damping [47][48][49]. Once the SMA actuators are heated, the SMA smart ring generates a contracting stress on the shell, leading to a stiffness increment in the shell, thus the vibration of the shell is suppressed [50,51]. At the same time, the constraining layer damping structure comes into action since the MR sheet (damping layer), which is a kind of high damping material [52][53][54], is sandwiched between the shell and the steel plate (constraining layer).…”