Saxena, Deepak Kumar

This work presents the dynamic modeling and analysis of a particle-reinforced and prestressed electro-magneto-viscoelastic plate actuator. The actuator belongs to a smart actuator category and is made of an electro-magneto-Active polymer filled with a particular volume fraction of suitable fillers. An energy-based electro-magneto-viscoelastic model is developed to predict the actuator response and interrogate the impact of particle reinforcement on the dynamic oscillations of a pre-stressed condition of the actuator. An Euler-Lagrange equation of motion is implemented to deduce the governing dynamic equation of the actuator. The findings of the model solutions provide preliminary insights on the alteration of the nonlinear behavior of the actuator driven by DC and AC dynamic modes of actuation. It is observed that the enrichment in the particle reinforcement characterized by the amount of fillers strengthens the polymer and depleted the associated level ofdeformation. Also, the depletion in the intensity of oscillation and enhancement in the frequency of excitation is perceived with an increase in the particle reinforcement. In addition, the time-history response, Poincare plots, and phase diagrams are also plotted to assess the stability, periodicity, beating phenomenon, and resonant behavior of the actuator. In general, the current study provides initial steps toward the modern actuator designs for various futuristic applications in the engineering and medical field. [DOI: 10.1115/1.4051911].

Electro-magneto-active (EMA) polymers-based smart actuators suffer from electro-magneto-mechanical instability (EMMI) phenomena arising due to the positive feedback between the applied electric and magnetic fields and reduction in the polymer thickness. This work presents a theoretical investigation of EMMI phenomena of an EMA polymeric actuator in both static and DC dynamic modes of operation. A physics-based non-affine material model is adopted here for capturing the effect of the polymer chain entanglements and crosslinks on the instability phenomena. Simultaneously, a computationally efficient energy approach for obtaining the DC dynamic instability parameters is constructed, which depends on the energy balance at the position of maximal overshoot in an oscillation cycle. The findings from the current study illustrate the trends of variation in the deformation, electric field, and magnetic field at the onset of static and dynamic EMMI with the polymeric entanglements and crosslinks parameters. It is observed that large entanglements and crosslinks in polymer chains improve the stable operation travel range, which positively impacts the actuator performance.

Actuation devices made of smart polymers typically show various instabilities, which can adversely affect their performance and lead to device failure. In general, smart polymers exhibit wrinkling instability when subjected to an electric or magnetic field. At the same time, wrinkles can be used constructively in certain applications demanding a controlled alternation of the surface morphology. Critical factors influencing thin films’ pull-in and wrinkling instabilities are discovered concerning the anisotropic taut domains with an applied electro-magneto-mechanical field control. A continuum mechanics-based electro-magneto-mechanical model is developed for predicting the thresholds on the taut domains in the plane of principal stretches. Also, the concept of natural width under simple tension is implemented to derive the coupled nonlinear equation that evaluates the associated taut domains. The findings of the model solution indicate that the extent of taut domains can be controlled by modifying the level and the principal direction of the transverse isotropy. Additionally, the taut domain for a particular level of applied electromagnetic field increases with an increase in the anisotropy parameter, while it depleted with an increase in the fiber orientations from 0° to 90° for an applied level of electromagnetic loading.