17 research outputs found
Analysis of Tristable Energy Harvesters Under Random Excitations
No full textThis manuscript analyzes the performance of a tristable vibration energy harvester under Gaussian white noise excitation. Broadband vibration energy harvesting has attracted significant research attention and is targeted toward obtaining large power output over a wide range of frequencies. Nonlinearity can be introduced into vibration energy harvesting systems through multi-stability. In cantilever-type vibration energy harvesters, multi-stability could be achieved by the introduction of magnetic interactions. When two external magnets are used, the harvester can have up to three stable static equilibrium positions. The harvester with two stable states has been explored widely, both theoretically and experimentally. Recently, the harvester with three stable states is shown to perform better than its bistable counterpart in the presence of a linearly increasing harmonic sweep excitation. Ambient vibrations are random in nature, and the performance of tristable energy harvesters under such excitations needs to be studied. To begin with, we study the performance of tristable energy harvesters under Gaussian white noise excitation through numerical simulations. The simulations show that beyond a certain critical amplitude of excitation, the harvesters undergo inter-well oscillations and harvest more power. This implies that if the variance of the random ambient excitation is known, then the harvester could be optimized so that the mean harvested power is maximized.</p
Fluid–Body Interactions in Fish-Like Swimming
No full textThe present study focuses on formulating a fluid–structure interaction (FSI) framework by coupling a finite element analysis (FEA) based structural solver and a lumped vortex method (LVM) based potential flow solver to study the coupled dynamics involved in the undulatory and oscillatory swimming of fishes. The caudal fin of a carangiform fish is modelled as a continuous cantilever beam with a periodic support motion. The effect of the actuation frequency on the thrust coefficient is investigated. A significant increase in the aerodynamic thrust is noticed for the support motion frequencies nearing to the structural natural frequencies of the beam. Next, the whole fish body, considering the full-body undulations, is modelled as a continuous free-free beam. This model incorporates a time-dependent actuating moment varying along the length of the body which can be attributed to the muscle moments generated by the fish. A parametric study is carried out to obtain maximum thrust output for the muscle power input in terms of the actuation moment. It is observed that the generated thrust increases significantly when the frequency of the actuation moment approaches towards the natural frequencies of the free-free beam. A comparative study of the average thrust coefficient is carried out for these two cases.</p
Dynamic Analysis of MRE Embedded Sandwich Plate Using FEM
No full textAbstractMagnetorheological elastomers (MRE) are class of smart materials, whose stiffness and damping characteristics can be changed by applying external magnetic field. In this work three layered rectangular plate is considered where top and bottom layers are made up of aluminium layers and middle layer is MRE material to study free vibration characteristics of the system. With help of Lagrange principle and finite element method (FEM), the governing equation of motion is derived. Natural frequencies and modal loss factors of MRE cored sandwich plate is obtained for different core and constraining layer thickness by using modal strain energy method (MSE) for different magnetic fields. This work will find applications in active reduction of vibrations by applying magnetic field
Evaluation of Electromechanical, Damping and Dynamic Mechanical Properties of Silver Electrode IPMC Actuator
No full textFabrication and Thermo-Mechanical Analysis of Pure Silver-Electrode Ionic Polymer-Metal Composite (IPMC) Actuator
No full textTill to date, fabrication of Ionic Polymer-Metal Composites (IPMC) are carried out successfully using noble metal such as platinum/gold as the surface electrode. In this work we have proposed cost effective fabrication method for IPMC actuator using non-precious metal electrode of silver (Ag). Chemical decomposition method is followed using Nafion as the ion exchange membrane to fabricate pure Ag-electrode IPMC. Microscopic and morphological analyses reveal that, silver particles penetrate well through the surface of Nafion membrane. The bending deformation measurement and analysis of the thermo-mechanical properties of the fabricated IPMC is carried out. The experiment results and performance of the IPMC actuator confirm that the fabrication of pure Ag-IPMC is feasible and can be used as artificial muscle material.</jats:p
