Bimorph

About: Bimorph is a research topic. Over the lifetime, 3339 publications have been published within this topic receiving 51880 citations.

Thermomechanical behavior of bulk NiTi shape-memory-alloy microactuators based on bimorph actuation

Abstract: Shape-memory-alloy (SMA) has attracted considerable attention in recent years as a smart and efficient material, due to its unique properties. SMA microactuators became one of the potential solutions for unresolved issues in microelectromechanical systems (MEMS). This paper presents a thermomechanical behavior analysis of bimorph SMA structure and studies the effect of varying the SMA layer thickness, the type of stress layer and its thickness, and the processing temperature on the displacement of the microactuator. Furthermore, the analyzed results were verified by experimental work, where the fabrication of the SMA microactuators followed the standards of the MEMS fabrication process. SiO2, Si3N4 and Poly-Si were used as stress layers. The fabrication results showed that the bimorph SMA structure achieved maximum displacement when SiO2 was used. The SMA structure with dimensions of 10 mm (length) × 2 mm (width) × 80 µm (thickness), had maximum displacement of 804 µm when 4.1 µm of SiO2 layer was deposited at a temperature of 400 °C.

Analysis and Testing of a Froude Scaled Helicopter Rotor with Piezoelectric Bender Actuated Trailing Edge Flaps

Abstract: This paper presents an analytical model and validation tests of a Froude scaled rotor featuring piezoelectric bender (bimorph) actuated trailing-edge flaps for active vibration suppression. The analytical model for the coupled bimorph actuator trailing-edge flap dynamic response in the rotating environment takes into account the aerodynamic, centrifugal, inertial and frictional loads acting on the actuator-flap system. The linkage arm length associated with the mechanical amplification mechanism is selected to maximize flap performance in the rotating environment. The bimorph clamping is improved to prevent actuator slippage under high centrifugal loads. The analytical model is validated by carrying out a series of bench tests, vacuum chamber tests and hover tests. In hover, flap deflections of ± 6 degrees at 4/rev flap excitation are achieved at 900 RPM, thus demonstrating the potential ofthe piezoceramic bender as a lightweight and compact actuation system for individual blade control purposes. This paper also includes a feasibility study for piezo-bimorph actuation of a trailing-edge flap for a Mach scaled rotor model.

Resonant nonlinearities of piezoelectric macro-fiber composite cantilevers with interdigitated electrodes in energy harvesting

Abstract: We explore the modeling and analysis of nonlinear nonconservative dynamics of macro-fiber composite (MFC) piezoelectric structures, guided by rigorous experiments, for resonant vibration-based energy harvesting, as well as other applications leveraging the direct piezoelectric effect, such as resonant sensing. The MFCs employ piezoelectric fibers of rectangular cross section embedded in Kapton with interdigitated electrodes to exploit the 33-mode of piezoelectricity. Existing modeling and analysis efforts for resonant nonlinearities have so far considered conventional piezoceramics that use the 31-mode of piezoelectricity. In the present work, we develop a framework to represent and predict nonlinear electroelastic dynamics of MFC bimorph cantilevers under resonant base excitation for primary resonance behavior. The interdigitated electrodes are shunted to a set of resistive electrical loads to quantify the electrical power output. Experiments are conducted on a set of MFC bimorphs over a broad range of mechanical excitation levels to identify the types of nonlinearities present and to compare the harmonic balance model predictions and experiments. The experimentally observed interaction of quadratic piezoelectric material softening and cubic geometric hardening effects is captured and demonstrated by the model. It is shown that the linearized version of the model yields highly inaccurate results for typical base acceleration levels and frequencies involved in vibration energy harvesting, while the nonlinear framework presented here can accurately predict the amplitude-dependent resonant frequency response.

Elastic properties of magnetostrictive thin films using bending and torsion resonances of a bimorph

Abstract: The modification of the elastic properties of giant magnetostriction alloy films due to an applied magnetic field (the ΔE effect), has been studied. Two different types of films were deposited on Si substrates: (i) single layers of TbDyFeCo alloys typically 1000 nm thick and (ii) nanocomposite multilayer films of FeCo/TbFeCo each having a typical thickness of 6 nm. Both types of films were rendered magnetically anisotropic with a well defined in-plane easy axis. Rectangular samples were cut out of these bimorphs and firmly glued at one end to a heavy base to form a simple cantilever structure. The variations of film elastic moduli were deduced from the shifts of the cantilever resonance frequencies as a function of bias field for two basic configurations: (i) field applied along the easy axis and (ii) field applied along the hard axis. In contrast with previous work, both flexural and torsion resonance modes were excited and studied. As a result the field induced variations of both planar traction modulus...

Modeling of the electromechanical performance of piezoelectric laminated microactuators

Abstract: Piezoelectric microactuators may be considered as multilayer laminated composites consisting of alternating layers of piezoelectric and non-piezoelectric materials A generalized analytical formulation of mechanical deformations as a function of applied electric field is derived for an arbitrary lay-up of such laminates Based on the generalized theory developed, specific formulae for the electromechanical performance of two cantilever microactuator lay-up geometries including a single piezo/elastic laminate and a bimorph, are derived In the modeling of the electromechanical performance of piezoelectric microactuators, the present model incorporates both d211 and d222 Furthermore, the elastic properties of both the piezoelectric and the elastic materials have been considered The developed model is evaluated based on a comparison with results from experiment