Muniswamappa Anjanappa

Magnetostrictive particulate actuators : configuration, modeling and characterization

Magnetostrictive particulate actuators (MPAs) that take advantage of easy embedability and remote excitation capability of magnetostrictive particles are proposed as new actuators for smart structure applications. A MPA is configured as a small rectangular polymeric beam with magnetostrictive particles dispersed uniformly. Based on the compatibility condition, a load line equation is developed that relates the free strain with the mechanical stress experienced by the magnetostrictive particles. The load line equation and the magnetoelastic property of the material are used to develop a macroscopic behavior model of a MPA. Characterization experiments are used to find the orientation factor and pre-stress. Experimental work shows that the static performance of MPAs for an applied magnetic field depends on the volume fraction, orientation field, mechanical preload, and the stiffness of the polymeric matrix. In general this actuator can be used where the structure needs to be excited with a large force and small strain over a wide frequency range. For example, embedded in a laminated composite, MPAs can be used as micropositioners, vibration dampers, platform stabilizers, and motors.

A high speed magnetostrictive mirror deflector

This paper discusses the development of a high speed magnetostrictive mirror deflector that is compact, power efficient, and requires only low voltage for excitation. The magnetostrictive mirror deflector was designed and fabricated, and its performance tested. Three kinds of experiments were conducted to evaluate the performance, namely, identification of resonance frequencies, measurement of the angle of deflection, and study of the stability of the actuator under continuous use. The measurements were made using a high speed charge coupled device camera integrated with a PC using a custom made data acquisition and analysis program. The deflector was able to produce more than 6.1 mrad at 5.28 kHz with a minimal power of 0.8 W. Experiments conducted to test the repeatability of the measurements made have shown that the device is suitable for continuous duty operation. The results obtained in this study showed that the magnetostrictive mirror deflector is a good candidate for lidar and rapidly tunable laser system use.

Health monitoring of composites embedded with magnetostrictive thick film without disassembly

A new method of detecting delaminations in a composite structure embedded with magnetostrictive particulate sensors is presented in this paper. The main advantages of this method are that it is non-contact, requires access to only one side of the structure, does not need disassembly, and is free of mechanical coupling errors. The composite structure is made of several carbon-fiber-reinforced-polymer (CFRP) layers and one layer of magnetostrictive thick film. To make the fabrication of composite structure simple and practical, a special magnetostrictive thick film whose thickness is comparable to the thickness of CFRP layers was developed. The magnetostrictive thick film consists of fine magnetostrictive particles uniformly distributed in a binding polymer, preferably cured under a bias magnetic field. Also, a compact non-contact sensing module that can be used to scan the surface of a composite structure was developed that consists of a U-shaped magnetic core with excitation and sensing coils on the two arms of the core. A mathematical model for sensing delamination in composite structures with an embedded magnetostrictive thick film layer was developed. Extensive experiments were conducted to validate the model. The open circuit voltage induced in the sensing coil changes significantly, in the range of 50?250?mV, in the presence of delamination.

Designing Piezoelectric Interdigitated Microactuators Using Finite Element Analysis

This paper presents a methodology toward designing, analyzing, and optimizing piezoelectric interdigitated microactuators using multiphysics finite element analysis. The models used in this paper were based on a circularly interdigitated design that takes advantage of primarily the d 33 electromechanical piezoelectric constant coefficient. Because of the symmetric nature of the devices, a small number of 2D axisymmetric parametric models were developed to characterize the behavior of the diaphragms. The parametric models offered a large range of possible results from a very small number of models. The variations in the design parameters and their effects on deflection were captured using these models. The models also showed that several of the design parameters were naturally coupled. Discrete models were then used to capture the variations in the key design parameters during fabrication. The numerical models correlate well to the maximum deflection of the experimental devices.

Numerical Modeling of a Circularly Interdigitated Piezoelectric Microactuator

Accurate modeling and simulation techniques are vital for actuated membranes. Using multiphysical modeling techniques, coupled with variation in design parameters, accurate performance predictions can be realized. A 2-D axis-symmetric model of a circularly interdigitated piezoelectrically membrane is presented. The model includes the piezoelectric material and properties, as well as the membrane materials and properties, and incorporates various design considerations. This model also includes the electromechanical coupling for piezoelectric actuation and highlights a novel approach to take advantage of the higher d33 piezoelectric coupling coefficient. Changes in parameters, including electrode pitch, electrode width, and piezoelectric material thickness, are evaluated.

Comparative analysis of the planar capacitor and IDT piezoelectric thin-film micro-actuator models

A comparison of the analysis of similarly developed microactuators is presented. Accurate modeling and simulation techniques are vital for piezoelectrically actuated microactuators. Coupling analytical and numerical modeling techniques with variational design parameters, accurate performance predictions can be realized. Axi-symmetric two-dimensional and three-dimensional static deflection and harmonic models of a planar capacitor actuator are presented. Planar capacitor samples were modeled as unimorph diaphragms with sandwiched piezoelectric material. The harmonic frequencies were calculated numerically and compared well to predicted values and deformations. The finite element modeling reflects the impact of the d31 piezoelectric constant. Two-dimensional axi-symmetric models of circularly interdigitated piezoelectrically membranes are also presented. The models include the piezoelectric material and properties, the membrane materials and properties, and incorporates various design considerations of the model. These models also include the electro-mechanical coupling for piezoelectric actuation and highlight a novel approach to take advantage of the higher d33 piezoelectric coupling coefficient. Performance is evaluated for varying parameters such as electrode pitch, electrode width, and piezoelectric material thickness. The models also showed that several of the design parameters were naturally coupled. The static numerical models correlate well with the maximum static deflection of the experimental devices. Finally, this paper deals with the development of numerical harmonic models of piezoelectrically actuated planar capacitor and interdigitated diaphragms. The models were able to closely predict the first two harmonics, conservatively predict the third through sixth harmonics and predict the estimated values of center deflection using plate theory. Harmonic frequency and deflection simulations need further correlation by conducting extensive iterative harmonic simulations and experiments. The results, conclusions and potential improvements are discussed.