Advanced Materials Research Vol. 745

Abstract: A paper focuses on the use of the efficient approach to three-dimensional (3D) exact solutions of electroelasticity for laminated piezoelectric plates and shells. This approach is based on the new method of sampling surfaces (SaS). We introduce inside the nth layer Ιn not equally spaced SaS parallel to the middle surface of the shell and choose displacements of these surfaces as basic shell variables. This permits the derivation of 3D exact solutions of electroelasticity for thick and thin laminated piezoelectric anisotropic structures with a specified accuracy using a sufficient number of SaS, which are located at interfaces and Chebyshev polynomial nodes.

Abstract: An algorithm, which combines the use of Domain Decomposition and Model Order Reduction methods based on Proper Orthogonal Decomposition, is proposed. The algorithm allows for the efficient handling of electro-mechanical coupled problems in MEMS, with a strong reduction of computing time with respect to standard monolithic or staggered solution strategies. Examples of coupled electro-mechanical problems, concerning a vibrating beam subject to variable electrostatic forces, are presented and discussed.

Abstract: A review of riblets as a smart flow control device is given. After the state-of-the-art examination of the drag reduction performance, different views on the drag reduction mechanism are put in perspective. Being a smart flow control device, riblets can control not only momentum, but also heat and flow noise. Some of the available results are summarized to encourage the readers to consider other applications of riblets. Although useful for research investigations, riblets films are not industrially friendly. Here, recent efforts in manufacturing the micro-groove surface in situ are reviewed, including an overview of patents relating to the production of riblets.

Abstract: Vibration monitoring based on wireless distributed sensors is currently used in steelmaking plants to early detect structural damage occurring in the rolling mill components. This approach allows overcoming some severe limitations of access to those industrial equipments, but sensors need a local power supply. Vibration energy harvesting based on piezoelectric materials is therefore proposed for this purpose. Nevertheless, very often it happens that dimensions of the energy scavenger are incompatible with the size of the system, thus not allowing a perfect tuning of its resonance upon the frequency of the dynamic excitation. Moreover, sometimes the amplitude of vibration is too low to induce a sufficient amount of energy conversion. Those problems motivated a previous work of the author, about the feasibility of plucking the flexible structure through either a relative motion or rotation of the harvested system and the energy scavenger, respectively. To avoid the drawbacks due to the wear in plucking the material, a contactless electromechanical coupling was proposed. The interaction between two permanent magnets, being one applied to the scavenger tip and the other fixed, was used to excite the vibration and the electromechanical conversion through the piezoelectric layer. The effectiveness of such hybrid system composed by the structure with surface bonded piezoelectric layers and the couple of magnets was investigated and compared to the power requirements of some sensors currently used to measure the dynamic response of the backup roll bearings located at the outer crown of the rolling mill. An optimisation of the whole device to increase the overall performance is proposed by following some approaches assessed in the literature and tested on some specimens of energy scavenger. The optimisation activity was based on a suitable selection of the piezoelectric material aimed at reaching the highest electromechanical coupling with a good mechanical strength and on a suitable shaping of the electrode surface aimed at assuring the largest efficiency in the energy conversion.

Abstract: Starting with some general and historical perspective, mechatronics is placed in the technological field map as a multidisciplinary discipline. The considered advantages of mechatronic systems are exposed from the human perspective, which enables the consideration of the social impact of this technological discipline. Due to the multidisciplinary character of mechatronics, the integration issues including synergetic effects consider both geometrical and functional aspects. The same reason provides a very large variety of different solutions to fulfill a certain functionality. Choosing an appropriate solution for a specific application is done using systematic methods which shape this problem to an optimization problem. General statements are illustrated with different application examples.

Abstract: This paper is concerned with the discussion of a general methodology to design continuously distributed strain sensors; the latter are also known as spatial filters. The methodology is based on the application of the principle of virtual work. Hence, solutions for the design problem can be computed from static auxiliary problems; yet, they are valid for actual dynamic problems as well. Moreover, the use of the principle of virtual work enables a simple and straightforward translation of the results to a structural level. Different types of spatial filters, such as modal filters, displacement filters and compatibility filters are presented and their use for structural and health monitoring is discussed. Some illustrative examples for each type of spatial filter are presented, in which piezoelectric sensor networks are used to put the filters into practice; in each example experimental results validate the presented design methodology.

Abstract: This paper makes a brief characterisation of some aspects related with the extensive research activity of the Laboratory of Vibrations and Structural Monitoring (ViBest) of the Faculty of Engineering of the University of Porto (FEUP) in the field of Continuous Dynamic Monitoring of Bridges and Special Structures, selecting four examples where large high quality databases have been created since 2007, namely Infante D. Henrique bridge, Pedro e Inês footbride, FEUP Campus stress-ribbon footbridge and Trezói railway bridge.

Abstract: A Unified Formulation for deriving several higher-order theories and related finite elements for beams is presented within this paper.Three-dimensional structures with piezo-electric layers are considered.Static and free vibration analyses are carried out.Models' main unknowns are the displacements and the electric potential.They are approximated above the beam cross-section via Lagrange's polynomials in a layer-wise sense.Finite elements stiffness and mass matrices are derived in a nucleal form using d'Alembert's Principle.This nucleal form is representative of the generic term in the approximating expansion of the displacements and electric potential over the cross-section.It is, therefore, invariant versus the theory expansion order and the element nodes' number.In such a manner, higher-order displacements-based theories that account for non-classical effectssuch as transverse shear deformations and cross-section in- and out-of-plane warping are straightforwardly formulated.Results are given in terms of displacements, electrical potential and stresses.Comparison with three-dimensional finite elements models are provided, showing thataccurate results can be obtained with reduced computational costs.

Abstract: A joint preliminary study has been performed to elucidate the capability of IPMC-based structures mimicking the behavior of biological systems. The structural deformation in response to an applied voltage is described within a nonlinear physics-based model of IPMC actuators. A characteristic of the model is the varying-along-the-thickness relative permittivity of the IPMCs, which takes into account the highly heterogeneous layers resulting from electrode deposition, where charge redistribution occurs. Preliminary experiments on an IPMC-based medusoid are presented to offer some validation of the modeling approach and provide directions for further studies.