editorial international conference on advances in mechanical engineering...

EditorialInternational Conference on Advances in MechanicalEngineering and Mechanics 2010

Sami El-Borgi1,2

1 Mechanical Engineering Program, Texas A&M University at Qatar, Doha, Qatar2 Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, University of Carthage, La Marsa, Tunisia

Correspondence should be addressed to Sami El-Borgi; sami.el [email protected]

Received 3 October 2013; Accepted 3 October 2013; Published 8 May 2014

Copyright © 2014 Sami El-Borgi.This is an open access article distributed under the Creative CommonsAttribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The present special issue of Shock and Vibration journalincludes six papers presenting studies conducted in variousfields of vibration. Papers were selected among those pre-sented at the Fifth International Conference on Advancesin Mechanical Engineering and Mechanics 2010 (ICAMEM2010) held on December 18–20, 2010, in Hammamet, Tunisia.All papers were reviewed by distinguished reviewers accord-ing to the journal’s procedures and standards. Among the vastnumber of papers that were presented at the conference, thefollowing studies were selected for this special issue.

Samaali et al. study the response of a capacitiveMEMS switch composed of two clamped-clamped flexiblemicrobeams. An electrostatic force is applied between themicrobeams to yield the switch to its ON and OFF states.The equations of motion of the system and the associatedboundary conditions are derived and the static and dynamicproblems are solved using the differential quadratic method.The obtained analytical results are validated using numer-ical finite element results. The transient behavior of themicroswitch was then investigated, indicating a reduction inactuation voltage, switching time, and power consumptionwhile maintaining a relatively good RF performance.

Jemai et al. develop a mathematical model that accuratelysimulates the dynamic behavior of active fiber composites(AFC). These composites are known for their flexibility andrelatively high actuation capacity compared with traditionalceramic piezoelectric materials.The AFC’s energy harvestingcapabilities, however, are low. The model uses homogeniza-tion techniques to describe piezoelectric properties of theAFC. The developed model is incorporated into a vibration-based energy harvesting system consisting on a cantilever

beam on top of which an AFC patch is attached. Analyticalsolutions of the dynamic behavior and the harvested voltageare proposed and validated with finite element simulations.

Gafsi et al. propose a new passive control strategy forthe vibration confinement in a flexible nonlinear beam byconsidering an inverse eigenvalue problem. The strategyconsists of determining the geometric parameters of a beamto yield a desired set of mode shapes and natural frequencies.The beam dynamics is described by a nonlinear partialdifferential equation that is linearized.The authors show that,using the linear model, the strategy of vibration confinementremains valid for the nonlinear beam. They also show thathaving higher amplitude on a larger frequency interval inconjunction with significant level of vibration confinementon a smaller region of the spatial domain presents an efficientdesign for energy harvesting.

El Ouni and Ben Kahla investigate numerically the activetendon control of a cable-stayed bridge in a constructionphase. A linear finite elementmodel of a small-scalemock-upof the bridge is first developed, coupled with a geometricallynonlinear model for the cable. Active damping is added tothe structure by using pairs of collocated force actuator-displacement sensors located on each active cable and con-trolled by decentralized first order positive position feedback(PPF) or direct velocity feedback (DVF). A decentralizedparallel PPF-DVF is proposed to obtain the best performancefrom the two compensators. The authors show that theproposed strategy can be used to control both deck and cablevibrations induced by parametric excitation.

Jiang et al. propose a methodology for fault diagno-sis of rotating machinery based on vibration multisensor

Hindawi Publishing CorporationShock and VibrationVolume 2014, Article ID 857385, 2 pageshttp://dx.doi.org/10.1155/2014/857385

2 Shock and Vibration

information fusion. Three case studies are used to show theeffectiveness of the proposed methodology, namely, diagnos-tic of faulty gear, rolling bearing, and identification of rotorcrack. For each case study, the sensibilities of the features areanalyzed.The obtained results indicate that the peak factor isthe most sensitive feature for identifying gear defect, amongthe twelve time-domain features that are considered. Themean, amplitude squared, root mean square, root amplitude,and standard deviation are all suitable for identifying gear,rolling bearing, and rotor crack defect on a comparative basis.

In identifying the modal signature of structures basedon output-only measurements, several algorithms have beendeveloped over the years among which is the family ofstochastic subspace identification techniques known for theirrobustness and convergence. For large-scale structures, theselection of the model order and the corresponding systempoles is often challenging. To address this problem, theconcept of the “stabilization diagram” is introduced. Theproblem with these diagrams is that the resulting spuriousmodes need to be eliminated. Mrabet et al. suggest a newstabilization criterion obtained through a novel numericalimplementation of the stabilization diagram.The new imple-mentation makes the alignment of the stabilization diagrammore robust, so that only the spurious modes are removed.The authors apply the new stabilization diagram and theimplemented identification technique to identify the modalsignature of an aircraft structure.

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