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Valder Steffen

Valder Steffen Jr obtained his Mechanical Engineering degree in 1976 from Campinas State University (UNICAMP), in Brazil. He received his Doctorate in Mechanical Engineering in 1979 from the University of Franche-Comté, Besançon, France.  He also had his Habilitation to direct research (H.D.R) in 1991 from the University of Franche-Comté. Prof. Steffen has co-organized a textbook, authored and co-authored more than two hundred scientific publications in international journals, conference proceedings, and book chapters, on the subject of dynamics of mechanical systems.

He is an associate editor of the Journal of Vibration and Control, the Shock and Vibration Journal, the Latin American Journal of Solids and Structures. He is a member of the Society for Experimental Mechanics (SEM), and a member of the Brazilian Society of Mechanical Sciences and Engineering (ABCM).

He has coordinated and participated of various national and international research projects in the area of dynamics of mechanical systems and has been responsible for the organization of various national and international conferences promoted by ABCM (at the moment he is one of the Chairmen of the International Symposium on Dynamic Problems of Mechanics – DINAME 2015).

His current research interests are rotor dynamics, direct and inverse problems in engineering, smart structures, and structural health monitoring.



SMART ROTORS DESIGN

 

Valder Steffen Jr

Federal University of Uberlândia

School of Mechanical Engineering

Uberlândia – MG – Brazil

vsteffen@mecanica.ufu.br

 

Abstract

 

An important trend in rotor dynamics design is to obtain smart rotors. Smart rotors in this context represent machines that are able to adapt to various working conditions by incorporating smart technology. In the case of flexible rotors, control techniques are mandatory. The control approaches for rotating machines are clustered into three main categories, namely passive, active, and semi-active techniques. Passive techniques are normally performed by devices known as absorbers or isolators. These techniques are effective over a limited frequency bandwidth and, consequently, are unable to adapt their characteristics to changes in the system. Differently, active approaches promise vibration suppression over a broadband of frequencies in which the suppression is performed by incorporating active actuators, such as PZT stacks, magnetic bearings, and electromagnetic actuators to the machine to act directly against the vibratory loads. In semi-active approaches, the vibration is attenuated through an indirect manner by changing the structural parameters of the machine, such as damping and/or stiffness. Another important issue in rotor dynamics is the so-called structural health monitoring techniques (SHM) for crack detection in rotating machines. In general, vibration based approaches are not able to detect incipient cracks. For this reason, using smart material technology, incipient faults in rotating shafts can be detected by using the electromechanical impedance method. This technique measures the electromechanical impedance of the structure by using patches of piezoelectric material (PZT patches) bonded on the surface of the structure (or embedded into it). Through the PZT sensor-actuators, the electromechanical impedance, which is directly related to the mechanical impedance of the structure, is obtained. Based on changes of the impedance signals (e.g., due to the growing crack), the damage can be detected. Consequently, the present contribution is dedicated to the presentation of various smart technologies applied to rotor dynamics design thus giving an overview of several available methods to monitor and evaluate the dynamic behavior of rotating machines, so that control techniques can be successfully applied. 

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