Piezoceramic transducers (PZTs) have been successfully employed for electromechanical impedance (EMI) technique based models of structural health monitoring (SHM) in the recent past. In the EMI models, the PZTs are generally surface bonded or embedded inside the host structure, and then subjected to actuation so as to interrogate the structure for the desired frequency range. The interrogation results in the prediction of electro-mechanical (EM) admittance signatures. These EM signatures serve as indicator of the health/integrity of the structure. However to effectively monitor structural health, understanding interaction mechanism of PZT with host structure is essential. Interaction of surface bonded PZT is different from that of an embedded PZT. This paper presents an over view of all the one, two and three dimensional interaction mechanisms considering different actuation of the PZT in the presence of electric field. Additionally it presents the existing single and multiple PZTs and their mathematical relationships.Key words: Single degree of freedom (SDOF), multiple degrees of freedom (MDOF), PZT, electromechanical impedance (EMI), non destructive evaluation (NDE), structural health monitoring (SHM), PZT-structure interaction.
The application of different types of evidence theories in the modeling, analysis and design of engineering systems is explored. In most studies dealing with evidence theory, the Dempster–Shafer theory (DST) has been used as the framework not only for the characterization and representation of uncertainty but also for combining evidence. The versatility of the theory is the motivation for selecting DST to represent and combine different types of evidence obtained from multiple sources. In this work, five evidence combination rules, namely, Dempster–Shafer, Yager, Inagaki, Zhang, and Murrphy combination rules, are considered. The limitations and sensitivity of the DST rule in the case of conflicting evidence are illustrated with examples. The application of all the five evidence combination rules for the modeling, analysis and design of engineering systems is illustrated using a power plant failure example and a welded beam problem. The aim is to understand the basic characteristics of each rule and develop preliminary guidelines or criteria for selecting an evidence combination rule that is most appropriate based on the nature and characteristics of the available evidence. Since this work is the first one aimed at developing the guidelines or criteria for selecting the most suitable evidence combination rule, further studies are required to refine the guidelines and criteria developed in this work.
Particle swarm methodologies are presented for the solution of constrained mechanical and structural system optimization problems involving single or multiple objective functions with continuous or mixed design variables. The particle swarm optimization presented is a modified particle swarm optimization approach, with better computational efficiency and solution accuracy, is based on the use of dynamic maximum velocity function and bounce method. The constraints of the optimization problem are handled using a dynamic penalty function approach. To handle the discrete design variables, the closest discrete approach is used. Multiple objective functions are handled using a modified cooperative game theory approach. The applicability and computational efficiency of the proposed particle swarm optimization approach are demonstrated through illustrate examples involving single and multiple objectives as well as continuous and mixed design variables. The present methodology is expected to be useful for the solution of a variety of practical engineering design optimization problems.
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