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چكيده انگليسي :

Vibration Analysis of a Beam with Embedded Shape Memory Alloy Wires Hojjat olla Rezaei Dolat Abadi hrezaei@me iut ac ir April 29 2009 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 8311 IranDegree M Sc Language FarsiSupervisors Hasan Nahvi hnahvi@cc iut ac irMahmood kadkhodaei kadkhodaei@cc iut ac irAbstractThe ability of tuning the dynamic response of a structure such as its performance in terms ofnoise and vibration control to be so that it fits the working conditions of the systems is achallenging objective Due to the limitations of practical conventional solutions and theimpossibility of producing significant changes of the main structural features innovativematerials and design strategies have been introduced Accordingly looking for non conventionalmaterials to satisfy control performance requirements has been the main task during the pastyears The application of fiber reinforced laminated composite materials to various engineeringstructures such as aircraft marine and space structures has increased significantly in recentyears because of their inherent highly specific stiffness and strength Shape memory alloys SMA s are a type of smart materials with shape recovery effect The unique ability of changingmaterial properties wide range of operational temperature excellent damping properties andhigh durability make SMA s useful for vibration tuning of structures The governing mechanismfor the behavior of SMAs is the reversible transformation process between martensite andaustenite It can be initiated by a change in temperature and or by a change in stress Combiningthe unique properties of SMA s with other materials can create intelligent or smart composites In this study the constitutive relations of SMA s are combined with elastic properties of thebeam to derive governing differential equations The constitutive equations used for SMA s arecapable of predicting both stress induced and temperature induced martensite fractions for abetter modeling of the SMA s various behaviors In this dissertation the influence of embeddingSMA wires in a fixed beam on the natural frequencies of the beam for different boundaryconditions and in the presence of recovery stress generated by pre strained wires is investigated Also in the present study dynamic behavior of a rotating beam with embedded shape memoryalloy wires is analyzed and the efficacy of applying shape memory alloy wires in the middle isinvestigated In this thesis the non linear vibration analysis of a beam with embedded SMA wires isperformed to investigate the effect of these functional materials on the dynamic behavior of thebeam The wires are embedded in the neutral layer of the beam Since a linear theory does notconsider mid plane stretching the non linear analysis should be employed to model somephenomena including damping effects that are diagnosed by other researchers Bye the use ofnon linear considerations although there is no distinct damping term in the governing equation the results show a decrease in the vibration amplitude This decrease has been observed in theexisting experimental findings however a linear analysis cannot predict it This decrease is dueto the phase transformation of the SMA wires in high temperatures that makes a hysteretic loop Key WordsShape Memory Alloy Beam Vibration

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