بررسي انتقال امواج آكوستيك از پوسته استوانه اي ساندويچي با هسته سيال الكترورئولوژيكال

چكيده انگليسي :

Acoustic Transmission through Sandwich Cylindrical Shells with Electrorheological Fluid Core Maryam Zabarjad Shiraz Zabarjad maria@yahoo com March 14 2011 Department of Mechanical Engineering Isfahan University of Technologym Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Dr Mohsen Saghafian saghafian@cc iut ac ir Abstract Vibration and sound transmission control of elastic structures is a crucial issue in many engineeringsystems ranging from ground based vehicles to machinery civil structures ships aircraft aerospacevehicles space based platforms and buildings Two distinct approaches are commonly used namely passivecontrol and active control In passive control the material properties of the structure itself such as dampingand stiffness are modified so as to change the structural response However the material properties of suchstructures are predetermined in their design or construction phase which can be hardly adapted to unexpectedenvironmental changes In order to overcome this disadvantage intelligent materials may be incorporatedinto conventional structures in order to adapt to the changes of the environment In this thesis acousticalcharacteristics of a cylindrical sandwich smart shell in wich included Electrorheological or Magnetorheologicalfluids and immerged in an ideal fluid and was excited by a planar acoustic wave was be studied The purposeof this study was be modelling and investigating of the acoustical properties of smart systems which includedelectrorheological and magnetorheological fluids The equations of motions of the system are obtained withsimultaneous implications of thin shell theory and Hamilton principal Then the displacement and pressurefields are deduced based on infinite series and using special vertical functions with considering to boundaryconditions of the cylinder Two types of modelling methods the model of complex tangential module andKelvin material are used for modelling the electrorheological and magnetorheological fluids In this study the method of Kelvin material was be used regarding to the natural property of this method in theimplemantation of viscos damping work which make this method more physically acceptable For thevalidation a comparsion between the natural frequencies which obtained by analytical solution and thoseobtained by Finite Element Method FEM was done which good agreement found between them One of thebasic important parameters in study of the response of acoustical vibration of cylindrical structures as well asanalyze of the sound transmission is the parameter of the sound Transmission Loss TL which defined asthe respect of the power of the inlet sound to power of transmitted sound that is a function of displacmentand pressure fields So transmission loss computed regarding this definition and then other importantphysical and geometrical parameters which are effective on transmission loss such as the intensity of theelectrical or magnetical fields the incident wave angle and thickness of the core layer of smart material wasbe investigated in a vast domain of frequency Also transmission loss was calculated for a diffusive acousticfield based on a directed normal distribution by the use of Gauss weighting function The altering of theelectric or magnetic field seemed to have no appreciable effect on sound transmission loss Furthermore itwas observed that with increasing the angle of incident wave transmission loss increased Changing thethickness smart layer had a broadband effect on TL over the entire range of the frequency But the shell willhave to be designed only as thick as necessary because of the weight constraint The type of analysisdeveloped in this work will be very useful in such a situation The obtained results for both of themagnetorheological and electrorheological fluids in same conditions were been compared and it wasobserved that the sound transmission loss was greater in magnetorheologicaal material thanelectrorheological material Key Words Cyl

زبرجد شيراز، مريم

بررسي انتقال امواج آكوستيك از پوسته استوانه اي ساندويچي با هسته سيال الكترورئولوژيكال

پوسته استوانه اي , اصل هميلتون , ساختارهاي هوشمند , كامپوزيت هاي الكترورئولوژيكال , انتقال صوت , كنترل صوت