تحليل پايداري و ارتعاش آزاد ورق هاي ساندويچي با هسته حاوي سيال ويسكوالاستيك مغناطيسي با استفاده از روش نوار محدود

چكيده انگليسي :

Stability and Free Vibration Analysis of Sandwich Plates With Magnetic Viscoelastic Fluid Core Using Finite Strip Method Sajjad Mohajeri Date of Submission June 2019 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Prof Mojtaba Azhari Dr Saeid SarramiAbstractSandwich plates containing magnetorheological fluid in the core are nowadays analyzed as an intelligentstructure Because of the rapid change in the viscosity of the fluid in the core this structure can be used tocontrol the forces of vibration and energy depreciation For this purpose in the present study the mostcommonly used problems in sandwich plates containing magnetorheological fluid in the core such as freevibration static and dynamic stability have been evaluated and analyzed In the leading research the upperand lower layers of the cores are considered in both thin and semi thick sheets of composite plates Since thecore of the structure is flexible it leads to the degree of freedom for each of the upper and lower sheets to beindependent of each other For this purpose in the present research efforts have been made to extract thestrain in the core by establishing interconnections between the core and the upper and lower surfaces of theprocess Various factors affect the critical buckling stress frequency modal loss factor and structuralinstability zone width in the dynamic stability problem These factors include the magnitude of the magneticfield the magneto logical fluid thickness the different boundary conditions and the fiber positioning of thefibers The effects of each of them in the area of stability and free vibration are discussed In order to extractthe relationships and indices in the leading research the classic finite strip method which is one of the mostpowerful numerical methods in analyzing plate problems has been used The results indicate that the finitestrip method has a good accuracy in analyzing sandwich plates containing a flexible magnetic core Among the results of this study it can be noted that the increase in the intensity of the magnetic fieldincreases the frequency and loss factor of each mode Also increasing the thickness of the fluid has a directeffect on the increase of the loss factor and loss of frequency On the other hand as the intensity of theapplied field increases the critical buckling stress and the width of the instability region in the dynamicalstability domain increase Also increasing the thickness of the core leads to increased buckling stress However increasing the thickness of the core causes the unauthorized frequencies and subsequently thewidth of the instability zone of the structure to decrease Other factors affecting the dynamic stabilityproblem are the different boundary conditions which increases the stiffness of the structure due to the greatercommitment of the boundaries increasing the instability zone Also the results show that the size of the plateis increased the width of the unauthorized area decreases Finally it should be noted that the angle of fiberson the surface of the upper and lower core when the plate has a simple boundary condition is so will be theangle increases from zero to 45 degrees the width of unstable structures increase Will find It is worth notingthat the effect of the position of the fibers in each of the upper and lower sides of the core is such that in theboundary conditions of the four sides of the joint the process of changes in the critical buckling stress andthe frequency of the vibration is completely symmetric so that at the angle of 45 degree the highest valuesare obtained Key words Sandwich plate Magnetic fluid Composite Free vibration Finite stripmethod Dynamic and static stability

مهاجري، سجاد

تحليل پايداري و ارتعاش آزاد ورق هاي ساندويچي با هسته حاوي سيال ويسكوالاستيك مغناطيسي با استفاده از روش نوار محدود

ورق ساندويچي , سيال مغناطيسي , كامپوزيت , ارتعاش آزاد , روش نوار محدود , پايداري ديناميكي و استاتيكي