بررسي ارتعاشات آزاد نانو لوله هاي كربني تك جداره تحت اثر ميدان حرارتي بر روي بستر پسترناك با استفاده از تئوري غير محلي تير تيموشنكو

چكيده انگليسي :

Thermal Vibration Analysis of Carbon Nanotubes Embedded in Two Parameter Elastic Found Beam Theory Benhour Amirian b amirian@me iut ac ir Date of Submission 2013 01 20 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Hassan Moosavi moosavi@cc iut ac ir Abstract This project presents a new model to consider the thermal effects Pasternak shear foundation transverse shear deformation and rotary inertia on vibration analysis of a single walled carbon nanotube Nonlocal elasticity theory is implemented to investigate the small size effect on thermal vibration response of rning equations are derived and then solved analytically in order to determine the nonlocal natural frequencies Then finite element analysis is employed to solve the frequency equations Also six different cases are reviewed in order to consider the various parameters Results show that unlike the Pasternak foundation the influence of Winkler constant on nonlocal frequency is negligible for low temperature changes Moreover the nonlocal frequencies are always smaller as compared with their local counterparts In addition in high shear modulus along with increase in aspect ratio the nonlocal frequency decreases Furthermore the thermal vibration analysis of a short single walled carbon nanotubes embedded in an elastic medium based on nonlocal Timoshenko beam model is considered in this study Analytical solution was used to solve the constitutive equations A Winkler and Pasternak type foundation is employed to model the interaction of short carbon nanotube and surrounding elastic medium Influence of all parameter such as nonlocal small scale effects high temperature changes Winkler modulus parameter Pasternak shear parameter vibration mode and aspect ratio of short carbon nanotubes on the natural frequency are analyzed and discussed The present study shows that for high temperature changes the effect of Winkler constant in different nonlocal parameters on natural frequency is negligible In addition for all temperatures the nonlocal frequency like the previous case are always smaller than the local counterparts Furthermore for high Pasternak modulus by increasing the aspect ratio the nonlocal frequency decreases It is concluded that short carbon nanotubes have the higher frequencies as compared with long nanotubes For short carbon nanotubes by increasing the temperature change in a constant nonlocal parameter the natural frequencies increase Generally it is concluded that the effect of Pasternak foundation on natural frequency is more significant as compared with the effects of thermal loading Winkler modulus and nonlocal parameter and should be considered in vibration analysis of short carbon nanotubes Finally it should be noted that the rotary inertia nonlocal parameter and thermal loading have the effect of reducing natural frequency in the case of high temperature changes for long single walled carbon nanotubes Keywords Nonlocal elasticity theory Carbon nanotubes Pasternak Foundation Finite element method PDF created with pdfFactory trial version www pdffactory com

اميريان، بن هور

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