بررسی ارتعاشات آزاد یک نانو تیر مدرج هدفمند طولی به همراه جرم متمرکز با استفاده از روش عددی جدید توسعه تقریبی و تئوری غیرموضعی گرادیان کرنشی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 مکانیک، دانشگاه زنجان، زنجان، ایران

2 گروه صنایع، مکانیک و هوافضا، دانشگاه فنی و مهندسی بوئین زهرا، بوئین زهرا، قزوین، ایران

3 دانشیار گروه مهندسی مکانیک معاون پژوهشی دانشکده مهندسی دانشگاه زنجان

چکیده

در این مقاله هدف، مطالعه ارتعاشات آزاد طولی یک نانو تیر مدرج هدفمند به همراه جرم متمرکز براساس تئوری غیرموضعی گرادیان کرنشی با استفاده از روش عددی توسعه تقریبی می‌باشد. امروزه با توجه به اهمیت و کاربرد روز افزون نانو سازه‌ها، بررسی و شناخت خصوصیات مکانیکی و ارتعاشی آن‌ها ضروری به نظر می‌رسد. به دلیل ابعاد کوچک سازه و رفتار وابسته به اندازه آن و عدم توانایی تئوری‌های کلاسیک در پیش‌بینی رفتارهای مکانیکی وابسته به اندازه، از تئوری‌های غیرکلاسیک استفاده گردیده است. معادلات حاکم و روابط شرایط مرزی با استفاده از اصل همیلتون استخراج گردیده و برای نانو تیر مدرج هدفمند با پنج شرط مرزی لولا-لولا، گیردار-آزاد، گیردار-گیردار، گیردار-لولا و گیردار-جرم متمرکز ارائه شده است. سپس، معادله دیفرانسیل به صورت تحلیلی حل گردیده است تا معادله‌های فرکانس برای پنج شرط مرزی به دست آیند. در ادامه با استفاده از روش عددی توسعه تقریبی و با حل مرتبه صفر و مرتبه یک، فرکانس‌های بی‌بعد استخراج گردیده است. مزایای استفاده از این روش سادگی روابط و زمان اجرا مناسب در کدنویسی می‌باشد. در نهایت تاثیر پارامترهایی مانند پارامتر غیرموضعی، مقیاس طول ماده، تاثیر نوع تغییر ماده و نسبت طول به ضخامت بر روی ارتعاشات آزاد نانو تیر بررسی شده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Free vibration of axially functionally graded nanobeam with an attached mass based on nonlocal strain gradient theory via new ADM numerical method

نویسندگان [English]

  • MohammadReza Eghbali 1
  • Seyyed Amirhosein Hosseini 2
  • Omid Rahmani 3
1 Mech. Eng., Zanjan University
2 Department of Industrial, Mechanical and Aerospace Engineering, Buein Zahra Technical University, Buein Zahra, Qazvin, Iran
3 University of Zanjan
چکیده [English]

The purpose of this paper is to study the free vibrations along a longitudinal line of a targeted graded nano beam with an attached mass based on the theory of nonlocal strain gradient theory using the asymptotic development method. nowadays due to the importance and usage of nano structures, investigation and recognition of their mechanical and mechanical properties seem necessary. Due to its small size and behavior depending on its size and the inability of classical theories to predict dependant mechanical behaviors, non-classical theories have been used. The governing equations and boundary condition relations of targeted graded nano beam with five boundary conditions simplesimple, clamped-free, clamped-clamped, clampedsimple, and clamped-attached mass have derived by using Hamiltonian principle. Then differential equation is solved analytically to obtain the frequency equations for the five boundary conditions. In the following, dimensionless frequencies by using the solving zero and the first order of numerical asymptotic development method have derived. Advantage of this method is simplicity, noncomplex mathematical relations and proper coding execution time. Eventually, the effect of nonlocal parameters, material length scale, type of material, the ratio of length to thickness, and mode number on free vibration nano beam has been investigated.

کلیدواژه‌ها [English]

  • Nano beam
  • Nonlocal strain gradient theory
  • Axially functionally graded
  • Natural frequencies
  • Asymptotic development method
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