تحلیل ناپایداری دینامیکی تیر ساندویچی ضخیم با هسته انعطاف‌پذیر تابعی تحت اثر نیروی تعقیب‌کننده

نوع مقاله : مقاله پژوهشی

نویسندگان

1 رئیس دانشکده مهندسی مکانیک/دانشگاه تربیت دبیرشهیدرجایی

2 استاد دانشگاه مالک اشتر تهران

3 دانشجوی دکترا

چکیده

سازه‌های هوایی هنگامی‌که تحت اثر نیروهای ناپایستار، به‌ویژه نیروهای تعقیب‌کننده قرار می‌گیرند، ممکن است علاوه بر ناپایداری استاتیکی در معرض ناپایداری دینامیکی (پدیده فلاتر) نیز قرار بگیرند. به‌همین علت ضروری است، سازه به‌نحوی طراحی گردد، تا از وقوع ناپایداری‌های استاتیکی و دینامیکی جلوگیری شود. در این مقاله به کمک تئوری مرتبه بالای تیرهای ساندویچی جدید برای اولین بار، ناپایداری دینامیکی تیر ساندویچی ضخیم با هسته انعطاف‌پذیر تابعی تحت اثر نیروی تعقیب‌کننده مورد بررسی قرار گرفته است. تیر ساندویچی از دو رویه و یک هسته انعطاف‌پذیر تشکیل شده است. سطح مشترک هسته با رویه‌ها شامل اتصال کامل است، که قابلیت تحمل تنش‌های برشی و عمودی را دارا می‌باشد. تیر ساندویچی به‌صورت الاستیک خطی با جابجایی‌ها و چرخش‌های کوچک در نظر گرفته شده است. معادلات حرکت تیر ساندویچی مرتبه بالا، تحت اثر نیروی تعقیب‌کننده به کمک اصل همیلتون استخراج شده است. با اعمال شرایط مرزی و با کمک روش حل عددی تربیع مربعات، پدیده فلاتر مورد بررسی قرار گرفته است. علاوه بر صحه‌گذاری نتایج، اثر پارامترهای مختلف هندسی و موادی تیر نیز بر آستانه نیروی فلاتر مورد مطالعه قرار گرفته است. نتایج نشان می‌دهد، برای تیرهای بلند، مقدار نیروی تعقیب‌کننده آستانه پدیده فلاتر به نتایج متناظر در تیر تیموشنکو میل می‌کند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Analysis of Dynamic Instability in Sandwich Thick Beams with Flexible Functional Core Subjected to a Follower Force

نویسندگان [English]

  • gholamhasan payganeh 1
  • keramat malekzadeh fard 2
  • fahimeh rashed saghavaz 3
1 University professor
2 University professor of malek ashtar
3 PHD student
چکیده [English]

Aerial structures under non-conservative forces especially follower loads, may be exposed to dynamic or static instabilities. Thus, it is essential to design these structures so that it would prevent this phenomenon. In this paper, for the first time, dynamic instability of a thick sandwich beam with a flexible core under the follower force is considered using the high-order theory of sandwich beams. In the present paper, shear and normal core plate stresses are also considered, which have been ignored in higher-order sandwich panel theory and improved higher-order sandwich panel theory. The sandwich beam consists of two surfaces and a flexible core. The common surface of the core with the surfaces comprises a complete connection, capable of withstanding shear and vertical stresses. The sandwich beam is considered as a linear elastic structure with small rotations and deformations. Equations of motion of high-order sandwich beams under follower force are derived using Hamilton’s principle. The Beam fluttering phenomenon is investigated by applying boundary conditions and using a generalized differential quadrature method. in addition to the verification of results, effects of the beam’s geometry and mechanical parameters have been studied. These results revealed that the threshold flutter force of the sandwich beam is similar to Timoshenko one.
 

کلیدواژه‌ها [English]

  • Pneumatic structures
  • sandwich structures
  • Dynamic instability
  • numerical solution method
  • Flexible functional core
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