نوع مقاله : مقاله پژوهشی

نویسنده

استادیار، مهندسی مکانیک، مجتمع آموزش عالی لارستان، لار.

10.22068/jstc.2020.131419.1672

چکیده

در این پژوهش ارتعاشات آزاد پوسته‌های کامپوزیتی کامل و دارای گشودگی مستطیلی بر پایه تئوری برشی مرتبه اول مورد مطالعه قرار گرفته است. معادلات در حالت کلی به گونه‌ای نوشته شده که قابل تبدیل به هر یک از تئوری‌های دانل، لاو و یا ساندرز هستند. برای مطالعه پوسته دارای گشودگی فضای حل مسئله به گونه‌ای المان‌بندی شده که شرایط مرزی و بارگذاری در لبه‌های هر المان یکنواخت باشد. برای هر المان، معادلات حاکم، شرایط مرزی لبه‌ها و شرایط سازگاری در مرز مشترک المان‌های مجاور به کمک روش مربعات تفاضلی تعمیم‌یافته در راستای طولی و محیطی گسسته شده و با مونتاژ آنها یک دستگاه معادلات جبری تشکیل شده است. در نهایت، با استفاده از حل مقدار ویژه فرکانس طبیعی سازه محاسبه شده است. برای اعتبارسنجی این روش، نتایج حاصل از آن با نتایج موجود در مقالات و نیز نتایج نرم‌افزار المان محدود آباکوس مقایسه شده است. پس از اطمینان از کارایی روش حاضر، از آن برای مطالعه اثر پارامترهای مختلف بر رفتار ارتعاشی پوسته‌های با و بدون گشودگی استفاده شده است. این بررسی‌ها نشان می‌دهد که مستقل از جنس و لایه‌چینی پوسته، گشودگی‌های نسبتاً کوچک (c/L<0.3) تاثیر چندانی بر فرکانس طبیعی پوسته ندارند. ضمن اینکه کاهش نسبت طول به شعاع و یا افزایش ضخامت پوسته نیز در کاهش اثرات گشودگی موثر است. علاوه‌ بر این، اثر گشودگی‌های محیطی به مراتب کمتر از گشودگی‌های طولی است.

کلیدواژه‌ها

عنوان مقاله [English]

Free vibration analysis of perforated composite cylindrical shell using Generalized Differential Quadrature Method

نویسنده [English]

  • Ali Talezadehlari

Department of Mechanical Engineering, Larestan University, Lar, Iran.

چکیده [English]

In this paper, the free vibration of a composite shell with and without a rectangular cutout was studied based on the first-order shear deformation theory. The equations were derived in a general form and can be converted to Donnell`s, Love`s, and Sanders` theories. To investigate the perforated shell a physical domain was decomposed into several elements with uniform boundary and loading conditions in each element edges. In each element, the governing equations were discretized in both longitudinal and circumferential directions by the use of generalized differential quadrature method (GDQM) as well as the boundary conditions at the cutout edges, and the compatibility conditions at the interface boundaries of adjacent elements. Assembling these discretized relations, a system of algebraic equations was generated. Finally, the natural frequencies were calculated by an eigenvalue solution. To validate the presented method, the results of GDQM were compared with the available ones in the literature and also with the ABAQUS finite element model. Then a parametric analysis was performed to investigate the effects of different parameters on the vibrational behavior of the shells with and without cutouts. This study illustrated that small cutouts (c/L<0.3) had no significant effect on the natural frequency of the shell. This was independent of both shell material and layup. In addition, decreasing the length to radius ratio or increasing the shell thickness decreased the effect of cutout on natural frequency. Moreover, circumferential cutouts had less effect than longitudinal ones.

کلیدواژه‌ها [English]

  • Vibration
  • Composite Shell
  • Cutout
  • First-order Shear Deformation Theory (FSDT)
  • Generalized Differential Quadrature (GDQ)

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