تحليل ارتعاش آزاد ورق هاي ساندويچي با هسته ي حاوي سيال ويسكوكشسان مغناطيسي با استفاده از روش نوار محدود اسپلاين

FREE VIBRATION ANALYSIS OF SANDWICH PLATES WITH THE MAGNETIC VISCOELASTIC FLUID CORE USING SPLINE FINITE STRIP METHOD

در پژوهش حاضر، يك ورق ساندويچي حاوي سيال ويسكوكشسان مغناطيسي در هسته با رويه هاي كامپوزيتي ارزيابي شده است. همچنين روابط حاكم با در نظر گرفتن درجه هاي آزادي مستقل ناشي از خمش براي لايه هاي فوقاني و زيرين هسته، بر مبناي اصل هميلتون و با استفاده از روش نوار محدود اسپلاين استخراج شده است. جهت صحت سنجي نتايج، نتايج به دست آمده با ساير پژوهش هاي مشابه، كه با روش هايي نظير المان محدود به بررسي ارتعاش آزاد ورق هاي ساندويچي پرداخته بودند، مقايسه شده است. در پژوهش حاضر، تاثير پارامترهاي گوناگون، از جمله شرايط مختلف مرزي، كه در ساير مطالعات چندان به آنها توجه نشده، ارزيابي شده است. همچنين تاثيرپذيري بسامد و ضريب استهلاك، تحت اثر عوامل مختلفي، نظير شدت ميدان مغناطيسي بررسي شده اند. نتايج بيان گر آن هستند كه روش نوار محدود اسپلاين، سرعت هم گرايي و دقت مناسبي دارد و نيز مشخص شد كه افزايش شدت ميدان مغناطيسي به افزايش بسامد و ضريب استهلاك منجر مي شود.

Sandwich plates containing magnetic fluids in the core are considered nowadays as a smart structure. Due to the ability of rapid change in the viscosity of the fluid in the core, plate can be used to control the vibration of the structure and to deplete the energy. In the present study, free vibration behavior of a sandwich plate, which is made of composite glass-epoxy fiber face sheets and contains magnetic fluid in the core, is investigated. Based on the Hamilton's principle and considering independent bending degrees of freedom for upper and lower faces, free vibration governing equations of the plate are derived using the spline finite strip method. To validate the proposed method, the results are compared with those of other similar studies using different methods. Then, the effects of different parameters, e.g., diverse boundary conditions, which are rarely considered elsewhere, are evaluated based on the proposed formulation. Moreover, the frequency impacts as well as the modal loss factor, which are the two main parameters in the vibration analysis of these structures, are considered and the effect of different factors such as magnetic field intensity and fluid thickness in the core are investigated. The results indicate that the spline finite strip method has good accuracy in analyzing sandwich plates containing a flexible core. Besides, the results show that increasing the intensity of the magnetic field causes an increase in the frequency and loss factor corresponding to each mode. Moreover, increasing the thickness of the fluid leads to increase in the loss factor and decrease in the frequency. The results indicate that despite the change in the strain energy of the structure, due to changes in the fiber orientation of the composite layers, the frequency of each mode does not change significantly. It was also found that the clamped plate had the highest frequency and the simply supported boundary condition had the lowest frequency.