بروز رسانی و تحلیل مدل ارتعاشاتی دو پوسته استوانه‌ای فلنج‌شده پیچی با روش تجربی- نیمه تحلیلی

In this study, the vibrations of a bolted double cylindrical–cylindrical flanged shell structure are investigated. The bolted joints cause changes in the stiffness and vibrational properties of the flanges, and therefore, the natural frequencies of the assembled system undergo significant variations compared to when the flanges are assumed to be perfectly integrated. For this reason, developing appropriate modeling approaches and updating the model using experimental modal test results can greatly aid the design process. In this research, in addition to simulating the bolted joints using finite element software, semi-analytical models based on three-dimensional elasticity theory are presented to enable detailed structural modeling. In this model, between each pair of corresponding grid points (defined using the generalized differential quadrature method) located on the mating flange surfaces, a set of artificial linear springs is placed, consisting of springs in the longitudinal, circumferential, and radial directions. After performing the model updating using a genetic optimization algorithm, it was found that the structural frequencies in the proposed models show strong agreement with the experimental results for the flanged shell in the bonded condition. It is noteworthy that several structural configurations are examined here based on a method that divides the main structure into several shells and then assembles them by directly enforcing displacement and stress continuity. These configurations include stepped, ringed, and perforated shells. The results indicate that employing artificial spring models at the joint interfaces effectively captures the vibrational behavior of bolted flanged cylindrical shells and provides satisfactory accuracy.