محمد فدائي قرق اقائي

The topic of improving the performance of submerged structures under shock loading has a long-standing history in the literature of underwater acoustics. The main objective of the present thesis is to investigate the resistance of conventional submerged composite cylindrical shells to shock loading and to compare their primary resistance parameters with each other. For this purpose, the powerful and flexible commercial software Abaqus has been employed to numerically solve the stated problems. In this context, numerical simulations were conducted for four different configurations: a single-layer submerged cylindrical shell, a sandwich panel with a metallic foam core, a sandwich cylindrical shell with a fluid core, and a sandwich cylindrical shell with a metallic foam core. The resistance performance of these configurations was eva‎luated and discussed based on key energy absorption parameters. To this end, the effects of varying parameters such as the porosity percentage and the thickness of the foam core on the energy absorption of the sandwich shell were studied. Specifically, it was observed that when foam is used instead of fluid as the core material, the energy absorption capacity improves by approximately 30%. Additionally, a maximum increase of up to two and a half times in foam thickness was shown to enhance energy absorption, while further increases beyond this point have a negligible effect on shock energy absorption. Moreover, the porosity percentage of the foam has a significant nonlinear effect on the energy absorption resulting from the explosion. Finally, it is suggested that for enhanced performance, more complex composite configurations should be explored, such as the simultaneous use of stiffening belts, sandwich structures with smart polymer cores, honeycomb materials, or shear-thickening fluids.

تحليل گذراي برهمكنش سازه و سيال , ، شوك ميدان نزديك زير آب , سازه هاي ساندويچي ضد شوك , هسته فوم جاذب , شبيه سازي المان محدود

Transient analysis of fluid-structure interaction , underwater near-field shock , shock-resistant sandwich structures , energy-absorbing foam core , finite element simulation

Mohamad Fadaei ghorogh aghaei

Dr.Mohamad Hashemi nejad