3D MODELLING AND STRUCTURAL ANALYSIS OF AN UNMANNED UNDERWATER VEHICLE: UNSTIFFENED AND FLAT RING STIFFENED STRUCTURE CONFIGURATION

The structural integrity of unmanned underwater vehicle (UUV) hulls under high external hydrostatic pressure is paramount for reliable deep-sea operations. This study presents a comprehensive finite element analysis (FEA) evaluating the performance of unstiffened versus flat ring stiffened hull configurations. Three-dimensional models were developed and analyzed using ANSYS to investigate critical parameters including stress distribution, deformation characteristics, and buckling stability. Aluminium Alloy AA7068 was selected as the structural material owing to its superior strength-to-weight ratio and compatibility with marine environments. Additionally, the effects of Retrogression and Re-Aging (RRA) heat treatment on corrosion resistance and overall durability were incorporated into the analysis. Results demonstrate that the incorporation of flat ring stiffeners significantly enhances the structural response when compared to unstiffened hulls, primarily by mitigating deformation and increasing load-bearing capacity. Nonetheless, localized stress concentrations were identified near stiffener junctions, indicating potential areas for further design optimization. The numerical findings exhibit strong correlation with analytical estimations, thereby validating the employed modeling approach. This investigation confirms that flat ring stiffening offers a practical and efficient method to improve the structural performance of UUV hulls while preserving design simplicity, thereby supporting their application in demanding underwater environments.