Structural Design and Failure analysis of a polymeric pressure vessel with Non-Uniform Wall Thickness

This study presents a comprehensive three-dimensional finite element failure analysis investigating the structural performance of polymeric pressure vessels with optimized, non-uniform wall thickness distributions. The primary objective was to reduce the generated stresses and deformation under operational conditions by varying the thickness of the cylindrical section. Five distinct model configurations, including a uniform 10 mm thickness (designated 1t) and four non-uniform models (designated 1.25t, 1.5t, 1.75t, and 2t), were rigorously analysed using ANSYS 2021. Case 1 (1t model) is for a polypropylene vessel. It is subjected to an internal pressure of 1 MPa. A meticulous mesh convergence analysis ensured solution accuracy, as well as confirming a linear relationship between Von Mises stresses and applied internal pressure. Results consistently demonstrated that increasing the thickness of the cylindrical section at its centre significantly reduces the stress values. For example, the '2t' model exhibited a remarkable 55% reduction in maximum Von Mises stress on the outer surface at the mid-length of the cylindrical part, and 47.7% at the inner surface, showcasing enhanced surface area distribution capacity and improved structural integrity. Attention was also given to critical mating points between the cylindrical and dome sections (Peak points). Additionally, an extra case was implemented to reduce the high stress values near the opening hose at the inner surface by thickening the critical area by 2 mm, resulting in a dramatic decrease of almost 30%, which demonstrates the high capability of varying the thickness at the desired spots. This work highlights the effectiveness of targeted geometric modifications in enhancing polymeric pressure vessel design, presenting a promising approach to creating robust, lightweight vessels that can safely withstand higher operating pressures without necessitating a uniform increase in overall wall thickness.