Nonlinear Thermo-Mechanical Stress Analysis of Thin-Wall Large-Bore Piping Systems Considering Ovalization and Buckling

Abstract

Thin-wall large-bore piping systems with a high diameter-to-thickness ratio (D/t > 100) are increasingly used in advanced industrial applications; however, their structural integrity is significantly affected by geometric instability, ovalization, buckling, and thermal loading effects. Conventional stress analysis approaches often underestimate these nonlinear behaviors, leading to inaccurate predictions of deformation and failure limits. An advanced framework for thermo-mechanical stress analysis of the stability and reliability evaluation of thin-wall piping systems in combined loading is proposed in this study. A class of methods designed to solve the problem through finite elements and nonlinear analysis is developed by considering all the geometric, material, pressure loading, bending effects, and thermal stress effects due to temperature changes in pipes. This proposed approach includes cross-sectional ovalization, critical buckling, and stress redistribution under different operating conditions. It is clearly seen that ovalization has a very negative effect on structural stiffness, while the thermal loads introduce additional regions of stress concentration. The proposed framework has potential for enhanced prediction accuracy of the structural performance as well as useful lessons for safer design, optimization, and integrity assessment of high D/t piping systems.