Analysis of tensile mechanical properties of LNG cryogenic flexible pipe

As one of the key equipment of the floating liquefied natural gas system, LNG cryogenic flexible pipes are known as the “blood vessels”. Under extreme marine environmental conditions of wind, wave, and current, the pipes are prone to significant tensile loads, which may lead to failure and damage. Due to the complex multi-layer structure, it is quite challenging to analyze tensile mechanical properties of the cryogenic flexible pipe. Based on the structural characteristics, a fine finite element model was established and numerical simulation was carried out to analyze tensile properties. Concurrently, an experimental platform for cryogenic flexible pipe was constructed, and the tensile mechanical experiments in ambient temperature condition were conducted. Compared with the experimental results, the error of the numerical simulation was within 5%, verifying the accuracy of the finite element model in this study. On this basis, influences of structural parameters and friction coefficients on the tensile stiffness were also discussed. It revealed that the tensile stiffness increased as the cross-sectional width of the tensile armor layer increased uniformly, exhibiting a trend consistent with that of thickness yet opposite to that of angle, while the friction coefficient between layers showed negligible influence. Furthermore, considering the cryogenic environment in applications, the tensile mechanical properties of the cryogenic flexible pipe in cryogenic conditions were investigated based on finite element analysis, displaying distinct nonlinear characteristics and a significant increase in tensile stiffness. This study may serve as a reference for the design and analysis of LNG cryogenic flexible pipe. • Based on the metal thin-walled corrugated, helically wound and thick-walled cylindrical structural characteristics of the cryogenic flexible pipe, fine finite element model was established and numerical simulation was carried out to analyze the tensile mechanical properties. • Experimental platform for cryogenic flexible pipe was constructed, and the tensile mechanical experiments were conducted. Compared with the tensile stiffness of experimental results, the error of the numerical simulation was within 5%, verifying the accuracy of the finite element model in this study. • Considering the cryogenic environment inside the pipe in practical applications, the tensile mechanical properties of the cryogenic flexible pipe in cryogenic conditions were further investigated, and comparative analysis was conducted with the tensile behaviors in ambient temperature condition. • The further influences of structural parameters and friction coefficients of cryogenic flexible pipe on the tensile stiffness were discussed.