Predicting creep failure time of thick-walled spherical vessels considering large strains

In this paper, the problem of predicting creep-failure time of thick-walled spherical vessels is investigated. Thick-walled spherical vessels are important structural components that are used in many industries such as oil, chemical, nuclear, and others. These industries are required to operate under complex thermal and mechanical loadings where creep deformation is prevalent. The fact that continuing deformation under creep may reach a value where the assumption of small strains becomes increasingly invalid has been incorporated by using a finite-strain formulation in the mathematical framework developed to perform the creep-failure prediction times of the vessels. The mathematical analysis is conducted by employing the equilibrium, compatibility, and constitutive equations for the finite (logarithmic) strain theory together with suitable boundary conditions. The creep-failure time prediction relation is developed and solved using analytical and/or numerical methods. Parametric studies for various wall thickness ratios, creep-law exponents and pressure magnitudes are performed and presented in the form of graphs. It is expected that this investigation, employing a combination of mathematics and nonlinear mechanics, will provide useful guidelines for predicting more accurate creep-failure time and may thus lead to a safer design of thick-walled spherical vessels.