Thermo-mechanical behavior of cylindrical pressure vessels made of functionally graded austenitic/ferritic steels

• Thermo-mechanical analysis of functionally graded steel (FGS) pressure vessels.
• Graded ferrite and austenite, bainite and martensite phases.
• Introducing a hybrid Fourier series expansion–Galerkin finite element approach.
• Benchmark results on displacement, stress and temperature fields of FGS cylinders.
• Insights into the influence of arrangement of material compositions of FGSs.

An axisymmetric thermo-mechanical analysis of functionally graded steel (FGS) cylindrical pressure vessels with finite length in thermal environments under internal pressure is addressed. FGSs containing graded ferritic and austenitic regions together with bainite and martensite intermediate layers are analyzed. Based on the two-dimensional theory of thermo-elasticity, the governing equations of equilibrium and steady-state heat transfer equation are derived. Two solution techniques including a hybrid Fourier series expansion–Galerkin finite element approach and a fully finite element method based on the Ritz approach are introduced to solve the governing equations of equilibrium. Two different arrangements of material compositions of FGSs including graded austenite/martensite/graded austenite and graded ferrite/bainite/graded austenite are considered. Thermo-mechanical material properties of FGS composites are predicted according to microhardness profiles of FGS composites and are approximated by suitable functions. Numerical results are presented to provide an insight into the influence of arrangements of material compositions of FGSs on the axisymmetric displacement, stress and temperature fields of FGS cylindrical pressure vessels in thermal environments under internal pressure. Due to lack of data on the thermo-elastic analysis of FGS structures, the results of this research are expected to contribute to a better understanding of the FGS behavior and to be instrumental toward a reliable design of FGS cylindrical pressure vessels under thermo-mechanical loadings.