Nonlinear isogeometric formulation for coupled thermo-mechanical behavior of multilayer cylindrical shell junctions

This paper presents a novel nonlinear isogeometric formulation for analyzing the coupled thermo-mechanical behavior of multilayer cylindrical shell junctions. The proposed framework integrates non-uniform rational B-splines (NURBS) basis functions with higher-order shell kinematics to achieve exact geometric representation and superior solution accuracy. The mathematical formulation accounts for geometric nonlinearities through the von Kármán strain-displacement relations, while the thermo-mechanical coupling is incorporated via temperature-dependent material properties and thermal expansion effects. The governing equations are derived from the principle of virtual work, incorporating through-thickness temperature gradients and nonlinear heat conduction. A consistent linearization procedure enables efficient Newton-Raphson iterative solution of the resulting nonlinear algebraic system. The formulation captures complex junction effects including stress concentrations, thermal gradients across interfaces, and nonlinear interaction between cylindrical shells of varying radii and thicknesses. Numerical results demonstrate the influence of junction geometry, temperature distribution, and layup configuration on the nonlinear response, highlighting the importance of accurate junction modeling for structural integrity assessment. The developed framework provides a powerful tool for analyzing shell structures with complex geometries and loading conditions, with direct applications in aerospace, nuclear, and pressure vessel engineering.