Severe Thermal and Pressure Transients and the Survival of Internally Coated Tubes with Interface Defects

Abstract

The effects of severe thermal and pressure transient pulses on the interior of coated tubes with known defects (cracks and blisters) have been analyzed using finite-element methods. For the modeling, both axisymmetric and three-dimensional (3-D) meshes were developed and used to assess the transient thermal- and stress-states and the propensity for fracture related damage. For all calculations, temperature dependent thermophysical and elastic properties were used during the analysis. The model also utilized uniform heating and pressure across the ID surface imposed via convective coefficients and a piece-wise linear pressure function. Results indicated that both had a significant influence on the maximum circumferential (hoop) stresses and temperatures and that the compressive thermal stresses help to offset the tensile stresses generated by the pressure. Calculations also looked into the influence of these factors when a cracks and/or blister defect was introduced at the interface of the coating and substrate with and without pressure.