Defect evolution in coated tubes under severe thermal transients applied to the ID

The effects of severe thermal-transients on coated substrates with indentation-induced, blister type defects were analyzed using finite-element methods. Both explicit and implicit approaches were used depending on the timeframe under scrutiny. For the modeling, an axisymmetric mesh and cohesive zone elements was used to assess the transient thermal - And stress-states and the propensity for fracture related damage and evolution. For all calculations (and when available), temperature dependent thermophysical and elastic properties were used during the analysis. The model also utilized uniform heating across the surface imposed via convective coefficients and a piece-wise linear pressure function. Preliminary results indicated complex interactions between the boundary conditions and their timing and the resulting propensity for damage evolution. Given the need for robust coatings, the modeling procedures developed during this study will have important ramifications for coated tube designs and the evaluation of candidate materials.