Fatigue, Repair, and Advanced Modeling in Petrochemical Infrastructure

This study critically assesses the limitations of conventional Tungsten Inert Gas (TIG) thermal repair for fatigue-cracked carbon steel nozzle junctions in petrochemical infrastructure. Advanced coupled thermomechanical fracture mechanics simulations reveal that TIG welding induces tensile residual stresses exceeding 300 MPa and embeds refractory tungsten inclusions, which amplify local stresses by over 45% and nucleate cracks, curtailing repaired service life to under 5.1 years-versus a 20-year baseline. In contrast, an externally bonded Carbon Fiber Reinforced Polymer (CFRP-Epoxy) patch restores ~50% of baseline structural capacity by bridging the flaw and redistributing loads, without thermal degradation. We introduce and validate a hybrid repair protocol: initial TIG sealing followed by CFRP reinforcement. This synergistically mitigates thermal drawbacks, yielding a ~75% service life extension while enhancing corrosion resistance. These findings redefine fatigue repair paradigms, offering predictive maintenance strategies for high-value energy assets.