Characterization of cyclic visco-plastic behavior, damage and failure in high temperature weldments via an inverse method

High-temperature fatigue failures often occur in the heat-affected zone of welded joints, threatening the integrity of high-temperature piping components under flexible operation. This study presents an experimental–numerical framework for determining cyclic visco-plastic and damage properties, including the parent metal, weld metal, and heat-affected zone. A unified visco-plastic damage constitutive model is developed, coupled with high-temperature low cycle fatigue test for each of the constituents in the weldment. An analytical inverse approach is formulated to optimize the visco-plastic and damage properties of the parent metal and weld metal using high temperature uniaxial low-cycle fatigue tests data, while an FE-based inverse method is used to optimize HAZ properties via cross-weld fatigue test simulation. The framework is validated using cyclic test data from a P91 weldment, demonstrating the effectiveness of the FE-based inverse approach in characterizing full-life cyclic behavior and fatigue failure of the weldments.