Creep Fatigue Damage Assessment of the Welded Structures of High-Temperature Pressure Equipment Based on DIC Technology

In recent years, pressure equipment tends to operate under higher temperature and higher pressure with the rapid development of world economy, resulting in greater significance of creep fatigue damage that is strongly temperature and time dependent. This brings new challenges to the design, manufacturing, operation and maintenance management of the high-temperature pressure equipment. The welded structure of high-temperature pressure equipment exhibits heterogenous microstructures with mismatched mechanical properties, as well as the unavoidable weld defects. Damage characterization, life design and failure assessment of welded structures have always been challenging difficulties. Hence, the welded structure is the weakest link for creep fatigue failure. The present paper introduces the research progress on creep fatigue damage assessment method for the welded structures of high-temperature pressure equipment in China, based on the digital image correlation (DIC) technology and the ductility exhaustion theory. It involves in-situ characterization of heterogenous creep deformation of welded joints by using the digital image correlation technology, creep damage assessment of welded structures by finite element modeling, evaluation of strain enhancement effect and life-based creep fatigue strength design of high-temperature welded structures, etc. This method can provide useful guidance for establishing the prevention and control schemes for creep fatigue damage of high-temperature welded structures.