ADVANCED CYCLIC PLASTICITY MODELS IN SIMULATING RATCHETING RESPONSES OF STRAIGHT AND ELBOW PIPING COMPONENTS, AND NOTCHED PLATES

摘要

Ratcheting is defined as the accumulation of strain or deformation in structures under cyclic loading. Damage accumulation due to ratcheting can cause failure of structures through fatigue cracks or plastic collapse. Ratcheting damage accumulation in structures may occur under repeated reversals of loading induced by earthquakes, extreme weather conditions, and mechanical and thermal operating conditions. A major challenge in structural and solid mechanics is the prediction of ratcheting responses of structures under any or combination of these loading conditions. Accurate prediction of ratcheting-fatigue and ratcheting-collapse is imperative in order to incorporate the ratcheting related failures into the ASME design Code in a rational manner. This would require predictions of both local (stress-strain) and global (load-deflection) responses simultaneously. In progressing towards this direction, a set of experimental ratcheting responses for straight and elbow piping components and notched plates is developed. Advanced cyclic plasticity models, such as, modified Chaboche, Ohno-Wang, and AbdelKarim-Ohno models, are implemented in ANSYS for simulation of these experimental responses. Various integration schemes for implementing the constitutive models into the structural analysis code ANSYS are studied. Results from the experimental and analytical studies are presented and discussed in order to demonstrate the current state of simulation modeling of structural ratcheting.