CYCLIC PLASTICITY AND FATIGUE-RATCHETING BEHAVIOUR OF SS304LN STAINLESS STEEL MATERIAL

摘要

The integrity assessment of the primary piping components needs to be demonstrated under cyclic loadings, during the normal operation and the design basis accidents such as earthquake event. In order to understand material's cyclic plasticity and failure behaviour, systematic experimental investigations on specimens and components have been carried on SS 304LN stainless steel material. The material specifications of this steel are same as proposed for Indian Advance Heavy Water Reactor (AHWR) Main Heat Transport (MHT) piping. The tensile and axial fatigue tests are conducted to establish the material's mechanical properties, low cycle fatigue and cyclic plasticity behaviour. Further to understand fatigue- ratcheting behaviour, a series of uniaxial ratcheting tests on specimens and fatigue-ratcheting tests on pressurized component, that is, elbow are carried out. Various cyclic plasticity models such as multiaxial kinematic hardening and Chaboche model are evaluated using tests data. Modifications have been proposed in the Chaboche model and modified model is able to simulate the cyclic plasticity response that is LCF and ratcheting behaviour for all the loading ranges considered. Effect of thickness variation on global and local response of elbow is analyzed. The test results, their analyses, interpretations and the finite element simulations have been presented in this paper.