Abstract:
Austenitic stainless steel is the preferred material for permanent components of
sodium-cooled fast breeder reactors due to its high-temperature tensile and creep
strength, compatibility with liquid sodium, ease of fabrication, and weldability. Type
SS316LN containing 0.02–0.03 wt.% carbon and 0.06–0.08 wt.% nitrogen is designated as
SS316LN. The metallic materials exhibit time-dependent deformation in high-temperature
applications of fast breeder reactors (FBR), such as primary and secondary piping, heat
exchangers, and the main vessel. To ensure the structural integrity of these components, it
is important to understand the crack behavior and the resistance offered by the materials
used in these components. In creep conditions, conventionally, C* and Ct parameter are
used for characterizing the crack tip. However, the true crack driving force or its rate
cannot be described by any of the conventional parameters. The theoretical validity of
conventional crack tip-characterizing parameters like Ct and J is also restricted, making it
hard to anticipate underlying cracks driving forces. To investigate the creep crack growth
behavior of this material, an experimental and numerical analysis of SS316LN is performed
with different constraint conditions.
This study explores the influence of in-plane constraint on the creep crack behavior
of a SS316LN with 0.07% nitrogen under stationary and growing cracks through
experimental and numerical approaches. To examine constraint Q parameter is calculated
to characterize the in-plane constraint, while the C∗ parameter is used to analyze
creep deformation and fracture behavior. Comprehensive experimental tests and finite
element simulations provide insights into the interaction between in-plane constraints and
crack-tip stress fields. The results enhance the understanding of constraint effects in
stationary crack scenarios, contributing to the development of improved methodologies for
high-temperature failure assessments and life prediction of structural components made
of SS316LN.
