No abstract

In the systems of fuel cell (FC) and nuclear safety (NS) components many liners of ultra-high pressure tanks and pipes are directly exposed to hydrogen. Austenitic stainless steels are used as material for FC and NS components because of their high resistance to hydrogen intrusion. It is reported that hydrogen degrades mechanical properties of metals significantly. In the hydrogen-charged specimen of SUS 304, a desired model would be able to capture the mechanisms found in experimental testing like large strain elasticity, rate dependence, amplitude dependence, creep and damage. Thus, a prediction of material failure/fracture, including its behavior at large plastic deformations is of importance. To validate existing failure models, the finite element (FE) simulations are used in terms of dependence on length scale and strain state. Restrictions made the selection limited to, in Abaqus, already existing models. Axisymmetric simulations are performed in Abaqus to verify the material model required in order to capture the necking phenomenon in tensile testing. The elasto-plastic modeling in the FE simulations is directed ultimately to initiation and propagation of tension processes. Furthermore, numerical simulation results using the sub-models of crack-tip meshes are discussed. In our experiments, the tensile test system MTS at a crosshead speed of 1 mm/s are conducted, which enabled accurate monitoring of displacements on the specimen surfaces. When a material reached the limit of its capacity to carry further loading, deformations localize into necking and became highly dependent on the length over which the strain evaluation is performed the length scale.