A numerical model to simulate ductile tearing-creep crack growth interaction

Ductile tearing and creep crack growth are generally treated independently but there are situations in which they can occur simultaneously. First, creep crack growth calculations in components are often continued to large defect sizes in order to determine when limiting conditions for short-term fracture are reached. Secondly, in order to obtain data in reasonable timescales, experimental creep crack growth tests are often performed at high loads such that plasticity occurs in the tests, particularly as the crack grows to larger sizes. This paper presents a numerical model to simulate the interaction of ductile tearing and creep crack growth to address such cases. A strain-based damage model is introduced with total damage assumed to be the linear summation of creep and plastic damage. The model is applied to Type 316H stainless steel at 550 degrees C with the parameters in the damage model determined from tensile, creep and fracture toughness test data. Predictions using the proposed model are then compared with notched creep tensile and creep crack growth test results and shown to be in good agreement with experimental measurements of creep deformation and crack growth.