Quantitative Evaluation of Irradiated Ductility Degradation Using the Indentation Technique Combined with Numerical Experiments.

The ductile properties of irradiated materials are among of the important indicators related to their structural integrity. These properties are generally determined by performing tensile tests on irradiated materials in the irradiation environment. Indentation tests are used for evaluating ductile properties easily and rapidly. Constants in the Swift-type material constitutive equation were identified via inverse analysis using the Kalman filter, such that the numerical experimental results reproduced the indentation test results. Numerical tensile experiments were conducted using stress-strain curves with the identified constants to obtain nominal stress and strain curves. The identified yield stress, work hardening coefficient, and exponent were 200-1000 MPa, 1100-1500 Ma, and 0.5-0.7, respectively. Furthermore, two methods were proposed for evaluating the total elongation. Method I was used to calculate the total elongation based on the relationship between the total and uniform elongations obtained from the tensile tests performed on irradiated materials. Method II was used to determine the total elongation from the ductile failure criterion based on the relationship between the stress and strain states in the tensile specimen model using the numerical tensile experiment and failure strain evaluated from actual tensile experiments. Evaluated minimum total elongation was 10%. The evaluation results for ion-irradiated materials were similar to the tensile test results for irradiated materials.