DIC for multi-scale model validation and structural integrity for fusion A. Harte1,∗, R. Spencer1, B. Poole1, D. Lunt1,2, C. Hardie1, C. Hamelin1 1 United Kingdom Atomic Energy Authority, United Kingdom 2 School of Materials, University of Manchester, M13 9PL, United Kingdom ∗ allan.harte@ukaea.uk Keywords: Ductile failure, Multi-scale, Irradiation, Digital image correlation, Simulation. Realising commercial power from nuclear fusion presents significant structural integrity challenges. Creep and ductile failure models are needed to ensure that fusion components are designed against plastic collapse, capturing both early plastic flow and strainto- failure as a function of stress triaxiality. Traditional notched bar experiments ignore triaxial stress state evolution throughout the test and result in design over-conservatism. Models require experimental validation within a multi-physics parameter space - time, thermal-, mechanicaland irradiation loadings - but representative combined loads are impossible to establish experimentally ahead of plant build. Hence, microstructurally informed predictive models are needed. Here we present a case study on a ferritic-martensitic steel that uses finite element (FE) simulation validated with full-field digital image correlation (DIC) to approach both problems. FE simulation can be used iteratively as an inverse tool to determine the constitutive behaviour of a material given the surface strain fields measured using optical DIC. We present solutions to the problem of global vs local matching and the need for full uncertainty quantification in reaching acceptable experimental-simulation comparison cost functions. We determine true stress – true strain constitutive laws for large strains in the neck to ductile failure by incorporating strain rate effects and appropriately capturing evolving triaxial stress states. Further, we leverage the DIC and FE-updating framework to enable complex specimen geometry testing, e.g., multiple stress triaxialities within a single specimen, a philosophy coined Material Testing 2.0 [1]. This reduces the number of tests needed for model validation. Under thermal-mechanical loading, irradiation causes a ductile-to-brittle transition [2]. Bulk neutron damage can be emulated by surface ion irradiation, but the aforementioned approach to model validation in bulk material is unsuitable because only DIC-FE comparisons in the ion irradiated surface layer are valid. We use microstructural-scale DIC to determine fundamental deformation mechanisms in the steel under tension and ion irradiation. These data are used to validate crystal plasticity FE simulations of deformation in the combined thermal-mechanicalirradiation environment and predictions of behaviour in untestable neutron environments. References [1] Pierron, F. & Grédiac, M. (2021). Towards Material Testing 2.0. A review of test design foridentification of constitutive parameters from full-field measurements. Strain, 57, 1-22. [2] Schaaf, B. van der et al. (2009). High dose, up to 80 dpa, mechanical properties of Eurofer 60
RkJQdWJsaXNoZXIy MjM0NDE=