José David Arregui-Mena

Multi-scale CAFE Framework for Simulating Fracture in Heterogeneous Materials Implemented in Fortran Co-arrays and MPI

Fortran coarrays have been used as an extension to the standard for over 20 years, mostly on Cray systems. Their appeal to users increased substantially when they were standardised in 2010. In this work we show that coarrays offer simple and intuitive data structures for 3D cellular automata (CA) modelling of material microstructures. We show how coarrays can be used together with an MPI finite element (FE) library to create a two-way concurrent hierarchical and scalable multi-scale CAFE deformation and fracture framework. Design of a coarray cellular automata microstructure evolution library CGPACK is described. A highly portable MPI FE library ParaFEM was used in this work. We show that independently CGPACK and ParaFEM programs can scale up well into tens of thousands of cores. Strong scaling of a hybrid ParaFEM/CGPACK MPI/coarray multi-scale framework was measured on an important solid mechanics practical example of a fracture of a steel round bar under tension. That program did not scale beyond 7 thousand cores. Excessive synchronisation might be one contributing factor to relatively poor scaling. Therefore we conclude with a comparative analysis of synchronisation requirements in MPI and coarray programs. Specific challenges of synchronising a coarray library are discussed.

Use of massively parallel computing to improve modelling accuracy within the nuclear sector

The extreme environments found within the nuclear sector impose large safety factors on modelling analyses to ensure components operate in their desired manner. Improving analysis accuracy has clear value of increasing the design space that could lead to greater efficiency and reliability. Novel materials for new reactor designs often exhibit non-linear behaviour; additionally material properties evolve due to in-service damage a combination that is difficult to model accurately. To better describe these complex behaviours a range of modelling techniques previously under-pursued due to computational expense are being developed. This work presents recent advancements in three techniques: Uncertainty quantification (UQ); Cellular automata finite element (CAFE); Image based finite element methods (IBFEM). Case studies are presented demonstrating their suitability for use in nuclear engineering made possible by advancements in parallel computing hardware that is projected to be available for industry within the next decade costing of the order of

Practical Application of the Stochastic Finite Element Method

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