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This paper discusses the issues involved in the development of combined finite/discrete element methods; both from a fundamental theoretical viewpoint and some related algorithmic considerations essential for the efficient numerical solution of large scale industrial problems. The finite element representation of the solid region is combined with progressive fracturing, which leads to the formation of discrete elements, which may be composed of one or more deformable finite elements. The applicability of the approach is demonstrated by the solution of a range of examples relevant to various industrial sections.

Large-scale discrete element simulations, combined ÿnite-discrete element simulations as well as a whole range of related problems, involve a large number of separate bodies that interact with each other and in general deform and fracture. In this context there is a need for a robust fracture algorithm applicable to simultaneous multiple fracturing of large numbers of bodies.In this work a fracture model for both initiation and propagation of mode I loaded cracks in concrete in the context of the combined ÿnite-discrete element method is reported. The algorithm is based on accurate approximation of experimental stress-strain curves for concrete in tension.

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SUMMARYDiscontinua simulations are becoming an important part of Computational Mechanics to the extent that Computational Mechanics of Discontinua is becoming a separate subdiscipline of Computational Mechanics. Among the most widely used methods of Computational Mechanics of Discontinua are Discrete Element Methods, Molecular Dynamics Methods, Combined Finite-Discrete Element Methods, DDA, Manifold Methods, etc. The common feature of all these methods is time discretization of the governing equations and the resulting mostly explicit time integration schemes. A wide range of time integration schemes is available in the literature. In this paper a comparative study of some of the most commonly used explicit time integration schemes is made in terms of accuracy, stability and CPU efficiency. The study has been performed using numerical experiments based on a one degree of freedom mass-spring system. The results are presented as charts that can be used when deciding which scheme to use for a particular discontinua problem.

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Heat transfer from nanoparticles to a surrounding liquid pool is an essential process for many applications. This work investigates the heat transfer process upon a continuous wave laser heating to a gold nanoparticle (GNP) in a water pool through molecular dynamics (MD) simulations based on realistic potentials. The interactions among gold atoms are described by the embedded atom method (EAM) potentials, both the rigid and flexible TIP3P water models are examined, and a modified Lennard-Jones potential is used for the interaction between the GNP and water. The results show that the interfacial thermal conductance is influenced by the selection of different water models and the interfacial wettability. The interfacial thermal conductance is smaller but increases slightly with the increase of heat flux for the flexible water model, while it keeps almost constant for the rigid model. Increasing the wettability between the particle and the fluid reduces the interfacial resistance. The rise of the interfacial water temperature is limited, due to the constraint of the boundary conditions, and no phase change in the water near the GNP is observed in the current simulation.