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The numerical analysis, based on the finite element modeling (FEM), presents nowadays an efficient computational tool. It allows a better understanding of several thermo-mechanical phenomena involved during the machining process. However, its reliability heavily depends on the accurate definition of the numerical model. In this regard, a FE analysis focused on the 2D modeling of the Ti6Al4V dry orthogonal machining was carried out in this study. The relevance of different numerical meshing approaches and finite elements topologies was studied. The effect of the friction coefficient on the numerical chip morphology, its geometry, the cutting and the feed forces was investigated. The adequacy of several compared adaptive meshing approaches, in terms of the modeling of severe contact conditions taking place around the cutting-edge radius, was underlined in the current study. However, numerical serrated chips, closer to the experimental ones, were only predicted when the pure Lagrangian formulation was adopted and a proper determination of the failure energy was carried out. The definition of different mesh topologies highlighted the efficiency of the 4-node quadrangular mesh, with a suitable edge length, in increasing the agreement with the experimental data, while reducing the computing times. [ABSTRACT FROM AUTHOR]

The dynamics of a single droplet under shear flow between two parallel plates is investigated by using the immersed boundary method. The immersed boundary method is appropriate for simulating the drop-ambient fluid interface. We apply a volume-conserving method using the normal vector of the surface to prevent mass loss of the droplet. In addition, we present a surface remeshing algorithm to cope with the distortion of droplet interface points caused by the shear flow. This mesh quality improvement in conjunction with the volume-conserving algorithm is particularly essential and critical for long time evolutions. We study the effect of wall confinement on the droplet dynamics. Numerical simulations show good agreement with previous experimental results and theoretical models. [ABSTRACT FROM AUTHOR]

In this study, we present an experimental/numerical methodology, which aims to improve 3D thin sheet hydroforming considering coupled constitutive equations formulated in the framework of the thermodynamics of irreversible processes accounting for isotropic hardening as well as isotropic ductile damage. The experimental study is dedicated to the identification of stress-strain flow from the global measure of pole displacement, thickness evolution, and internal pressure expansion. During the hydroforming processes severe mesh distortion of element occurs and an automatic remeshing generation is essential to carry out the FEA. Some examples are given to demonstrate the efficiency of the proposed methodology. [ABSTRACT FROM AUTHOR]

The target is to develop computational techniques for studying aerodynamic interactions between multiple objects with emphasis on studying the fluid mechanics and dynamics of an object exiting and separating from an aircraft. In these cases, the computational challenge is to predict the dynamic behaviour and path of the object, so that the separation process is safe and effective. This is a very complex problem because it has an unsteady, three-dimensional nature and requires the solution of complex equations that govern the fluid dynamics of the object and the aircraft together, with their relative positions changing in time. The gravitational and aerodynamic forces acting on the object determine its dynamics and path. The computational tools developed are based on the simultaneous solution of the time-dependent Navier-Stokes equations governing the airflow around the aircraft and the separating object, as well as the equations governing the motion of that object. These computational methods must include suitable mesh update techniques. In the research presented, focus is given to development of mesh update methods to increase the numerical accuracy and efficiency of the computations. These methods range from update tactics, reducing distortion and methods reducing the error introduced through projection. [ABSTRACT FROM AUTHOR]

Procedures for synthesizing digital polycrystalline microstructures are illustrated, from either 2D statistical data or 3D deterministic data. Finite element meshes representing the digital microstructures are generated using anisotropic and adaptive mesh refinement close to the grain boundaries. Digital mechanical testing based on crystal plasticity theory provides an estimate of the spatial distribution of strain energy within the polycrystalline aggregate. The latter quantity is used as an input for modelling subsequent static recrystallization, grain boundary motion being described within a level set framework. The kinetic law for interface motion accounts for both the stored strain energy and the grain boundary energy. The possibility to include nucleation events within the level set framework is illustrated, as well as the evolving topology of the grain boundary network. The recrystallization model is tested in different configurations and compared to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. [ABSTRACT FROM AUTHOR]

A fluid-structure interaction (FSI) model for heart valve simulation is presented. In a partitioned framework, separate fluid and structure solvers are weakly coupled, which in combination with the use of artificial compressibility in the fluid solver, leads to a stable and efficient approach. An Arbitrary Lagrangian Eulerian formulation is employed in the fluid solver to permit the accurate calculation of shear stresses next to the valve boundary. The mesh quality is maintained through a combination of smoothing and local remeshing in 3D. The FSI algorithm is validated on experiments of an idealised quasi-2D mechanical heart valve, and the efficiency of the remeshing approach is demonstrated on a realistic 3D heart-valve geometry. [ABSTRACT FROM AUTHOR]