1,721,112 research outputs found
Finite Element Quadrature of Regularized Discontinuous and Singular Level Set Functions in 3D Problems
Full text linkRegularized Heaviside and Dirac delta function are used in several fields of computational physics and mechanics. Hence the issue of the quadrature of integrals of discontinuous and singular functions arises. In order to avoid ad-hoc quadrature procedures, regularization of the discontinuous and the singular fields is often carried out. In particular, weight functions of the signed distance with respect to the discontinuity interface are exploited. Tornberg and Engquist (Journal of Scientific Computing, 2003,19: 527-552) proved that the use of compact support weight function is not suitable because it leads to errors that do not vanish for decreasing mesh size. They proposed the adoption of non-compact support weight functions. In the present contribution, the relationship between the Fourier transform of the weight functions and the accuracy of the regularization procedure is exploited. The proposed regularized approach was implemented in the eXtended Finite Element Method. As a three-dimensional example, we study a slender solid characterized by an inclined interface across which the displacement is discontinuous. The accuracy is evaluated for varying position of the discontinuity interfaces with respect to the underlying mesh. A procedure for the choice of the regularization parameters is propose
Trattato di diritto costituzionale, a cura di M. Benvenuti e R. Bifulco, vol. V
No full textTrattato di diritto costituzionale, a cura di M. Benvenuti e R. Bifulco, vol.
A Regularized XFEM framework for continuous discontinuous displacement
No full textA numerical strategy for modelling both diffuse and localized cracking in elastodamaging continua is proposed. The approach is based on the REgularized eXtended Finite Element Method (REXFEM), which has been presented in [1] [2] for assigned interfaces of elastic and cohesive type. Here, the crack development and propagation and the determination of the discontinuity path within the strain localization band are considered. The potential of the approach is that a regularization length is introduced, which can be both larger and smaller than the representative size of the finite element, while all variables remain local. © CIMNE
Advances in Discretization Methods - Discontinuities, Virtual Elements, Fictitious Domain Methods
No full textThis book gathers selected contributions on emerging research work presented at the International Conference eXtended Discretization MethodS (X-DMS), held in Ferrara in September 2015. It highlights the most relevant advances made at the international level in the context of expanding classical discretization methods, like finite elements, to the numerical analysis of a variety of physical problems. The improvements are intended to achieve higher computational efficiency and to account for special features of the solution directly in the approximation space and/or in the discretization procedure. The methods described include, among others, partition of unity methods (meshfree, XFEM, GFEM), virtual element methods, fictitious domain methods, and special techniques for static and evolving interfaces. The uniting feature of all contributions is the direct link between computational methodologies and their application to different engineering areas
A FAST FEM ALGORITHM FOR NON-LOCAL INTEGRAL MODELS
No full textThe Fast Gauss Transform (FGT) is applied to non-local finite element models of integral type (FEFGT) for problems requiring fine geometry discretization, as in the case of solutions that exhibit high gradients or boundary layers
A mesh-independent framework for crack tracking in elastodamaging materials through the regularized extended finite element method
No full textWe propose a formulation for tracking general crack paths in elastodamaging materials without mesh adaptivity and broadening of the damage band. The idea is to treat in a unified way both the damaging process and the development of displacement discontinuities by means of the regularized finite element method. With respect to previous authors’ contributions, a novel damage evolution law and an original crack tracking framework are proposed. We face the issue of mesh objectivity through several two-dimensional tests, obtaining smooth crack paths and reliable structural results
An elastic-damaging cohesive law for cell–substrate adhesion with positive and negative durotaxis
No full textDurotaxis of cells anchored to the extracellular matrix through focal adhesions has been systematically studied through both analytical and computational approaches. However, recent experiments have revealed the attitude of certain cells to unexpectedly migrate towards comparatively softer substrates, thus suggesting the possibility for negative durotaxis to manifest. Cell migration is possible because focal adhesions grow and disrupt, thus operating like adhesive structures undergoing a chemo-physical degradation process. In the present contribution, this degradation process is described through an elastic-damaging cohesive law deduced from a convex–concave pseudo-elastic potential, which confers a variational structure to the mechanical model of the adhesion structure and makes the derivation of analytical solutions possible. Furthermore, the obtained traction-separation cohesive law is amenable to a straightforward implementation into finite element codes. Finite elasticity of the cell body is considered while durotaxis is triggered by applying a contractile pre-stretch to the cell. It is shown that displacement- or force-driven degradation processes may lead to different kinds of durotaxis. The consistency and effectiveness of the proposed approach are showcased in one- and three-dimensional examples of cell–substrate systems
Prospettive di diagnosi su turbogas
No full textNel lavoro si presenta una metodologia per la determinazione dello stato di funzionamento di turbogas industriali che si basa sulla elaborazione delle misure termofluidodinamiche effettuate con la strumentazione standard della macchina.
L’applicazione della metodologia ad un turbogas industriale ha mostrato come essa sia in grado di individuare alterazioni imposte ai parametri caratteristici della macchina, prospettandone quindi un’applicazione nel campo diagnostico
A thermodynamically consistent nonlocal formulation for damaging materials
No full textA thermodynamically consistent nonlocal formulation for damaging materials is presented. The second principle of thermodynamics is enforced in a nonlocal form over the volume where the dissipative mechanism takes place. The nonlocal forces thermodynamically conjugated are obtained consistently from the free energy. The paper indeed extends to elastic damaging materials a formulation originally proposed by Polizzotto et al. for nonlocal plasticity. Constitutive and computational aspects of the model are discussed. The damage consistency conditions turn out to be formulated as an integral complementarity problem and, consequently, after discretization, as a linear complementarity problem. A new numerical algorithm of solution is proposed and meaningful one-dimensional and two-dimensional examples are presented. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved
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