Estudio de estructuras sometidas a esfuerzos de impacto en régimen elastoplástico y con grandes deformaciones por el método de los elementos finitos. Parte I: Formulación teórica

Se desarrolla en este primer artículo, la formulación teórica para el estudio tridimensional de cuerpos sometidos a acciones de contacto-impacto. Despues de desarrollar las ecuaciones básicas de equilibrio, se estudian las ecuaciones constitutivas utilizadas. El elemento usado es el hexaedrico de ocho nodos, del cual se establecen algunas propiedades, que serán de utilidad para la integración numérica. En un artículo posterior, se desarrollará el algoritmo de contacto-impacto estudiado, así como varios ejemplos.Peer Reviewe

Estudio de estructuras sometidas a esfuerzos de impacto en régimen elastoplástico y con grandes deformaciones por el método de los elementos finitos. Parte II: Algoritmo de contacto-impacto y ejemplos

En este segundo articulo, se expone el algoritmo de contacto-impacto utilizado para problemas tridimensionales. Se desarrolla fundamentalmente el metodo de las penalizaciones hallando el valor de la máxima rigidez estable. Se incluyen asimismo tres ejemplos de aplicación.Peer Reviewe

Estudio de estructuras sometidas a esfuerzos de impacto en régimen elastoplástico y con grandes deformaciones por el método de los elementos finitos. Parte I: Formulación teórica

Se desarrolla en este primer artículo, la formulación teórica para el estudio tridimensional de cuerpos sometidos a acciones de contacto-impacto. Despues de desarrollar las ecuaciones básicas de equilibrio, se estudian las ecuaciones constitutivas utilizadas. El elemento usado es el hexaedrico de ocho nodos, del cual se establecen algunas propiedades, que serán de utilidad para la integración numérica. En un artículo posterior, se desarrollará el algoritmo de contacto-impacto estudiado, así como varios ejemplos.Peer Reviewe

Estudio de estructuras sometidas a esfuerzos de impacto en régimen elastoplástico y con grandes deformaciones por el método de los elementos finitos. Parte II: Algoritmo de contacto-impacto y ejemplos

En este segundo articulo, se expone el algoritmo de contacto-impacto utilizado para problemas tridimensionales. Se desarrolla fundamentalmente el metodo de las penalizaciones hallando el valor de la máxima rigidez estable. Se incluyen asimismo tres ejemplos de aplicación.Peer Reviewe

A computational framework for polyconvex large strain elasticity

This paper presents a novel computational formulation for large strain polyconvex elasticity. The formulation, based on the original ideas introduced by Schröder etal. (2011), introduces the deformation gradient (the fibre map), its adjoint (the area map) and its determinant (the volume map) as independent kinematic variables of a convex strain energy function. Compatibility relationships between these variables and the deformed geometry are enforced by means of a multi-field variational principle with additional constraints. This process allows the use of different approximation spaces for each variable. The paper extends the ideas presented in Schröder etal. (2011) by introducing conjugate stresses to these kinematic variables which can be used to define a generalised convex complementary energy function and a corresponding complementary energy principle of the Hellinger-Reissner type, where the new conjugate stresses are primary variables together with the deformed geometry. Both compressible and incompressible or nearly incompressible elastic models are considered. A key element to the developments presented in the paper is the new use of a tensor cross product, presented for the first time by de Boer (1982), page 76, which facilitates the algebra associated with the adjoint of the deformation gradient. For the numerical examples, quadratic interpolation of the displacements, piecewise linear interpolation of strain and stress fields and piecewise constant interpolation of the Jacobian and its stress conjugate are considered for compressible cases. In the case of incompressible materials two formulations are presented. First, continuous quadratic interpolation for the displacement together with piecewise constant interpolation for the pressure and second, linear continuous interpolation for both displacement and pressure stabilised via a Petrov-Galerkin technique

A variationally consistent Streamline Upwind Petrov–Galerkin Smooth Particle Hydrodynamics algorithm for large strain solid dynamics

This paper presents a new Smooth Particle Hydrodynamics (SPH) computational framework for explicit fast solid dynamics. The proposed methodology explores the use of the Streamline Upwind Petrov–Galerkin (SUPG) stabilisation methodology as an alternative to the Jameson–Schmidt–Turkel (JST) stabilisation recently presented by the authors in Lee et al. (2016) in the context of a conservation law formulation of fast solid dynamics. The work introduced in this paper puts forward three advantageous features over the recent JST-SPH framework. First, the variationally consistent nature of the SUPG stabilisation allows for the introduction of a locally preserving angular momentum procedure which can be solved in a monolithic manner in conjunction with the rest of the system equations. This differs from the JST-SPH framework, where an a posteriori projection procedure was required to ensure global angular momentum preservation. Second, evaluation of expensive harmonic and bi-harmonic operators, necessary for the JST stabilisation, is circumvented in the new SUPG-SPH framework. Third, the SUPG-SPH framework is more accurate (for the same number of degrees of freedom) than its JST-SPH counterpart and its accuracy is comparable to that of the robust (but computationally more demanding) Petrov–Galerkin Finite Element Method (PG-FEM) technique explored by the authors in Lee et al. (2014), Gil et al. (2014,2016), Bonet et al. (2015), as shown in the numerical examples included. A series of numerical examples are analysed in order to benchmark and assess the robustness and effectiveness of the proposed algorithm. The resulting SUPG-SPH framework is therefore accurate, robust and computationally efficient, three key desired features that will allow the authors in forthcoming publications to explore its applicability in large scale simulations

An upwind vertex centred Finite Volume solver for Lagrangian solid dynamics

A vertex centred Jameson–Schmidt–Turkel (JST) finite volume algorithm was recently introduced by the authors (Aguirre et al., 2014 [1]) in the context of fast solid isothermal dynamics. The spatial discretisation scheme was constructed upon a Lagrangian two-field mixed (linear momentum and the deformation gradient) formulation presented as a system of conservation laws [2], [3] and [4]. In this paper, the formulation is further enhanced by introducing a novel upwind vertex centred finite volume algorithm with three key novelties. First, a conservation law for the volume map is incorporated into the existing two-field system to extend the range of applications towards the incompressibility limit (Gil et al., 2014 [5]). Second, the use of a linearised Riemann solver and reconstruction limiters is derived for the stabilisation of the scheme together with an efficient edge-based implementation. Third, the treatment of thermo-mechanical processes through a Mie–Grüneisen equation of state is incorporated in the proposed formulation. For completeness, the study of the eigenvalue structure of the resulting system of conservation laws is carried out to demonstrate hyperbolicity and obtain the correct time step bounds for non-isothermal processes. A series of numerical examples are presented in order to assess the robustness of the proposed methodology. The overall scheme shows excellent behaviour in shock and bending dominated nearly incompressible scenarios without spurious pressure oscillations, yielding second order of convergence for both velocities and stresses

Bounds and adaptivity for 3D limit analysis

In the present paper we compute upper and lower bounds for limit analysis in two and three dimensions. From the solution of the discretised upper and lower bound problems, and from the optimum displacement rate and stress fields, we compute an error estimate defined at the body elements and at their boundaries, which are applied in an adaptive remeshing strategy. In order to reduce the computational cost in 3D limit analysis, the tightness of the upper bound is relaxed and its computation avoided. Instead, the results of the lower bound are used to estimate elemental and edge errors. The theory has been implemented for Von Mises materials, and applied to two- and three-dimensions examples.Peer Reviewe

Mucocele de la glandula submaxilar: a propósito de un caso

El mucocele es un término que incluye dos conceptos: el quiste de extravasación, que resulta de la ruptura del conducto de la glándula salival y el consiguiente derrame de la mucina en los tejidos blandos que rodean a dicha glándula, y el quiste de retención, que tiene su origen en la disminución o ausencia de la secreción glandular como consecuencia de la obstrucción del conducto de la glándula salival. No se puede considerar al mucocele como un verdadero quiste, ya que su pared carece de revestimiento epitelial. Este tipo de patología es muy común en las glándulas salivales menores ( sobretodo en las labiales), pero es muy poco frecuente en las glándulas salivales mayores y en concreto, en la glándula submaxilar. El presente trabajo expone el caso clínico de un mucocele de glándula submaxilar derecha, resuelto mediante tratamiento quirúrgico y revisa todas aquellas entidades con las que se debe establecer el diagnóstico diferencial.The term mucocele is referred to two concepts: the extravasation cysts resulting from salivary glandular duct rupture, with mucin leakage into the surrounding peri - glandular soft tissue, and the retention cysts, caused by a glandular duct obstruction and resulting in a decrease or even an absence of glandular secretion. Mucocele can not be considered as a true cyst because its wall lacks an epithelial lining. These lesions are very common in the minor salivary glands (particularly in the labial glands), but are very infrequent in the major salivary glands ' including the submaxillary glands. The present study describes a clinical case of a right submaxillary gland mucocele resolved by surgical treatment and reviews the differential diagnosis with other clinical entities