Suchergebnisse

These lines constitute a reflection on the possibilities of scientific knowledge of law within contemporary society. Undoubtedly, it is about suggesting some unfinished but controversial hypotheses about the meaning, social and political function of research in the field of legal science. For this purpose, it is necessary to discern in the first place about the nature and character of the normative world, that is, about the broad and controversial object of law. Second, it is necessary to investigate what role does knowledge of law play in the production process of the legal field. Third, it is necessary to contextualize the characteristics of the legal research process within the contemporary social organization, understanding that the law-society relationship has been reconsidered by the dynamics of productive social relations to which we are all attending. ; Estas líneas constituyen una reflexión sobre las posibilidades del conocimiento científico del derecho dentro de la sociedad contemporánea. Sin duda, se trata de sugerir algunas hipótesis inacabadas pero polémicas alrededor del sentido, la función social y política de la investigación en el campo de la ciencia jurídica. Para tal efecto es necesario discernir en primer lugar sobre la naturaleza y carácter del mundo normativo, es decir, sobre el amplio y controvertible objeto del derecho. En segundo lugar, se requiere investigar qué papel juegael conocimiento del derecho en el proceso de producción del campo jurídico. En tercer lugar, es necesario contextualizar las características del proceso de la investigación jurídica dentro de la organización social contemporánea, entendiendo que la relación derecho sociedad viene siendo replanteada por la dinámica de las relaciones sociales productivas a las cuales estamos todos asistiendo. ; Estas linhas constituem uma reflexão sobre as possibilidades do conhecimento científico do direito na sociedade contemporânea. É sem dúvida uma questão de sugerir algumas hipóteses inacabadas mas controversas sobre o significado, a função social e política da investigação no campo da ciência jurídica. Para o fazer, é necessário primeiro discernir a natureza e o carácter do mundo normativo, ou seja, o objecto amplo e controverso do direito. Em segundo lugar, é necessário investigar que papel desempenha o conhecimento do direito no processo de produção do campo jurídico. Em terceiro lugar, é necessário contextualizar as características do processo de investigação jurídica dentro da organização social contemporânea, entendendo que a relação entre o direito e a sociedade está a ser redefinida pela dinâmica das relações sociais produtivas a que todos estamos a assistir.que todos estamos a testemunhar.

In this paper, we have modified the stress integration scheme proposed by Choi and Yoon [1]; which is based on the numerical approximation of the yield function gradients, to implement in the finite element code ABAQUS three elastic isotropic, plastic anisotropic constitutive models with yielding described by Yld2004-18p [2], CPB06ex2 [3] and Yld2011-27p [4] criteria, respectively. We have developed both VUMAT and UMAT subroutines for the three constitutive models, and have carried out cylindrical cup deep drawing test simulations and calculations of dynamic necking localization under plane strain tension, using explicit and implicit analyses. An original feature of this paper is that these finite element simulations are systematically compared with additional calculations performed using (i) the numerical approximation scheme developed by Choi and Yoon [1]; and (ii) the analytical computation of the first and second order yield functions gradients. This comparison has shown that the numerical approximation of the yield function gradients proposed in this paper facilitates the implementation of the constitutive models, and in the case of the implicit analyses, it leads to a significant decrease of the computational time without impairing the accuracy of the finite element results. In addition, we have demonstrated that there is a critical loading rate below which the dynamic implicit analyses are computationally more efficient than the explicit calculations. ; The research leading to these results has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme. Project PURPOSE, grant agreement 758056.

Proceeding of: IUTAM Symposium on Dynamic Instabilities in Solids, May 17-20, 2016, Madrid, Spain ; A nonlinear rate-independent overstress model with a smooth elastic-inelastic transition is used to analyze instabilities during dynamic necking of a bar. In the simplified model the elastic strain epsilone determines the value of stress and the hardening parameter kappa determines the onset of inelasticity. These quantities {epsilone, kappa} are obtained by integrating time evolution equations. The main and perhaps surprising result of this paper is that, based on the critical growth rate omegacr of a perturbation, two rate-independent materials with a smooth elastic-plastic transition due to overstress and nearly the same loading curve (elastic strain or stress versus total strain) can have different susceptibilities to tensile instabilities. Specifically, increase in overstress causes decreased material instability near the onset of the smooth elastic-inelastic transition and increased instability when the elastic strain approaches its saturated value. To the authors' knowledge, this new insight has not been reported in the literature. ; JARM is indebted to the Ministerio de Economía y Competitividad de España (Projects EUIN2015-62556 and DPI2014-57989-P) for the financial support which permitted to conduct part of this work. The research leading to these results has received funding from the European Union's Horizon2020 Programme (Excellent Science, Marie-Sklodowska-Curie Actions) under REA grant agreement 675602 (Project OUTCOME). This research was also partially supported by MB Rubin's Gerard Swope Chair in Mechanics.

In this paper, we extend the dynamic spherical cavity expansion model for rate-independent materials developed by Durban and Masri (Int J Solids Struct 41(20):5697-5716, 2004), Masri and Durban (J Appl Mech 72(6):887-898, 2005), and Cohen et al. (J Appl Mech 77(4):041009, 2010) to viscoplastic media. For that purpose, we describe the material behavior with an isotropic Perzyna-type overstress formulation (Perzyna in Q Appl Math 20:321&#-332, 1963; Adv Appl Mech 9:243-377, 1966) in which the material rate dependence is controlled by the viscosity parameter η. The theoretical predictions of the cavity expansion model, which assumes that the cavity expands at constant velocity, are compared with finite element simulations performed in ABAQUS/Explicit (Abaqus Explicit v6.13 User's Manual, ABAQUS Inc., Richmond). The agreement between theory and numerical simulations is excellent for the whole range of cavitation velocities investigated, and for different values of the parameter η. We show that, as opposed to the steady-state self-similar solutions obtained for rate-independent materials (Durban and Masri 2004; Masri and Durban 2005; Cohen et al. 2010), the material viscosity leads to time-dependent cavitation fields and stress relaxation as the cavity enlarges. In addition, we also show that the material viscosity facilitates to model the shock waves that emerge at the highest cavitation velocities investigated, controlling the amplitude and the width of the shock front. ; The research leading to these results has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme. Project PURPOSE, Grant Agreement 758056. RR wishes to acknowledge the support of CNPq, Conselho Nacional de Desenvolvimento Científico e Tecnológico, grant number 306058/2018-9.

The onset of necking in dynamically expanding ductile rings is delayed due to the stabilizing effect of inertia, and with increasing expansion velocity, both the number of necks incepted and the number of fragments increase. In general, neck retardation is expected to delay fragmentation as necking is often the precursor to fracture. However, in porous ductile materials, it is possible that fracture can occur without significant necking. Thus, the objective of this work is to unravel the complex interaction of initial porosity and inertia on the onset of necking and fracture. To this end, we have carried out a series of finite element calculations of unit cells with sinusoidal geometric perturbations and varying levels of initial porosity under a wide range of dynamic loading conditions. In the calculations, the material is modeled using a constitutive framework that includes many of the hardening and softening mechanisms that are characteristics of ductile metallic materials, such as strain hardening, strain rate hardening, thermal softening, and damage-induced softening. The contribution of the inertia effect on the loading process is evaluated through a dimensionless parameter that combines the effects of loading rate, material properties, and unit cell size. Our results show that low initial porosity levels favor necking before fracture, and high initial porosity levels favor fracture before necking, especially at high loading rates where inertia effects delay the onset of necking. The finite element results are also compared with the predictions of linear stability analysis of necking instabilities in porous ductile materials. ; J.A.R.-M. acknowledges the financial support provided by the European Research Council under the European Union's Horizon 2020 research and innovation programme (Project PURPOSE, Grant agreement 758056).