Articulos(CIMEC)
http://hdl.handle.net/11336/282
Articulos de CENTRO DE INVESTIGACION DE METODOS COMPUTACIONALESThu, 23 May 2019 23:27:39 GMT2019-05-23T23:27:39ZCohesive surface model for fracture based on a two-scale formulation: computational implementation aspects
http://hdl.handle.net/11336/70546
Cohesive surface model for fracture based on a two-scale formulation: computational implementation aspects
Toro, Sebastian; Sánchez, Pablo Javier; Podestá, Juan Manuel; Blanco, Pablo Javier; Huespe, Alfredo Edmundo; Feijóo, Raúl Antonino
The paper describes the computational aspects and numerical implementation of a two-scale cohesive surface methodology developed for analyzing fracture in heterogeneous materials with complex micro-structures. This approach can be categorized as a semi-concurrent model using the representative volume element concept. A variational multi-scale formulation of the methodology has been previously presented by the authors. Subsequently, the formulation has been generalized and improved in two aspects: (i) cohesive surfaces have been introduced at both scales of analysis, they are modeled with a strong discontinuity kinematics (new equations describing the insertion of the macro-scale strains, into the micro-scale and the posterior homogenization procedure have been considered); (ii) the computational procedure and numerical implementation have been adapted for this formulation. The first point has been presented elsewhere, and it is summarized here. Instead, the main objective of this paper is to address a rather detailed presentation of the second point. Finite element techniques for modeling cohesive surfaces at both scales of analysis (FE2 approach) are described: (i) finite elements with embedded strong discontinuities are used for the macro-scale simulation, and (ii) continuum-type finite elements with high aspect ratios, mimicking cohesive surfaces, are adopted for simulating the failure mechanisms at the micro-scale. The methodology is validated through numerical simulation of a quasi-brittle concrete fracture problem. The proposed multi-scale model is capable of unveiling the mechanisms that lead from the material degradation phenomenon at the meso-structural level to the activation and propagation of cohesive surfaces at the structural scale.
Sat, 01 Oct 2016 00:00:00 GMThttp://hdl.handle.net/11336/705462016-10-01T00:00:00ZOptimization-based design of heat flux manipulation devices with emphasis on fabricability
http://hdl.handle.net/11336/70173
Optimization-based design of heat flux manipulation devices with emphasis on fabricability
Peralta, Ignacio; Fachinotti, Victor Daniel
In this work, we present a new method for the design of heat flux manipulating devices, with emphasis on their fabricability. The design is obtained as solution of a nonlinear optimization problem where the objective function represents the given heat flux manipulation task, and the design variables define the material distribution in the device. In order to facilitate the fabrication of the device, the material at a given point is chosen from a set of predefined metamaterials. Each candidate material is assumed to be a laminate of materials with high conductivity contrast, so it is a metamaterial with a highly anisotropic effective conductivity. Following the discrete material optimization (DMO) approach, the fraction of each material at a given finite element of the mesh is defined as a function of continuous variables, which are ultimately the design variables. This DMO definition forces the fraction of each candidate to tend to either zero or one at the optimal solution. As an application example, we designed an easy-to-make device for heat flux concentration and cloaking.
Fri, 01 Dec 2017 00:00:00 GMThttp://hdl.handle.net/11336/701732017-12-01T00:00:00ZOptimization-based design of a heat flux concentrator
http://hdl.handle.net/11336/70160
Optimization-based design of a heat flux concentrator
Peralta, Ignacio; Fachinotti, Victor Daniel; Ciarbonetti, Angel
To gain control over the diffusive heat flux in a given domain, one needs to engineer a thermal metamaterial with a specific distribution of the generally anisotropic thermal conductivity throughout the domain. Until now, the appropriate conductivity distribution was usually determined using transformation thermodynamics. By this way, only a few particular cases of heat flux control in simple domains having simple boundary conditions were studied. Thermal metamaterials based on optimization algorithm provides superior properties compared to those using the previous methods. As a more general approach, we propose to define the heat control problem as an optimization problem where we minimize the error in guiding the heat flux in a given way, taking as design variables the parameters that define the variable microstructure of the metamaterial. In the present study we numerically demonstrate the ability to manipulate heat flux by designing a device to concentrate the thermal energy to its center without disturbing the temperature profile outside it.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11336/701602017-01-01T00:00:00ZHybridisation effect on operating costs and optimal sizing of components for hybrid electric vehicles
http://hdl.handle.net/11336/69531
Hybridisation effect on operating costs and optimal sizing of components for hybrid electric vehicles
Carignano, Mauro; Nigro, Norberto Marcelo; Junco, Sergio Jose; Orbaiz, Pedro Jose
Reductions of fuel consumption and gas emissions count among the main advantages of hybrid electric vehicles (HEV). It is well known that the level of hybridisation has a large influence on the fuel consumption, the manufacturing cost and the battery lifetime. Therefore, a proper selection of the size of components could be the result of a trade-off between them. This paper provides models and a methodology to address the sizing of components of a HEV. Specifically the work is focused on the series architecture with internal combustion engine and battery. The sizing criteria are oriented to reduce the operating costs, in which are included the fuel consumption and the battery-life consumption. Finally, the methodology proposed is applied in a case study. It corresponds to a real hybrid electric bus operating under urban driving conditions. Simulation results show that the best solutions are obtained by oversizing the battery with respect to power requirements.
Fri, 01 Dec 2017 00:00:00 GMThttp://hdl.handle.net/11336/695312017-12-01T00:00:00Z