andres felipe gonzalez tovar - Academia.edu (original) (raw)

Papers by andres felipe gonzalez tovar

52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2011

The field of topology design of compliant mechanisms has developed from infancy to well grown sta... more The field of topology design of compliant mechanisms has developed from infancy to well grown state in last 15 years. Born from the need of hingeless mechanisms in MicroElec-troMechanical Systems (MEMS), compliant mechanims are finding their use in wide range of applications like snap-through mechanisms, piezoelectric actuators and wing flapping mechanisms among many others. Most of the work developed so far, consider linear elastic material behavior and small displacment theory to design compliant mechanisms. In order to account for the effect of large displacements in mechanism design, geometric nonlinearity is considered by many researchers, however, nonlinearities arising from plasticity and contact are seldomly studied. One of the major challenges in the design of mechanisms considering nonlinearities is sensitivity analysis. Analytical expressions for sensitivities of objective function with respect to design variables can not be expressed in closed form when nonlinear finite element methods are used. Moreover, commercial finite element softwares which use implicit/explict solvers can not be used for such sensitivity calculations as they do not store stiffness matrices. In this work, optimal design for compliant mechanisms using control based material update scheme (HCA) is developed for linear case and the idea is extended to obtain concept topologies for nonlinear cases. Since this method does not involve sensitivity calculations when nonlinearities are considered, commercial FEA packages can be used which help in handling complex design problems in 2D and 3D. Although the final designs for nonlinear cases can not be claimed 'optimal', this method gives designer, a candidate designs which perform satisfactorily well under nonlinear conditions. This method is developed particularly for potential applications of compliant mechanisms in crashworthy designs where considering nonlinearity becomes essential. The applicability of the proposed method is shown by considering 2 examples.

51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference<BR> 18th AIAA/ASME/AHS Adaptive Structures Conference<BR> 12th, 2010

10th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, 2004

In this investigation the hybrid cellular automaton (HCA) method for structural synthesis is exte... more In this investigation the hybrid cellular automaton (HCA) method for structural synthesis is extended to facilitate simultaneous topology and shape optimization. The HCA methodology has been developed for application to continuum structures. The development of this methodology has been inspired by the biological process of bone remodeling. In bone remodeling, only those elements located on the surface of the mineralized structure can be modified. In the HCA methodology implemented in this research only surface elements are allowed to change density during the structural synthesis process. The HCA method combines local design rules based on the cellular automaton paradigm and finite element analysis. Closed-loop control is used to modify the mass distribution on the internal and external surfaces of the design domain to find an optimum structure. The local control maintains a balance between mass and rigidity. The new methodology effectively combines elements of topology optimization and shape optimization into a single tool. Three classes of test problems are used to illustrate the method's efficacy.

Advances in Engineering Software, 2005

The hybrid cellular automaton (HCA) algorithm is a methodology developed to simulate the process ... more The hybrid cellular automaton (HCA) algorithm is a methodology developed to simulate the process of structural adaptation in bones. This methodology incorporates a distributed control loop within a structure in which ideally localized sensor cells activate local processes of the formation and resorption of material. With a proper control strategy, this process drives the overall structure to an optimal configuration. The controllers developed in this investigation include two-position, proportional, integral and derivative strategies. The HCA algorithm combines elements of the cellular automaton (CA) paradigm with finite element analysis (FEA). This methodology has proved to be computationally efficient to solve topology optimization problems. The resulting optimal structures are free of numerical instabilities such as the checkerboarding effect. This investigation presents the main features of the HCA algorithm and the influence of different parameters applied during the iterative optimization process.

Journal of Mechanical Design, 2009

Crashworthiness design is an evolving discipline that combines vehicle crash simulation and desig... more Crashworthiness design is an evolving discipline that combines vehicle crash simulation and design synthesis. The goal is to increase passenger safety subject to manufacturing cost constraints. The crashworthiness design process requires modeling of the complex interactions involved in a crash event. Current approaches utilize a parametrized optimization approach that requires response surface approximations of the design space. This is due to the expensive nature of numerical crash simulations and the high nonlinearity and noisiness in the design space. These methodologies usually require a significant effort to determine an initial design concept. In this paper, a heuristic approach to continuum-based topology optimization is developed for crashworthiness design. The methodology utilizes the cellular automata paradigm to generate three-dimensional design concepts. Furthermore, a constraint on maximum displacement is implemented to maintain a desired performance of the structures synthesized. Example design problems are used to demonstrate that the proposed methodology converges to a final topology in an efficient manner.

Revista S, 2010

La identidad discursiva en la cronica Ladrones, pecuecudos, cobardes, cochinos, perezosos, asesin... more La identidad discursiva en la cronica Ladrones, pecuecudos, cobardes, cochinos, perezosos, asesinos…, de Juanita Jeon El proposito de este breve articulo, nacido en el marco de la investigacion sobre las identidades discursivas divergentes en las cronicas Desterrados: cronicas del desarraigo , de Alfredo Molano, y No somos machos pero somos muchos , de Juanita Leon, es poner en evidencia los diferentes recursos discursivos empleados en la construccion de cierto tipo de identidades. Para ello, se recurre, en gran medida, a la propuesta teorico-metodologica de la semiotica discursiva de la Escuela de Paris, conservando el concepto de identidad discursiva propuesto por el construccionismo social y la psicologia narrativa. A traves del estudio de algunos pasajes claves en una de las cronicas de Leon, este escrito procura revelar la manera como el enunciador ha configurado las relaciones y los roles identitarios de ciertos actores presentes en el relato, todo mediante el hacer pragmatico y discursivo que de ellos pone en escena. Los resultados del analisis (siempre en un contante vaiven entre la teoria y el texto) hallan que la construccion discursiva de la identidad se caracteriza por la riqueza de estrategias enunciativas y, esencialmente, enuncivas, empleadas. P alabras clave Sujeto, axiologico, pasional, cognitivo, roles, actantes, imagen, programa narrativo. A bstract D iscourse identity in the chronicle L adrones , pecuecudos , cobardes , cochinos , perezosos , asesinos …, by J uanita L eon . The aim of this short article – borne within the framework of the study on the diverging discourse identities in the chronicles Desterrados: cronicas del desarraigo , by Alfredo Molano, and No somos machos, pero somos muchos , by Juanita Leon – is to make evident the different discourse resources employed in the construction of certain types of identities. In order to do that, the theoretical methodological proposal of discourse semiotics of the School of Paris is vastly utilized, maintaining the concept of discourse identity proposed by social constructionism and narrative psychology. Upon studying some key passages in one of Leon’s chronicles, this text tries to reveal the way in which the enunciator has set the relationships and identitary roles of certain actors in the story, all through the pragmatic and discourse acts that she attributes to them. The results of this analysis (in constant bounce between theory and text) find out that the discourse construction of identity is characterized by the many enunciative strategies and, essentialy, enuncive strategies employed. K eywords Subject, axiologic, passional, cognitive, roles, actants, image, narrative program.

III European Conference on …, 2006