Ruben Ansola

Universidad del País Vasco UPV/EHU, Mechanical Engineering, Faculty Member

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Papers by Ruben Ansola

Study of Topology Optimization Parameters and Scaffold Structures in Additive Manufacturing

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016), 2016

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Sequential element rejection and admission method (SERA) for topology optimization using a constraint on perimeter

This paper presents an implementation of the perimeter constraint for topology optimization of el... more This paper presents an implementation of the perimeter constraint for topology optimization of elastic structures using the Sequential Element Rejection and Admission Method (SERA). The perimeter constraint allows the designer to control the number of holes in the optimal design and to establish their characteristic length scale. This work shows an improved SERA methodology incorporating a strategy to efficiently control the optimization process satisfying a constraint on structural perimeter.

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Topology optimization of 3D compliant actuators by a sequential element rejection and admission method

IOP Conference Series: Materials Science and Engineering, 2016

This work presents a sequential element rejection and admission (SERA) method for optimum topolog... more This work presents a sequential element rejection and admission (SERA) method for optimum topology design of three dimensional compliant actuators. The proposed procedure has been successfully applied to several topology optimization problems, but most investigations for compliant devices design have been focused on planar systems. This investigation aims to progress on this line, where a generalization of the method for three dimensional topology optimization is explored. The methodology described in this work is useful for the synthesis of high performance flexure based micro and nano manipulation applications demanding for both sensing and control of motion and force trajectories. In this case the goal of the topology optimization problem is to design an actuator that transfers work from the input point to the output port in a structurally efficient way. Here we will use the classical formulation where the displacement performed on a work piece modelled by a spring is maximized. The technique implemented works with two separate criteria for the rejection and admission of elements to efficiently achieve the optimum design and overcomes problems encountered by other evolutionary methods when dealing with compliant mechanisms design. The use of the algorithm is demonstrated through several numerical examples. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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Procedimiento integrado para el diseño óptimo de forma y topología en estructuras laminares

En este trabajo se presenta el desarrollo e implementacion de un procedimiento integrado para la ... more En este trabajo se presenta el desarrollo e implementacion de un procedimiento integrado para la optimizacion de forma y topologia en estructuras laminares. En esta memoria se combinan ambos tipos de optimizacion para el diseno de maxima rigidez en estructuras laminares, alterando secuencialmente la modificaicon de la forma y la redistribucion del material, de manera que la estrucutra laminar de base sobre la que se formula al optimizacion de la topologia,no permanece constante en el curso del proceso de diseno optimo. En lo referente a la optimizacion de la topologia, se estudian dos posibles soluciones: los problemas de distribucion de masa propiamente dichos (material/vacio) y los problemas de rigidizacion. El procedimiento se ha implementado en un programa de ordenador, el cual se ha utilizado para resolver numerosos ejemplo de aplicacion y cuyos resultados se recogen en la presente memoria.Dichos resultados permiten comprobar la validez del desarrollo efectuado para determinar la forma y distribucion de material optimas de estructuras laminares con las que se obtiene una rigidez maxima. Finalmente se incluyen las conclusiones extraidas de los diferentes ejemplos de palicaicon resueltos aplicando lo desarrollado en la presente tesis y se exponen las principales lineas futuras de investigacion que surgen a raiz de la investigacion realizada.

Design of Compliant Mechanisms with a Sequential Element Rejection and Admission Method

Proceedings of 10th World Congress on Computational Mechanics, 2014

A Sequential Element Rejection and Admission (SERA) method to design compliant mechanisms with to... more A Sequential Element Rejection and Admission (SERA) method to design compliant mechanisms with topology optimization techniques is presented in this work. This procedure, successfully applied to structural optimization problems, allows material to flow between two different material models: 'real' and 'virtual'. This bi-directional method works with two separate criterions for the rejection and admission of elements to efficiently achieve the optimum design. Three benchmark problems are presented here to demonstrate the validity of the proposed method.

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Modelo detallado para análisis estático de conjuntos de rodamiento de vuelco

INTRODUCCIÓN Los rodamientos de vuelco (Slewing bearings, en nomenclatura internacional) son roda... more INTRODUCCIÓN Los rodamientos de vuelco (Slewing bearings, en nomenclatura internacional) son rodamientos de grandes dimensiones cuyos campos de aplicación van desde generadores de energía eólica, grúas, tanques, centros de torneado… En general se utilizan en casos en los que se ven implicados elementos funcionales de grandes dimensiones. Es muy común que estos rodamientos sean elementos conducidos, y por tanto bien el anillo exterior o bien el interior suelen tallarse a modo de engranaje. Por último, la unión de ambos anillos a la aplicación y a la fuente de potencia suele ser atornillada. Existen diferentes tipos de rodamientos de vuelco que difieren entre ellos en el número de hileras y en el tipo de elemento rodante considerado. Por ello, existen rodamientos con una o dos hileras, y los elementos rodantes pueden ser bolas, rodillos cónicos o rodillos cilíndricos. En la Fig. (1) se presenta un esquema de un rodamiento de vuelco de contacto angular de cuatro puntos. Las cargas actu...

On the Design of a Compliant Mechanism with Non-Uniform Thermal Effects using Evolutionary Structural Optimization

Proceedings of the Eleventh International Conference on Computational Structures Technology

ABSTRACT

Aplicación de las técnicas de optimización estructural al diseño de estructuras espaciales monocapa

Publicado en el número monográfico dedicado al XIV Congreso Nacional de Ingeniería Mecánica, Lega... more Publicado en el número monográfico dedicado al XIV Congreso Nacional de Ingeniería Mecánica, Leganés, 13, 14 y 15 de diciembre de 2000, Escuela Politécnica Superior, Universidad Carlos III de Madrid. El presente trabajo recoge parte de los resultados que pueden obtenerse cuando se aplican las técnicas de diseño estructural óptimo a estructuras espaciales tubulares monocapa. Se pretende determinar la influencia que tienen los distintos parámetros y restricciones que caracterizan este tipo de estructuras, lo que premitirá determinar la mejor configuración de las mismas, en términos económicos, para unas condiciones de contorno dadas. Para ellas se ha desarrollado una herramienta de diseño estructural óptimo capaz de optimizar variables de tamaño (secciones de las barras) y de forma (ángulo de apertura de las bóvedas). Este trabajo ha sido parcialmente subvencionado por la CICYT, Programa Nacional de Tecnologías Avanzadas de la Producción. Proyecto TAP98-0377-C02-02.

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An alternative full-pivoting algorithm for the factorization of indefinite symmetric matrices

Journal of Computational and Applied Mathematics, 2015

ABSTRACT This paper presents an algorithm for the factorization of indefinite symmetric matrices ... more ABSTRACT This paper presents an algorithm for the factorization of indefinite symmetric matrices that factors any symmetric matrix AA into the form LDLTLDLT, with DD diagonal and LL triangular, with its subdiagonal filled with zeros. The algorithm is based on Jacobi rotations, as opposed to the widely used permutation methods (Aasen, Bunch–Parlett, and Bunch–Kaufman). The method introduces little increase in computational cost and provides a bound on the elements of the reduced matrices of order 2nf(n), which is smaller than that of the Bunch–Parlett method (≃3nf(n)≃3nf(n)), and similar to that of Gaussian elimination with full pivoting (nf(n)). Furthermore, the factorization method is not blocked. Although the method presented is formulated in a full-pivoting scheme, it can easily be adapted to a scheme similar to that of the Bunch–Kaufman approach. A backward error analysis is also presented, showing that the elements of the error matrix can be bounded in terms of the elements of the reduced matrices.

Dental Implants with Conical Implant-Abutment Interface: Influence of the Conical Angle Difference on the Mechanical Behavior of the Implant

The International Journal of Oral & Maxillofacial Implants, 2013

Purpose: Misfit in the conical implant-abutment interface plays an important role on the mechanic... more Purpose: Misfit in the conical implant-abutment interface plays an important role on the mechanical behavior of the implant when masticatory forces are applied. The origin of the misfit adopted in this work is a conical angle difference between implant and abutment, which can be due to a combination of design decisions and manufacturing tolerances. The goal of this work was to investigate the effects of the implant-abutment conical angle difference in the following mechanical features: interfacial microgap, preload loss on the bolt, stress level in the bone, and abutment removal force and/or torque. Materials and Methods: A simplified three-dimensional nonlinear monoparametric finite element model of an OsseoSpeed TX 4.5 S 9-mm implant (Astra Tech) with a tapered implant-abutment interface was built to evaluate the variability of the mechanical features cited above with the conical angle difference, keeping constant the overall geometry, load and boundary conditions, material properties, frictional behavior, and mesh structure. Results: As the conical angle difference increased, the following effects were observed: the microgap decreased and remained almost constant for values over a given positive angle difference, the stress level in the bone increased sensitively, the removal force and/or torque needed to separate the abutment from the implant varied slightly, and the bolt preload loss increased. Conclusions: In light of the results provided, the conical angle difference in the implant-abutment interface had a significant influence on the overall mechanical behavior of the implant. Among the four mechanical features considered, the interfacial microgap and the bone stress were demonstrated to be the most sensitive to the conical angle difference, and therefore the most relevant when selecting an optimum value in the design process of a conical interface.

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Parameter study of a SERA method to design compliant mechanism

12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conference and 14th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, 2012

A Sequential Element Rejection and Admission (SERA) method is used in this work to design complia... more A Sequential Element Rejection and Admission (SERA) method is used in this work to design compliant mechanisms. This discrete method allows material to flow between two different material models: ‘real’ and ‘virtual’. It is bi-directional in nature and works with two separate criteria for the rejection and admission of elements to efficiently achieve the optimum design. The aim of this paper is to study the robustness and versatility of the SERA method for compliant mechanisms design by means of a study of the main problem parameters (mesh density, target volume fraction, input and output stiffness, initial design domain, and filtering radius). Also, as part of the study of different initial design domains, an explanation is given on why the additional version of the ESO method is needed to design compliant mechanisms when an unidirectional approach is considered.

An Evolutionary Approach for the Topology Synthesis of Compliant Mechanisms

Proceedings of the Ninth International Conference on Computational Structures Technology

Static Load Carrying Capacity in Four Contact Point Slewing Bearings: Theoretical and Preliminary Finite Element Calculations

Volume 3: Design and Manufacturing, Parts A and B, 2010

This paper presents a theoretical model to calculate the general static load-carrying capacity of... more This paper presents a theoretical model to calculate the general static load-carrying capacity of four-contact-point slewing bearings under axial, radial and tilting-moment loads, compared with preliminary results obtained from a detailed parametric finite element model of the bearing. The theoretical model is based on a generalization of Sjova¨ll and Rumbarger’s equations and provides an acceptance surface in the load space. The finite element model is based on the modelization of the balls via nonlinear traction-only equivalent spring concept. The aim is to validate the theoretical model to be used as an acceptance curve generator for slewing bearing design.

A Sequential Element Rejection and Admission (SERA) method for compliant mechanisms design

Structural and Multidisciplinary Optimization, 2012

A Sequential Element Rejection and Admission (SERA) method to design compliant mechanisms with to... more A Sequential Element Rejection and Admission (SERA) method to design compliant mechanisms with topology optimization techniques is presented in this work. This procedure allows material to flow between two different material models: 'real' and 'virtual'. The method works with two separate criteria for the rejection and admission of elements to efficiently achieve the optimum design. The SERA method overcomes the problems encountered by the ESO method when used to design compliant mechanisms. Three benchmark problems are presented to show the validity and robustness of the SERA method to design complaint mechanisms, regardless of the design parameters chosen.

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Second order mobility analysis of mechanisms using closure equations

Meccanica, 2012

This paper presents a general method for the second order local mobility analysis of kinematical ... more This paper presents a general method for the second order local mobility analysis of kinematical chains using closure equations. As it is known, one can obtain the mobility of a mechanism as the nullspace of its Jacobian Matrix. But in the event of a singular configuration, not all of the linear combinations of these vectors represent finite movements. This phenomena leads to branching, kinematotropy and other kinds of particular behavior of mechanisms. The exposed algorithm allows one to obtain the restrictions that appear in these cases, thus providing a better understanding of the behavior of the mechanism. The solution of these restrictions gives information about not only the real number of second order finite motions, but also the vectors defining the branches of finite movements, if any. Although the algorithm itself is applicable with other kind of methods for the definition of the Jacobian Matrix, the use of closure equations leads to simplicity. One of the advantages of the presented method is that it takes advantage of the work performed to solve the velocity and acceleration analysis. This reduces the amount of operations needed to perform the analysis The paper presents some examples of application, including complex mechanisms in singular configurations and a kinematotropic mechanism.

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Topology synthesis of multi-material compliant mechanisms with a Sequential Element Rejection and Admission method

Finite Elements in Analysis and Design, 2014

The design of multi-material compliant mechanisms by means of a multi Sequential Element Rejectio... more The design of multi-material compliant mechanisms by means of a multi Sequential Element Rejection and Admission (SERA) method is presented in this work. The SERA procedure was successfully applied to the design of single-material compliant mechanisms. The main feature is that the method allows material to flow between different material models. Separate criteria for the rejection and admission of elements allow material to redistribute between the pre-defined material models and efficiently achieve the optimum design. These features differentiate it to other bi-directional discrete methods, making the SERA method very suitable for the design of multimaterial compliant mechanisms. Numerous examples are presented to show the validity of the multi SERA procedure to design multi-material compliant mechanisms.

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Evolutionary optimization of compliant mechanisms subjected to non-uniform thermal effects

Finite Elements in Analysis and Design, 2012

In this research, an evolutionary optimization procedure is proposed for the design of compliant ... more In this research, an evolutionary optimization procedure is proposed for the design of compliant thermal microactuators subjected to non-uniform temperature fields. Compliant micro-mechanisms that are responsible for movement play a crucial role in MEMS design, which cannot be manufactured using typical assembly processes and may not make use of traditional hinges or bearings. During the past decades topology optimization techniques have been shown to be efficient tools to conceive these kinds of distributed compliant mechanisms. The procedure applied in this paper is based in the evolutionary structural optimization (ESO) method, which has been successfully applied to several optimum material distribution problems but not for non-uniformly heated compliant mechanisms including conduction and convection effects. In previous works, this group has successfully applied this method for compliant mechanism optimization under directly applied input loads and under simple uniform temperature fields. The present paper aims to progress on this work line developing an extension of this procedure, based on an additive version of the method, to approach the more complicated case of non-uniformly heated thermal microactuators. The validity of this technique is demonstrated in several examples and the designs obtained are compared favourably with the analytical solutions and with results by other methods. Future works will be based on electro-thermal actuation and non-uniform Joule heating will be considered as well, which lead to more elegant and real solutions.

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Electro-thermal compliant mechanisms design by an evolutionary topology optimization method

Engineering Computations, 2013

Purpose – This paper aims to show an evolutionary topology optimization procedure for the design ... more Purpose – This paper aims to show an evolutionary topology optimization procedure for the design of compliant electro-thermal mechanisms. Design/methodology/approach – The adopted methodology is based in the evolutionary structural optimization (ESO) method. This approach has been successfully applied by this group for compliant mechanisms optimization under directly applied input loads and simple thermal loads. This work proposes an extension of this procedure, based on an additive version of the method, to solve the more complicated case of electro-thermal actuators optimum design, based on Joule's resistive heating. Findings – Examples solved for the design of plane compliant mechanisms are presented to check the validity of this technique. The designs obtained are compared favorably with results obtained by other authors to illustrate and validate the method, showing the viability of this technique for the optimization of compliant mechanisms under electro-thermal actuation....

Topology optimization of uniformly heated actuators by ESO method

This work presents an element addition strategy for topology optimization of thermally actuated c... more This work presents an element addition strategy for topology optimization of thermally actuated compliant mechanisms under uniform temperature fields. The proposed procedure is based in the evolutionary structural optimization (ESO) method, which has been successfully applied to several optimum material distribution problems, but not for thermal compliant mechanisms. The present paper aims to progress on this work line and an extension of this procedure, based on an additive version of the method, is developed to approach the more complicated case of thermal actuators. As an initial simple approach, this research considers only uniform heating of the system. The adopted method has been tested in several numerical applications and benchmark examples to illustrate and validate the approach.

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Overhang constraint for topology optimization of self-supported compliant mechanisms considering additive manufacturing

Computer-Aided Design, 2019

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Study of Topology Optimization Parameters and Scaffold Structures in Additive Manufacturing

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016), 2016

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Sequential element rejection and admission method (SERA) for topology optimization using a constraint on perimeter

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Topology optimization of 3D compliant actuators by a sequential element rejection and admission method

IOP Conference Series: Materials Science and Engineering, 2016

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Procedimiento integrado para el diseño óptimo de forma y topología en estructuras laminares

Design of Compliant Mechanisms with a Sequential Element Rejection and Admission Method

Proceedings of 10th World Congress on Computational Mechanics, 2014

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Modelo detallado para análisis estático de conjuntos de rodamiento de vuelco

On the Design of a Compliant Mechanism with Non-Uniform Thermal Effects using Evolutionary Structural Optimization

Proceedings of the Eleventh International Conference on Computational Structures Technology

ABSTRACT

Aplicación de las técnicas de optimización estructural al diseño de estructuras espaciales monocapa

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An alternative full-pivoting algorithm for the factorization of indefinite symmetric matrices

Journal of Computational and Applied Mathematics, 2015

Dental Implants with Conical Implant-Abutment Interface: Influence of the Conical Angle Difference on the Mechanical Behavior of the Implant

The International Journal of Oral & Maxillofacial Implants, 2013

Download

Parameter study of a SERA method to design compliant mechanism

12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conference and 14th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, 2012

An Evolutionary Approach for the Topology Synthesis of Compliant Mechanisms

Proceedings of the Ninth International Conference on Computational Structures Technology

Static Load Carrying Capacity in Four Contact Point Slewing Bearings: Theoretical and Preliminary Finite Element Calculations

Volume 3: Design and Manufacturing, Parts A and B, 2010

A Sequential Element Rejection and Admission (SERA) method for compliant mechanisms design

Structural and Multidisciplinary Optimization, 2012

A Sequential Element Rejection and Admission (SERA) method to design compliant mechanisms with to... more A Sequential Element Rejection and Admission (SERA) method to design compliant mechanisms with topology optimization techniques is presented in this work. This procedure allows material to flow between two different material models: 'real' and 'virtual'. The method works with two separate criteria for the rejection and admission of elements to efficiently achieve the optimum design. The SERA method overcomes the problems encountered by the ESO method when used to design compliant mechanisms. Three benchmark problems are presented to show the validity and robustness of the SERA method to design complaint mechanisms, regardless of the design parameters chosen.

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Second order mobility analysis of mechanisms using closure equations

Meccanica, 2012

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Topology synthesis of multi-material compliant mechanisms with a Sequential Element Rejection and Admission method

Finite Elements in Analysis and Design, 2014

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Evolutionary optimization of compliant mechanisms subjected to non-uniform thermal effects

Finite Elements in Analysis and Design, 2012

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Electro-thermal compliant mechanisms design by an evolutionary topology optimization method

Engineering Computations, 2013