Infill topology optimization of porous structures with discrete variables by the sequential element rejection and admission method

This article presents an infill topology optimization procedure to generate lightweight porous structures. The proposed method is based on discrete variables and builds upon the sequential element rejection and admission method, extending previous work on topology optimization for infill structures. Local volume constraints are introduced in the conventional formulation of the topology optimization problem for maximum stiffness design instead of the global volume constraint. The local constraints are applied, dividing the interior of a given design shape into quadrangular subdomains with variable aspect ratios. The localized material within these subordinate cells is allowed to flow between two discrete material models, ‘real’ and ‘virtual’, where two separate criteria are considered for the rejection and admission of elements. The results demonstrate the effectiveness of the method, showing that detailed porous designs are efficiently achieved with the proposed strategy. Numerical examples demonstrate the effects of the different design parameters

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

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

Study on the element rejection and addition strategies of discrete topology methods

The discrete methods such as ESO/AESO/BESO/SERA methods are some of the topology optimization methods that contributed to the rapid expansion of the optimization field. Between the different approaches, an issue that remains unstudied is the key difference between the two strategies to add and remove material that can be found in the literature for discrete topology optimization methods. They can be differentiated in two groups: 1) ne criterion Topology methods that consider one criterion to add and remove material (hard and soft kill BESO); 2) wo criteria Topology methods that consider two separate criteria to add and remove material (original BESO, SERA). In this paper, a study of the two strategies using examples of structural and compliant mechanisms design is performed to understand the implications of each option. This analysis shows that the elements that are added and removed are not the same in the two strategies, especially in compliant mechanisms design. In addition, the study concludes that with the ne criterion-strategy there is no control in the process as the method does not consider the current material status in order to select which elements to add and remove from the design domain

Results comparison between SIMP and SERA for compliant mechanisms design

The SERA method was extended to the design of compliant mechanisms. This method allows material to be added and removed from the design domain until the optimum topology is reached. The main difference with respect to other bi-directional methods that add and remove elements from the design domain is the separate treatment of ‘real’ and ‘virtual’ material. Separate criteria for each material model are defined to efficiently add and remove elements and achieve the optimum topology. The SIMP method is still the most widely used method in the field of topology optimization though. In this approach, the effective property of each element consists of its density raised to a power and multiplied to the material properties of the solid material. This paper presents a comparison of results between these two methods including evolution histories for different examples

INFILL OPTIMIZATION WITH THE SEQUENTIAL ELEMENT REJECTION AND ADMISSION METHOD: POROUS STRUCTURES FOR ADDITIVE MANUFACTURING

This paper presents an infill topology optimization procedure to generate lightweight porous structures by the Sequential Element Rejection and Admission (SERA) method. The proposed procedure evaluates the material volume of small neighbourhoods guaranteeing the presence of material within each of them by means of a set of local volume constraints. Local material varies between solid (“real”) and void (“virtual”) material models, where the element rejection and admission processes are conducted by two separate criteria. The novelty of the method is substantiated on the division of the domain into smaller subdomains where the material rejection and admission process is performed by means of the discrete topology optimization method SERA. The effectiveness of the method is demonstrated by analysing an MMB beam, where the impact of different neighbourhood sizes is studied

Tratamiento de aguas residuales mediante sistemas integrados de lagunas artificiales: implicaciones en el paisaje

P. 95-102El cumplimiento de la normativa europea en materias de depuración de agua exige la aplicación de metodologías que cumplan con el requisito fundamental de adecuación e integración en el paisaje. El diseño de depuración por macrófitos, que se presenta como ejemplo práctico en este trabajo, para resolver el problema de aguas residuales del núcleo de población de Cantejeira, verterá sus aguas en un arroyo, afluente del río Valcarce, subsidiario del Sil. Los sistemas de depuración más adecuados para el tratamiento integral del agua residual son las lagunas artificiales con macrófitos. La eficacia en depuración supera de forma significativa los umbrales marcados por la norma, pero requieren un diseño especial para su acoplamiento topográfic