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

El modelo PETROMAR-3D bajo el paradigma del sistema de innovación

Este trabajo muestra una reflexión vinculada a los Problemas de la Ciencia, la Tecnología y la Sociedad. Se presenta el modelo PETROMAR-3D (desarrollado en el Instituto de Meteorología de Cuba) en sus dos variantes de modelación: numérica y probabilística. Bajo el enfoque de la innovación tecnológica, se describe el estado actual del monitoreo de derrames de petróleo en el mar, que es gestionado por el Grupo Anti-derrames del Ministerio de Transporte de Cuba. El paradigma tecnológico del sistema de innovación es analizado como posible solución viable en la implementación del modelo PETROMAR-3D para describir la dispersión de contaminantes en el mar, proponiendo la ampliación del mencionado grupo con la incorporación de varias entidades estatales que lo harían funcionar como sistema de innovación. Se hace un análisis de las principales características estructurales y organizativas que debe tener el sistema de innovación vinculado con el modelo de pronóstico de derrames de petróleo en los mares territoriales de Cuba, el cual garantiza una máxima eficiencia en su función. Estas propuestas tienen implicaciones en la visibilidad, la eficiencia y el aporte económico del grupo del sistema de innovación propuesto

Barium and its Importance as an Indicator of (Paleo)Productivity

Barium (Ba) is a trace element which occurs predominantly as barite mineral (BaSO4) in the marine environment. Previous work suggests that barite concentrations are related to the organic carbon flux and marine biological debris in the water column suggesting a direct or indirect involvement in the marine biological cycling. In addition, barite has a high preservation rate (~30%) in sediments and it is less affected by early diagenesis than other proxies for productivity such as carbonates (~10%) and organic carbon (~1%), for example. Therefore, Ba is considered an excellent proxy for ocean (paleo)productivity. However, correlating barite to productivity involves some caveats. Specifically, the post-depositional formation of barite in oxic sediments can lead to Ba release into porewaters under anoxic conditions, which can form barite again under oxic conditions. This diagenetic formation is not correlated to export production as the seawater authigenic barite formed with decaying organic matter in the water column. Therefore, the main goal of this work is to briefly review the marine Ba cycle and highlight its importance for (paleo)productivity research