Additive Manufacturing of a Microbial Fuel Cell - A detailed study

In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency. We explored the limits, if any, of additive manufacturing (AM) technology to fabricate a fully AM-based powering device, exploiting low density, open porosities able to host the microbes, systems easy to fuel continuously and to run safely. We obtained an optimal energy recovery close to 3 kWh m−3 per day that can power sensors and low-power appliances, allowing data processing and transmission from remote/harsh environments

From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering

In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS) is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of specimens built along different orientations parallel and perpendicular to the powder deposition plane. With respect to a similar aluminum alloy as-fabricated, a higher yield strength of about 40% due to the very fine microstructure, closely related to the mechanisms involved in this additive process is observe

Convergence of Natural pp-Means for the pp-Laplacian in the Heisenberg Group

In this paper we prove uniform convergence of approximations to $p$-harmonic functions by using natural $p$-mean operators on bounded domains of the Heisenberg group $\mathbb{H}$ which satisfy an intrinsic exterior corkscrew condition. These domains include Euclidean $C^{1,1}$ domains

Privilege (Caso de estudio)

Privilege, es la marca con la que lafamilia Jaramillo se lanzó al mercadocaleño, ofreciendo ropa sobre mediday talla para hombres y mujeres, conaltos estándares de calidad, serviciopersonalizado y diseños de moda; suportafolio de productos incluye ropaformal y casual para ejecutivos(as).Esta marca, pese a no tener competidoresdirectos, sí observaba que algunasmarcas y diseñadores exclusivosse encontraban dentro del grupo deconsideración de los consumidoresobjetivo de Privilege.La gerencia de la compañía enfrentacostos Þ jos elevados (ocupación demaquinaria al 50%) que afectan larentabilidad; un nuevo punto de ventaque presenta promedio de ingresosinferiores a los necesarios para su autosostenibilidad;bajo reconocimientode marca por parte del target, competidorescon gran músculo Þ nancieroy marcas altamente reconocidas contrayectoria y precios competitivos.Target, mercado meta, posicionamientode marca, recordación y capitalde marca.

Laser powder bed fusion of aluminum alloys

The aim of this study is to analyze and to summarize the results of the processing of aluminum alloys, and in particular of the Al-Si-Mg alloys, by means of the Additive Manufacturing (AM) technique defined as Laser Powder Bed Fusion (L-PBF). This process is gaining interest worldwide thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical strength and hardness related to a very fine microstructure. L-PBF is very complex from a physical point of view, due to the extremely rapid interaction between a concentrated laser source and micrometric metallic powders. This generate very fast melting and subsequent solidification on each layer and on the previously consolidated substrate. The effects of the main process variables on the microstructure and mechanical properties of the final parts are analyzed: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power, scanning speed and scanning strategy. Furthermore, some examples of applications for the AlSi10Mg alloy are illustrated.</p

Experimental validation of topology optimization of Additive Manufactured polymeric beams subjected to three-point bending test

Topology Optimization (TO) is a powerful tool for the optimization of product geometry and weight for compliance with structural requirements. The shapes generated by TO are generally complex and intricated, but nowadays they can be produced by Additive Manufacturing (AM) or 3D Printing. 3D Printing is the term that is widely used to address layered manufacturing in the case of consumer applications with polymeric materials, while AM mostly refers to industrial applications. The basic algorithm for TO is based on the Solid Isotropic Material with Penalisation (SIMP) method. The increasing importance of AM has recently driven researchers to develop modified versions of the SIMP algorithm for considering the constraints and peculiarities of layered manufacturing, such as the use of lattice structures with intermediate densities or the need to include support structures in the case of overhanging features. Owing to the diffusion of AM and 3D Printing, SIMP methods have also been implemented in many commercial computer aided design and engineering (CAD/CAE) software packages. Specific TO software is also available outside CAD packages. However, the anisotropic nature of layered technologies brings additional challenges for TO methods, especially in the case of load bearing structures. There is the need of improving the performances and the accuracy of TO by considering the peculiarities of the adopted AM techniques and the properties of the specific material. In this work a commercial TO software, SolidThinking Inspire, is used to optimize the geometry of polymeric beams subjected to a three-point bending test under different loading levels. Two different AM technologies are considered to produce the beams: powder bed Selective Laser Sintering (SLS) and material extrusion 3D Printing. Several polymeric materials are used and for the specific AM process the TO calculations are defined by considering the mechanical properties declared by the supplier on the material datasheet. The results of TO are then validated by fabricating and testing replicas of the optimized beams with the corresponding material and process. Starting from the CAD model of a three-point bending beam with some design space for TO, the TO is then executed with different load levels for the different materials and the optimized beam is then fabricated using the corresponding AM process. Finally, the results of the three-point bending test performed on the replicas of the optimized beams are compared to the TO results. Correlation and differences between the experimental behaviour of the beam and the flexural resistance predicted by TO are analysed and discussed

Evaluation of a Laboratory-Scale Gas-Atomized AlSi10Mg Powder and a Commercial-Grade Counterpart for Laser Powder Bed Fusion Processing

Laser powder bed fusion (LPBF) is an additive manufacturing technology that implies using metal powder as a raw material. The powders suitable for this kind of technology must respect some specific characteristics. Controlled gas atomization and post-processing operations can strongly affect the final properties of the powders, and, as a consequence, the characteristics of the bulk components. In fact, a complete characterization of the powders is mandatory to fully determine their properties. Beyond the most used tests, such as the volume particle size distribution (PSD) and flowability, the PSD number, the Hausner ratio and the oxidation level can give additional information otherwise not detectable. The present work concerns the complete characterization of two AlSi10Mg powders: a commercial-grade gas atomized powder and a laboratory-scale gas atomized counterpart. The laboratory-scale gas atomization allows to better manage the amount of the fine particles and the oxidation level. As a consequence, a higher particle packing can be reached with an increase in the final density and tensile strength of the LPBF bulk samples

Production of Dense Cu-10Sn Part by Laser Powder Bed Fusion with Low Surface Roughness and High Dimensional Accuracy

Tin-bronze alloys with a tin content of at least 10 wt% have excellent mechanical properties, wear resistance, and corrosion resistance. Among these alloys, Cu-10Sn was investigated in this study for production with the laser powder bed fusion process with a 500W Yb:YAG laser. In particular, a design of experiment (DoE) was developed in order to identify the optimal process parameters to obtain full density, low surface roughness, and high dimensional accuracy. Samples were characterized with Archimedes’ method and optical microscopy to determine their final density. It was shown that the first method is fast but not as reliable as the second one. A first mechanical characterization was performed through microhardness tests. Finally, a set of process parameters was identified to produce fully dense samples with low surface roughness and high accuracy. The results showed that the volumetric energy density could represent an approach that is too simplified, therefore limiting the direct correlation with the physical aspects of the process

Short Heat Treatments for the F357 Aluminum Alloy Processed by Laser Powder Bed Fusion

Conventionally processed precipitation hardening aluminum alloys are generally treated with T6 heat treatments which are time-consuming and generally optimized for conventionally processed microstructures. Alternatively, parts produced by laser powder bed fusion (L-PBF) are characterized by unique microstructures made of very fine and metastable phases. These peculiar features require specifically optimized heat treatments. This work evaluates the effects of a short T6 heat treatment on L-PBF AlSi7Mg samples. The samples underwent a solution step of 15 min at 540 °C followed by water quenching and subsequently by an artificial aging at 170 °C for 2-8 h. The heat treated samples were characterized from a microstructural and mechanical point of view and compared with both as-built and direct aging (DA) treated samples. The results show that a 15 min solution treatment at 540 °C allows the dissolution of the very fine phases obtained during the L-PBF process; the subsequent heat treatment at 170 °C for 6 h makes it possible to obtain slightly lower tensile properties compared to those of the standard T6. With respect to the DA samples, higher elongation was achieved. These results show that this heat treatment can be of great benefit for the industry