Additive manufacturing (AM) is a particularly useful manufacturing method for components designed using topology optimization (TO) since it allows for a greater part complexity than any traditional manufacturing method. However, the AM process potentially leads to anisotropic material properties due to the layer-by-layer buildup of parts and the fast and directional cooling. For Ti6Al4V tensile specimens built using electron beam melting (EBM), it has been observed that flat built specimens show superior strength and elastic moduli compared to top built specimens. Designs with the loading direction parallel to the build layers are therefore expected to show greater reliability. In this thesis a procedure is developed to optimize the AM build orientation considering anisotropic elastic material properties. A transversely isotropic material model is used to represent the in-plane and out-of-plane characteristics of AM produced parts. Two additional design variables are added to the TO formulation in order to control the orientation of the material using a coordinate transformation. Sensitivity analysis for the material direction variables is conducted for compliance as well as maximum von-Mises stress using a -norm stress aggregation function. The procedures for the AM build orientation optimization and stress constraints are implemented in the finite element software TRINITAS and evaluated using a number of examples in 2D and 3D. It is found that the procedure works well for compliance as well as stress but that a combination of these may lead to convergence issues due to contradicting optimal material orientations. An evaluation of the -norm stress aggregation function showed that a single global stress measure in combination with a stress correction procedure works well for most problems given that the mesh is refined enough to resolve the stresses accurately.

The traditional approaches to training surgeons are becoming increasingly difficult to apply to modern surgical procedures. The development of Minimally Invasive Surgery (MIS) techniques demands new and complex psychomotor skills, and means that the apprentice-based system described by 'see one, do one, teach one' can no longer be expected to fully prepare surgeons for operations on real patients, placing patient safety at risk. The use of cadavers and animals in surgical training raises issues of ethics, cost and anatomical similarity to live humans. Endoscopic sinus surgery involves further risk to the patient due to the proximity of vital structures such as the brain, eyes, optic nerve and internal carotid artery. In recent years, simulation has been used to overcome these problems, exposing surgeons to complex procedures in a safe environment, similarly to its use in aviation. However, the cases simulated in this manner may not be customised by training staff to present desired pathology. This thesis describes the design and development of a new tool for the creation of customised cases for the training of sinus surgery. Users who are inexperienced and non-skilled in the use of three-dimensional (3D) Computer Aided Design (CAD) modelling software may use the tool to implement pathology to the virtual sinus model, which was constructed from real CT data. Swelling is applied in five directions (four horizontal, one vertical) to the cavity lining of the frontal and sphenoid sinuses. Tumours are individually customised and positioned in the frontal, sphenoid and ethmoid sinuses. The customised CAD model may then be latterly manufactured using Three-Dimensional Printing (3DP) to produce the complex anatomy of the sinuses in a full colour physical part for the realistic simulation of surgical procedures. An investigation into the colouring of the physical model is also described, involving the study of endoscopic videos to ascertain realistic shades. The program was evaluated by a group of medical professionals from a range of fields, and their feedback was taken into account in subsequent redevelopment of the program, and to suggest further work.

Additive manufacturing (AM) is a general name used for manufacturing methods which have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final componentis achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study. Laser Metal Powder Deposition (LMPD) is an AM method which builds components by fusing metallic powder together with a metallic substrate, using a laser as energy source. The powder is supplied to the melt-pool, which is created by the laser, through a powder nozzle which can be lateral or coaxial. Both the powder nozzle and laser are mounted on a guiding system, normally a computer numerical control (CNC) machine or a robot. LMPD has lately gained attentionas a manufacturing method which can add features to semi-finished components or as a repair method. LMPD introduce a low heat input compared to conventional arc welding methods and is therefore well suited in, for instance, repair of sensitive parts where too much heating compromises the integrity of the part. The main part of this study has been focused on correlating the main process parameters to effects found in the material which in this project is the superalloy Alloy 718. It has been found that the most influential process parameters are the laser power, scanning speed, powder feeding rate and powder standoff distance.These process parameters have a significant effect on the temperature history ofthe material which, among others, affects the grain structure, phase transformation, and cracking susceptibility of the material. To further understand the effects found in the material, temperature measurements has been conducted using a temperature measurement method developed and evaluated in this project. This method utilizes a thin stainless steel sheet to shield the thermocouple from the laser light. This has proved to reduce the influence of the laser energy absorbed by the thermocouples.

Policymakers in the United States and elsewhere have recognized that a broad and competitive manufacturing sector is crucial to a robust economy and that to remain competitive, a nation must invent and master new ways of making things. Moving technologies from laboratory to commercial success poses considerable challenges however. If the technology is radically new, this transition can be so risky and investment-heavy that only very large private firms can attempt it. One such new technology is metal additive manufacturing (MAM). MAM provides a vivid illustration of the tensions policymakers must resolve in simultaneously supporting the commercialization of early-stage innovations of strategic national interest, while fulfilling the government’s duty to ensure human health and safety. After an initial chapter with a general overview of additive manufacturing technologies, this dissertation explores these tensions from the perspective of two very different industrial contexts: the U.S. as a technology leader and trailblazer in the development of the technology, and Portugal as a technology follower with severely constrained resources. In the first case study, I use the extreme case of MAM (an emerging technology with many sources of process uncertainty) in commercial aviation (an industry where lapses in safety can have catastrophic consequences) to unpack how the characteristics of a technology may influence the options for regulatory intervention. Although my work focuses on the U.S. and the Federal Aviation Administration’s regulation, I expect this work to have an international scope, given that in most countries regulation is heavily influenced by, if not an exact copy of, the U.S. regulation. Based on my findings, I propose an adaptive regulatory framework in which standards are periodically revised and in which different groups of companies are regulated differently as a function of their technological capabilities. I conclude by proposing a generalizable framework for regulating emerging process-based technologies in safety-critical industries in which the optimal regulatory configuration depends on the industry structure (number of firms), the performance and safety requirements, and the sources of technological uncertainty. In the second case study, I analyze the adoption of polymer (PAM) and metal (MAM) additive manufacturing technologies in the Portuguese molds industry, both of which offer important benefits to their products. Leveraging archival data (related to the history of Portuguese institutions, and the development of additive manufacturing both globally and in Portugal), insights from 45 interviews across academia, industry, and government; and 75 hours of participant observations, we develop insights about why institutional instability affected the adoption of Polymer Additive Manufacturing (PAM) and Metal Additive Manufacturing (MAM) differently. In both cases, Portugal invested in the technology relatively early, and in the case of PAM the research community has been able to move towards high-tech applications. In contrast, the adoption of MAM has been modest despite its potential to greatly improve the performance and competitiveness of metal molds. From the comparison between PAM and MAM, we generate theory about which technological and contextual factors affect their ‘technological forgiveness’, defined as the resiliency of a new technology’s adoption to institutional instability. We conclude by proposing a generalizable framework for ‘forgiveness’ in different industrial contexts. The final chapter of this dissertation contains practical recommendations for regulators and managers interested in adopting the technology. Policymakers in the aviation industry may want to encourage the creation of programs to gather more flight experience with MAM parts. Small aircraft and other applications with higher risk tolerance than commercial aviation might represent more important channels to gather information, as the history of composite materials suggests. More importantly, regulators may need to introduce clauses in their rules to regulate MAM to avoid situations of ‘regulatory lock-in’ which could harm the long-term potential of the technology. Despite the potential of additive manufacturing, we believe that near-term expectations for it are overblown. In general, additive manufacturing holds great promise, but in many areas the cart has gotten ahead of the horse. Much of the technology is still under development. The history of comparable technologies such as composite materials and high-performance castings shows that the problems may take decades to resolve. For now, additive manufacturing is cost-competitive only in niche applications — for instance, those involving plastics. Businesses that want to plunge into additive manufacturing should be cognizant of the challenges. Determining whether it makes sense to invest in additive manufacturing will require experimentation and learning.

Aluminum and aluminum-alumina powder mixtures were used to produce pyramidal fin arrays on aluminum substrates using cold spray as an additive manufacturing process. Using aluminum-alumina mixtures instead of pure aluminum powder could be seen as a cost-effective measure, preventing nozzle clogging. The fin geometries that were produced were observed using a 3D digital microscope to determine the flow passages width and fins geometric details. Heat transfer and pressure tests were carried out using different ranges of appropriate Reynolds numbers for the sought commercial application to compare each fin array and determine the effect of alumina content. It was found that the presence of alumina reduces the fins’ performance when compared to pure aluminum but that they still outperform traditional fins. Numerical simulations were performed and were used to explain the obtained experimental results. The numerical model opens up new avenues in predicting different parameters such as pressure and substrate temperature.

As órteses de membro superior são dispositivos que auxiliam na reabilitação da mão e que tem como objetivo estabilizar, imobilizar, prevenir e corrigir deformidades, melhorando assim a função. O processo tradicional de confecção de órteses é realizado por meio do uso de termoplásticos de baixa temperatura, material moldado diretamente sobre o membro do usuário, sendo neste processo relatados inúmeros problemas, que envolvem desconforto durante o processo, alto custo e baixa adesão do paciente ao uso. O presente trabalho, portanto, teve por objetivo propor a construção de um framework com abordagem metodológica projetual para a produção de órteses de membro superior baseada no processo de design e design colaborativo, com auxílio de recursos de fabricação digital, como digitalização tridimensional e manufatura aditiva (impressão 3D). Através de uma pesquisa exploratória, foram discutidas questões relativas ao projeto de órteses de membro superior (MMSS) pela forma tradicional, utilizando termoplástico de baixa temperatura, e questões do processo de design no desenvolvimento de novos produtos a serem aplicadas do desenvolvimento de órteses utilizando a manufatura aditiva A coleta de dados contou com a participação dos principais personagens envolvidos no processo, usuários de órteses, Terapeutas Ocupacionais e Designers. Com base na técnica de card sorting e entrevistas, foi elaborado um framework da abordagem projetual para a criação de órteses utilizando processos de fabricação digital, de forma colaborativa. O framework ainda foi aplicado no desenvolvimento de uma órtese a fim de avaliar os resultados e melhorias levantadas durante a fase de entrevistas com profissionais e usuários. Ao final do processo, obteve-se uma órtese funcional em que foram atendidos os requisitos necessários para a produção de uma órtese levantada pelo trabalho, além da criação do framework servindo como um guia para o desenvolvimento de órteses utilizando a manufatura aditiva. / Upper limb orthoses are devices that assist in the rehabilitation of the hand and that aim to stabilize, immobilize, prevent and correct deformities, thus improving the function. The traditional process of making orthotics is accomplished through the use of thermoplastics of low temperature, molded material directly on the member of the user, being in this process reported numerous problems, that involve discomfort during the process, high cost and low adhesion of the patient to the use. The present work, therefore, aimed to propose the construction of a framework with a design methodological approach for the production of upper limb orthosis based on the process of design and collaborative design, with the aid of digital manufacturing resources such as three - dimensional digitization and additive manufacturing (3D printing). Through an exploratory research, questions regarding the design of upper limb orthoses (MMSS) in the traditional way, using low-temperature thermoplastic, and design process issues in the development of new products to be applied in the development of orthoses using the additive manufacture The data collection was attended by the main characters involved in the process, users of orthoses, Occupational Therapists, and Designers. Based on the technique of card sorting and interviews, a framework of the design approach for the creation of orthoses using digital manufacturing processes was developed in a collaborative way. The framework was also applied in the development of a bracing in order to collaborate with the results and improvements raised during the interviews phase with professionals and users. At the end of the process, a functional orthosis was obtained, in which the necessary requirements for the production of an orthosis were obtained by the work, besides the creation of a framework serving as a guide for the development of orthoses using the additive manufacture.

Additive manufacturing processes of many alloys are known to develop texture during the deposition process due to the rapid reheating and the directionality of the dissipation of heat. Titanium alloys and with respect to this study beta titanium alloys are especially susceptible to these effects. This work examines Ti-20wt%V and Ti-12wt%Mo deposited under normal additive manufacturing process parameters to examine the texture of these beta-stabilized alloys. Both microstructures contained columnar prior beta grains 1-2 mm in length beginning at the substrate with no visible equiaxed grains. This microstructure remained constant in the vanadium system throughout the build. The microstructure of the alloy containing molybdenum changed from a columnar to an equiaxed structure as the build height increased. Eighteen additional samples of the Ti-Mo system were created under different processing parameters to identify what role laser power and travel speed have on the microstructure. There appears to be a correlation in alpha lath size and power density. The two binary alloys were again deposited under the same conditions with the addition of 0.5wt% boron to investigate the effects an insoluble interstitial alloying element would have on the microstructure. The size of the prior beta grains in these two alloys were reduced with the addition of boron by approximately 50 (V) and 100 (Mo) times.

Orientador: João Eduardo Guarnetti dos Santos / Resumo: O ombro por ser uma articulação muito instável está mais vulnerável a lesões. Afim de proteger e imobilizar a articulação o tratamento é seguido com o uso de tipoia. No entanto, a imobilização deixa as articulações sob os efeitos deletérios do desuso, o que pode favorecer o surgimento de lesões secundárias como a capsulite adesiva. O design e a ergonomia são considerados disciplinas científicas capazes de desenvolver e ajustar produtos às necessidades e às capacidades humanas. O objetivo deste estudo foi gerar parâmetros para o design ergonômico de uma tipoia alternativa utilizando as tecnologias de manufatura aditiva, a fim de minimizar os desconfortos termofisiológicos e o índice de capsulite adesiva após imobilização. Nesse contexto, desenvolveu-se com o auxílio do design um modelo de tipoia mais confortável, adequado, funcional e que não favorece o surgimento de complicações após imobilização do ombro. Foi realizada uma coleta de dados com indivíduos adultos, de ambos os gêneros, entre 18 e 85 anos de idade, 71 voluntários, que fizeram uso de tipoia para lesão do ombro. Seguiu com uma investigação ergonômica dos modelos de tipoia disponíveis no mercado, para desenvolver um modelo alternativo com as devidas adequações ergonômicas. O projeto da tipoia foi modelado no software CAD SolidWorks e a impressão foi por FDM (Fusão por Deposição de Material), em uma impressora 3D Creality CR-10, com material PLA (Ácido Polilactico). Para testar a percepção do usuário frente aos mode... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The shoulder because it is a very unstable joint is more vulnerable to injury, in order to protect and immobilize the joint, treatment is followed with the use of a sling. However, immobilization leaves the joints under the harmful effects of disuse, which can favor the appearance of secondary lesions such as adhesive capsulitis. Design and ergonomics are considered scientific disciplines capable of developing and adjusting products to human needs and capacities. The aim of this study was to generate parameters for the ergonomic design of an alternative sling using additive manufacturing technologies, in order to minimize thermophysiological discomfort and the adhesive capsulitis index after immobilization. In this context, a more comfortable, adequate, functional tipoia of model was developed with the aid of design, which does not favor the appearance of complications after shoulder immobilization. A data collection was carried out with adult individuals, both genders, between 18 and 85 years of age, 71 volunteers, who made use of tipoia for shoulder injury. It continued with an ergonomic investigation of the sling models available on the market, to develop an alternative model with the appropriate ergonomic adaptations. The design of the tipoia was modeled in SolidWorks CAD software and the printing was by FDM (Melting by Deposition of Material) in a Creality CR-10 3D printer with PLA material (Polylactic Acid). To test the user's perception of sling models, a semantic diff... (Complete abstract click electronic access below) / Doutor

abstract: Additive manufacturing (AM) has been extensively investigated in recent years to explore its application in a wide range of engineering functionalities, such as mechanical, acoustic, thermal, and electrical properties. The proposed study focuses on the data-driven approach to predict the mechanical properties of additively manufactured metals, specifically Ti-6Al-4V. Extensive data for Ti-6Al-4V using three different Powder Bed Fusion (PBF) additive manufacturing processes: Selective Laser Melting (SLM), Electron Beam Melting (EBM), and Direct Metal Laser Sintering (DMLS) are collected from the open literature. The data is used to develop models to estimate the mechanical properties of Ti-6Al-4V. For this purpose, two models are developed which relate the fabrication process parameters to the static and fatigue properties of the AM Ti-6Al-4V. To identify the behavior of the relationship between the input and output parameters, each of the models is developed on both linear multi-regression analysis and non-linear Artificial Neural Network (ANN) based on Bayesian regularization. Uncertainties associated with the performance prediction and sensitivity with respect to processing parameters are investigated. Extensive sensitivity studies are performed to identify the important factors for future optimal design. Some conclusions and future work are drawn based on the proposed study with investigated material. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2020

No description available.