Additive manufacturing (AM) is a general name used for production methodswhich have the capabilities of producing components directly from 3D computeraided design (CAD) data by adding material layer-by-layer until a final component is achieved. Included here are powder bed technologies, laminated object manufacturing and deposition technologies. The latter technology is used in this study.Laser metal deposition using powder as an additive (LMD-p) is an AM processwhich uses a multi-axis computer numerical control (CNC) machine or robot toguide the laser beam and powder nozzle over the deposition surface. Thecomponent is built by depositing adjacent beads layer by layer until thecomponent is completed. LMD-p has lately gained attention as a manufacturing method which can add features to semi-finished components or as a repair method. LMD-p introduce a low heat input compared to arc welding methods and is therefore well suited in applications where a low heat input is of an essence. For instance, in 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 processparameters 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 and that these parameters has a significant effect on the dimensionalcharacteristics of the material such as height and width of a single deposit as wellas the straightness of the top surface and the penetration depth.To further understand the effects found in the material, temperaturemeasurements has been conducted using a temperature measurement methoddeveloped 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 emitted laser light on the thermocouples.

Det här examensarbetet har utrett riskerna för att få bindfel vid gasmetalbågsvetsning av halv V-fog på uppdrag för DEKRA Industrial AB som utför teknisk kontroll, certifiering, provning och besiktning. Arbetet utreder ett tidigare fall där indikationer från ultraljudsprovning visade att bindfel och ofullständig inträngning fanns i den större delen av svetsförbanden i en konstruktion. De svetsförbanden var svetsade med gasmetalbågsvetsning och har en halv V-fogs utformning. En litteraturstudie gjordes om ljusbågsteorin och orsaken till bindfel. Sedan svetsades fyra prover upp, två med snäv fogvinkel och två med bred fogvinkel, där det tidigare fallet försöktes efterliknas. Proverna provades med ultraljudsprovning och makroskopisk provning för att finna bindfel och andra defekter. Litteraturstudien visar att bindfel uppkommer så fort ljusbågen inte hinner smälta upp det underliggande materialet och smältan läggs på osmält material. En av orsakerna till det är fel pistolvinkel vilket ger att ena fogen inte smälts och bindfel erhålls. Dessutom så spelar elektrodutsticket stor roll där ett för långt elektrodustick antingen ger en för kall process eller ett för stort smältbad beroende på om parametrarna ändras av svetsaren. Vid svetsning i halv V-fog så är åtkomligheten dålig så det är stor risk att få både fel pistol vinkel och ett felaktigt elektrodutstick. Provsvetsningens resultat var att de snäva halva V-fogarna var svår svetsade och fick ofullständig inträngning och innehöll bindfel och slagginneslutningar. Dessutom var topsträngarna svårsvetsade med WPS:ens parameterar. Slutsatsen efter svetsningen och provningen är att risken för bindfel är hög vid snäva fogar samt att de som svetsat i det tidigare fallet inte kan ha följt sina WPS:er för att uppnå godkända toppsträngar. / This thesis work has evaluated the risks of getting lack of fusion during gas metal arc welding of single-bevel prepared T-joints. The work has been done at DEKRA Industrial AB that is specialized in certification, testing and inspection. The reason for this work is an earlier case where ultrasound testing indicated lack of fusion and lack of penetration was located in the major part of the weld joints in a construction. Those weld joints had been gas metal arc welded and had a single-bevel preparation. A literature study was done on the subject of weld arc theory and the cause of lack of fusion. Then four samples were welded trying to imitate the earlier case, two with a wide joint preparation and two with a narrow preparation. The samples were subjected to ultrasound testing and macroscopic analysis to evaluate the existence of lack of fusion and other defects. The literature study shows that lack of fusion appear as soon the weld arc miss the base material and the molten weld consumable solidify on unmelted material. One of the causes is a wrong pistol angle which will make the weld arc miss one of the joint walls. Also, another important parameter is the electrode stick-out. A too long stick-out generates a too cold process or a too large puddle of melted metal depending if the welding parameters are adjusted to compensate the stick-out. When welding with a single-bevel joint, there is a heightened risk of getting the described problems because of the bad accessibility. The results from the welding were that the narrow prepared joints were hard to weld with and get proper quality, with lack of penetration and lack of fusion. The conclusion from the welding and testing is that the risk of getting lack of fusion is high while welding narrow single-bevel prepared Tjoints.

This work concerns the fatigue crack growth behaviour of nickel base single crystal superalloys. The main industrial application of this class of materials is in gas turbine blades, where the ability to withstand severe mechanical loading in combination with high temperatures is required. In order to ensure the structural integrity of gas turbine blades, knowledge of the fatigue crack growth behaviour under service-like conditions is of utmost importance. The aim of the present work is both to improve the understanding of the crack growth behaviour of single crystal superalloys and also to improve the testing and evaluation methodology for crack propagation under thermomechanical fatigue loading conditions. Single crystal superalloys have anisotropic mechanical properties and are prone to localization of inelastic deformation along the close-packed planes of the crystal lattice. Under some conditions, crystallographic crack growth occurs along these planes and this is a complicating factor throughout the whole chain of crack propagation life simulation; from material data generation to component calculation. Fatigue crack growth testing has been performed, both using conventional isothermal testing methods and also using thermomechanical fatigue crack growth testing. Experimental observations regarding crystallographic crack growth have been made and its dependence on crystal orientation and testing temperature has been investigated. Quantitative crack growth data are however only presented for the case of Mode I crack growth under isothermal as well as thermomechanical fatigue conditions. Microstructural investigations have been undertaken to investigate the deformation mechanisms governing the crack growth behaviour. A compliance based method for the evaluation of crack opening force under thermomechanical fatigue conditions was developed, in order to enable a detailed analysis of the test data. The crack opening force evaluation proved to be of key importance in the understanding of the crack driving force under different testing conditions. / <p>In the printed version of the thesis the series name <em>Linköping Studies in Science and Technology Licentiate of engineering thesis</em> is incorrect. The correct series name is <em>Linköping Studies in Science and Technology Licentiate thesis</em>.</p>

The work presented in this thesis was conducted at Uppsala University and at Fraunhofer IKTS, Dresden. The thesis aims to study design optimizations for increasing the diodicity and thereby performance of a Tesla valve, a type of “no moving parts” (NMP) valve, through design freedoms offered by ceramic additive manufacturing. Tesla valves are capable of creating a pressure differential across them purely by virtue of mechanical design, and do not employ any moving parts. By geometry manipulation, Tesla valves enable fluid to flow in a way that hinders its own flow, thereby creating fluidic resistance and increasing pressure in one fluid direction, while allowing relatively unimpeded flow in the opposite direction. The manufacture of Tesla valves in the past has been restricted to simple geometries because conventional manufacturing processes such as CNC machining are unable to produce intricate geometries, something that Tesla valves require. With the recent innovations in additive manufacturing, design of these complex geometries has become feasible but still requires further research. Prior literature has only explored relatively simpler constructs of Tesla valves, not fully utilizing the design freedoms offered by additive manufacturing. In this thesis, ceramic additive manufacturing and stereolithography has been used to manufacture complex Tesla valves. In addition to just complex design, this thesis also presents design optimizations that can be utilized for simpler Tesla valves for increasing a metric known as diodicity. Diodicity refers to the ratio of reverse to forward pressure difference, and a high diodicity of a valve indicates that the valve is able to hinder fluid flow more effectively in one direction than the opposite. Additive manufacturing boasts an ability to construct complex geometries, due to the layer-by-layer process of building the final component. Stereolithography (in particular, ceramic stereolithography) is capable of producing parts that have high resolution and dimensional accuracy, while also maintaining desirable material properties, such as resistance to high temperatures and mechanical durability. Since the envisioned Tesla valve is to be used at elevated temperatures, this makes stereolithography a viable method of producing Tesla valves for aerospace applications. Design optimizations were carried out and subsequently verified for effectiveness through fluid flow simulations and practical evaluations. Certain design optimizations were shown to have drastic effects on the diodicity of the Tesla valve, and these have been subsequently incorporated into the designs of the Tesla valve in an effort to increase the diodicity of the designed Tesla valves. For practical evaluation, the optimized Tesla valves were 3D printed through ceramic stereolithography and stereolithography and extensively tested on a testing rig, with experimental parameters congruent to the fluid flow parameters applied during fluid flow simulations. It was found that the results of the fluid flow simulations and experimental testing were somewhat consistent with each other, and that it is feasible to produce optimized Tesla valves through ceramic stereolithography. However, it was found through practical evaluation that certain design optimizations were found to have little to no effect on the diodicity of the final Tesla valve, with some optimizations even reducing the diodicity.

GPA INNOVATIVE S.L. (also known from now as GPA) was founded in Barcelona in 2013, legally constituted as STEROS GPA Innovative S.L., in order to provide solutions to various strategic challenges in the field of product design and the development of industrial applications. Among the eight different business lines, the main one is known as DLyte®. DLyte® is based on the patented DryLyte® Technology, the world's first dry-electropolishing process and it is suitable for the most common industrial metals, alloys and composite materials. It automates, simplifies and standardizes the post-processing of these set of materials, improving the surface finish obtained with traditional polishing processes. Within 918 machines on the market, 521 are used in the dental industry (representing the 56.75% of the total business). Therefore, to improve the polishing surface quality of dental alloys is a must for the company. Within this context, the very first aim of this Master thesis is to determine which DryLyte® electrolyte and/or electrical parameters are more suitable for polishing dental materials and in particular CoCr RPDs (chrome cobalt - Removable Partial Dentures). For that, an exhaustive electrolyte characterization and a surface analysis of the workpieces before and after being polished with this technology is realized. Also, another goal is to find a compromise between the electrical parameters and the better surface quality finish of RPDs and, last but not least, to ascertain if CoCr RPDs can be successfully polished under direct current (DC).

To address the concerns of simultaneously improving crash performance and fuel efficiency in the automotive industry, multi-material car bodies are becoming increasingly popular. Aluminium and steel are two materials whose properties complement each other well for this application. However, ultra-high strength steel (UHSS) and aluminium alloy is a hard-to-join material combination. In the last decades different solutions to this problem have been proposed, one of these being friction element welding (FEW). In this work, different UHSS have been joined to different aluminium alloys through the FEW equipment EJOWELD developed by EJOT. The joints have been evaluated though visual inspection, cross-section analysis, and mechanical tests. All materials could successfully be joined by the EJOWELD process.

Surface engineering is increasingly becoming inevitable for meeting the high-performance requirements constantly expected from modern engineering components. Higher demands for combined functionalities, which a base material alone cannot provide, motivate intensive academic studies on various types of coatings, with the ultimate objective of their practical utilisation in industries. Especially the study of wear has become of critical importance for the industry development of new components, as wear-related mechanisms frequently compromise the durability and reliability of machines. Consequently, the need for effective wear control has become progressively vital in pursuing advanced and dependable technology for the future. Different coating technologies are being developed to forestall the wear of engineering components. More specifically, the thermal spraying technique of atmospheric plasma spraying (APS) has been proven particularly efficient in implementing thick film coating for aeronautic, automotive and medical applications. However, advanced coatings are required for improved performance and extended durability in harsh operating environments. These developments have stimulated research on developing novel coating through optimised deposition parameters and modified feedstock characteristics to achieve a more redefined microstructure. The primary scope of the research associated with this thesis is to target the study and research of plasma-sprayed ceramic coatings designed to provide exceptional wear resistance to targeted components as well as improved mechanical properties. The presented work involves an investigation of varying feedstock powder particle-size distributions, different coating chemistries and comparing the suspension plasma injection technology to its more traditional powdered feedstock variant. The result obtained suggested that the influence of powder-size particles affects the resultant microstructure with a finer composition, denoted by a lower porosity of 1.3% compared to the coarser powder fed 1.9% (both presenting a standard deviation of 0.2%). However, it could be seen that both the presence of optimised spraying parameters and finer feedstock particles were significant in obtaining improved mechanical properties. Furthermore, an examination of the powder-fed coating revealed slightly improved hardness properties to the newly developed suspension-sprayed samples. However, the powder-fed coatings distinctly exhibited superior resistance to sliding wear with an average specific wear of 5.7 (± 0.9 standard deviation) compared to the 12.8 (± 1 standard deviation) × 10-6 mm3∙N-1∙m-1of suspension-based coatings. In conclusion, it was observed that the chemical composition of the alumina-chromia composite coating demonstrated exceptional hardness properties among the analysed samples (1603 Vicker Hardness 0.2) and superior sliding wear resistance (0.59 × 10-6mm3∙N-1∙m-1).

This thesis presents an experimental study on how to track zero gaps between metal sheets to be joined by laser beam butt welding. Automated laser beam welding is gaining interest due to its ability to produce narrow and deep welds giving limited heat input and therefore less distortions compared to other processes, such as arc-welding. The automated laser beam welding process is however sensitive to how the high power laser is positioned with regards to the joint position. Deviations from the joint position may occur due to inaccuracies of the welding robot and fixturing, changes in joint geometry, process induced distortions, etc. Welding with an offset from the joint position can result inlack of sidewall fusion, a serious defect that is hard to detect. This work develops and evaluates three monitoring systems to be used during welding in order to be able to later control the laser beam spot position. (i) A monitoring systemis developed for three different photo diodes, one for the visual spectrum of the process emissions, one for the infrared spectrum, and one for the reflected highpower laser light. The correlation between the signals from the photodiodes and the welding position relative to the joint is analysed using a change detection algorithm. In this way an indication of a path deviation is given. (ii) A visual camera with matching illumination and optical filters is integrated into the laser beam welding tool in order to obtain images of the area in front of the melt pool. This gives a relatively clear view of the joint position even during intense spectral disturbances emitted from the process, and by applying animage processing algorithm and a model based filtering method the joint positionis estimated with an accuracy of 0.1 mm. (iii) By monitoring the spectral emissions from the laser induced plasma plume using a high speed and high resolution spectrometer, the plasma electron temperature can be estimated from the intensities of two selected spectral lines and this is correlated to the welding position and can be used for finding the joint position.

The Plug &amp; Produce manufacturing system is a visionary concept that promises to facilitate the seamless integration and adaptation of manufacturing resources and production processes. The Plug &amp; Produce control system allows for the automatic addition and removal of manufacturing resources, minimizing human intervention. However, the reconfigurability and autonomous decision-making features of Plug &amp; Produce control systems pose challenges to safety design and control functions. In contrast to conventional manufacturing systems with fixed layouts and processes, ensuring safety in Plug &amp; Produce systems is complicated due to the complex risk assessment process, the difficulty of implementing non-restrictive safety measures covering all possible hazards, and the challenge of designing a reliable controller for consistent safe operation. This thesis addresses these challenges through various contributions. It introduces an automatic hazard identification method, considering emergent hazards after reconfiguration. A novel domain ontology is developed, incorporating safety models specific to Plug &amp; Produce systems. The work also proposes a generic, model-based, and automatic risk assessment method, along with a method for the safe execution of plans based on the results of the risk assessment. The results of this research offer benefits to process planners, who are responsible for coordinating the manufacturing processes with product design in the Plug &amp; Produce system. The proposed solution provides tools for process planners to validate their plans and reduces their safety-related responsibilities. The proposed safety assurance method seamlessly integrates into the multi-agent control of Plug &amp; Produce, providing the control system with risk scenarios associated with process plans. This enables proactive and reliable control, effectively avoiding potential risks during system operation. / Föreställ dig en automatiserad produktionsanläggning som omedelbart och automatiskt kan anpassa sig till förändringar utan att kompromissa med säkerheten för den personal som arbetar där. Denna avhandling strävar efter att uppnå just detta genom ett smartare sätt att säkerställa att produktionsanläggningar baserat på Plug &amp; Produce kan hantera säkerhet. Dettainnebär att konceptet Plug &amp; Produce nu närmar sig ett industriellt förverkligande. Säkerhet för automatiserade produktionsanläggningar innebär att alla maskiner ska vara utrustade med skydd för att göra arbetet säkrare. Idag är det vanligt med övervakning som skydd, dvs en dator som övervakar att allt går rätt till och stänger av om något är på väg att hända. I ett produktionsavsnitt som är baserat på Plug &amp; Produce kan man enkelt ställa om, det vill säga, lägga till eller ta bort maskiner, ändra layouten eller ändra på produkter som produceras. Efter en sådan omställning så måste säkerheten i produktionsanläggningen ses över enligt föreskrivna lagar och regler. Traditionellt så kräver detta anlitande av en säkerhetsexpert. Detta medför att en omställning utifrån ett säkerhetsperspektiv är både kostsamt och tidskrävande. Med resultatet från denna avhandling så går det nu att ställa om utan att behöva implementera nya säkerhetsfunktioner efter varje förändring. Denna forskning har utvidgat kunskapsområdet inom produktionsteknik för att skapa en "smartarefabrik" genom att inkludera säkerhetsfunktioner.Resultatet inkluderar algoritmer som kan upptäcka potentiella faror i fabriken och automatiskt tillämpa säkerhetsåtgärder för ett övervakat system. Detta innebär mindre tidsåtgång och lägre kostnader för säkerhetsarbetet. De som drar mest nytta av detta är människorna som planerar för hur saker skall tillverkas med hjälp av Plug &amp; Produce. Resultatet av detta arbete underlättar deras arbetsuppgifter och bevarar flexibiliteten i Plug &amp; Produce, vilket eliminerar behovet av att välja mellan flexibilitet och säkerhet

Multi-material structures are increasingly used in vehicle bodies to reduce weight of cars. The use of these lightweight structures is driven by requirements to improve fuel economy and reduce CO2 emissions. The automotive industry has replaced conventional steel components by lighter metals such as aluminium alloy. This is done together with cutting weight of structures using more advanced strength steels. However, sound joining is still difficult to achieve due to differences in chemical and thermal properties.   This research aims to develop a new innovative welding technique for joining aluminium alloy to ultra-high strength steels. The technique is based on friction stir welding process while the non-consumable tool is made of an ordinary tool steel. Welding was done by penetrating the rotating tool from the aluminium side without penetrating into the steel surface. One grade of Al-Mg aluminium alloy was welded to ultra-high strength steels under lap joint configuration. Different types of steel surface coatings including uncoated, hot-dipped galvanised and electrogalvanised coating have been studied in order to investigate the influence of zinc on the joint properties. The correlation among welding parameters, microstructures, intermetallic formation and mechanical properties are demonstrated in this thesis.  Results have shown that friction stir welding can deliver fully strong joints between aluminium alloy and ultra-high strength steels. Two intermetallic phases, Al5Fe2 and Al13Fe4, were formed at the interface of Al to Fe regardless of surface coating conditions. The presence of zinc can improve joint strength especially at low heat input welding due to an increased atomic bonding at Al-Fe interface. The formation of intermetallic phases as well as their characteristics has been demonstrated in this thesis. The proposed welding mechanisms are given based on metallography investigations and related literature. / <p>QC 20170519</p>