This diploma thesis deals with the design of a universal muzzle device for the assault rifle. The device is designed to produce Selective Laser Melting. The main objective is the elimination negative effects of gunshot. The paper explores possibilities of using porous structures for this type of equipment. The influence of individual types of porous structures on the flow of gases is monitored. The universal muzzle device itself is optimized using CFD analyzes. The device was made using SLM technology and experimentally verified. His impact on the impact, gun lift, noise and flame elimination was investigated.

In the work is used the processing of metallic material by the method of Selective Laser Melting. The main objective is to verify and describe the influence of the individual process parameters entering the production process when processing the alloy Cu7.2Ni1.8Si1Cr with SLM. This alloy contains 90 % copper. The first theoretical part of the thesis describes so far processed copper alloys with a high content of copper using the method of Selective Laser Melting. The practical part then deals with the specification of the main process parameters, which are optimized in the next part of the work solution. On the basis of the information obtained experimental bodies have been created, which will be tested and analyzed in several steps. The work focuses on thin-walled samples, which have a perspective use in the creation of highefficiency heat exchangers. The main results that the work deals with are the relative density and mechanical properties of the material. Also, great emphasis is placed on the resulting surface quality

The thesis deals with the processing of pure iron by Selective laser melting technology as a material with good electromagnetic properties. The main area is the optimization of the production of thin-walled samples, which monitor the influence of process parameters on the thickness and quality of the wall surfaces. In addition to the perpendicular walls, walls built at an angle of 45° are also examined. Another phase of the thesis is the determination of process parameters for bulk bodies to achieve the lowest porosity and high surface quality. An important part of the research is the application of acquired knowledge in the production of samples designed to test magnetic properties as well as part for a specific application. These considerations concern not only the setting of the printing parameters, but also the heat treatment and its influence on the magnetic and mechanical properties of the material. Mechanical properties were determined by tensile tests and hardness tests. All samples were made on a SLM 280HL using a 400W ytterbium laser.

This thesis discusses how to test the mechanical properties of openlattice truss structures and hybrids being a tube containing a latticetruss structure. By properties we mean strength, stiffness, thermalconductivity and so forth.Mechanical testing was done on two different structures to betterunderstand how the load-bearing properties change when these structuresare subjected to tensile, compressive and bending forces. The structuresinvestigated were Diamond and Octagon built at 45° and 90°. Acousticemission was also used to evaluate and analyze the different behaviour ofthe structures. The test results were used to produce design criteria forproperties in different cell structures manufactured of Hastelloy X™. Amap with design criteria containing stiffness and weight per cubiccentimetre was produced for parts that would be subjected to compressiveforces.

During this master thesis a crushing material composite was developed in order to determine if a specific design consisting of a pointy hard phase with a ductile phase in between can reduce the load needed to crush stone and therefor decrease the energy consumption during stone crushing. The steel hard phase (ASP 2012) was printed using an additive manufacturing method called selective laser melting (SLM). A process parameter optimization was performed in order to achieve a dense material and a pre-heated building platform was used to prevent cracking. The hard phase designs were printed and then filled with bronze (JM3 and JM7). The composites and steel references were tested by placing a stone on each sample and applying pressure until the stone broke. After the tests, the loads and the deterioration of the samples was analyzed. The results showed that it was possible to print the hard phase, but some defects like micro cracking were hard to eliminate entirely. Several methods were tested to cast the bronze but the most suitable during this project was melting of the bronze in an induction furnace with vacuum atmosphere. The results from the crushing simulations showed that there was a small difference between the references and the developed macro composites. The composites began to crush stones at lower loads than the references. Nevertheless, due to a large dispersion of the results a statistical difference could not be established.

<p> The Selective Laser Melting (SLM) process is a manufacturing technique that facilitates the  production of metallic parts with complex geometries and reduces both materials waste and lead  time. The high tunability of the process parameters in SLM allows the design of the as-built part’s  characteristics, such as controlled microstructure formation, residual stresses, presence of pores,  and lack of fusion. The main parameter in the SLM process that influences these parts’  characteristics is the transient temperature field resulting from the laser-matter interaction.  Nanosecond pulsed lasers in SLM have the advantage of enabling rapid and localized heating and  cooling that make the formation of ultrafine grains possible. This work shows how different pulse  durations can change the near-surface microstructure and overall mechanical properties of metallic  parts. The nanosecond pulses can melt and resolidify aluminum parts’ near-surface region to form nanograined gradient structures with yield strengths as high as 250.8 MPa and indentation  strengths as high as 725 MPa, which are comparable to some steel's mechanical properties. Knowing that the nanosecond pulsed lasers cause microstructure refinement for high-purity metals,  the microstructure variations effects were also investigated for the cast iron alloy. Cast iron was  used alone and mixed with born or boron nitride powders to induce the precipitation of  strengthening phases only enabled under high cooling rates. Although producing parts with  superior mechanical properties and controlling the precipitation of strengthening phases, the SLM  process with nanosecond pulsed lasers is still accompanied by defects formation, mainly explained  by the large thermal gradients, keyhole effect, reduced melt pool depth, and rapid cooling rates.  Ideally, a smooth heating rate able to sinter powder grains, facilitating the heat flow through the  heat-affected zone, followed by a sharper heating rate that generates a fully molten region, but  minimizes ablation at the same time are targeted to reduce the porosity and lack of fusion. Then, a  sharp cooling rate that can increase the nucleation rate, consequently refining the final  microstructure is targeted in the production of strong materials in SLM with pulsed lasers. This  work is the pioneer in controlling the transient temperature field during the heating and cooling  stages in pulsed laser processing. The temperature field control capability by shaping a nanosecond  laser pulse in the time domain affecting defects formation, residual strains, and microstructure was  achieved, opening a wide research niche in the additive manufacturing field.  </p>

Selective laser melting process is an additive manufacturing technique that allows obtaining, from a 3D model, a physical model through a layer-by-layer manufacturing strategy. Several machines are commercially available, known as 3D printers. Recently, technology improvements have allowed the use of metallic materials; however, the amount of materials available is low due to the difficulty to find adequate manufacturing parameters. The thesis proposes a methodology, using an inclined plane, to set the minimum energy density to melt a continuous track, the first step of the melting process. Different process parameters from several commercials machines have been used to evaluate dimensional and mechanical properties. Replicas of traditional products have been fabricated using additive process and they have been compared. Finally, a protocol to use a selective laser melting process to reconstruct a personalized jaw prosthesis has been shown / La fusió selectiva per làser és un procés de fabricació additiva que permet obtenir, d'un disseny en 3D, un model físic de forma ràpida i a través d'una estratègia de fabricació capa a capa. Existeixen diferents màquines comercials anomenades impressores 3D. Actualment, les millores tècniques desenvolupades han permès la utilització de materials metàl·lics, no obstant, la quantitat de materials que es poden utilitzar és baix degut a la dificultat per trobar els paràmetres de fabricació més adequats. La tesis proposa una metodologia, a través d’un pla inclinat, que permet definir la densitat d’energia mínima per fondre un cordó continu, el primer pas del procés de fusió làser. Diferents paràmetres de varies màquina comercials s'han utilitzat per avaluar variables dimensionals i mecàniques. S'han comparat rèpliques fabricades mitjançant processos tradicionals i processos additius. Finalment, s'ha realitzat un protocol per a reconstruir una mandíbula personalitzada utilitzant la fusió selectiva per làser

Selected mapping (SLM) is a well-known technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. Although SLM scheme can reduce PAPR efficiently, the side information (SI) must be transmitted to the receiver to indicate the candidate signal that generates the OFDM signal with the lowest PAPR. Robust channel coding schemes are typically adopted to prevent erroneous decoding of SI, leading to the lower bandwidth efficiency. To reduce PAPR efficiently and avoid the bandwidth efficiency loss caused by the transmission of SI, two novel PAPR reduction methods are proposed in SFBC MIMO-OFDM systems with two transmitter antennas that employs the Alamouti coding. The candidate signals are constructed in the frequency-domain and time-domain in the first proposed scheme and the second proposed scheme, respectively. In addition, the orthogonality of the space frequency block code is preserved resulting in the data recovery and the corresponding SI can be easily obtained from the conventional Alamouti detection method for both transmission methods. Simulation results show that the BER performance of a SFBC MIMO-OFDM system with the proposed SI detection algorithm is very close to that of perfect SI detection if the extension factor is larger than 1.3.

Bioanalytical chemistry is a challenging field, often involving complex samples, such as blood, plasma, serum or urine. In many applications, sample cleanup is the most demanding and time-consuming step. In the work underlying this thesis a novel dynamic miniature extractor, known as a hollow-fibre liquid-phase microextractor (HF-LPME), was designed, evaluated and studied closely when used to clean plasma samples. Aqueous-organic-aqueous liquid extraction, in which the organic liquid is immobilised in a porous polypropylene membrane, was the principle upon which the extractor was based, and this is discussed in all the papers associated with this thesis. This type of extraction is known as supported-liquid membrane extraction (SLM). The aim of this work was the development of a dynamic system for SLM. It was essential that the system could handle small sample volumes and had the potential for hyphenations and on-line connections to, for instance, LC/electrospray-MS. The design of a miniaturised HF-LPME device is presented in Paper I. The extraction method was developed for some weakly acidic pesticides and these were also used for evaluation. In the work described in Paper II, the method was optimised on the basis of an experimental design using spiked human plasma samples. Paper III presents a detailed study of the mass-transfer over the liquid membrane. The diffusion through the membrane pores was illustrated by a computer-simulation. Not surprisingly, the more lipophilic, the greater the retention of the compounds, as a result of dispersive forces. The main focus of the work described in Paper IV was to make the HF/LPME system more versatile and user-friendly; therefore, the extractor was automated by hyphenation to a SIA system. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript.

Au cours de la dernière décennie, le procédé de fabrication additive par fusion sélective d'un lit de poudre SLM a attiré une grande attention dans le domaine de l'industrie, car il permet de produire rapidement des pièces de formes complexes. Le but de ce travail est d'étendre les performances des procédés SLM en étudiant la possibilité d'élaborer des pièces en atmosphère raréfiée. Pour atteindre cet objectif, une approche théorique et expérimentale a été développée, avec la mise en place d'une machine de fusion sélective par laser capable de travailler dans le domaine de pression de 1 à 10-2 mbar.Le travail sous vide permet d'éviter la formation du "bouclier" de plasma généré à partir de l'atmosphère de gaz ionisé par l'énergie du laser. Ceci permet d'une part d'éviter la contamination chimique du matériau (oxydation, nitruration,...) au cours des processus de fusion et d'autre part de réduire le taux de porosité. L'effet des paramètres du laser et des variables d'environnement sur la qualité de pièces a été étudié en considérant le cas du fer pur, de l'acier Inox 316L et du titane.Par ailleurs nous avons étudié la possibilité d'obtenir des alliages in-situ au cours de la fabrication par la technique SLM à partir de mélanges de poudres.Des essais ont été conduits à partir de mélanges Mg/Al, Fe/Ni et Ti/Ni. Dans tous les cas nous avons pu obtenir des alliages in-situ pour les domaines de composition visés qui correspondent à des applications pratiques (structures légères, alliage magnétique à faible coercivité, alliage à mémoire de forme). Les propriétés des matériaux obtenus, d'après les premières caractérisations effectuées, se comparent de façon favorable par rapport aux techniques classiques d'élaboration et de mise en œuvre.