The purpose of this work is to understand the reasons for varied mechanical properties among three polymer Powder Bed Fusion (PBF) Additive Manufacturing (AM) processes. Parts for this work were manufactured from Polyamide 12 (PA12) using the Laser Powder Bed Fusion (L-PBF), Multi-Jet Fusion (MJF), and the recently developed Large Area Projection Sintering (LAPS) processes. Previous works have shown that LAPS parts demonstrate significantly higher density, ductility, and toughness than parts from the L-PBF and MJF processes. A hot isostatic pressing (HIP) treatment was developed to reduce porosity in L-PBF and MJF parts and determine if increasing part density would improve ductility for these processes. It is found that density is not strongly correlated with mechanical properties for high density parts (ρ > 0.98 g/cm3) for the L-PBF and MJF processes, and a following study confirms that this is the case for the LAPS process as well. Differential Scanning Calorimetry (DSC) and microtome sectioning are performed on parts from all three processes, and it is found that neither percent crystallinity nor crystalline morphology are strongly correlated with mechanical properties. A heat treatment at temperatures well over the melting point for the material is developed and is shown to improve ductility and toughness for all three processes. It is concluded that the improved ductility observed in the LAPS process stems from long exposure to high temperature, rather than increased density or a specific crystalline structure, and is associated with post-condensation reactions increasing polymer chain length. Work is also presented on the development of a production-scale LAPS system at Ascend Manufacturing. This research focuses on the results of "tiling" and "scanning" methods for producing larger parts than previously possible with prototype LAPS systems. Tensile testing showed that the methods both produced parts with similar properties, though with lower ductility than previous LAPS parts. Analysis of thermal data identifies areas for improvement of the system to attain high strength and high ductility parts. Preliminary work is done to demonstrate avenues for process improvement. Analysis of data from across the entire powder bed shows that process defects can be observed from the thermal data available in the LAPS process, and that weak spots in parts may be related to this data. Finally, the potential for process improvement through a multiple-input, multiple-output (MIMO) control scheme is discussed.

Cold laps are defined as micro-lack of fusion defects at the weld toe more or less parallel to the surface of the parent plate. These defects are known to negatively influence the fatigue properties of weldments. Previous studies suggest that cold lap formation can not be avoided completely in Gas Metal Arc Welding (GMAW). Therefore, a better understanding of formation mechanisms is imperative to be able to minimize the number and size of these defects. The main objective of this work has been to provide a more comprehensive understanding of cold laps, including categorising, characterisation and defining the most significant factors for formation. GMAW was used to produce welds that were investigated by metallographic methods using light optical microscopy, scanning electron microscopy and energy dispersive spectrometry. A novel classification of cold laps was introduced and three types of cold laps were identified: spatter cold laps, overlap cold laps and spatter-overlap cold laps. It was shown that cold laps are partially or fully filled by oxides. The most common oxides are manganese silicon oxides which were concluded to be formed primarily by oxidation of droplets. The presence of oxides was found to significantly increase the tendency to form spatter cold laps as well as overlap cold laps. Particularly for overlap cold laps, it was found that the depth (in transverse direction of weld) is reduced when welding in a non-oxidising environment. Welding on blasted surfaces increased the cold lap formation by entrapment of gas. The droplet and base metal temperatures were also found to be significant factors in cold lap formation. For overlap cold laps the occurrence frequency decreased with increased preheating temperature of the base metal. Mechanisms of overflowing resulting in overlap cold laps were discussed based on an extensive literature review. Several phenomena are believed to contribute to overflow including Rayleigh instability, the balance of forces, transfer of lateral momentum by droplets and an outward Marangoni fluid flow of the weld pool. The present studies suggest that cold lap formation can be suppressed by ensuring that the welding process (arc) is as stable as possible and by welding on a preheated work piece in a non-oxidising environment.

The aim of this qualitative study was to map the preparation and process of relapse prevention programs in therapeutic community for treating addictions in Czech republic called Magdaléna o.p.s.. The next aim was to describe the specifics of these programs and analyse methods that are mostly applied. For fullfilling these aims, four methods were chosen: analisys of documents, semistructured interwiews with the members of the team of therapists, observation of the researcher in the specific relapse prevention program during her internship and one semistructured interview with client of this therapeutic community. The final number of respondents for this research was four therapists and one client. Three metodic relapse prevention documents were analysed and for setting the final outcomes of this research were also used the outputs from the observation of the researcher from the specific relapse prevention program. Based on this research it was found out, that the specific relapse prevention programs in Magdaléna have been part of the long-term structured schedule of the treatment. This program is on the schedule once per week in duration of one hour and it is managed by one of the therapists. The program have been carried out in group and it is always based on one specific topic. Educational and...