The interfacial heat transfer coefficient is an important variable regarding the subject of metal castings. The error associated with the experimental temperature data must be dealt with appropriately so that they do not significantly affect the resulting interfacial heat transfer coefficient. The systematic and random errors are addressed using a combination of three-dimensional finite element modeling and the matrix transform method, respectively. Experimentally obtained A356 permanent mold casting data was used to estimate the interfacial heat transfer coefficient corresponding to common industrial mold coatings.

In the early days of gear manufacturing, engineers aimed to produce teeth as close to the theoretical shape as possible. As machinery advanced and demand for high-speed, high-torque, and quieter transmissions grew, optimizing gear teeth became increasingly important [1]. Techniques such as tip and root relief reduced engagement shocks, while lead modifications like lead slope and crowning increased load-carrying capacity. Gas turbines are complex, high-load machines that require the use of suitable gearboxes with highly reliable components. The importance of this reliability cannot be overstated, as any downtime can result in significant financial repercussions. By implementing the right modifications, it is possible to reduce the causes of failure and improve the overall performance of the gearboxes, leading to more efficient and cost-effective operations. The primary focus of this thesis is to explore the use of various modification methods to achieve the most optimal load distribution across the face width of a double helical gear. This is accomplished through the use of FVA workbench and analytical calculations, allowing for a thorough and comprehensive analysis of these modifications. / Ingenjörer när växeltillverkning var i sin linda, hade som avsikt att producera kuggar så nära dess teoretiska form som möjligt. I takt med att maskiner utvecklades ökade proportionell efterfrågan på transmissioner med hög hastighet och vridmoment med tystare drift, sedan dess har optimeringen av kuggarna fått grepp. Profilmodifieringar som topp- och fotavlättning minskade ingreppsstötar, på engelska ”lead modification”, ”lead slope” och ”crowning” ökade lastkapaciteten. Gasturbiner är höglastade maskiner som kräver behov av lämplig växellåda med behov av mycket pålitliga komponenter för att minska och eventuellt undvika stillestånd då antalet maskiner är många och det kommer att kosta mycket i sådana fall. Om det görs rätt kan modifieringar minska orsakerna till fel och förbättra växellådornas prestanda. Denna avhandling behandlar användningen av dessa modifieringsmetoder för att erhålla den mest optimala lastfördelningen över kuggflanken på en snedkuggsväxel, vilket görs med FVA-Workbench och analytiska beräkningar.

This thesis presents a multiscale investigation and characterization of additive manufactured Polyamide material using fused deposition modelling technique. Manufacturing was performed using Markforgeds – Mark one 3D printer.  A multiscale investigation dedicated to minimizing the effect of shape distortion during 3D printing are presented, focusing on both molecular alignment in microstructure and implementing internal structures in mesostructure. Characterization on samples investigating microstructure was performed with coefficient of linear thermal expansion measurement and 3-point bending experiment. Different samples with varying infill patterns are tested and results indicates an isotropic behaviour through the manufactured samples and implies no molecular alignment due to printing pattern. In meso-structure, an implemented internal pattern is investigated. All samples are measured with 3D scanning equipment to localize and measure the magnitude of shape distortion. Attempts to find relationships in shape distortion and porosity between the samples resulted in no observed trends. Compressive experiments where performed on samples in axial- and transverse directions resulting in anisotropic behaviour. The largest compressive stiffness is recorded in axial direction reaching 0,33 GPa. The study is done in collaboration with Swerea SICOMP and Luleå University of Technology.

The thesis is focused on the current issues of concrete resistance to high temperatures. The theoretical part has been processed the changes taking place in the individual components of concrete and changes affecting the physical - mechanical properties of concrete and color-changing effects manifesting high. In the experimental part of the load was, carried concrete test samples to a temperature of 400 ° C, 600 ° C and 800 ° C. After the thermal load, has been on test samples tested changes in physico - mechanical properties, especially concrete compressive strength, water absorption but also a visual assessment of the concrete surface

<p>The Powder Bed Fusion (PBF) process is increasingly employed by industry to fabricate complex parts with stringent standard criteria. However, fabricating parts free of defects using this process is still a major challenge. As reported in the literature, thermally induced abnormalities form the majority of generated defects and are largely attributed to thermal evolution. Various methodologies have been introduced in the literature to eliminate or mitigate such abnormalities. However, most of these methodologies are post-process in nature, lacking adaptability and customization to accommodate different geometries or materials. Consequently, they fall short of adequately addressing these challenges. Monitoring and controlling temperature, along with its distribution throughout each layer during fabrication, is an effective and efficient proxy to control the thermal evolution of the process. This, in turn, provides a real-time solution to effectively overcome such challenges. </p> <p>The objective of this dissertation is to introduce a novel online thermography and closedloop hybrid-control (NOTCH)©, an ultra-fast and practical control approach, to modify the scan strategy in metal PBF in real time. This methodology employs different mathematical-thermophysical concept-based or thermophysical-based models combined with optimization algorithms designed to optimize the printing sequence of islands/stripes/zones in order to avoid or mitigate residual stress and distortion. This methodology is adaptable to different geometries, dimensions, and materials, and is capable of being used with machines having varying ranges of specifications. </p> <p>NOTCH’s objective is to achieve a uniform temperature distribution throughout an entire layer and through the printed part (between layers) to mitigate residual stress and thermally related distortion. To attain this objective, this study explores modifying or optimizing the printing sequence of islands/stripes in an island or the strip scanning strategy. This dissertation presents three key contributions: </p> <p>First, this work introduces two potential models: the Genetic Algorithm Maximum Path (GAMP) strategy and Generalized Advanced Graph Theory. Preliminary results for a printed/simulated prototype are presented. These models, along with the Tessellation algorithm (developed in my M.Sc. thesis), were employed within NOTCH.</p> <p>Second, I developed two optimization algorithms based on the greedy and evolutionary approaches. Both algorithms are direct-derivative-free methods. The greedy optimization provides a definitive solution at each printing step, selecting the island/stripe that ensures the highest temperature uniformity. Conversely, the evolutionary algorithm seeks to obtain the final optimal solution at the end of the printing process, i.e., the printing sequence with the highest uniformity in the last printing step. This approach is inspired by the concept of Random Search algorithms, offering a non-definitive solution to find an optimal solution. </p> <p>Last, this work presents the NOTCH methodology, enabling real-time modification of printing sequences through the integration of a novel thermography methodology (developed in my M.Sc. thesis), developed models, and optimization algorithms.</p> <p><br></p>

The master thesis is focused on current issues of concrete behaviour under high temperatures. In the theoretical part, a search of knowledge about changes in concrete, which take place when exposed to thermal loads, which simulates the effect of fire, is performed, and summarized. It is also important to summarize the changes in the individual components that are used to produce concrete. This work describes the effect of high temperatures on mechanical and physical properties as well. There is an information about the most used fibres and their function in concrete. Emphasis is placed on describing the possibility of using recycled PET or cellulose fibres due to the positive environmental impact. In the experimental part, recipes with different types and amounts of fibres are proposed. The subject of the research was to determine how individual types and amounts of fibres affect the physical mechanical properties of concrete and their suitability for use at high temperatures. Microscopic scanning and study of changes in the structure of concrete was also performed.

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