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Leakages from seals are one of the important factors that are taken into consideration while designing any machining element. This is because leakages can affect the performance of any component and can also turn into a catastrophe. If looked into it, many parameters can be pointed out that can enhance leakages within the system, some of them may be pressure, temperature, clamping force and bolt distance etc. But the main parameter is the surface roughness, higher the roughness more the leakage and vice-versa. Thus, in this thesis an attempt has been made how the surface roughness can affect the performance of the sealing concept for metal bounded gasket with above four mentioned parameters. Also how leak proof surface can be defined using standard tribological parameters is the aim of this thesis. This report includes the results for methodologies implemented during the thesis and track down the leakages. The leaked surfaces were carefully studied and analyzed using different standards compared with the non leaked surfaces’ roughness parameters. / Läckagerisk från tätande förband är en av de viktigaste faktorerna som beaktas vid utformning av konstruktionsartiklar. Detta på grund av att konsekvenserna kan bli förödande. Det tätande förbandet påverkas av många olika parametrar såsom till exempel tryck, temperatur, klämkraft, skruvavstånd och val av packning. En viktig faktor är ytans beskaffenhet; Generellt läcker en grov yta och vågig yta mer än en fin och plan yta. Således har i denna avhandling ytans beskaffenhet studerats tillsammans med en packning av typen metallburen gummipackning för att påvisa täthetfunktionen som en funktion av tryck, temperatur, klämkraft och skruvavstånd. Denna rapport innehåller resultat och analys av olika standardmetoder för de ytor som ingick i utredningen.

Zirconia has been established as a promising material for dental implants. Various surface treatment methods have been utilized to promote better osseointegration and improve the success rate of dental implants. However, a better understanding of the influences of topographic characteristics on cell attachment, proliferation, and differentiation is needed. Different surface topographic zirconia specimens, As sintered, Mild rough, Moderate rough, and Rough zirconia groups were fabricated with sandblasting method in various distances and stages. The surface texture, microstructure, and wettability were inspected with the optical profiler, SEM, and contact angle measurement respectfully. Human primary osteoblast cells were cultured on the four groups of zirconia with different surface modifications in 24 well plates and on plates without test material as control. Crystal violet and triton X-100 solution were used to evaluate cell attachment efficiency at 9 hours and proliferation rate at 7, 14, and 21 days after seeding. ALP activity was measured with fluorometric assay. The expression of osteocalcin was measured with an ELISA kit. Alizarin red staining was conducted to evaluate the mineralization. The cell morphologies were inspected under SEM after cell fixation and critical point drying process. The data were analyzed with one-way ANOVA for experiment on each time interval and two-way ANOVA for all time points. Tukey post hoc test was used for pairwise comparison. P value < 0.05 was considered statistically significant. Topographic parameters and contact angle measured in As sintered, Mild rough, Moderate rough, and Rough surface groups were as follow: Sa = 0.23, 0.50, 2.13, 5 µm, Sal = 49.88, 21.20, 30.42, 49.87 µm, Sdq = 64.64, 248.60, 511, 734.66 µm/mm, Sk = 0.7, 1.54, 4.19,16 µm, Spk = 0.31, 0.64, 1.47, 5.13 µm, Svk = 0.35, 0.71, 5.96, 6.18 µm respectively, and contact angle = 64.6°, 55.2°, 43.5°, 38.6° respectively. The result showed that Rough zirconia group induced the highest cell attachment efficiency at 9 hours (p<.001). As sintered zirconia group promoted significant cell proliferation rate at 21 days (p<.001) while Rough zirconia group drastically down-regulated cell proliferation (p<0.001). The most elevated levels of ALP, osteocalcin, and mineralization expressions at 21 days were found in the Moderate rough group with significant differences (p<.001, p<.001, p<.001 accordingly) Within the limitations of this in vitro study, it can be concluded 1) the modified microroughened zirconia surfaces of Sa 5 µm would promote human osteoblast attachment but down-regulate cell proliferation, 2) the As sintered zirconia surface would stimulate cell proliferation, and 3) the microroughened surfaces of Sa 2 µm would up-regulate osteoblast differentiation. These findings could be incorporated into designing and fabricating the dental implant surfaces for optimal osseointegration.

The modern gas turbine engine requires innovative cooling techniques to protect its internal components from the harsh operating environment typically seen downstream of the combustor. Much research has been performed on the design of these cooling techniques thus allowing for combustion temperatures higher than the melting point of the parts within the turbine. As turbine inlet temperatures and efficiencies continue to increase, it becomes vitally important to correctly and realistically model all of the turbine's external cooling features so as to provide the most accurate representation of the associated heat transfer to the metal surfaces. This study examines the effect of several realistic endwall features for a turbine vane endwall. The first study addresses the effects of a mid-passage gap, endwall misalignment, and roughness on endwall film-cooling. The second study focuses on the effect of varying the combustor-to-turbine gap width. Both studies were performed in a large-scale low speed wind tunnel with the same vane geometry. Geometric and flow parameters were varied and the variation in endwall cooling effectiveness was evaluated. Results from these studies show that realistic features, such as surface roughness, can reduce the effectiveness of endwall cooling designs while other realistic features, such as varying the combustor-to-turbine gap width, can significantly improve endwall cooling effectiveness. It was found that, for a given coolant mass flowrate, a narrow combustor-turbine gap width greatly increased the coverage area of the leaked coolant, even increasing adiabatic effectiveness upstream of the vane stagnation point. The turbine designer can also more efficiently utilize leaked coolant from the combustor-to-turbine gap by controlling endwall misalignment, thereby reducing the overall amount of film-cooling needed for the first stage. / Master of Science

High strength boron steels are commonly used as structural reinforcements or energy absorbing systems in automobile applications due to their favourable strength to weight ratios. The high strength of these steels leads to several problems during forming such as poor formability, increased spring back, and tendency to work-harden. In view of these difficulties, high strength boron steels are usually formed by press hardening at elevated temperatures with a view to facilitate forming and simultaneous hardening by quenching of complex shaped parts.The high strength steel sheets are used with an Al–Si coating with a view e.g. to prevent scaling of components during hot-metal forming. The Al-Si coated high strength steel can lead to problems with galling (i.e. material transfer from the coated sheet to the tool surface) which have a negative influence on the quality of the produced parts as well as the process economy. The available results in the open literature pertaining to high temperature galling are very scarce. With this in view, the friction and wear behaviours of different tool steel coatings and different roughness lay directions sliding against Al–Si-coated high-strength steel at elevated temperatures have been investigated by using a high-temperature reciprocating friction and wear tester at temperature of 900 °C.The results have shown that parallel sliding with respect to the surface roughness lay reduces the severity of galling compared to perpendicular sliding. None of the coatings included in this study have shown beneficial effects in view of galling. The DLC coating experienced less galling compared to the AlCrN and TiAlN. Post polishing of the coated tool steel has resulted in more severe material transfer with higher and more unstable friction. / <p>Validerat; 20111022 (anonymous)</p>

Binder jetting is an additive manufacturing process that layer by layer builds a 3D model by selectively binding regions of powder using binder deposited though an inkjet printhead. The process offers several advantages over other additive manufacturing processes including fast build rates, vast material selection, decreased cost, and part resolution. The main disadvantage of binder jetting is poor mechanical properties, stemming from a poor understanding of the process physics. Porosity in final parts is not uncommon, but there is little understanding of where the porosity originates. The purpose of this thesis is to report the investigation of increased powder bed cohesion and its effects on part formation, part properties, and printing parameters in binder jetting. The interaction between binder and powder is complex. Binder exiting the printhead impacts the powder bed at speeds up to 10 m/s. The kinetic energy carried by the droplet disperses into the powder bed on impact, causing some powder particles to eject from the bed and other particles to rearrange within the bed. The particle ejection and rearrangement is theorized to be the physical cause of porous regions in binder jetted parts. This work uses a method called pre-wetting to introduce small amounts of moisture into the powder bed to effectively increase the cohesive forces between powder particles. Increased cohesion makes particle ejection and rearrangement during the powder/binder interaction more difficult. A method of accomplishing pre-wetting was developed and achieved successful moisture delivery using water and a water/tri-ethylene glycol mixture. Printed lines were used to characterize moisture content and study its effects on line formation and saturation levels. Low levels of moisture were shown to perform the best. Particle ejection and rearrangement was shown to decrease with moisture addition. Pre-wetting was shown to eliminate the defect known as balling, increasing the parameters known to successfully print lines. Water was identified as a poor substance for pre-wetting due to rapid evaporation, but tri-ethylene glycol/water solutions succeeded in proper moisture delivery. Saturation levels in lines decrease with added moisture and part dimensions increase. high-speed x-ray imaging verified pre-wetting reduction in particle ejection and rearrangement as well as supply some preliminary understanding of void formation during the printing process. The first few layers of the binder jetting process have been shown to increase in surface roughness values when compared to the undisturbed powder bed. This is likely due to a balling-like effect seen in layers. The effects of pre-wetting on layer and multi-layer formation were studied. Pre-wetting reduced the surface roughness levels in printed layers to the levels near the levels seen in undisturbed powder beds. In contrast, saturation levels in layers and multi-layers increased in value above those found in parts printed into dry powder, giving indication that porous regions within bound parts are being eliminated. Layer and multi-layer parts showed increased part dimensions with the addition of moisture. Overall, pre-wetting was shown to greatly reduce the effects of the binder/powder interaction and results strongly suggest that pre-wetting mitigates defect creation during the printing process. Further research should include testing of thicker multi-layer parts to study how saturation trends continue with increased layer numbers. In-process drying should be used in conjunction with pre-wetting in multi-layer parts to determine its effects on saturation levels and part dimensions. Post processing should be done to partially sinter, or infiltrate multi-layer parts created with and without pre-wetting to analyze porosity.

In the near future hydropower will be used to regulate intermittent energy sources, shallow water ways can then occur in close proximity to the power plants, where the bottom often consists of stones in a similar length scale as the water depth. The idea of this project, which has been initiated by Vattenfall R\&amp;D, is to compare experimental measurements in a laboratory environment with numerical simulations with CFD, this to find a way to represent roughness structures where there is low relative submergence. For the measurements in the lab, gravel were attached to the bottom of a flume and the water depth were measured for different flow rates and a CFD model were calibrated against the measurement data. A conversion of the Manning coefficient, originating from experimental measurements to equivalent Sand-grain size used in the CFD to model the roughness has been proposed and has shown good predictions of the maximum water depth. To capture the entire flow field, it is not enough to just model the friction from the roughness, it needs to be resolved and it may be necessary to consider the influence by form drag.

Castings made of aluminum 319 and A356.2 alloy were examined to determine the effectiveness of using pressure application during solidification to reduce porosity levels. Pyknometry was the method chosen to measure porosity. It was determined that the porosity of castings poured in both alloys was reduced in some instances. During the study, the surfaces of these castings were also examined and some were found to have defects present. After the porosity was evaluated, specimens of castings poured in both alloys were tested to determine whether or not the surface intrusions affected the castings. The defects were found to reduce the strength of the castings poured in aluminum 319. The castings poured in A356.2 did not have surface intrusions or any significant decreases in strength. Therefore it was concluded that of the two alloys tested, A356.2 alloy is most suited for using pressurization as a method of reducing porosity.

The Turbulent Heat Transfer Test Facility (THTTF) has been refurbished and the data acquisition system upgraded. The THTTF is now controlled by a LabView 4.1 program which replaces the old program in BASIC. Heat transfer data acquired using this new program is presented as Stanton number distributions. The new data set is compared to previously reported data obtained with this facility and other wellepted published data. This project has successfully qualified the THTTF for zero-pressure gradient, isothermal wall temperature, incompressible boundary-layer flow over smooth flat plates without transpiration. The THTTF is now set to accommodate modifications which will facilitate heat transfer investigations with high freestream turbulence.

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