The diploma thesis discusses laser cutting of non-ferrous metals using fiber YbYag laser and evaluation of the roughness of cutting edge samples. To manufacture samples of aluminium Al 99,5, deoxidized copper Cu – DHP and brass CuZn37 were used combinations of process parameters according to Taguchi statistical method. Samples were subsequently evaluated, according to the ČSN EN ISO 9013 standard and sorted into roughness cathegories, and by technical and economical evaluation, the most economical process parameter combinations were found. Experimantal part is preceded by description of general methods of cutting, description of laser types, process parameters and their influence on the occurrence of the cutting edge defects and description of roughness measurement and standard ČSN EN ISO 9013.

Magister Theologiae - MTh / This study aimed to determine the association between dimensional change and surface roughness (Ra) of Vitremer, Activa and Cention N after immersing them into two different media: acidic and artificial saliva media for the period of a year. Measurements were made at 10 time intervals during the observation period.

Drop impacts are present in our everyday lives, from showering and washing the dishes to inkjet printing and many industrial processes, such as spray coatings and spray cooling. In many of these applications it may be undesirable to have air entrained within the drop when it impacts a surface. As a drop approaches a surface, the gas beneath the drop is unable to fully escape resulting in a rising pressure which becomes sufficient to form a dimple in the bottom center of the drop. Therefore, when the drop makes contact with the surface, it is around the perimeter of this dimple, thus entrapping a disc of air which contracts into a minute bubble. In this dissertation, we study the very early time dynamics of the formation of the central air disc under a variety of circumstances using ultra-high-speed interferometry at rates up to 5 million frames per second. We show the effects of the liquid viscosity for viscosities spanning 7 orders of magnitude, for impacts of drops onto solid surfaces or a film of the same liquid. We find that the size of the air disc is weakly dependent on the drop viscosity to the -1/9 power. We also explore the extended gliding of the drop on a less than 160 nm thick film of air. For impacts onto a solid surface, this gliding layer is rupture in multiple random locations and each localized contact wets the surface at extreme rates compared with the expected viscous-capillary velocity. For impacts onto liquid films, the localized contacts are rarely observed and the gliding layer ruptures at a uniform location. The central bubble contracts much faster than expected in this case as well. Furthermore, we study the effects of reducing the ambient air pressure discovering a compressible and rarified-gas regime wherein the drop makes a double contact with the surface. Lastly, we study the effects of nano-scale surface roughness on the central bubble and the formation of thick bands of microbubbles around the periphery of the air disc.

Indiana University-Purdue University Indianapolis (IUPUI) / Erosive tooth wear (ETW) is an emerging dental condition manifested clinically as tooth surface loss, eventually impairing the teeth’s structural integrity, function, and esthetics. Both research and practice are in need of a quantitative, non-destructive method to monitor ETW. Cross-polarization optical coherence tomography (CP-OCT), an advanced imaging tool, shows great potential to fulfill this need, but its feasibility and shortcomings remain unclear. In this dissertation, I explored the capability of CP-OCT to monitor ETW in three in vitro studies, one per chapter. Chapter 2 investigated the effects of enamel surface roughness and dental erosion severity on CP-OCT dental surface loss measurements. Chapter 3 tested the effects of enamel surface roughness and dental erosion on CP-OCT enamel thickness measurements at different simulated wear levels. Chapter 4 explored the ability of CP-OCT to quantify the thickness of natural and wornout enamel surfaces and to estimate longitudinally the wear depths resulting from simulated wear. I concluded: (1) enamel surface roughness did not affect CP-OCT measurements of enamel surface loss, however, the estimated error limited the appropriate assessment of the initial stages of dental erosion surface loss using CP-OCT; (2) enamel surface roughness and dental erosion did not affect CP-OCT enamel thickness measurements, and the CP-OCT differentiated the simulated enamel wear levels; and (3) CP-OCT quantified thickness of natural enamel before, during, and after the tooth wear simulation and allowed wear depth estimation following the simulated wear. / 2021-07-03

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19184号 / 工博第4061号 / 新制||工||1626(附属図書館) / 32176 / 京都大学大学院工学研究科マイクロエンジニアリング専攻 / (主査)教授 田畑 修, 教授 琵琶 志朗, 准教授 土屋 智由, 教授 松原 厚 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19687号 / 工博第4142号 / 新制||工||1639(附属図書館) / 32723 / 京都大学大学院工学研究科航空宇宙工学専攻 / (主査)教授 斧 髙一, 教授 稲室 隆二, 教授 青木 一生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

The focus of the project was to alter and optimize the water repellant textile coating formulations to reach enhanced durability. For this purpose, the project was approached with three methods. Firstly, bio-based components were implemented in the mother emulsion to act as surfactant and crosslinking agent and to provide hydrophobic properties. Secondly different binders were added to crosslink and increase the coating resistance towards washes. Lastly additives at nano-scale were added to increase surface roughness in order to obtain higher hydrophobicity and improved of crosslinking capacity due to the presence of more functional groups.  The stability of all emulsions was controlled using different techniques such as optical microscopy to determine particle size, distribution and any observable instability (flocculation etc.), normal aging at room temperature and accelerated aging using higher temperature. All coatings were applied using a laboratory padder on standard PA and PES pieces of textiles and hydrophobic performance was evaluated through ISO 4920 spray test. By standard washing and repeating spray test, durability could be assessed. Further structure and property studies have been run using other tests such as: contact angle measurement, breathability of the coating and SEM observations. Based on the obtained results the incorporation of low HLB, bio-based surfactants in low amount (~0,25%) resulted in an increase in the hydrophobic performance of the tested textiles. However, a decrease in shelf life could be observed with these surfactants at room temperature. Sonication was successfully used to increase both stability and shelf life significantly. Some binders and nanoparticles proved to be successful in increasing the coating quality and thus the durability. Overall many of the developed formulations could enhance performance on PA compared to the already present commercial product. On PES textile, however, the developed strategies yielded hydrophobic effect close to the commercial product.

<p>This is a dissertation by Funing Li submitted to the Faculty of Purdue University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.</p>

The curing characteristics of photopolymer resin determine the relationship between the vat polymerization (VP) process parameters and the layer thickness, geometric accuracy, and surface quality of the 3D printed specimen. Dispersing filler material into the photopolymer resin changes its curing characteristics because the filler scatters and absorbs light, which modifies the curing reaction. However, the ability to cure photopolymer resin with high filler volume fraction is important to 3D print material specimens for specific engineering applications, e.g. structural polymer composite materials, electrical and thermal conductive materials, and ceramic materials for biological and high-temperature environments. We methodically measure the curing characteristics of diacrylate/epoxy photopolymer resin with dispersed glass microspheres. The experiments show that the curing depth, degree-of-cure, and surface roughness depend on both the light exposure dose and the filler fraction. We determine that the degree-of-cure increases with increasing filler fraction for constant exposure dose, and approaches 90% with increasing exposure dose, independent of the filler fraction. The geometric accuracy of the 3D printed specimens decreases with increasing exposure dose and with increasing filler volume fraction due to so-called profile broadening. Finally, we show that the average surface roughness of the 3D printed specimens decreases with increasing exposure dose and filler fraction. This work has implications for VP of photopolymer resins with high filler fraction. / Master of Science / Photopolymer resin is a gel-like liquid material that hardens (cures) into solid after absorbing light energy, and such a material is often used in the field of additive manufacturing (3D printing) to create complex geometry. Certain types of filler materials, such as metal powder or carbon fiber, can be added into the photopolymer resin to tailor the material properties, and thus, affects the curing behavior of photopolymer resin mixed with these filler materials. We conducted an experiment to understand how adding glass microspheres to a consumer grade photopolymer resin affects the process of creating 3D objects. This is important in the context of 3D printing engineered composite materials that derive their function from the organization and orientation of filler material in a matrix. To do this, we created many samples in the shape of a "VT" logo using the composite resin we made and measured their thickness (curing depth), degree-of-cure, surface roughness, and geometric accuracy, as a function of the amount of light energy being exposed to the resin (exposure dose) and the amount of the glass filler being added into the resin (filler fraction). We observed that when we increased the amount of light exposure, it resulted specimens that are thicker and more in degree of cure. Adding the glass filler to the liquid had mixed effects on the hardening process, because glass can scatter light and change how light travels within the resin. As a result, the printed objects became less accurate in shape and have smoother surface with increasing exposure dose and filler fraction, because more light is scattered off the designed curing profile and unintentionally cured the surrounding resin.