The thesis contains theoretical analysis of drilling by twist drill focused on the step drill. The review includes description of the drill geometry, calculation of the basic parameters of drilling, including forces and process optimization. Following is manufacturing process and analysis of the monolithic step drill designed for the required hole parameters. The optimal cutting conditions are necessary to find for the correct function of the tool. The load values of the tool are accurately assessed using a piezoelectric dynamometer, thereby obtaining the overall progress of individual loads. The roughness of the workpiece is evaluated by the optical measuring device.

Thesis aims on efficient milling of stainless steels. Groups of these steels are characterized and their machinability is analyzed in theoretical part of this thesis. In the practical part of thesis were face milled stainless steels ČSN 17 240.4 a ČSN 17349.4. There are evaluated edge durability, roughness of surface, loading of total cutting force and effectiveness of test tools.

In the diploma thesis dividing of ceramic materials is made, their bonds and other attributions, which define ceramic materials. There is also described how ceramic materials are manufactured and the thesis is including information about machining ceramic materials. In the experimental part sample of ceramic material R-S67K was machined by milling. During the experiment cutting forces were measured and roughness of surface after finishing, these data were finally evaluated.

The purpose of this diploma thesis is to describe the influence of artificially produced surface grooves on transition from full EHL regime to mixed lubrication in point contact using optical interferometry. This article focuses on influences of grooves orientation, length in contact area, elastic properties of contact surfaces and different types of oil defined by pressure-viscosity coefficient. Empirical prediction model of groove influence on film thickness was established based on experimental data. The groove influence was incorporated into lubrication parameter. This modified definition was compared to classic one. It showed that avoiding groove influence in classic definition lead to significant underestimation. Influence of groove on friction coefficient is also studied.

Experimental work evaluated the dependence of the thickness of the cutting edge, its roughness and assessment of appearance with regard to the defects resulting from the diameter of the focal spot during oxidative cutting Yb:YAG laser. Other variables include the experiment: process parameters such as laser power, cutting speed, oxygen pressure and focus position. Experiment is based on the Taguchi tables. Test samples were cut off from sheet thickness 10, 15 and 20 mm. Representatives of conventional steel were S235JRC+N, S235JR, S235JR+N and steel type RAEX developed for laser and plasma cutting. Samples were evaluated according to the ČSN EN ISO 9013. The evaluation of samples was into classes according to standards of quality. Hardness measurements were performed on the samples thickness 20 mm of convectional steel and steel type RAEX.

Diploma thesis deals with the assessment of runoff conditions on the water flow Luha in the river kilometer 8,120 – 13,900. The river flows in the urban area of Polom and undeveloped area of Polom and Heřmanice. The thesis is focused on an assessment of the condition of the riverbed, capacity of the river and on design of a flood protection. The thesis includes an assessment of the condition of fishponds. The assessment is based on personal visit and photos taken as record. Program HEC-RAS was used to calculate the water levels. The outcome is an evaluation of the river condition according to a method HEM and design of the flood protection.

Lors de cette thèse nous avons étudié le phénomène de convection thermique turbulente. La compréhension des mécanismes du flux thermique induit est encore un défi. Dans cette optique, deux approches innovantes ont été utilisées. La première a consisté en une approche Lagrangienne. Dans un premier temps, nous avons immergé une particule instrumentée munie de capteurs de température. Sa vitesse a été mesurée simultanément afin de calculer le flux thermique local transporté. En comparant les mesures effectuées à des simulations numériques et à des mesures Eulériennes, la pertinence de cette méthode a été révélée. Nous avons ensuite ensemencé l'écoulement avec des particules de diamètre inférieur à l'échelle dissipative du système. Nous avons alors pu effectuer les suivre en 3D et nous intéresser aux statistiques turbulentes, ainsi qu'à la dispersion de paires. Nous avons ensuite étudié une configuration où la plaque du bas comporte des rugosités contrôlées. Il est reconnu que cela amène une augmentation du transfert thermique supérieure à celle reliée à l'augmentation de surface. Nous avons mis en évidence des mécanismes possibles qui expliquent ce phénomène. Des mesures thermométriques dans une cellule remplie d'eau ainsi que des mesures vélocimétriques dans une cellule six fois plus grande remplie d'air ont permis d'observer un changement radical de la structure des couches limites au voisinage des rugosités, notamment l'apparition d'une couche limite turbulente. Ces mesures ont été accompagnées de mesures de vitesse de l'écoulement global qui ont révélé une augmentation drastique des fluctuations de vitesse ainsi que l'apparition d'un nouveau régime de turbulence. / In this work, turbulent thermal convection is studied. Undestanding the mechanisms of induced thermal flux is still a challenge. In this context we used two innovative approaches.The first one consists in a Lagrangian approach. An instrumented particle, designed for temperature measurements, is immersed in the flow. The simultaneous measurement of the temperature view from the particle and its velocity allowsto obtain local Lagrangian heat flux. By comparing these measurements with numerical simulation and Eulerian investigations we can assert the relevance of this method. Then we seeded the flow with particles whose diameter is smaller than the dissipative scale of the system. We performed 3D tracking to access to turbulent statistics and pair dipersion.On the other hand we study a configuration with controlled roughness on the bottom plate. It is well-known that it leads to thermal flux enhancement higher than the one linked to the surface increasing. We bring out possible mechanisms to explain this phenomenon. Thermometric measurements in water-filled cell and anemometric measurements in a six-time larger air-filled cell point out a dramatic change of the boundary layers structure close to roughness. Particularly a turbulent viscous boundary layer appears. Theses investigations are supplemented by velocity measurements of the global flow and reveal a large increase of velocity fluctuations and the appearance of a new turbulence regime.

Most theoretical treatments of Nuclear Magnetic Resonance (NMR) measurements of porous media assume ideal pore geometries for the pores (i.e. slabs, spheres or cylinders) with welldefined surface-to-volume ratios (S/V). This same assumption is commonly adopted for naturally occurring materials, where the pore geometry can differ substantially from these ideal shapes. In this paper the effect of the roughness of the pore surface on the T2 relaxation spectrum is studied. By homogenization of the problem using an electrostatic approach it is found that the effective surface relaxivity can increase dramatically in the presence of rough surfaces. This leads to a situation where the system responds as a pore with a smooth surface, but with significantly increased surface relaxivity. As a result the standard approach of assuming an idealized geometry with known surface to-volume and inverting the T2 relaxation spectrum to a pore size distribution is no longer valid. The effective relaxivity is found to be fairly insensitive to the shape of the roughness but strongly dependent on the width and depth of the surface geometry.

Prediction of vehicle disc brake roughness noise is a non-trivial challenge. In fact, neither the source mechanisms, nor the transfer paths are so far well understood. Traditionally, disc brake noise problems are studied as part of the friction-induced noise field, where the source is considered to be a more or less local phenomenon related to the brake disc and brake pad. However, for the roughness noise of interest here this viewpoint is not adequate when attempting to solve the interior noise problem since the transfer of vibro-energy from the brake into the vehicle body is a crucial aspect and plays an important role in the understanding and solution to the problem. The vibroacoustic energy transfer associated with the brake roughness noise is a problem where geometrical complexity and material combinations, including rubber bushings, pose an intricate modelling problem. Additionally, system altering effects from moving parts and loadings are important, e.g. due to the steering or brake systems. In addition, the source mechanisms themselves must also be understood to be able to solve the problem. The current work constitutes a combined experimental and theoretical investigation, aiming at an increased understanding of the source, the transfer paths and how they are a affected by change in the operational state. The experimental study of the vehicle disc brake roughness noise, is based on measurements conducted in a laboratory using a complete passenger car. It is found that the interior noise is a structural-borne broadband noise event well correlated to vehicle speed and brake pressure. The results suggest that the friction source may be divided into vibrations created in the sliding direction and vibrations created normal to the contact plane, where the sliding direction levels appear to be proportional to brake pressure according to Coulomb’s friction law; the vibration level in the normal direction of the contact plane on the other hand has behaviour proportional to Hertz contact theory. The measurements also indicate that the brake force created carried by the suspension system when braking will also alter the vibro-acoustic response of the system. To facilitate the theoretical simulations, an approach for modelling of the suspension system is developed. The vibro-acoustic transfer path model developed is using a modal based on the Craig-Bampton method where a restriction on the coupling modes is suggested. The approach suggested uses undeformed coupling interfaces, to couple structures of fundamentally different stiffness such as may be the case in a vehicle suspension system where for instance rubber bushings are combined with steel linking arms. The approach show great potential inreducing computational cost compared to the classical Craig-Bampton method. / QC 20110913

This study examined the micro- and surface structures of objects manufactured by selective laser melting (SLM). The results show that the surface roughness in additively manufactured objects is strongly dependent on the geometry of the built part whereas the microstructure is largely unaffected. As additive manufacturing techniques improve, the application range increases and new parameters become the limiting factor in high performance applications. Among the most demanding applications are turbine components in the aerospace and energy industries. These components are subjected to high mechanical, thermal and chemical stresses and alloys customized to endure these environments are required, these are often called superalloys. Even though the alloys themselves meet the requirements, imperfections can arise during manufacturing that weaken the component. Pores and rough surfaces serve as initiation points to cracks and other defects and are therefore important to consider. This study used scanning electron-, optical- and focus variation microscopes to evaluate the microstructures as well as parameters of surface roughness in SLM manufactured nickel based superalloys, Inconel 939 and Hastelloy X. How the orientation of the built part affected the surface and microstructure was also examined. The results show that pores, melt pools and grains where not dependent on build geometry whereas the surface roughness was greatly affected. Both the Rz andRa values of individual measurements were almost doubled between different sides of the built samples. This means that surface roughness definitely is a factor to be considered when using SLM manufacturing.