<p>Detta examensarbete har utförts vid Linköpings universitet i samarbete med Scania Transmission i Södertälje och behandlar kravsättning av ytstrukturer samt processer för hårdbearbetning av kugghjul och axlar. Aktuella artikelritningar innefattar endast krav för Ra-värde, den aritmetiska medelavvikelsen för ytjämnhetsprofilen (R-profilen). Förslag på nya parametrar enligt av Scania tillämpade SS-EN ISO standards har tagits fram, detta för att ge en noggrannare beskrivning av vilken ytstruktur som skall uppnås. Resultatet är generellt tillämpningsbart men fokuseras mot kugghjulens hål, plan och diametrar. Vidare presenteras en jämförelse mellan metoder så att transmissionsverkstäderna kan tillverka kugghjul/axlar på ett kostnadseffektivare sätt. Arbetet grundas på en litteraturstudie av handböcker och standards kompletterat med kartläggning av nuläget genom insamling av mätdata. En omvärldsanalys och några bearbetningsprover med hårdsvarvning har också utförts. Till skillnad från nuläget föreslås en övergång från att ange Ra-värde på ritningarna till att ange en övre gräns för Rz-värde som en begränsning av amplituden. Ytor i relativ rörelse och ytor som ingår i pressförband föreslås kompletteras med en undre gräns för Rz-värde samt en undre gräns för relativ bärighet. Med införandet av ett bärighetskrav ges även en specifikation för profilens fördelning. Angivelse av bearbetningsmetod och eventuellt bearbetningsmönster föreslås att anges i klartext på ritningen då parametrar som beskriver karakteristiska drag för olika bearbetningsmetoder visat sig väldigt variationsbenägna i nulägesanalysen. Jämförelse av hårdbearbetningsmetoder har visat att det i kombinationsmaskiner, hårdsvarvning och slipning, vore intressant att enbart hårdsvarva kugghjulens glidlagerytor, något som enligt bearbetningsprover och omvärldsanalys verkar rimligt. Detta bör efter godkännda riggprover anammas som ett första optimeringssteg. Fler intressanta koncept för framtida bearbetningsalternativ finns att studera i rapportens resultat och diskussionskapitel.</p> / <p>This master thesis report was performed at Linköpings University in cooperation with Scania Transmission in Södertälje and deals with specification of surface textures and processes for hard part machining of cogwheels and shafts. Present blueprints only include requirements for Ra-values, arithmetic mean deviation of the roughness profile (R-profile). Suggestions of new parameters according to SS-EN ISO standards used by Scania have been compiled with the aim of providing a more accurate description of the surface texture that is to be achieved. The result can be applied in general but are focused towards holes of cogwheels, planes and diameters. Furthermore a comparison between different methods is presented so that the transmission workshops can manufacture cogwheels and shafts in a costefficient manner. The work is based on a comparative literature study of handbooks and standards with complementary documentation of the present situation through collecting of measurements. A reference analysis and a few manufacturing tests of hard turning have also been performed. In difference from the present situation a transition from providing Ra-values on the blueprints to specify an upper limit for Rz-value to restrict the amplitude is recommended. Surfaces in relative motion and surfaces in heavy force fit are suggested to be complemented with a lower limit for Rz-values and a lower limit for relative material ratio. With an introduction of material ratio requirements the profiles distribution are also specified. Denunciation of manufacturing method and surface lay if any is suggested to be stated en clair on the blueprint being so that parameters describing characteristic features for different manufacturing methods have shown a wide range of distribution in the present state analysis. Comparison of hard part machining methods have shown that in combination machines, hard turning and grinding, solely hard turning of the cogwheels slide bearing surfaces would be interesting, which also seems plausible due to manufacturing samples and the reference analysis. After approved rigg tests this method can be adopted as a first step of optimization. More interesting concepts for future manufacturing alternatives are provided in the reports result and discussion chapters.</p>

Detta examensarbete har utförts vid Linköpings universitet i samarbete med Scania Transmission i Södertälje och behandlar kravsättning av ytstrukturer samt processer för hårdbearbetning av kugghjul och axlar. Aktuella artikelritningar innefattar endast krav för Ra-värde, den aritmetiska medelavvikelsen för ytjämnhetsprofilen (R-profilen). Förslag på nya parametrar enligt av Scania tillämpade SS-EN ISO standards har tagits fram, detta för att ge en noggrannare beskrivning av vilken ytstruktur som skall uppnås. Resultatet är generellt tillämpningsbart men fokuseras mot kugghjulens hål, plan och diametrar. Vidare presenteras en jämförelse mellan metoder så att transmissionsverkstäderna kan tillverka kugghjul/axlar på ett kostnadseffektivare sätt. Arbetet grundas på en litteraturstudie av handböcker och standards kompletterat med kartläggning av nuläget genom insamling av mätdata. En omvärldsanalys och några bearbetningsprover med hårdsvarvning har också utförts. Till skillnad från nuläget föreslås en övergång från att ange Ra-värde på ritningarna till att ange en övre gräns för Rz-värde som en begränsning av amplituden. Ytor i relativ rörelse och ytor som ingår i pressförband föreslås kompletteras med en undre gräns för Rz-värde samt en undre gräns för relativ bärighet. Med införandet av ett bärighetskrav ges även en specifikation för profilens fördelning. Angivelse av bearbetningsmetod och eventuellt bearbetningsmönster föreslås att anges i klartext på ritningen då parametrar som beskriver karakteristiska drag för olika bearbetningsmetoder visat sig väldigt variationsbenägna i nulägesanalysen. Jämförelse av hårdbearbetningsmetoder har visat att det i kombinationsmaskiner, hårdsvarvning och slipning, vore intressant att enbart hårdsvarva kugghjulens glidlagerytor, något som enligt bearbetningsprover och omvärldsanalys verkar rimligt. Detta bör efter godkännda riggprover anammas som ett första optimeringssteg. Fler intressanta koncept för framtida bearbetningsalternativ finns att studera i rapportens resultat och diskussionskapitel. / This master thesis report was performed at Linköpings University in cooperation with Scania Transmission in Södertälje and deals with specification of surface textures and processes for hard part machining of cogwheels and shafts. Present blueprints only include requirements for Ra-values, arithmetic mean deviation of the roughness profile (R-profile). Suggestions of new parameters according to SS-EN ISO standards used by Scania have been compiled with the aim of providing a more accurate description of the surface texture that is to be achieved. The result can be applied in general but are focused towards holes of cogwheels, planes and diameters. Furthermore a comparison between different methods is presented so that the transmission workshops can manufacture cogwheels and shafts in a costefficient manner. The work is based on a comparative literature study of handbooks and standards with complementary documentation of the present situation through collecting of measurements. A reference analysis and a few manufacturing tests of hard turning have also been performed. In difference from the present situation a transition from providing Ra-values on the blueprints to specify an upper limit for Rz-value to restrict the amplitude is recommended. Surfaces in relative motion and surfaces in heavy force fit are suggested to be complemented with a lower limit for Rz-values and a lower limit for relative material ratio. With an introduction of material ratio requirements the profiles distribution are also specified. Denunciation of manufacturing method and surface lay if any is suggested to be stated en clair on the blueprint being so that parameters describing characteristic features for different manufacturing methods have shown a wide range of distribution in the present state analysis. Comparison of hard part machining methods have shown that in combination machines, hard turning and grinding, solely hard turning of the cogwheels slide bearing surfaces would be interesting, which also seems plausible due to manufacturing samples and the reference analysis. After approved rigg tests this method can be adopted as a first step of optimization. More interesting concepts for future manufacturing alternatives are provided in the reports result and discussion chapters.

Theoretical and experimental results show that the performance of a load-bearing surface in hydrodynamic lubrication may be enhanced by engineering a definable surface texture onto the surface. These surface textures are in the form of protrusions (positive asperities) or cavities (negative asperities) of known size and geometry. The benefits of such surface textures include lower friction torque, higher load capacity and lower operating temperatures. This Thesis details a fabrication process to manufacture such surface textures/asperities on flat surfaces. The asperities are fabricated using a UV photolithography process followed by electroplating. A complete surface characterization is done to evaluate the effectiveness of the manufacturing process. From the characterization results, some errors in asperity geometry are identified and statistically quantified. These errors are found to be normally distributed and the random surface roughness is 1 to 3 orders of magnitude less than the deterministic feature size. The accuracy of the manufacturing process for fabricating the asperities was found to lie within 6.5 % of the desired value over all the errors studied. Finally, a sensitivity analysis is done to theoretically evaluate the effect of some of these errors in the hydrodynamic lubrication regime.

In order to achieve enhanced and cost-effective performance of engineering components, Surface Engineering embraces traditional and innovative surface technologies which modify the surface properties of metallic and non-metallic engineering components for specific and sometime unique engineering purposes. The surface roughness of an engineered surface may be classified as: the random surface roughness which is a product of surface finishing and the deterministic surface roughness which is engineered to increase the lubrication characteristics of the hydro dynamically lubricated thrust ring. The effect of stochastic/random roughness can not be ignored when the roughness is of the same amplitude as that of fluid film thickness. Average flow model derived in terms of flow factors which are functions of the roughness characteristics is used to study the random surface roughness effects on hydrodynamic lubrication of deterministic asperity. In addition, the effect of boundary conditions on flow factors is studied by calculating the pressure and shear flow factor using two different new boundary conditions. The results are obtained for random surface roughness having a Gaussian distribution of roughness heights.

This work deals with experimental analysis of fluid film instability in rotor bearing systems stored in hydrodynamic plain bearings with focus on bearing surface modification. The experiments were performed on a journal bearing dynamics simulator. The aim was to determine the influence of individual operating parameters on the occurrence and course of turbulence instability. The emphasis here was on the effect of surface micro textures. The work also included the preparation of textured samples. Experiments were divided into experiments monitoring the influence of temperature, pressure, bearing geometry and surface modification. The output of the individual experiments were the values of the threshold speed of formation and termination of instability or the magnitude of the amplitude depending on the above described parameters. These values were plotted in graphs. This data was then confronted with previously published articles. The results showed that instabilityin rotor systems is very sensitive to temperature, pressure and bearing geometry changes. The fundamental influence on the unstable behavior of the rotor system has been demonstrated by the use of textured surfaces, where the threshold speed was significantly shifted to a higher speed range compared to the non-textured bearing.

In nature, microscopic surface textures impact useful function, such as the drag reduction of shark skin (Dean & Bhushan, 2010) and superhydrophobicity of the lotus leaf(Pan, Kota, Mabry, & Tuteja, 2013). In this study, we explore these phenomena by re-creating microscopic surface textures via the method of interfacial flow instability in drying polyvinylidene fluoride (PVDF) acetone solutions. In general, PVDF films can be made using either spin coating or electrospray deposition with various weight concentrations in acetone. In order to study the morphology of the porous structure of PVDF films, wet deposition samples were fabricated by spin coating or near-field electrospray. Possible theories are discussed and examined to explain the formation of these porous structures resulting in development of a well-controlled method to create porous PVDF films with various pore sizes and pore densities. All samples are characterized and found to exhibit superhydrophobicity and drag reduction. To connect porous PVDF film morphology to the established field of dry particle fabrication, PVDF particle synthesis by far-field electrospray is also reviewed and discussed. An established method to generate polymer particles of different morphologies in other polymers (Almeria-Diez, 2012) by electrospray drying is confirmed using PVDF as well. Due to the ability of scalable and re-configurable electrospray, the microscopic surface textures can be applied to areas of any size to reduce drag or impart water-repelling properties.