<p>The demands on decreased environmental impact from vehicles force the automotive industry to develop engines with reduced engine oil and fuel consumption. Engine oil consumption is recognized to be a significant source of pollutant emissions. Unburned or partially burned oil in the exhaust gases contribute directly to hydrocarbon and particulate emissions. Engine oil and fuel consumption are to a great extend controlled by the topography of the cylinder liner surface.</p><p>Recent engine tests have shown a promising reduction in oil consumption when using cylinder liners with a smoother finish than the current plateau honing.</p><p>One approach to produce smoother liner surfaces is to replace SiC ceramic honing stones with diamond tools. However, event though the diamond honing process results in higher productivity, improved demands of quality control is needed to monitor the degree of cold worked material - “blechmantel” (German), and the resulting risk of increased wear and scuffing.</p><p>A number of petrol and diesel engine cylinder liners have been mapped to be able to verify the quality and consequences, in terms of wear and function, of the honing process. A new mapping method, combining SEM images and quantitative image analysis with traditional 2D profilometry has been developed and tested in this study. The liners where tested in a reciprocating rig of 8 mm stroke and with a frequency of 10 Hz, simulating the top-dead center conditions in a running engine. </p><p>The tests where carried out in high- and low pressure conditions with smooth respectively rough liner roughnesses against PVD coated piston rings. The developed surface mapping method was employed before and after the test to study effect of running-in wear on the surface, features characterized with the SEM- and the 2D profilometer.</p><p>The results show that combining SEM- and profilometric methods gives a good picture of the effects of varying the cylinder liner pressure and roughness. The roughness of the core decreases more for diesel liners than for petrol liners. In average (rough and smooth liners) the diesel core roughness decreases 265% while the petrol liners average on a 60% decrease. Blechmantel- and Irregularities ratio show a high sensitivity to varying conditions and decrease 1180% to 100% for the diesel liners while the parameters increase between 106% to 18% for all the petrol liners. A probable cause is the more severe diesel high pressure run-in conditions are able to effectively “truncate” the plateaux and remove residing plastically deformed un-cut honing residues while the less severe petrol liner conditions not manage to remove the blechmantel and irregularities in an important extent.</p>

The demands on decreased environmental impact from vehicles force the automotive industry to develop engines with reduced engine oil and fuel consumption. Engine oil consumption is recognized to be a significant source of pollutant emissions. Unburned or partially burned oil in the exhaust gases contribute directly to hydrocarbon and particulate emissions. Engine oil and fuel consumption are to a great extend controlled by the topography of the cylinder liner surface. Recent engine tests have shown a promising reduction in oil consumption when using cylinder liners with a smoother finish than the current plateau honing. One approach to produce smoother liner surfaces is to replace SiC ceramic honing stones with diamond tools. However, event though the diamond honing process results in higher productivity, improved demands of quality control is needed to monitor the degree of cold worked material - “blechmantel” (German), and the resulting risk of increased wear and scuffing. A number of petrol and diesel engine cylinder liners have been mapped to be able to verify the quality and consequences, in terms of wear and function, of the honing process. A new mapping method, combining SEM images and quantitative image analysis with traditional 2D profilometry has been developed and tested in this study. The liners where tested in a reciprocating rig of 8 mm stroke and with a frequency of 10 Hz, simulating the top-dead center conditions in a running engine. The tests where carried out in high- and low pressure conditions with smooth respectively rough liner roughnesses against PVD coated piston rings. The developed surface mapping method was employed before and after the test to study effect of running-in wear on the surface, features characterized with the SEM- and the 2D profilometer. The results show that combining SEM- and profilometric methods gives a good picture of the effects of varying the cylinder liner pressure and roughness. The roughness of the core decreases more for diesel liners than for petrol liners. In average (rough and smooth liners) the diesel core roughness decreases 265% while the petrol liners average on a 60% decrease. Blechmantel- and Irregularities ratio show a high sensitivity to varying conditions and decrease 1180% to 100% for the diesel liners while the parameters increase between 106% to 18% for all the petrol liners. A probable cause is the more severe diesel high pressure run-in conditions are able to effectively “truncate” the plateaux and remove residing plastically deformed un-cut honing residues while the less severe petrol liner conditions not manage to remove the blechmantel and irregularities in an important extent.

No description available.

<p>Nowadays, the polishing process is one of the most important steps of the manufacturing of moulds and dies. Occupying up to 40% of the total production time and cost, it is decisive for the final appearance and quality of a surface. Because of its complexity, the polishing is mainly carried out manually; and the final quality depends of the expertise of the operator. That is why an automation of the polishing process is necessary.</p><p>The purpose of this project was to find out the optimized sequence of polishing for a Mirrax ESR steel (Uddeholm Tooling AB) using the Strecon RAP-200 (robot assisted polishing equipment). Using a Design of Experiment, the machine parameters were tested in order to better understand their influences and interactions. The report starts with a description of general polishing knowledge and ends up with the results from a Design of Experiment.</p><p>The information from this test are a first step in the evaluation of the Strecon RAP-200. Even if many results have been found out, only four parameters have been tested, and to be able to optimize the polishing sequence, further studies need to be carried out.</p>

Nowadays, the polishing process is one of the most important steps of the manufacturing of moulds and dies. Occupying up to 40% of the total production time and cost, it is decisive for the final appearance and quality of a surface. Because of its complexity, the polishing is mainly carried out manually; and the final quality depends of the expertise of the operator. That is why an automation of the polishing process is necessary. The purpose of this project was to find out the optimized sequence of polishing for a Mirrax ESR steel (Uddeholm Tooling AB) using the Strecon RAP-200 (robot assisted polishing equipment). Using a Design of Experiment, the machine parameters were tested in order to better understand their influences and interactions. The report starts with a description of general polishing knowledge and ends up with the results from a Design of Experiment. The information from this test are a first step in the evaluation of the Strecon RAP-200. Even if many results have been found out, only four parameters have been tested, and to be able to optimize the polishing sequence, further studies need to be carried out.

<p>Today, manual polishing is the most common method to improve the surface finish of mould and dies for e.g. plastic injection moulding, although it is a cumbersome and time-consuming process. Therefore, automated robots are being developed in order to speed up and secure the final result of this important final process.</p><p>The purpose of this thesis is to find out some clues about the influence of different parameters for the polishing of a steel grade called Mirrax ESR (Uddeholm Tooling AB) using a Design of Experiment. The report starts with a brief description of mechanical polishing (the techniques and polishing mechanisms) and ends up with the optimization of the polishing procedure with a polishing machine, the Strecon RAP-200 made by Strecon A/S.</p><p>Even if all the runs of the Design of Experiments couldn’t be carried out, the surfaces studied revealed some information about the importance of the previous process (turning marks not removed) and about the link between the aspect of the surfaces and the roughness parameters.</p>

Today, manual polishing is the most common method to improve the surface finish of mould and dies for e.g. plastic injection moulding, although it is a cumbersome and time-consuming process. Therefore, automated robots are being developed in order to speed up and secure the final result of this important final process. The purpose of this thesis is to find out some clues about the influence of different parameters for the polishing of a steel grade called Mirrax ESR (Uddeholm Tooling AB) using a Design of Experiment. The report starts with a brief description of mechanical polishing (the techniques and polishing mechanisms) and ends up with the optimization of the polishing procedure with a polishing machine, the Strecon RAP-200 made by Strecon A/S. Even if all the runs of the Design of Experiments couldn’t be carried out, the surfaces studied revealed some information about the importance of the previous process (turning marks not removed) and about the link between the aspect of the surfaces and the roughness parameters.

The replacement of chromate conversion coatings for zinc coated components has been necessitated by the materials finishing industries due to the inherent toxicity issues with Cr(VI) and the legislative enforcement of WEEE and ELV Directives by the European Union. Current replacements are based on non-chromate , Cr(III) systems, these may be perceived by some to be problematic as they still contain chromium . Molybdate based conversion coatings have long been viewed by many researchers to be a viable non-chromium alternative due to their low toxicity. An extensive literature review of the research carried out in the last 20 years was carried out, highlighting areas of interest for improving the corrosion resistance of the coatings studied. These were, primarily, the synergesis that exists with molybdate and phosphate compounds for corrosion resistance and the incorporation of nanoparticle silica into treatment solution. Also discovered was the importance of the acid used to adjust treatment solution pH, immersion time, oxidising agent additions and the incorporation of rare earth metal species. Silicate sealant layers were also highlighted as a post treatment. Molybdate-based coatings were formed on commercial electrodeposited acid zinc surfaces. Many treatment conditions were investigated, and initially performance analysed using DC Linear Polarisation Resistance (LPR) trials. Subsequently, the highest performing coatings were subjected to the more aggressive, industry standard, ASTM B 117 Neutral Salt Spray (NSS) corrosion test. The highest performing molybdate coatings were found to have an average LPR of ~ 9 000 Ω. cm2, in contrast to ~ 12 000 Ω. cm2 for the Cr(VI) based reference. NSS results were amongst the highest performing for molybdate based coatings documented, at 24 h until 5% white rust, however remained inferior to Cr(VI) coatings, which lasted 120 h. The highest performing coatings were characterised using FEG-SEM, Cryofracture EDXA and site specific AES. These techniques revealed that the enhanced molybdate coatings had a columnar structure that was around 300 nm thick, with pores that appeared to expose the substrate. AES showed this type of coating to have a mixed Mo, P and Zn oxide surface. Corrosion initiation was also studied; this can be thought of as an investigation to determine the point(s) of weakness or the mechanism that causes coating failure. Coatings were immersed in 5 % wt/ vol NaCl(aq) until they showed any surface change. Initial signs of corrosion were deemed to be any appearance of pitting or discolouration of the film, not a voluminous corrosion product. Untreated Zn, Cr(VI) and simple molybdate coatings were studied as well as enhanced molybdate coatings. There were clear differences in the way the coatings behaved at the onset of corrosion. Cr(VI) coatings delaminated, leaving an area of decreased Cr concentration. The enhanced molybdate coatings failed by the appearance of localised pores of ~ 70 µm in diameter. Substrate exposure was indisputably the reason for coating failure in chloride environments. In light of the work carried out in the present thesis the outlook for the use of molybdate as a potential replacement for chromate for the conversion coating of electrodeposited zinc surfaces is a positive one.

Silicone rubber based on polydimethylsiloxane is used ashigh voltage outdoor insulation, due to its ability to preservethe hydrophobic surface properties during service and evenregain hydrophobicity after exposure to electrical discharges.The underlying processes for the hydrophobic recovery arediffusion of low molar mass siloxanes from the bulk to thesurface and reorientation by conformational changes ofmolecules in the surface region. Only little is known of whichfactors are responsible for the long-term stability of thishydrophobic recovery. It is therefore important to increase theknowledge about the fundamental mechanisms for the loss andrecovery of hydrophobicity of silicone rubbers, exposed toelectrical discharges. Addition-cured polydimethylsiloxanenetworks, with known crosslink densities, were exposed tocorona discharges and air/oxygen-plasma and the loss andrecovery of hydrophobicity was characterised by contact anglemeasurements. The degree of surface oxidation increased withincreasing exposure time with a limiting depth of 100- 150 nm,as assessed by neutron reflectivity measurements. The oxidationrate increased with increasing crosslink density of the polymernetwork, according to X-ray photoelectron spectroscopy. Withinthe oxidised layer, a brittle, silica-like layer was graduallydeveloped with increasing exposure time. The hydrophobicrecovery following the corona or air/oxygen- plasma exposuresoccurred at a slow pace by diffusion of cyclic oligomericdimethylsiloxanes through the micro-porous but uncrackedsilica-like surface layer or at a much higher pace by transportof the oligomers through cracks in the silica-like layer. Theoligomers were present in the bulk, but additional amounts wereformed during exposure to corona discharges. High-temperaturevulcanised silicone rubber specimens were aged in a coastalenvironment under high electrical stress levels (100 V/mm). Thechanges in surface structure and properties were compared tothe data obtained from specimens exposed to coronadischarges/plasma. The dominating degradation mechanism wasthermal depolymerisation, initiated by hot discharges. Thisresulted in the formation of mobile siloxanes, of which the lowmolar mass fraction consisted of cyclic oligomericdimethylsiloxanes. Oxidative crosslinking resulting insilica-like surface layers was not observed during theseconditions. <b>Keywords:</b>silicone rubber, polydimethylsiloxane,hydrophobicity, corona, air-plasma, oxygen-plasma, surfacecharacterisation, degradation products, crosslink density.

<p>Silicone rubber based on polydimethylsiloxane is used ashigh voltage outdoor insulation, due to its ability to preservethe hydrophobic surface properties during service and evenregain hydrophobicity after exposure to electrical discharges.The underlying processes for the hydrophobic recovery arediffusion of low molar mass siloxanes from the bulk to thesurface and reorientation by conformational changes ofmolecules in the surface region. Only little is known of whichfactors are responsible for the long-term stability of thishydrophobic recovery. It is therefore important to increase theknowledge about the fundamental mechanisms for the loss andrecovery of hydrophobicity of silicone rubbers, exposed toelectrical discharges. Addition-cured polydimethylsiloxanenetworks, with known crosslink densities, were exposed tocorona discharges and air/oxygen-plasma and the loss andrecovery of hydrophobicity was characterised by contact anglemeasurements. The degree of surface oxidation increased withincreasing exposure time with a limiting depth of 100- 150 nm,as assessed by neutron reflectivity measurements. The oxidationrate increased with increasing crosslink density of the polymernetwork, according to X-ray photoelectron spectroscopy. Withinthe oxidised layer, a brittle, silica-like layer was graduallydeveloped with increasing exposure time. The hydrophobicrecovery following the corona or air/oxygen- plasma exposuresoccurred at a slow pace by diffusion of cyclic oligomericdimethylsiloxanes through the micro-porous but uncrackedsilica-like surface layer or at a much higher pace by transportof the oligomers through cracks in the silica-like layer. Theoligomers were present in the bulk, but additional amounts wereformed during exposure to corona discharges. High-temperaturevulcanised silicone rubber specimens were aged in a coastalenvironment under high electrical stress levels (100 V/mm). Thechanges in surface structure and properties were compared tothe data obtained from specimens exposed to coronadischarges/plasma. The dominating degradation mechanism wasthermal depolymerisation, initiated by hot discharges. Thisresulted in the formation of mobile siloxanes, of which the lowmolar mass fraction consisted of cyclic oligomericdimethylsiloxanes. Oxidative crosslinking resulting insilica-like surface layers was not observed during theseconditions.</p><p><b>Keywords:</b>silicone rubber, polydimethylsiloxane,hydrophobicity, corona, air-plasma, oxygen-plasma, surfacecharacterisation, degradation products, crosslink density.</p>