This study aims to develop coatings which show wear resistant behaviour along with multiple functions such as improved ice adhesion, better freezing delay etc which help in improving the effectiveness of the wind turbine efficiency. The significance of anti-icing/de-icing solutions for wind turbines is emphasized since ice accretion can cause serious issues in generation of power and might lead to damage of blades. The use of active and passive anti-icing/de-icing technologies in wind turbine blade applications is reviewed. The discrepancy between passive anti-icing, which depends on surface treatment, coatings, de-icing fluids and active anti-icing, which uses heating devices, sensors such as actuators, transducers, is explored along with the current challenges in industry. In this study we’ve developed interesting methods for improving the anti-icing/de-icing capabilities of wind turbine blades by using gelcoat coatings in which are filler particles (boron nitride and graphene) and oils (vegetable and paraffin oil) are incorporated. Evaluating the impacts of type of fillers, oils, their concentrations on anti-icing efficacy, as well as the prospects for this technique to enhance wind energy production's reliability and productivity will be explored. In summary, this study aims to develop multi-functional polymer coatings for anti-icing/de-icing application in wind turbine blades. The coatings with boron-nitride and graphene showed an increase in the surface roughness and contact angles, while there’s no change in the chemical composition in comparison with pure gelcoat. The thermal conductivity of the coatings was increased with addition of fillers. For the wear test, the operating parameters chosen are a load of 5N and 1Hz frequency of slider, which is run for a duration of 10 min. The COF for both the coatings is lesser than baseline coatings whereas graphene provided better wear resistance. The hardness was increased for boron-nitride coatings and it remained almost same for graphene coatings. The ice adhesion strength, freezing delay and thermal analysis (TGA) for these coatings showed better performance than pure gelcoat. Whereas for coatings with vegetable and paraffin oils, the contact angles were increased and surface roughness was increased in case of paraffin oil coatings whereas it reduced for vegetable oil coatings. Both the coatings offered better wear resistance and reduced COF, whereas the hardness was reduced. The ice adhesion strength and freezing delay improved drastically and are much better than both pure gelcoat as well as coatings with boron-nitride and graphene. There is slight increase in the glass transition temperature than pure gelcoat coating.

Without lubrication, machines are not imaginable to perform over a long period of time and complete their designated operations. With its omnipresent availability, the air is capable of functioning as a lubricant in long operations very efficiently. Moreover, thrust bearings support axial loads and transmit power at the same time under heavy loads. Therefore, to provide separation under heavy loads in lubricated rotating devices such as thrust pad bearings keeping the power losses at a minimum, film thickness and pressure distribution are very important to investigate at the bearing interfaces. Thrust pad gas (air) bearings are being used in very high-speed rotating machines. Usages of these air bearings are increasing nowadays in industries. In this thesis project, simulations of lubricated contacts of a thrust pad air bearing are performed utilizing multiphysics phenomena and surface textures as mathematical functions. Structural mechanics and fluid mechanics physics are used to model multiphysics functionality. Ideal surface texture models defined by mathematical functions are utilized. More efficient techniques such as homogenization techniques to model the influences of surface roughness are introduced for multiscale study. The current work also presents the Reynolds equation for incompressible and iso-viscous Newtonian fluid flow and formulation for a stationary study. The air bearing with three pads is presented and a virtual twin of this model is built for simulation in COMSOL Multiphysics software. Simulation results are obtained using a single pad from the air bearing considering periodicity of the mathematical formulation. Numerical solutions for pressure build-up and film thickness distributions are achieved from a stationary study performed in COMSOL Multiphysics. MATLAB is used for rigid body solutions. Numerical verification is carried out between the rigid body solutions from MATLAB and fluid physics solutions from COMSOL Multiphysics only for the simulations with tilting pad configuration. Obtained rigid body solutions are also compared to the trends of thrust pad bearing design diagrams to verify the modelling approach and the results. A tilting pad lubricating configuration is used for the thrust pad bearing first. Then pocket geometries for optimization of the bearing pads are explored. For that purpose, separate digital models of the bearing pad are built in COMSOL and analysed for the best performances. Material properties of steel AISI 4340 and Polylactic Acid (PLA) material are used to model virtual bearing pads. To understand the performance of the bearing better, its performance parameters such as load carrying capacity (LCC), relative power loss, and coefficient of friction torque (COT) solutions from the simulations of lubricated contacts of the thrust pad air bearing are analysed. To characterize the performance of the bearing, dimensionless LCC, relative power loss, and COT are explicitly formulated and computed from the pressure and film thickness solutions obtained in the simulations. Relative power loss and COT are resulted from the development of shear stresses in the lubricating fluid due to motion. Parametric analysis is also performed for these parameters in COMSOL Multiphysics. Additionally, performances of several pocket geometry design configurations are also analysed for the best values reached such as the maximum LCC. Pockets with shallower depths are found to have provided higher LCC in general than deeper pocket geometries and plane pads with tilting pad lubricating configuration. Finally, a physical model of an air thrust pad bearing with 3D-printed bearing segments made of PLA material is tested. The physical bearing performed very well in achieving full film separation in the test.

The development of lightweight design for automotive applications has lasted for many years and is still increasing. Vehicles with light structures use less fuel, emit less CO2, and are better for the environment. The next generation of lightweight vehicle structures will be realized using materials with a high strength-to-weight ratio, corrosion resistance, and high bending stiffness such as high-strength aluminium alloys. Increased formability, lower spring-back, and the ability to incorporate age-hardening heat treatments into the process are all advantages of the hot forming of aluminium alloys. However, because aluminium is prone to adhesion even at low temperatures, it can be difficult to avoid its transfer onto the tool. When forming aluminium, lubrication is always required to lower the interfacial shear strength and avoid direct contact between the interacting surfaces, to promote low friction and wear. However, lubricants can fail and significant issues with material transfer arise. Because of this, interruptions are needed for tool refurbishing, this issue affects process efficiency. Developing new or improved lubrication technologies to prevent adhesion and high friction, surface engineering solutions, as well as effective testing platforms related to aluminium forming, are vital. A significant challenge when studying the interaction between lubricant, aluminium, and tools often result in poor reproducibility of tests and uncertainties regarding the effect of lubricant thickness/weight on the friction behavior. Problems associated with reproducibility also affect modelling and simulations of the forming operation, as there are many uncertainties in the experimental campaigns, thus affecting the validation stages. The current study aim is to optimize the tribology test methodology used in the hot strip drawing method, with emphasis on the lubricant application methodology, to improve the reproducibility of tribological tests. Lubricant application methodology was developed by using air-brush equipment, and a consistent amount of lubricant. Different lubricant weights were characterized using two different types of lubricants (graphite-based and polymer-based lubricants), and then the tribological response was evaluated after the tribological tests. Lubricants were applied on cast iron and tool steel (CrN coated) to take into consideration the effect of the surface material and topography on the reproducibility, and consistency of the lubricant application methodology. The hot strip drawing method was used to perform tests at 350°C temperature, 10MPa pressure and 100mm sliding distance. To simulate the forming conditions encountered in hot stamping of aluminium, solubilization of a 6XXX aluminium alloy at 540°C was done before testing. An optical microscope, 3D optical profilometry, and SEM were used for the characterization of specimens after the tribological tests. With the lubricant application method, good reproducibility was obtained and it was determined that, in the case of cast iron, as the amount of both lubricants (polymer-based, graphite-based) increases the effective sliding also increases, but tool steel (CrN coated) shows slightly good results only when lubricant amounts are highest.

Environmentally adaptable grease (EAG) lubricants are essential in applications with loss lubrication due to their biodegradable nature. This is because the lubricants could be expelled into the environment during usage in some applications e.g., marine and mining applications. However, although this type of grease is sustainable to use, it also needs to bridge the performance gap it has with the mineral-based grease counterpart.  In this thesis project, a tribological evaluation comparison between the performance of EAGs and traditional mineral-based greases in large open gears is carried out. A twin disc tribometer is used to mimic the contact mechanisms of the test gears while being lubricated automatically by the grease samples through a syringe pump. For the experiments, the material surface of all the discs in the tribometer setup is steel while the different grease samples are tested for each setup. Two of the grease samples; UPL 04123 (NLGI 1.5) and UPL 04124 (NLGI 0.5) are fully formulated EAGs, while the third is a popular commercial mineral-based grease currently used in large open gears in the mining industry. An investigation of the wear of the discs used in each grease test is carried out using optical interferometry and a Scanning electron microscope (SEM). The wear volumes and wear rates are then analysed and compared to evaluate the performance of the grease samples. The wear results from the tribological characterisation using the twin disc are validated with the ISO 14635-3 standard on the FZG back-to-back test rig. Also, chemical characterisation of the unused and used grease is carried out using the advanced ATR-FTIR method to evaluate additive depletion and lastly an SEM-EDS analysis to confirm the presence of tribofilm on the surfaces of the disc samples. In conclusion, it is found that there is a correlation between the consistency of the grease sample and wear prevention; where the commercial grease with the least consistency performs best, followed by the 0.5G and lastly the 1.5G. Also, there are clear indications in the wear rates of the actions of extreme pressure additives activation at high contact pressures between the discs. The inadequacies of the ATR-FTIR and SEM-EDS methods to evaluate additives and tribofilm respectively are also discussed.

Environmentally friendly lubricants are in demand in response to the rising concerns and restrictive legislation that surround the use of mineral oil lubricants. One area of importance is understanding the service life of the environmentally friendly base oils of these non-toxic, biodegradable and renewable alternatives. The service life of a lubricant is directly influenced by its degradation behavior, especially oxidation.  In this research, selected environmentally friendly base oils; Glycerol, Rapeseed oil, Polypropylene glycol, Polyethylene glycol, Bis(di-2-ethyl hexyl) sebacate, Squalene and reference mineral oil; paraffin,  were subjected to thermo-oxidative ageing at 150oC. The changes in the chemical structures of the samples were followed using Spectroscopic, chromatographic, rheological and corrosivity studies. Tribological tests were also carried out to quantify the changes in these lubricants. The results obtained showed that the thermal oxidation affected the physicochemical properties and the lubricating ability of the base oils. However, each base oil degraded distinctly to the accelerated ageing conditions.

Gears are machine elements essential for mechanical transmission. Wear of gear teeth can causechanges in their profile geometry, causing vibration, noise, and subsequent gear failure. In this thesisproject, a twin disc tribometer has been used to mimic the actual Alfa Laval separator screw gearsystems. An investigation of the wear of different material pairs has been done using a twin disctribometer machine. In the twin disc tribometer, the material surface for one disc was bronze and thematerial for the counter disc surface was varied with steel of different types. Each bronze-steel pair wastested against different loading, lubricating and surface roughness conditions. For the wear tests, twodifferent loads, 75 N and 150 N and two different types of lubricants, Polyalphaolefin (PAO) andPolyalkylene Glycol (PAG) were taken. Wear tests were also done with the Applied Nano Surfaces(ANS) triboconditioning (TCG) steel disc samples which are surface treated to obtain a lower surfaceroughness. To obtain the wear volume and wear rate values the disc pairs were further analysed usinglaboratory equipment and computer software such as the digital microscope, optical interferometer andMountainsLab premium 9. Analytical calculations for minimum film thickness and thermally correctedminimum film thickness between the disc surfaces were obtained using the Dowson-Hamrock equationand Gupta formula, respectively. It has been found that the wear on the bronze disc is minimum if thecounter steel discs are Applied Nano Surfaces (ANS) of TCG 1 type followed by counter disc as casehardened steel, all of it at 75 N and with Polyalphaolefin (PAO) lubricant oil.

Electric machines are widely used in for instance the automotive industry in electric vehicles and in wind turbines. The electrical machines have mechanical bearings as an integral part used to transmit power and load. In addition, the main function includes reducing friction between interacting surfaces. However, it is one of the most failing machine elements in these machines. To improve operational sustainability and reduce maintenance costs, understanding bearing failure mechanisms under electrical influence is important. One of the main reasons of bearing failure is linked to high frequency power switches typically used to enhance electric machines’ efficiency. The increase in switching rate induces more frequent common mode voltage fluctuations making the system vulnerable to bearing currents. A small voltage difference of a few ten volts can induce significant electric stress on the bearing depending on the lubricant film thickness and related tribological parameters. The electric charge build-up leads to electric current conduction (arc discharge which happens when the voltage exceeds the breakdown voltage) ultimately damaging the bearing. There are different mitigation strategies which are used to restrict bearing currents through grounding or using completely insulative bearings such as ceramic ones. However, at the moment, there are no satisfactory solutions and there is a need for efficient and economical solutions to the problem. On the other hand, various filters are used to reduce the amplitude and its frequency of bearing currents, but they only partly solve the problem. Similarly, the insulative surface coatings provides high electrical resistance but start acting as capacitors. At a sufficiently high voltage difference, the current passes through the system. Therefore, mitigation strategies are still being explored to improve system performance and service-life. To understand the bearing discharge activity and electrical breakdowns, an electrified ball bearing rig is developed with the ability of testing different electrical properties of lubricants and running conditions. To be able to characterize the electrical properties of a bearing, two electrical circuits are designed. Experimental tests are carried out with PAO-15 and an electrical conductivity-enhanced PAO-15/P-SiSO lubricant with addition of ionic liquids. The influence of different tribological parameters such as rotational speed and viscosity are compared with respect to discharge activity. In addition, two fully formulated experimental oils are compared and evaluated in terms of their electrical performance. The bearing is found to be in different states showing electric-field dependent insulation breakdown ranging from resistive to resistive-capacitive to capacitive states. The electric characterization shows a difference between the boundary, mixed and full film lubrication regimes. Conclusively, the electrical behavior of a mechanical bearing is characterized experimentally to understand discharge problem and roadmap solution opportunities.

Obtaining an enhanced lifespan for mechanical transmissions has become a challenge in diverse application sectors. Micropitting as a contact fatigue mechanism has seriously jeopardized the well-being of rolling-sliding elements present for instance in gearboxes. Additivation through copper nanoadditives has demonstrated promising results in preventing contact fatigue. There is a need to assess the influence of copper nanoadditives on micropitting and mild wear before contemplating employing them in real transmission gearboxes. Consequently, this research work aims to acquire knowledge of the tribological behavior of rolling-sliding contacts additivated with a copper nanoadditive, emphasizing the influence of two different copper nanoadditive concentrations (0.3% and 3%) on wear and micropitting as failure mechanisms. Tests were performed using a micropitting test rig. Micropitting and wear were analyzed at different slide-to-roll ratios (1%, 5%, and 30%), different load conditions (1.5 GPa and 2.5 GPa), and different temperatures (60 °C and 100 °C), for all versions of the studied lubricant. There was no change in friction behavior between the versions of the oil additivated with the copper nanoadditive and its original version. Furthermore, it was found a reduction of micropitting for the 3% version of the studied oil in some operating conditions, and a reduction of the average wear volume for this same concentration in all studied operating conditions. On the other hand, it was found that the 0.3% version of the studied oil promoted wear with an increasing slide-to-roll ratio when compared with the original version of the studied oil. A higher reduction in wear was obtained for the 0.3% version of the studied oil with an increasing temperature when compared with the 3% version. These results indicate that copper nanoadditives exhibit the potential to reduce micropitting in non-conformal rolling-sliding contacts typically found in gears and rolling-element bearings.

The objective of this thesis work was to develop a method to detect early damage on small planetary gear sets that are installed in Atlas Copco nutrunners. The project has gone through several stages of product development, from idea to working product and signal analysis. Currently, Atlas Copco have a test rig for testing these planetary gears, this rig has been proven to be insufficient at detecting faults during an ongoing test. A new tailored test rig was therefore designed and manufactured. Low noise and low amount of vibration was of interest when designing the rig. Four concepts was thought of and evaluated through simulations using Matlab and Simulink. Most of the components of the rig were manufactured in the workshop at Atlas Copco in Nacka. Methods fo rmeasuring torsional, transverse and acoustic vibration was implemented and analyzed. There are many different parameters considering fault of fixed shaft gears. However, these are not easily applicable on a planetary gear because of the nature of its design. Therefore, special techniques are required. Two “new” parameters were tested (NSDS,FRMS [Lei. et al.]) with positive results. Pitting of individual gear members could befound.

No description available.