The modern painting process in automotive industry is complex and a lot of factors affect the result. The trial and error method is used today to control the quality and introduce new colours. This method takes a lot of time and does not show any clear numbers of how the process is affected by changing the parameters. During this thesis, we have investigated a delimited number of parameters. The work is based on experiments performed on samples that represents a flat surface of the cab, to reduce experimental costs. Our master thesis is done at Scania in Oskarshamn, where all the cabs for the European production is produced. The objectives with this thesis has been to explain how the process parameters of the robotic applicator affect the paint distribution, paint thickness and the colour of the top coat. We also optimised the process by finding which settings gives an even paint distribution, a correct thickness and an accepted colour of the top coat. We have been using Design of Experiments to achieve the goals of this study. Design of Experiments is a statistic method that is used to perform experiments effectively. It also shows the effect of changing the factors from a low to a high level. We have chosen to divide the workflow into three parts: screening, optimisation and confirmation. The experiments are performed during the daily production to replicate the real circumstances. The shape air, paint flow and high rotation is the most important parameters to control. Paint flow also seems to have a linear impact on the thickness of the top coat layer. The Shape air and the high rotation on the other hand mainly affect the distribution of the top coat layer. Different levels are needed for the shape air and high rotation depending on what paint flow is used. The optimal settings of the factors for our colour were found to be paint flow at 82 %, the shape air at 90 %, the high rotation at 90 % and high voltage at 100 %. The optimal settings give a result of 1,535 μm in spread and 40,08 μm in mean thickness. Our settings compared to today’s results contributes to a reduced paint consumption, better quality and therefore less rework.

Reliability experiments provide important information regarding the life of a product, including how various factors may affect product life. Current analyses of reliability data usually assume a completely randomized design. However, reliability experiments frequently contain subsampling which is a restriction on randomization. A typical experiment involves applying treatments to test stands, with several items placed on each test stand. In addition, raw materials used in experiments are often produced in batches. In some cases one batch may not be large enough to provide materials for the entire experiment and more than one batch must be used. These batches lead to a design involving blocks. This dissertation proposes two methods for analyzing reliability experiments with random blocks and subsampling. The first method is a two-stage method which can be implemented in software used by most practitioners, but has some limitations. Therefore, a more rigorous nonlinear mixed model method is proposed. / Ph. D.

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Flood cooling is primarily used to cool and lubricate the cutting tool and workpiece interface during a machining process. But the adverse health effects caused by the use of flood coolants are drawing manufacturers' attention to develop methods for controlling occupational exposure to cutting fluids. Microlubrication serves as an alternative to flood cooling by reducing the volume of cutting fluid used in the machining process. Microlubrication minimizes the exposure of metal working fluids to the machining operators leading to an economical, safer and healthy workplace environment. In this dissertation, a vegetable based lubricant is used to conduct mist, microstructure and wear analyses during end milling AISI 1018 steel using microlubrication. A two-flute solid carbide cutting tool was used with varying cutting speed and feed rate levels with a constant depth of cut. A full factorial experiment with Multivariate Analysis of Variance (MANOVA) was conducted and regression models were generated along with parameter optimization for the flank wear, aerosol mass concentration and the aerosol particle size. MANOVA indicated that the speed and feed variables main effects are significant, but the interaction of (speed*feed) was not significant at 95% confidence level. The model was able to predict 69.44%, 68.06% and 42.90% of the variation in the data for both the flank wear side 1 and 2 and aerosol mass concentration, respectively. An adequate signal-to-noise precision ratio more than 4 was obtained for the models, indicating adequate signal to use the model as a predictor for both the flank wear sides and aerosol mass concentration. The highest average mass concentration of 8.32 mg/m3 was realized using cutting speed of 80 Surface feet per minute (SFM) and a feed rate of 0.003 Inches per tooth (IPT). The lowest average mass concentration of 5.91 mg/m3 was realized using treatment 120 SFM and 0.005 IPT. The cutting performance under microlubrication is five times better in terms of tool life and two times better in terms of materials removal volume under low cutting speed and feed rate combination as compared to high cutting speed and feed rate combination. Abrasion was the dominant wear mechanism for all the cutting tools under consideration. Other than abrasion, sliding adhesive wear of the workpiece materials was also observed. The scanning electron microscope investigation of the used cutting tools revealed micro-fatigue cracks, welded micro-chips and unusual built-up edges on the cutting tools flank and rake side. Higher tool life was observed in the lowest cutting speed and feed rate combination. Transmission electron microscopy analysis at failure for the treatment 120 SFM and 0.005 IPT helped to quantify the dislocation densities. Electron backscatter diffraction (EBSD) identified 4 to 8 µm grain size growth on the machined surface due to residual stresses that are the driving force for the grain boundaries motion to reduce its overall energy resulting in the slight grain growth. EBSD also showed that (001) textured ferrite grains before machining exhibited randomly orientated grains after machining. The study shows that with a proper selection of the cutting parameters, it is possible to obtain higher tool life in end milling under microlubrication. But more scientific studies are needed to lower the mass concentration of the aerosol particles, below the recommended value of 5 mg/m3 established by Occupational Safety and Health Administration (OSHA).

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While wind energy has emerged as a popular source of renewable energy, the traditional wind turbine has an inherent limitation, namely that it only generates power in the presence of sufficiently high and consistent wind speeds. As a result, wind farms are typically built in areas with a high probability of the required wind speeds, which are geographically sparse. One way of overcoming this drawback is to tap into the energy available in winds at high altitudes which are not only consistent and of high magnitude, but also globally pervasive. An airborne wind energy device based upon the phenomenon of autorotation could potentially be used to exploit the abundance of wind of energy present at high altitudes. The work in this thesis first presents our study of a tethered-airfoil system as a candidate airborne wind energy (AWE) system. A mathematical model was used to show the feasibility of energy capture and the stability of the device in a wind field. Subsequently, the research identified the principle of autorotation to be better suited for high altitude energy harvesting. To this end, the thesis first presents a theoretical basis of the principle of autorotation, which is developed from existing models in literature. The model was adapted to predict aerodynamic conditions when used for harvesting energy. Encouraging simulation results prompted the main emphasis of this thesis, namely design of an experimental framework to corroborate the theory. Several experiments were devised to determine basic performance characteristics of an autogyro rotor and the data from each experiment is presented. A lab-scale experimental setup was developed as part of this thesis. The setup, consisting of a flapping-blade autogyro rotor and sensors, was used to acquire preliminary aerodynamic performance data. It is envisioned that refinements to this setup will ultimately provide a means of directly comparing analytical and experimental data. In this regard, we provide conclusions and make comments on improvements for future experiments.

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The purpose of this study was to characterize the craze growth behavior of polycarbonate (PC) as a function of stress level, model the residual mechanical properties of PC at various craze levels and strain rates, and determine if the total surface area of crazing is the sole factor in residual properties or if the crazing stress plays a role. To obtain these goals, a new in-situ reflective imaging technique was developed to quantify the craze severity in transparent polymers. To accomplish the goal of craze growth rate characterization, polycarbonate samples were placed under a creep load in a constant temperature, constant humidity environment. Using the new technique, the relative craze density was measured as a function of time under load at stresses of 40, 45, and 50 MPa. The craze growth rates were found to increase exponentially with stress level, and the times to 1% relative craze density were found to decrease exponentially with stress level. One exception to this behavior was found at a crazing stress of 50 MPa at which over half of the samples tested experienced delayed necking, indicating competitive mechanisms of crazing and shear yielding. The draw stress was found to be a lower bound below which delayed necking will not occur in a reasonable time frame. The yield stress, elastic modulus, failure stress, and ductility were correlated to crazing stress, relative craze density, and strain rate using a Design of Experiments (DOE) approach. The yield stress was found to correlate only to the strain rate, appearing to be unaffected by the presence of crazes. No correlation was found between the elastic modulus and the experimental factors. The failure stress was found to decrease with an increase in relative craze density from 0 to 1%, increase with an increase in crazing stress from 40 to 45 MPa, and correlate to the interaction between the crazing stress and the strain rate. The ductility of polycarbonate was found to decrease significantly with an increase in relative craze density, a decrease in crazing stress, and an increase in strain rate. The craze microstructure was correlated to the magnitude of stress during craze formation. The area of a typical craze formed at 40 MPa was measured to be more than 2.5 times larger than the area of a typical craze formed at 45 MPa. The fewer, but larger, crazes formed at the lower stress level were found to decrease the failure strength and ductility of polycarbonate more severely than the large number of smaller crazes formed at the higher stress level. / Ph. D.