¡@¡@An electrical discharge coating method, which an isolated sleeve is used to form a closed space between the end surface of electrode and the workpiece so that the particles, the ions, and the pressure during the discharge process are concentrated on this space, is employed to increase the coating speed and the quality of the coating. The electrode for the cathode is made of brass, and the workpiece for the anode SKD11. They are immersed in kerosene containing W/C powder with the concentration of 50g/L. The time for the pulse-on is 25£gs and that for the pulse-off times 500£gs. The growing thickness and the quality of coating layer are investigated under the supply voltage of 50-400V, discharge coating time of 34-284s, and the gap distance of 50-300£gm. ¡@¡@Experimental results show that when the supply voltage is larger than 100V, the gap distance less than 150£gm and discharge coating time 142s, the area covered by the coating can achieve more than 90 percent of the total surface area. Moreover, the coating thickness increases with increasing gap distance and discharge coating time, but as the gap distance is larger than 150£gm, the coating thickness decreases with increasing gap distance. ¡@¡@For a special case, under the supply voltage of 200V, the gap distance of 100£gm and the discharge coating time of 142s, the coating thickness can achieve about 17£gm with little pore in the coating layer. The hardness of the coating layer can almost achieve the level of W/C hardness.

This project has as main goal to study the influence of the coating thickness, deposited by arc-PVD- technology, on the wear resistance of coated cemented carbide inserts in three different turning operations. An additional effort has also been made to develop a new test method for evaluating flank wear resistance. Three different coating types (Coating A, Coating B and Coating C) have been studied in three distinctive thicknesses (2, 4 and 6 μ m) for each type. For two of the coating types (Coating A and B) special studies has been done with the thickest coating, creating two additional coating versions of the thickest coating, by changing various deposition parameters, with the aim to enhance the cohesive properties of the coating and lower the residual stresses at the cutting edge. The results show increased crater wear resistance with increased coating thickness for all coating types, but the amount of increase changes with coating type (Coating A>B>C). Flaking wear resistance decreased with increased coating thickness for all coating types. Further the high temperature version of Coating A, showed a significant increase in the flaking wear resistance compared to the standard version of Coating A. The flank wear test showed an increased resistance with thicker coatings in all cases except for the 6 μ m version of Coating C. The flank wear resistance of the most flank wear resistant coatings (Coating B, C) was also successfully examined in a new developed test method. The method suppressed excessive crater wear on the rake face and presented a high abrasive wear rate on the flank and some flaking on the rake face. The amount of flaking is judged not to influence the testing of the flank wear resistance. For all the tested coatings in the new test an increase in the coating thickness resulted in better flank wear resistance.

Minimizing adhesion of ice has been the subject of extensive studies for applications such aircraft wings, wind turbine blades spacecraft, power transmission wires, while a growing interest concerns coatings for aerospace applications. The work described here describes progress for coatings and ice release test method development over the last few years. Major achievements include: (1) New Rigid Adherent-Resistant Elastomers (RARE), (2) A new Epoxied Cylinder (EC) adhesion test, (3) Validation of an ice release test, and (4) Study of ice adhesion strength on coating thickness for a PDMS elastomer. Rigid Adhesion-Resistance Elastomers (RARE) are comprised of 3F 1 terminated with triethoxysilane moieties and linear 3F polyurethane (U-3F). Hybrid compositions U-3F-x are designated by polyurethane weight percent “x”. Interestingly, RARE coatings spontaneously “self-stratify” during coating deposition and cure. Cured RARE coatings are comprised of (1) a nanoscale surface layer with low work of adhesion, (2) a low modulus mesoscale and (3) a tough U-3F bulk, where “Mesoscale” is defined as a near surface region with a depth ~ 1000 nm. An EC adhesion test was developed to evaluate the fouling release characteristics of RARE. EC adhesion testing was devised by using the commercially available instrument, TA RSA-3. The TA RSA-3 is well suited for these tests as the 3.5 kg load cell facilitates accurate measurements. This test gives peak force (Ps) for EC removal. A striking compositional dependence was found for EC adhesion. A U-3F-50 hybrid coating had the lowest adhesion (Ps = 0.078 MPa) with good toughness (6.2 MPa). Bulk and surface characterization together with adhesion measurements established U-3F-x hybrid coatings, and U-3F-50 in particular, as new fluorous rigid adherent-resistant elastomers (RARE) that are tough, oil resistant, and optically transparent. Inspired by the Epoxied Cylinder (EC) adhesion test, a laboratory method for ice adhesion measurement with a commercially available instrument was established in the Wynne Laboratory. This is the first laboratory ice adhesion test that does not require a custom built apparatus. The temperature controlled chamber on TA RSA-3 is an enabling feature that is essential for the test. The method involves removal of an ice cylinder from a polymer coating with a probe and the determination of peak removal force (Ps). To validate the test method, the strength of ice adhesion was determined for a prototypical glassy polymer, poly(methyl methacrylate). The distance of the probe from the PMMA surface has been identified as a critical variable for Ps. The new test provides a readily available platform for investigating fundamental surface characteristics affecting ice adhesion. In addition to the ice release test, PMMA coatings were characterized using DSC, DCA and TM-AFM. This new laboratory ice release test was then employed to obtain the thickness dependence of ice adhesion for Sylgard 184, a filled polydimethylsiloxane elastomer. A correlation between ice adhesion and coating thickness (t) was found, that follows a relationship developed by Kendall over 40 years ago for removal of a rigid object from an elastomer. In particular, a nearly linear relationship between peak removal stress (Ps) and 1/t1/2 was found, with Ps decreasing from 550 kPa to 100 kPa with coating thickness increasing from 12 μm to 800 μm. While work of adhesion, which is related to surface free energy, is recognized as an important factor that can affect ice release, the results reported herein show that coating thickness can override this single parameter for elastomeric substrates. Base on the result, a general model is proposed for the removal of ice from low modulus elastomers (~10 MPa).

In this thesis, the contact behavior of the conduct particles in the anisotropic conductive film (ACF) packaging process is investigated. The thermal elastic-plastic finite element (FE) model is employed to simulate the contact process. The commercial MARC finite element method package is used in this work. Two contact models of the ACF packaging are studied : the single particle and the multiple-particles models. In the single particle model a simple axial symmetric FE model is used to simulate the variation of elastic-plastic deformations during packaging process. The effect of coating thickness on the contact deformation is discussed. To explore the effect of particle distribution on the contact deformation and the conduct behavior in the ACF packaging, the multiple-particles 3D model has also been studied. However, to overcome the computing difficulties introduced from huge degrees of freedom, the equivalent nonlinear springs are employed to stand for some conductive particles. The effect of particle distribution and particle parameters on the conductive behavior are studied. Results indicate that the conductive particle parameters may affect the conductive characteristics significantly in the ACF packaging process.

The rise of the Environmentalism in every sector of the Industry has lead the aircraft and engine manufacturing companies to develop new generations of more environmentally friendly engines. The companies, encouraged to this purpose, are in a constant research for new manufacturing and production techniques, in order to improve their products, from the environmental point of view, by gaining efficiency in the manufacturing techniques and reduce the fuel consumption and emissions in-flight. Having in mind this scenario, the sponsor of this Project is interested in understanding how changing the materials of the blades, titanium alloys currently, for other lighter materials, such as composites, is going to have an effect in the overall gas turbine efficiency. In the particular case of this Project, it will be studied the influence of the Stiffness and coating Thickness of those non-metallic materials suitable to be employed as coatings on gas turbine fan blades, from the icing point of view. The work procedure will be based on a study of Linear Elastic Fracture Mechanics of bi-material junctions and will extrapolate the general problem to the ice-coatings case, by getting experimental data from tests carried out in an Icing Tunnel. It will be observed that the coating Stiffness has an influence on the Adhesion Level of ice to less stiff materials, if compared with the Adhesion Level of ice to metals. Besides, it will be described how a 0.5 millimetres thin polymeric coating placed over a metallic substrate is enough to reduce the Adhesion Level of ice, hiding any effect that the underneath materials might have on the Adhesion Level.

The rise of the Environmentalism in every sector of the Industry has lead the aircraft and engine manufacturing companies to develop new generations of more environmentally friendly engines. The companies, encouraged to this purpose, are in a constant research for new manufacturing and production techniques, in order to improve their products, from the environmental point of view, by gaining efficiency in the manufacturing techniques and reduce the fuel consumption and emissions in-flight. Having in mind this scenario, the sponsor of this Project is interested in understanding how changing the materials of the blades, titanium alloys currently, for other lighter materials, such as composites, is going to have an effect in the overall gas turbine efficiency. In the particular case of this Project, it will be studied the influence of the Stiffness and coating Thickness of those non-metallic materials suitable to be employed as coatings on gas turbine fan blades, from the icing point of view. The work procedure will be based on a study of Linear Elastic Fracture Mechanics of bi-material junctions and will extrapolate the general problem to the ice-coatings case, by getting experimental data from tests carried out in an Icing Tunnel. It will be observed that the coating Stiffness has an influence on the Adhesion Level of ice to less stiff materials, if compared with the Adhesion Level of ice to metals. Besides, it will be described how a 0.5 millimetres thin polymeric coating placed over a metallic substrate is enough to reduce the Adhesion Level of ice, hiding any effect that the underneath materials might have on the Adhesion Level.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology. / For the last few decades, methods to improve the engine efficiency and reduce the fuel consumption of jet engines have received increased attention. One of the solutions is to increase the operating temperature in order to increase the exhaust gas temperature, resulting in an increased engine power. However, this approach can be degrading for some engine parts such as turbine blades, which are required to operate in a very hostile environment (at ≈ 90% of their melting point temperature). Thus, an additional treatment must be carried out to protect these parts from corrosion, oxidation and erosion, as well as to maintain the substrate’s mechanical properties which can be modified by the high temperatures to which these parts are exposed. Coating, as the most known protection method, has been used for the last few decades to protect aircraft engine parts. According to Wolfe and Co-workers [1], 75% of all engine components are now coated. The most promising studies show that the thermal barrier coating (TBC) is the best adapted coating system for these high temperature applications. TBC is defined as a fine layer of material (generally ceramic or metallic material or both) directly deposited on the surface of the part In order to create a separation between the substrate and the environment to reduce the effect of the temperature aggression. However, the application of TBCs on surfaces of components presents a challenge in terms of the consistency of the thickness of the layer. This is due to the nature of the processes used to apply these coatings. It has been found that variations in the coating thickness can affect the thermodynamic performance of turbine blades as well as lead to premature damage due to higher thermal gradients in certain sections of the blade. Thus, it is necessary to optimise the thickness distribution of the coating.

Es wird gezeigt, dass mit dem Fluoreszenzmesssystem sowohl die Schichtdicke als auch die Aushärtung detektiert werden kann. Durch das Erstellen von Eichkurven ist es so möglich, vollflächig, die genaue Schichtdicke der Beschichtung im laufenden Prozess inline zu bestimmen und Abweichungen in Echtzeit entgegenzuwirken. Zudem können so Unregelmäßigkeiten bei der Aushärtung der Lacke direkt erkannt und bei unzureichender Aushärtung der Anteil von Fehlproduktionen minimiert werden. Auch bei hochvernetzten Acrylatklebstoffen konnte gezeigt werden, dass mit dem System eine genaue Analyse der inneren Festigkeit vorgenommen werden kann. Diese Klebstoffe, mit teilweise unterschiedlichem chemischen Aufbau, aber gleichem E-Modul, emittieren dasselbe Maß an Fluoreszenz. Somit konnte gezeigt werden, dass mit der Fluoreszenzmessung, unabhängig von der chemischen Struktur, gleichbleibende Intensitäten gemessen und damit der Aushärtegrad bestimmt werden kann. Zur genauen Bestimmung der Schichtdicken mit dem Fluoreszenzmesssystem ist es notwendig genaue Eichkurven für jedes einzelne System zu erstellen. Auch ist es, im Falle der Molkeprotein Beschichtungen notwendig weitere Formulierungen zu testen um eine exakte Vorhersage des Vernetzungsgrads zu gewährleisten. Durch die Ergebnisse die mit den Acrylatklebstoffen erzielt wurden stellt sich die Frage, inwieweit eine Korrelation zwischen der chemischen Struktur des untersuchten Materials und der gemessenen Fluoreszenz dabei besteht. Es sollte die Fluoreszenz von weiteren Materialien, unterschiedlicher chemischer Struktur, gemessen und überprüft werden, ob ein Zusammenhang zu deren E-Modul besteht. Außerdem sind Materialien wie z.B. Klebstoffe und Lacke auf Polyurethanbasis, deren Aushärtung erst nach mehreren Tagen oder Wochen abgeschlossen ist, interessant. Dabei stellt sich die Frage, ob Abweichungen der Aushärtung schon direkt nach der Beschichtung, durch das Fluoreszenzmesssystem, detektiert und somit Fehlproduktionen schon frühzeitig erkennt werden können. [... aus Zusammenfassung und Ausblick]

Es wird gezeigt, dass mit dem Fluoreszenzmesssystem sowohl die Schichtdicke als auch die Aushärtung detektiert werden kann. Durch das Erstellen von Eichkurven ist es so möglich, vollflächig, die genaue Schichtdicke der Beschichtung im laufenden Prozess inline zu bestimmen und Abweichungen in Echtzeit entgegenzuwirken. Zudem können so Unregelmäßigkeiten bei der Aushärtung der Lacke direkt erkannt und bei unzureichender Aushärtung der Anteil von Fehlproduktionen minimiert werden. Auch bei hochvernetzten Acrylatklebstoffen konnte gezeigt werden, dass mit dem System eine genaue Analyse der inneren Festigkeit vorgenommen werden kann. Diese Klebstoffe, mit teilweise unterschiedlichem chemischen Aufbau, aber gleichem E-Modul, emittieren dasselbe Maß an Fluoreszenz. Somit konnte gezeigt werden, dass mit der Fluoreszenzmessung, unabhängig von der chemischen Struktur, gleichbleibende Intensitäten gemessen und damit der Aushärtegrad bestimmt werden kann. Zur genauen Bestimmung der Schichtdicken mit dem Fluoreszenzmesssystem ist es notwendig genaue Eichkurven für jedes einzelne System zu erstellen. Auch ist es, im Falle der Molkeprotein Beschichtungen notwendig weitere Formulierungen zu testen um eine exakte Vorhersage des Vernetzungsgrads zu gewährleisten. Durch die Ergebnisse die mit den Acrylatklebstoffen erzielt wurden stellt sich die Frage, inwieweit eine Korrelation zwischen der chemischen Struktur des untersuchten Materials und der gemessenen Fluoreszenz dabei besteht. Es sollte die Fluoreszenz von weiteren Materialien, unterschiedlicher chemischer Struktur, gemessen und überprüft werden, ob ein Zusammenhang zu deren E-Modul besteht. Außerdem sind Materialien wie z.B. Klebstoffe und Lacke auf Polyurethanbasis, deren Aushärtung erst nach mehreren Tagen oder Wochen abgeschlossen ist, interessant. Dabei stellt sich die Frage, ob Abweichungen der Aushärtung schon direkt nach der Beschichtung, durch das Fluoreszenzmesssystem, detektiert und somit Fehlproduktionen schon frühzeitig erkennt werden können. [... aus Zusammenfassung und Ausblick]

<p>This thesis investigates the wall pressure distributions of the single-slot impinging jet and multiple-slot impinging jet as a function of various parameters and compares the results obtained with the computational study of Tamadonfar [2010]. The process of gas wiping is used in many industrial applications such as tempering of the plate glass, the chemical mixing process, and turbine blade cooling. One of the most important industrial applications of gas jet wiping is the production of galvanized steel strip in a continuous hot-dip galvanizing line. In this process, an impinging jet is used to remove the excess zinc alloy from the steel strip and control the final coating weight by applying wall pressure and shear stress on the moving substrate emerging from the bath of molten zinc. Changing the various operating parameters such as jet Reynolds number (<em>Re</em>), the jet to strip distance (<em>z</em>), the jet slot width (<em>d</em>), and jet inclination angles (<em>α</em>) allows manufacturers manipulate the final coating weight on the substrate. Production of high quality sheet steels, which have a very thin coating weight and high uniformity quality, is one of the goals of the automotive industry. In order to obtain thinner and more uniform coating weight, a new model of impinging jet which is comprised of one main jet with two auxiliary jets, one on each side of the main jet, called a multiple-slot impinging jet, is of considerable interest.</p> <p>For the current study, a multiple-slot impinging jet was designed and manufactured and measurements were performed for both the single-slot impinging jets, the current model used in continuous hot-dip galvanizing lines, and the multiple-slot impinging jet subjected to a wide range of gas wiping parameters which include the main jet Reynolds number (<em>Re_m</em>), the auxiliary jet Reynolds number (<em>Re_a</em>), and the plate-to-nozzle ratio (<em>z/d</em>). A comparison between the measured results obtained for the two impinging jet configurations and the numerical results by Tamadonfar [2010] has been provided. The similarities and differences between the experimental and numerical results are presented and discussed.</p> / Master of Science in Mechanical Engineering (MSME)