In recent years, it has been recognised that a better understanding of processes involving particulate material is necessary to improve manufacturing capabilities and product quality. The use of Discrete Element Modeling (DEM) for more complicated particulate systems has increased concordantly with hardware and code developments, making this tool more accessible to industry. The principal aim of this project was to study DEM capabilities and limitations with the final goal of applying the technique to relevant Johnson Matthey operations. This work challenged the DEM numerical technique by modelling a mixer with a complex motion, the Turbula mixer. The simulations revealed an unexpected trend for rate of mixing with speed, initially decreasing between 23 rpm and 46 rpm, then increasing between 46 rpm and 69 rpm. The DEM results were qualitatively validated with measurements from Positron Emission Particle Tracking (PEPT), which revealed a similar pattern regarding the mixing behaviour for a similar system. The effect of particle size and speed on segregation were also shown, confirming comparable results observed in the literature. Overall, the findings illustrated that DEM could be an effective tool for modelling and improving processes related to particulate material.

Active Screen Plasma Nitriding (ASPN) is a novel surface engineering technique, the main advantage of which is the capacity to treat homogeneously all kind of materials surfaces of any shape. Here, ASPN is used to modify the surface properties of ionomer glasses and polymers in order to improve the surface cellular compatibility of these materials. A conventional DC nitriding unit has been used together with an AS experimental arrangement. The materials that were treated were an ionomer glass composition and UHMWPE. All treated/untreated samples were seeded with the 3T3 fibroblasts. In order to identify the effect of the plasma treatment, chemical and mechanical properties characterization was conducted. For the cellular samples, SEM, Interferometry, AFM and MTT assay were conducted in order to observe cells’ behavior on the untreated and treated materials. The inert surface of the untreated glass showed good interaction with fibroblasts only after the ASPN treatment which resulted in enhanced fibroblasts attachment and proliferation. The treatment temperature, the length of treatment and the presence of nitrogen had an influence on the surface properties of glass. UHMWPE treated samples chemical characterization showed the formation of C-N and N-H groups resulting in an increase of the functionality of treated surfaces. 3T3 fibroblasts cell culture studies showed that the ASPN treatment had a positive effect on the adhesion and proliferation of cells according to the time of treatment and the increase of the nitrogen concentration in the gas mixture. As a conclusion ASPN treatment can be a very effective method to modify inorganic and organic polymeric surfaces in order to improve cellular compatibility.

In the presented thesis, lead-free Ba(Ti0.8Zr0.2)O3-(Ba0.7Ca0.3)TiO3 (BZT-BCT) thin films were deposited on Pt/TiO2/SiO2/Si substrates using chemical solution deposition method and then the effect of process parameters were investigated to obtain optimum parameters of these lead-free thin films. The phase was selected near to the morphotropic phase boundary (MPH) to increase the number of polarization directions where rhombohedral and tetragonal phases exist together. In this study, the effect of sintering temperatures on microstructure, dielectric and ferroelectric properties were studied systematically. Among the various high-quality BZT-BCT thin films with uniform thickness, the optimum dielectric and ferroelectric responses were observed for films annealed at 800 oC for 1 h sintering time. The thickness was kept constant for all measurements as 500 nm (triple layered films). Therefore, the average grain sizes were found around 60 nm for samples sintered at 700,750 and 800 oC. BZT-BCT thin films sintered at 800 oC showed effective remnant polarization and coercive field values of 2.9 &micro / C/cm2 and 49.4 kV/cm, together with a high dielectric constant and low loss tangent of 365.6 and 3.52 %, respectively, at a frequency of 600 kHz due to pure perovskite phase showing full crystallization and minimum surface porosity obtained at this temperature.

Data Envelopment Analysis (DEA) is a powerful technique for relatively efficiency measurement and it is intensively used in different kind of disciplines but this technique has some drawbacks. In the conventional DEA technique, total number of inputs and outputs is determined by the number of evaluated firms. Therefore, this powerful efficiency measurement technique cannot be employed for limited number firm problems. DEA uses realized data so it can be used for objective evaluations. However, in some Occupational Health and Safety (OHS) and mining cases, subjective evaluation is also very important so it should be included in DEA analyses. To get rid of these drawbacks, a new technique is developed with integration of DEA and Analytical Hierarchy Process (AHP) and it is named as AHP.DEA Method. The developed method creates an opportunity using more inputs and outputs in the relatively efficiency measurement for limited number firm cases. Therefore, reliability of the estimation is increased with increasing the number of inputs and outputs in the estimations. The AHP.DEA technique also integrates both subjective opinion of experts and objective evaluation. Combination of them can give more consistent results when compared only subjective or objective evaluation methods. After the application of AHP.DEA method in mining and OHS industry, managers of mining companies can compare their organizations with the competitors or their branches and they can identify strengths and weakness of them. Therefore, quantity and quality of output may be increased while number of accidents is decreased and also new opportunities can be identified to upgrade current operations.

Fatigue crack growth behavior of AA7050 T7451 aluminum alloy under mode II loading condition in two orientations was investigated. Compact shear specimens were prepared in TL and LT directions. A loading frame for mode II type of loading was manufactured. Using the loading frame and the specimen, KIIC values and mode II fatigue crack growth rates were calculated. Fractographic analysis of the fracture surfaces of both mode II fracture toughness test specimens and mode II fatigue crack growth test specimens were done to examine the effects of mode II load. KIIC values were measured between 1.3 and 1.5 times the KIC values for this alloy. As for mode II fatigue crack growth rates, TL orientation shows the highest mode II fatigue crack growth resistance.

For the last decades usage of aluminium alloys have been increasing tremendously. They have been used in aerospace industry widely and now aluminium alloys are becoming more and more popular in automotive and defense industries. Consequently / successful welding of aluminium alloys gains importance. In this study a research is carried out on eldability of plates having different thicknesses of composition 5754 aluminium and 6063 aluminium in T-fillet geometry using Gas-metal Arc Welding technique. It was aimed to have a successful joint without using pre-weld and post-weld heat treatments. During tests welding current and voltage were the varying parameters as welding speed was held constant. Macro-examinations were performed to see the penetration of the weld metal. It was seen that the type of filler wire greatly effects weld penetration. Hardness tests, tensile tests were done to compare the mechanical properties of the welded joints with different filler wires. Despite having better penetration in 4043 filler wire used weld joints, 5356 filler wire used weld joints had higher tensile strength and ductility. In the second part of the study, a dynamic loading machine was designed and manufactured to see the behavior of the fillet welds under dynamic loading. The amount of stress and strain given to the specimen on this machine was adjustable but can&rsquo / t be measured. The tests that were made with this machine aimed only to compare the number of cycles of specimens before fracture. For dynamic loading tests two groups of specimens were prepared with filler wire 4043 / each group having been welded with different heat inputs. It was aimed to see the effect of welding heat input on service lifes but no significant difference between cycle numbers of specimen groups having been welded with different heat inputs was observed. Microstructure examinations of these specimens revealed that coarsening the grains, grain boundaries, particles in PMZ and HAZ regions between Al 6063 base metal and weld zone made these areas more susceptible and favorable for crack propogation than Al 6063 base metal.

The effect of different aging treatments on fatigue crack growth behavior of AA6013 aluminum alloy was investigated. C(T) (Compact Tension) specimens were prepared in L-T and T-L direction for fatigue crack growth tests. Samples were in T651 as received, T42 which is solution heat treated at 538 &ordm / C for 90 minutes, water quenched and aged in room temperature for 96 hours, and one group of samples were overaged at 245 &ordm / C for 12 hours after T42 condition was achieved. Hardness and conductivity measurements were achieved for all conditions after the heat treatments. Fatigue crack growth tests were performed at as received condition T651, T42 and 245 &ordm / C aged samples in laboratory air with sinusoidal loading of stress ratio R=0.1 and at a frequency of 1 Hz. The highest fatigue crack growth resistance is observed for T651 T-L and 245 &ordm / C overaged L-T condition.

The analysis presented in this thesis provides a methodology for grouted bolts design, based on empirical and analytical methods. Hence, the main objectives of this thesis are to offer practical means for better characterisation of poor to very poor rock masses, to better predict support pressure, and to develop an elasto-plastic analytical model for design of grouted bolts in tunnels excavated in such rock masses. To improve the applicability of the GSI (Geological Strength Index) in poor to very poor rock masses, using Broken Domain Structure (BSTR), Structure Rating (SR), and Intact Core Recovery (ICR), some modifications have been offered, resulting in the Modified-GSI. Applying rock-load height concept and Modified-GSI, an approach to estimate support pressure has been developed. The main advantage of this approach is its applicability in squeezing ground and anisotropic stress conditions. Numerical modelling was carried out in order to adjust the proposed support pressure equation. Considering convergence reduction approach, an elasto-plastic model based on the latest version of Hoek- Brown failure criterion has been developed for a more effective and practical grouted bolt design. The link between empirical approach and elasto-plastic solution makes it possible to reach more realistic and appropriate bolting pattern design. In this way, the need for the redesign procedure in the convergence reduction approach is eliminated. The results of the proposed elastic-plastic solution have been compared with a numerical model using FLAC2D, and a reasonable agreement was observed. The practical application of the developed methodology is depicted by an analysis of a case study in Turkey.

Obtaining high magnetic susceptibility phases from Hekimhan&amp / #8211 / Deveci siderite orevia preliminary thermal treatment has been the basic target of the thesis study.Thermal decomposition characteristics of samples, determined bythermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC), were referenced in advancement of thestudy. Heat treatment experiments, particularly roasting, were carried out byconventional heating and microwave heating. Results showed that roasting of Hekimhan&amp / #8211 / Deveci siderite samples could not be achieved by microwave energywhilst conventional heating experiments recorded success. Subsequentlow&amp / #8211 / intensity magnetic separation of roasted samples gave recovery above 90%, where low&amp / #8211 / intensity magnetic separation of run&amp / #8211 / of&amp / #8211 / mine sample had failed. Formation of high magnetic susceptibility phases was verified by magneticsusceptibility balance and x&amp / #8211 / ray diffraction analysis (XRD), on roasted samples. Statistical modeling was applied to determine the optimum conditions of roastingin conventional heating system / based on heating temperature, time of heating, particle size as factors.It was concluded that roasting at T= 560 &ordm / C, for t= 45 minutes was adequate toobtain desired results. Particle size was noted to be not much effective on the process as other factors at the studied size range. Kinetics (E, n) and reaction mechanism for the thermal decomposition in conventional heating system were evaluated with different solid&amp / #8211 / state reaction models by interpretation of the model graphs.Three&amp / #8211 / dimensional diffusion reaction models reported to characterize the thermal decomposition well, with values of activation energy (E), E= 85.53 kJ/mol (Jander) / E= 85.49 kJ/mol, (Ginstling&amp / #8211 / Brounshtein).

Directional and horizontal drilling operations are increasingly conducted in all over the world, especially parallel to the growth of the technological developments in the industry. Common application fields for directional and horizontal drilling are in offshore and onshore when there is no way of drilling vertical wells. During directional and horizontal well drilling, many additional challenges occur when compared with vertical well drilling, such as limited weight on bit, harder hole cleaning, trajectory control, etc. This makes even harder to select the proper drilling parameters for increasing the rate of penetration. This study aims to propose a rate of penetration model considering many drilling parameters and conditions. The proposed model is a modified Bourgoyne &amp / Young&rsquo / s model which considers formation compaction, formation pressure, equivalent circulating density, and effective weight on bit, rotation of the bit, bit wear, hole cleaning, inclination, fluid loss properties and bit hydraulics. Also, a bit wear model is developed for roller cones and PDCs. The model performance is tested using field data obtained from several directional and horizontal offshore wells drilled at Persian Gulf. It is observed that the model can estimate rate of penetration with an error of &plusmn / 25 % when compared with the field data.