@masterthesis{Michev, type = {Bachelor Thesis}, author = {Michev, Dimitar}, title = {Recrystallisation Behaviour of Extruded 3000-series Aluminium after Minor Deformation}, school = {Hochschule Rhein-Waal}, abstract = {A large part of the tube elements of a conventional tube/fin heat exchanger, designated in industry under the names multi-port extrusion (MPE) or micro-multiport (MMP) tubes, are produced from aluminum of the 3XXX series. The production of that tubing commonly consists of direct chill (DC) casting of the raw material, homogenization of the billet, extrusion, coating, coiling and final dimensioning. Additionally, to being straightened and cut to the final length, those tubes undergo height and width calibration through cold forming, to meet the customer tolerances. Consequently, this critical amount of cold work done to the material leads to recrystallization followed by the growth of very coarse grains during the brazing process. This coarsening of the microstructure reduced the strength, hardness and corrosion resistance of the material. In this paper, a characterization of the behavior of the microstructure in relation to the level of deformation is done by examining multiple samples. Three different coils each having different cross-sectional profiles, two made from the same alloy AlMn0.5 and the third made from AlMn0.2Cu0.4 were examined. From each coil samples were produced and calibrated to different changes in height and width: none (Δh=Δb=0), medium (Δh=Δb=0.05) and high (Δh=Δb=0.1). The specimens were exposed to diverse temperatures and dwell times, simulating brazing conditions. Temperatures chosen, varied from 510°C to 590°C and holding times were between 3 and 10 minutes. Optical microscopy was used to inspect and quantify the fraction recrystallized microstructure of the samples in metallographically prepared cross-sections. The data gathered from the microscopic investigation was analyzed using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The resulting graphs showed the effects of other parameters on the recrystallized fraction/dwelling time function. An approximation of the model was used to show the percent recrystallized microstructure and temperature dependency. This allowed the determination of the temperature at which nearly 100\% of the microstructure has recrystallized, hence the process is completed.}, language = {en} } @masterthesis{Oh, type = {Bachelor Thesis}, author = {Oh, Hyeryeon}, title = {45S5 Bioglass scaffold coated with a drug loaded mesoporous bioactive glass for bone tissue engineering}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:1383-opus4-2689}, school = {Hochschule Rhein-Waal}, pages = {48}, abstract = {Bioactive glass scaffold is a promising substitute of the bone grafts in bone tissue engineering. To improve its potential in bone repair, it needs to be more mechanically stable and provide a controlled drug delivery. Thus, 45S5 Bioglass® scaffolds that are fabricated via a foam replication technique, are coated with the amine-functionalized mesoporous bioactive glass nanoparticles by the slurry dip coating method. These nanoparticles are able to load the therapeutic biomolecules in their mesopores in size range of 2-50 nm and release the drug at a controlled rate when they are exposed to a physiological fluid. The compressive strength of the scaffolds is improved by coating them with gelatin, a biocompatible polymer. The influence of these modifications on the bioactivity of the scaffolds is analyzed by immersing them in the simulated body fluid for up to 21 days. FTIR and XRD analysis confirms that the coating of bioglass nanoparticles and gelatin does not inhibit the formation of the hydroxyapatite layer, while it improves the drug loading capacity and mechanical strength of the scaffolds.}, language = {en} } @masterthesis{Menon, type = {Bachelor Thesis}, author = {Menon, Praanav Mahadev}, title = {Using the U-Net Model for Steel Microstructure Identification and Analysis}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:1383-opus4-20600}, school = {Hochschule Rhein-Waal}, pages = {95}, abstract = {This thesis presents the development and training of a U-Net- a convolutional neural network (CNN) model for the segmentation and classification of 4 microstructural phases in C45 steel: retained austenite, martensite, pearlite, and ferrite. It also features the steps taken to prepare the metallographic samples. The U-Net was designed and developed for biomedical microscopy imaging but has a wide array of uses for semantic segmentation in other fields as well. Utilizing Nital-etched microscopy images, the network was trained to identify and differentiate between these microstructures, which is critical for determining the mechanical properties of the steel. The dataset is comprised of a set of 35 grayscale images, and its corresponding labels/masks annotated with 4 colours for the various phases. Moreover, this thesis is an attempt at using deep learning to segregate retained austenite from martensite through visual LOM methods, as opposed to EBSD and XRD which are the widely used methods for identifying and quantifying retained austenite in a sample. The trained network demonstrated reasonable performance in segmenting the microstructural components. This research highlights the potential of deep learning approaches in materials science, particularly for automating the analysis of metallographic images, contributing to more efficient and precise material characterization.}, language = {en} } @masterthesis{Karst, type = {Bachelor Thesis}, author = {Karst, Melina}, title = {Determination of Total Carbon with Infrared Absorption Method After Combustion in an Induction Furnace for Ferro-Chromium Alloys}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:1383-opus4-19927}, school = {Hochschule Rhein-Waal}, pages = {86}, abstract = {In this thesis, an evaluation of the determination of the total carbon in ferroalloys, with a focus on ferrochromium, via infrared absorption after combustion in an induction furnace is conducted. The experiments were performed over a period of 4 months with the goal of setting a robust calibration for carbon detection in ferroalloys. Ferrochromium ranging from 0,01 \% to 9,03 \% carbon was used as a reference material for the calibration. It was tested by using independent certified reference materials of ferrochromium but also additional ferroalloys like ferro-manganese, -silicon, - niobium, -titanium and -vanadium for the validation process. The statistical calculations were performed using the NORDTEST standards to ensure reliable results. Additionally, the drift of the machine and the detection and quantification limits were investigated. It revealed that the drift had to be applied daily, and that the quantification limit of the detector in the CS-analyzer is around 0,012 \% carbon. As a result of the statistical calculations, it appeared that the measurement uncertainty is carbon percentage dependent. This led to the creation of a function that can estimate the measurement uncertainty dependent on the carbon percentage for future analysis. Subsequential testing proved the emission of reasonable results for all tested materials, validating that the set calibration can be applied to those materials without further refinement of the calibration method.}, language = {en} } @masterthesis{Elzoghby, type = {Bachelor Thesis}, author = {Elzoghby, Abdalla}, title = {An Elaborated Environmental Life Cycle Assessment on Renewable Energy in Germany}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:1383-opus4-20295}, school = {Hochschule Rhein-Waal}, pages = {93}, abstract = {Life Cycle Assessment is a method of assessing the environmental impacts throughout the life cycle of a product. It was standardized by ISO to aid comparison of different studies employing the method of Life Cycle Assessment. The standard contains the phases: Goal and Scope, Life Cycle Inventory, Life Cycle Impact Assessment, and Interpretation. A Life Cycle Assessment is conducted on renewable energies in Germany, namely Wind Energy, Solar Energy, Bioenergy, and Green Hydrogen Energy. The data collection phase of the life cycle inventory was performed under several assumptions and limitations which extend to the results. It is established through the results of the study that Green Hydrogen energy holds the greatest environmental impacts out of the four energies. This impact is justified as Green Hydrogen is an energy carrier, rather than a producer. The impacts of Wind Energy, Solar Energy, and Bioenergy are compared in the absence of Green Hydrogen Energy, as they are all energy producers. It is found that the overall environmental impacts of Bioenergy are the greatest of the three, while Wind Energy has the lowest impacts. Solar Energy had greater impacts than Bioenergy in certain impact categories. Comparison of this study with previous Life Cycle Assessments reveals some similarities and differences. Contrasting this study to the German Sustainable Development Strategy shows that the strategy as well as the current trends are supported by the results of this study, but can be improved in certain aspects.}, language = {en} } @masterthesis{Sturza, type = {Bachelor Thesis}, author = {Sturza, Loredana}, title = {Selection of Global Standardization Samples for Optical Emission Spectrometry from Practical and Materials Science Perspectives}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:1383-opus4-20939}, school = {Hochschule Rhein-Waal}, abstract = {The focus of this thesis is to address the task of alloy selection for Optical Emission Spectrometry (OES) applications. The main goal is to develop standardised samples for SPECTRO OES devices that can be utilised during routine analysis in automatic processes. The selection criteria include machinability, signal performance, and homogeneity. To achieve these goals, a set of practical tests were carried out. The initial research involves using the existing SPECTRO sample library to identify suitable alloys for standardised production in large batches. In the end, a database is suggested with existing alloys as possible candidates for future production. The chosen alloy must generate signals within specified wavelength ranges and exhibit machinability for post-analysis processing. The thesis introduces a unique approach to assessing machinability using chip analysis, emphasising the role of chip characteristics in understanding the material's suitability for machining. The study found that the E/3 sample, especially among samples with zirconium, demonstrated exceptional machinability. Moreover, the research delves into the importance of power consumption measurements during milling as an informative parameter for machining requirements. The study examines the chemical composition necessary to produce consistent and robust signals across the spectrum, with a particular focus on elements like zirconium, nickel, iron, copper, titanium, and manganese, but also phase diagrams to understand the homogeneity of aluminium alloying elements. Sample 518X905 is highlighted for its role in enhancing emission lines. In conclusion, the thesis proposes an alloy composition that blends aluminium with various alloying elements to meet specific research requirements. Copper, iron, zinc, silicon, nickel, zirconium, chromium, and vanadium provide flexibility for crafting tailored samples. Existing primary alloying elements, including those with copper, zinc, and silicon, can be considered. However, zirconium with a concentration of 0.6\% to 1\% is pivotal in the proposed alloy recipe.}, language = {en} } @misc{Bhatti, type = {Master Thesis}, author = {Bhatti, Saad Ali}, title = {Investigating the possibilities of AC GMA welding for in-situ alloying in additive manufacturing}, school = {Hochschule Rhein-Waal}, abstract = {Additive manufacturing is a transformative approach of building 3D objects by layer-upon-layer method, adding digital flexibility and efficiency into the industrial production process. Different categories of materials such as plastics, metals, concrete, etc., can be used for Additive Manufacturing. At present, WAAM (Wire Arc Additive Manufacturing) is of high interest for many industries, as it allows creating large-scaled metallic components of moderate complexity with high density and good mechanical properties. In this master's Thesis, the capabilities of Gas Metal Arc (GMA) welding for in-situ alloying in multi-material WAAM are being investigated. A 6-axis FD-V6 welding robot by OTC Daihen along with Welbee W400 power supply was used to produce weldments both, with alternating current (AC), as well as pulsed direct current (DC). Two of Photron's High-Frequency cameras were used to investigate the process behavior. An All-in-one oscilloscope, Yokogawa DL850E ScopeCorder, was used to record the voltage and current signals. Single-layer, straight weldments were made to investigate the impact of different welding parameters over the weld seam shape and deposition rate. Later, the setup was extended to induce cold wire to change the chemical composition of the weld seams by in-situ alloying. Therefore, a clamp with adjustable angle, height, and distance was created to position the cold wire feeder along with the GMA welding nozzle. Cross-sections of weldments were taken to extract geometrical information related to the weld seam. In the end, combined experiments were done to investigate the process capabilities of generating weld seams of equal shape but different chemical composition by changing the wire feed speeds and the process parameters. This was the fundamental step for making the process ready for multi-material additive manufacturing. To demonstrate the process performance, two multi-material demonstrator components have been manufactured at the end of the thesis.}, language = {en} } @misc{Mulani, type = {Master Thesis}, author = {Mulani, Arshad}, title = {Modelling and Multi-Objective Optimization of a Building Heating Generation System: A case study of Hechingen, Germany}, school = {Hochschule Rhein-Waal}, abstract = {Nowadays, the world is facing major environmental problems such as climate change and energy scarcity. If we consider only European countries, Heating and cooling industry accounts for more than half of the total EU's energy consumption. And about 75\% of the heat is generated by using fossil fuels. Therefore, the major non-renewable energy sources are depleting at the rapid rate and at the same time also producing the climate-changing greenhouse gases. To achieve the climate change objectives, optimised and efficient use of the energy and the decarbonisation of the heating systems are some of the critical steps. The investigation process in this thesis involves the modelling and modifying the case study heating system by using Energy Plus and Design-Builder whole building energy simulation software. It also includes the investigation of the three different possible renewable and non-renewable solutions to optimize the current heating system and analyse their effects in terms of total energy consumption (Gas and Electricity consumption) Economic benefits, environmental and other benefits. With the detail and adequate data inputs modelling and desired modifications has been done to the heating system and the building properties. The annual simulation has been performed to all the three cases and the results have been analysed. The outcome of the analysis of the results shows a significant improvement in overall energy and electricity consumption. Also provides a detailed insight into the total economical investment needed in all three cases and simple payback periods for the investments. And Most importantly the results replicate the environmental benefits such as a considerable reduction in the overall emissions of greenhouse and other toxic gases.}, language = {en} }