Examensarbeten för masterexamen // Master Theses (IMS)

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Browsar Examensarbeten för masterexamen // Master Theses (IMS) efter Program "Applied physics (MPAPP), MSc"

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    Correlation between material properties, grinding effects and Barkhausen noise measurements for two crankshaft steels
    (2012) Doverbo, Marie; Chalmers tekniska högskola / Institutionen för material- och tillverkningsteknik; Chalmers University of Technology / Department of Materials and Manufacturing Technology
    The crankshaft steel of two suppliers has been shown to yield differing Barkhausen measurements despite corresponding material specifications and identical manufacturing. In this thesis the reason for this discrepancy is investigated and an hypothesis regarding its cause is formulated. The conclusions are reached through experimental work, wherein the material properties of the two steels are compared. The difference in ductility is related to the difference in Barkhausen Noise Amplitude (BNA) through the grinding process such that the increased ductility is believed to increase the chip build up in the grinding wheel, thus resulting in higher grinding temperature. This would increase the risk for grinding burns and moves the residual stresses towards tensile, which changes the BNA. Suggestions for future work all concern the verification of this hypothesis.
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    High Entropy Alloys: Breakthrough Materials for Aero Engine Applications?
    (2015) Svensson, Daniel; Chalmers tekniska högskola / Institutionen för material- och tillverkningsteknik; Chalmers University of Technology / Department of Materials and Manufacturing Technology
    In this project the current literature regarding a relatively new materials type, high entropy alloys (HEAs), was reviewed to find if they are applicable to aero engines, and in particular the engine parts made by GKN Aero Engine Systems in Trollhättan. To manage this the current state of the art of aero engine materials was reviewed as well, partly via a literature survey and partly via discussions with company specialists at GKN Aero Engine Systems in Trollhättan. Based on these two reviews, several issues requiring further studies for future researchers to fill in the gap was identified, with possible solutions suggested where possible, and finally possible HEA systems were suggested for use in the specific engine parts manufactured by GKN Aero Engine Systems.
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    Hot Rolled Wire Descaling
    (2012) Svonni, Jon-Henrik; Chalmers tekniska högskola / Institutionen för material- och tillverkningsteknik; Chalmers University of Technology / Department of Materials and Manufacturing Technology
    In the process of making welding wire an important step is to descale an oxide layer from the surface of the wire. If the oxide layer is not entirely removed it will affect the quality of the finished product. A common way of descaling is to use acids which is not quite environmental friendly. It is possible to mechanically descale the wire but the method needs to be better since the current methods does not give consistent results. In this work the possiblity to descale the wire using ultrasounds have been investigated. It has been theoretically analysed, modelled in MATLAB and compared with results from an existing mechanical wire descaler. The results have not been validated through experimental analysis. The results show that ultrasound may be an interesting technique to investigate further, and guidelines and important variables for future experiments are given.
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    Nonlinear Impedance Spectroscopy - Using higher harmonics response and differential impedance for electrical characterization of DC insulation materials
    (2015) Almquist, Louise; Chalmers tekniska högskola / Institutionen för material- och tillverkningsteknik; Chalmers University of Technology / Department of Materials and Manufacturing Technology
    With the growing relevance of high-voltage direct current (HVDC) technologies comes an increased need of reliable electrical characterization of insulation materials. Electrical conduction mechanisms in insulation materials under DC voltages are rather complicated and appropriate characterization tools need to be further developed. This thesis investigates the potential of using nonlinear impedance spectroscopy(IS) for electrical characterization of insulation materials at DC fields, or at low frequency AC fields. A theoretical background is provided where it is shown for different models how nonlinear current-field dependence give rise to currents that contain amplitudes at higher frequencies than that of the exciting voltage (the fundamental frequency). Experimentally, different material systems were studied with two advanced nonlinear IS measurement techniques; higher harmonics measurements at high fields and differential conductivity measurements with small amplitude AC spectroscopy at large superimposed DC. The main results are presented in form of steady state current-field characteristics. We therefore conclude that nonlinear IS is in principle useful for electrical characterization of nonlinear insulation materials, particularly field grading materials. Limitations of the methods are related to non-robust material properties and problems with reaching a quasi-steady state at reasonable frequencies.