Thesis (Ph. D.)--University of Notre Dame. / "List of references": p. 23-24.

Thesis (Ph. D.)--University of Notre Dame. / "List of references": p. 23-24.

M.Ing. (Mechanical Engineering) / This report describes an investigation into structural damping in simple steel structures. More specifictly, an attempt is made to obtain and compare the logarithmic decrement for different types of steel structures. The effect that welded and rivetted connections have on the logarithmic decrement is also examined. Four different types of steel are used, namely: mild steel and three types of chromium based steel. Vibration tests are performed on both cantiliver and simple bridge structures. An estimate of the inherent damping that is present in the vibrating structures are obtained from the approximate displacement-time response plots (as obtained from vibration tests). All the step input tests are modelled with a finite element. computer package to test the accuracy of the approximated response functions. Shaker tests are also performed on bridge structures. On the theoretical side the term damping is fully defined and discussed.

Aufgabenstellung: Aus einem Rohrstück des Materials P91 soll nach der Erarbeitung eines Probenplans zunächst das Gefüge in allen 3 Orientierungen metallographisch charakterisiert werden. Anschließend wird das Material mechanisch - technologisch sowie bruchmechanisch und fraktographisch untersucht. Die daraus erhaltenen Werkstoffkennwerte sollen mit dem Gefüge und dem fraktographischen Befund in Beziehung gesetzt werden.

M.Comm. (Business Management) / Please refer to full text to view abstract

Aufgabenstellung: Aus einem Rohrstück des Materials P91 soll nach der Erarbeitung eines Probenplans zunächst das Gefüge in allen 3 Orientierungen metallographisch charakterisiert werden. Anschließend wird das Material mechanisch - technologisch sowie bruchmechanisch und fraktographisch untersucht. Die daraus erhaltenen Werkstoffkennwerte sollen mit dem Gefüge und dem fraktographischen Befund in Beziehung gesetzt werden.

Bibliography: pages 107-108. / The effects of exposure to temperatures in the range 475 - 800°C on the hardness and associated microstructure of high chromium ferritic steels has been investigated. Low-carbon 26Cr-1Mo steels containing 0,02 - 0,04% nitrogen were found to constitute an age hardening system when quenched from a temperature of nitrogen solubility and exposed at temperatures in the range 600 - 700°C. TEM observations on thin foils revealed that hardening was associated with the formation of a high density of Cr-N zones. These grew on over-ageing into disc-shaped Cr-N precipitates situated on {100} lattice planes, and ultimately became large incoherent precipitates. Ageing at 475°C and 550°C produced hardening due to the formation of chromium-rich ferrite phases α' as a result of the miscibility gap in the Fe-Cr phase diagram. However the presence of interstitial nitrogen in solution in the steel considerably reduced the rate of hardening, especially at 475°C. TEM examination confirmed that this effect was due to the formation of Cr-N zones in preference to α'. This type of decomposition occurs by a mechanism of nucleation and growth, forming zones similar to those formed during an ageing at 600°C. When depleted of interstitial nitrogen, through precipitation at 800°C or through zone formation at 475°C, the specimens aged at 475°C underwent spinodal decomposition. Thus nitrogen in solid solution was found to have a significant effect on the 475°C hardening reaction. Precision X-ray diffraction measurements revealed the presence of secondary diffraction peaks associated with the Bragg peaks, which comfirmed the formation of Cr-rich phases during ageing at 475°C. The calculated associated lattice parameter measurements allowed estimates of the compositions of the decomposition phases to be made. These were calculated to be about 6-18% Cr in the Fe-rich and 60-80% Cr in the Cr-rich phases of the 26Cr-1Mo steel.

Made available in DSpace on 2016-04-18T21:36:01Z (GMT). No. of bitstreams: 2 Douglas Marquezin Felippe1.pdf: 1519362 bytes, checksum: 40709b1c88a4aa5d83632f3034ffa9cf (MD5) Douglas Marquezin Felippe2.pdf: 3740401 bytes, checksum: c124e8cef0b0b36e025714367db7c937 (MD5) Previous issue date: 2010-02-23 / Fundo Mackenzie de Pesquisa / Heat treatment processes are related to control heating and quenching with the aim of improving physical properties, such as: hardness, abrasion resistance, toughness, among others. During the heat treatment process, the quenching media are of great importance steps, because it extracts heat from the part with the achieve of obtaining specification properties. However, the hardening process causes undesired distortion that can be related to the permanent residual stress in the parts, generated during quenching. Some conventional hardening heat treatments do not have the control of the position during quenching, this control is usually applied in induction heat treatment, improving the homogeneity of heat exchange in the quenching process, suggesting lower distortion. The induction process can be a sustainable one, because the heating is applied just in the part. This survey compared both metallurgical and mechanical properties between two heat treatment processes of DIN 100Cr6 steel bearings: conventional and induction. With the result of this survey, it is intended, to change the conventional heat treatment process for the induction process in bearing manufacturing, with the objective of reducing the typical out-of-roundness from the conventional heat treatment process, and a reduction the bearing manufactured costs. / A têmpera compreende operações de aquecimento e resfriamento controlado, que objetivam melhorias nas propriedades físicas como dureza, resistência à abrasão, tenacidade entre outras. Durante o processo de têmpera, o meio de resfriamento é uma das etapas mais críticas, pois extrai calor da peça com o objetivo de obter as propriedades desejadas. Porém, o processo de têmpera gera deformações não desejadas, que podem estar relacionadas às tensões residuais que ficam permanentes na peça, introduzidas durante o resfriamento. Alguns tratamentos térmicos de têmpera convencional não têm controle da posição da peça durante o resfriamento. Este controle é normalmente utilizado em processos de têmpera por indução, melhorando a homogeneidade da extração de calor durante o resfriamento, sugerindo menores índices de deformação. O processo por indução pode ser considerado sustentável, pois o aquecimento é localizado apenas no componente. Este trabalho comparou as propriedades metalúrgicas e mecânicas entre dois processos de têmpera de rolamentos do aço DIN 100Cr6: convencional e por indução. Como resultado deste trabalho, pode-se substituir o tratamento térmico com aquecimento convencional pelo tratamento térmico com aquecimento por indução para a manufatura de rolamento, com objetivo de redução da deformação de ovalização característica do processo de tratamento térmico convencional.

This diploma thesis deals with measuring touches problems in industrial metrology. Thesis describes adhesive wear and tear which is caused by measuring probes when dynamical measuring is being concluded. Measuring of damaged component made of silumin and its different changes of texture by different measuring probes are evaluated. Measuring touches are made of titanium nitride, silicon nitride, zirconium, bearing chrome steel, ruby, experimental composite material and nanocrystalline diamond.