Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7614. Adviser: Robert D. Moser. Includes bibliographical references (leaves 137-140) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7516. Adviser: Keith D. Hjelmstad. Includes bibliographical references (leaves 174-182). Available on microfilm from Pro Quest Information and Learning.

Thèse (M.Sc.A.)--Université de Sherbrooke (Canada), 2008. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1187. Adviser: Glaucio H. Paulino. Includes bibliographical references (leaves 177-186). Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6491. Adviser: Mark Short. Includes bibliographical references (leaves 136-143) Available on microfilm from Pro Quest Information and Learning.

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In the transition from conventional to green energy production resources, steam turbines are used to satisfy the lack of energy during peaks in the demand times and the limited access of renewable resources. This type of usage for steam turbines makes them operate on a flexible schedule, which leads to unpredictable issues related to shorter component life and faster crack propagation. Thus, the steam turbine components must be examined to determine their specific life period. This will help set proper maintenance intervals and prevent unexpected failures. For that, thermo-mechanical fatigue (TMF) testing is used, where a specimen made of the same material as the turbine component is subjected to both temperature and load variation. The specimen is pre-cracked to investigate the crack propagation behavior, which is the focus of this study. This thesis work concentrates on simulating the TMF cycle for the steam turbine casing component. The material is 9%-10%Cr ferritic steel. The aim is to understand the material behavior during crack propagation and to predict a useful testing parameter. The method provided in this work discusses two cases, both are out-of-phase (OP) TMF tests with strain control. The maximum and minimum temperatures for the cycle are 600 ˚C and 400 ˚C respectively, while the maximum and minimum strain levels are 0 and  respectively. The study will investigate different , which is the maximum compressive strain level. Case 1 has a dwell time at the maximum temperature only, while case 2 has dwell times at both maximum and minimum temperatures. The method utilizes the stress intensity factor (SIF) to characterize the crack tip conditions. Also, it uses Paris' law to estimate the duration of the tests. For simplification, only the elastic behavior of the material is considered. The results obtained show no effect of using different pre-crack lengths due to the strain control condition. Minor effects can be observed by using different dwell times, however very short dwell times must be avoided to produce reliable results. A recommended dwell time of 5 minutes could be used, since longer dwell times will make the test prohibitively time-consuming. The compressive strain levels used in the work shows large effects on the results. Using low compressive strain values will produce a very long time for the tests, while very high compressive strains produce large plasticity. Thus, high compressive strains must be avoided since the SIF describes cracks for only elastic or near elastic cases. Also, small compressive strain levels in case 2 should not be used since it will lead to results like case 1. This is due to the small creep effect at the minimum temperature. Finally, compressive strain levels of 0.6 %, 0.5 % and 0.4 % are recommended for case 1, while only 0.6 % compressive strain level is recommended for case 2. This thesis contributes to the fields of solid mechanics, fracture mechanics and the use of TMF testing, where a recommended set of testing parameters are provided.

In computational fluid dynamics (CFD), the computational domain can be discretized using mesh- based methods or particle based methods. During this project; a CFD method that uses smoothed particle hydrodynamics (SPH), in which the computational domain is discretized by particles, is modelled and compared to mesh-based CFD methods, in which the domains are broken into a set of discrete volumes. The aim with this master thesis project is to determine whether the SPH method can replace mesh-based methods in cases that involve free surface flows and fluid-structure interac- tions (FSI’s) in order to avoid mesh-deformations. The comparison is done by studying a free fall of a torpedo shaped object, 500 mm in length, both experimentally and with numerical simulations. The CFD methods that are compared are mesh-based one-way FSI, mesh-based two-way FSI and the SPH method. The methods are created in the two simulation software ANSYS (one-way and two-way FSI) and LS-DYNA (two-way FSI and SPH). The comparisons are made by looking at experimental and numerical accelerations. The experiment gave uncertain results and there were difficulties in comparing experimental results to numerical results. When looking at all results, it is concluded that the mesh-based methods give reasonable maximum values while the SPH method gives too high values. For the mesh-based methods in ANSYS, air is present which is not the case for the methods mod- elled in LS-DYNA. When comparing the computation time for all methods, it is concluded that the presence of air increases the computation time considerably and based on the results in this project, air is not necessary to take into consideration. The aim of this project is reached by concluding that the mesh-based method in LS-DYNA is the most suitable method for the studied case, based on the following: acceleration behaviour, maximum acceleration values, computation time and the possibility to neglect air. The conclusion might be revised when future work on the SPH method has been done.

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