Die vorliegende Untersuchung behandelt den Homogenitätsbereich, sowie die strukturellen und physikalischen Eigenschaften der Clathrat-I-Phasen im System Ba-Au-Ge. Im Zustandsdiagramm existieren zwei separate Phasenbereiche mit Clathrat-I-Phasen unterschiedlicher Symmetrie, welche durch Au-Gehalt und Leerstellenkonzentration bestimmt wird. Bei niederem Goldgehalt existiert die Clathrat-I-Phase mit einer 2 × 2 × 2 Überstruktur des Basistyps in der Raumgruppe Ia-3d. Der Existenzbereich dieser Phase reicht bei 800 °C bis zur Zusammensetzung Ba8Aux•3–0.563xGe43–0.437x mit x = 1.1. Nach einem schmalen Zweiphasenbereich im Bereich 1.1 < x < 1.6 folgt für höhere Au-Konzentrationen eine neue, tetragonale Clathrat-I-Variante mit Raumgruppe P42/mmc. Diese umfasst den gesamten Homogenitätsbereich von x = 1.6 - 5.4. Für höherer Au-Konzentrationen nähert sich die Symmetrie dem Pm-3n-Basistyp an. Der thermoelektrische ZT-Wert steigt jeweils mit der Temperatur und erreicht für die Proben im Bereich x ≈ 5.4 bei 670 K ein Maximum von ≈ 0.9. Die Aufskalierung der Präparation und Voraussetzungen für den Generatorbau werden untersucht. / The present study deals with the homogeneity range as well as the structural and physical properties of clathrate I phases in the Ba-Au-Ge system. The phase diagram comprises phases with the clathrate I type of structure in two separate regions. The symmetry of the respective crystal structures is governed by both, Au content and vacancy concentration. At low gold content, the clathrate I phase forms a 2 × 2 × 2 superstructure of the base type with space group Ia-3d. At 800 °C this phase exists for the general composition formula Ba8Aux•3–0.563xGe43–0.437x till x = 1.1. After a narrow two-phase range in the region 1.1 < x < 1.6, a new, tetragonal clathrate I variant with space group P42/mmc follows for higher Au concentrations x = 1.6 - 5.4. For higher Au concentrations the crystal symmetry gradually approximates the common Pm-3n type of structure. The thermoelectric ZT value increases with temperature reaching a maximum of ≈ 0.9 for the samples in the range x ≈ 5.4 at 670 K. The upscaling of the preparation and other requirements for generator construction are examined.

<p>In the process of designing an electric power supply system for an aircraft, parameters like low weight and low losses are important. Reliability, robustness and low cost are other important factors. In the Saab Gripen aircraft, the design of the primary power supply of the electric flight control system was updated by exchanging a switching transistor regulator to a magnetic amplifier (magamp). By introducing a magamp design, weight was saved and a more reliable power supply system at a lower cost was achieved.</p><p> In this particular case, with the power supply of the electric flight control system in the Saab Gripen fighter, advantage could be taken of a specific permanent magnet generator (PM-generator). The frequency of the generator offered the perfect conditions for a magamp controller. A key parameter in designing magnetic amplifiers (magamps) is low losses. New amorphous alloys offer new possibilities of the technique in designing magnetic amplifiers, because of their extremely low losses.</p><p> The core losses are evaluated by studying the equations and diagrams specifying the power losses. The core losses are evaluated and compared with the copper losses in the process of optimizing low weight and low losses. For this an engineering tool is developed and demonstrated.</p><p> Evaluations of the hysteresis characteristics for the magnetic alloys, as well as modeling and simulation of the core losses, are presented in this work. The modeling of the core losses includes hysteresis losses, eddy current losses and excess losses as well as copper losses. The losses are studied dynamically during realistic operational conditions. The model can be used for any generic analysis of hysteresis in magnetic circuits. Applications of magnetic amplifiers in aircrafts have been demonstrated to be a feasible alternative</p>

This diploma thesis deal with the building survey and evaluating the state of existing constructions. In theoretical part are described the types of civil engineering surveys and diagnostic methods for conducting a survey of reinforced concrete structures. The practical part deal with describes the structural and technical survey of the production hall in the industrial area Fatra Napajedla, evaluating the strength of concrete on the existing structure through donations cores and verification of compliance with the reinforcement according to project documentation. The last part is focused on a static assessment of selected supporting elements of the structure.

No description available.

In the process of designing an electric power supply system for an aircraft, parameters like low weight and low losses are important. Reliability, robustness and low cost are other important factors. In the Saab Gripen aircraft, the design of the primary power supply of the electric flight control system was updated by exchanging a switching transistor regulator to a magnetic amplifier (magamp). By introducing a magamp design, weight was saved and a more reliable power supply system at a lower cost was achieved. In this particular case, with the power supply of the electric flight control system in the Saab Gripen fighter, advantage could be taken of a specific permanent magnet generator (PM-generator). The frequency of the generator offered the perfect conditions for a magamp controller. A key parameter in designing magnetic amplifiers (magamps) is low losses. New amorphous alloys offer new possibilities of the technique in designing magnetic amplifiers, because of their extremely low losses. The core losses are evaluated by studying the equations and diagrams specifying the power losses. The core losses are evaluated and compared with the copper losses in the process of optimizing low weight and low losses. For this an engineering tool is developed and demonstrated. Evaluations of the hysteresis characteristics for the magnetic alloys, as well as modeling and simulation of the core losses, are presented in this work. The modeling of the core losses includes hysteresis losses, eddy current losses and excess losses as well as copper losses. The losses are studied dynamically during realistic operational conditions. The model can be used for any generic analysis of hysteresis in magnetic circuits. Applications of magnetic amplifiers in aircrafts have been demonstrated to be a feasible alternative / QC 20101103

No description available.

No description available.

The focus of strategy research has long revolved around strategy formulation rather thanstrategy implementation, despite the evidence indicating that intended strategies are rarelyachieved. Project portfolio management, PPM, assumes a crucial role in enabling strategyimplementation and can be regarded as a representation of the organization's actual pursuedstrategy. Existing research on PPM has predominantly centered around portfolios in the contextof new product development, NPD, and research and development, R&amp;D. However, there hasbeen relatively less exploration of PPM within internal development departments, warrantingfurther investigation. To contribute to the understanding on strategy implementation throughPPM and its conditional factors, this qualitative case study expands the existing research bystudying the PPM process within an internal development department. The study wasconducted at the Business Improvement department, which oversees improvement projects forthe service branch of EnergyComp, a company specializing in the development of complexenergy solutions. Using an abductive research approach, a literature review was conducted inparallel with data collection and analysis. The empirical data was mainly collected throughsemi-structured interviews at the company, but also through meetings and companydocumentation. The results of the study show that PPM actions connected to projects, portfolio and resourceallocation are undertaken to effectively implement the organization's strategy within theinternal development department. Common to all areas is the importance of accurate andavailable information that effects the decisions connected to strategy implementation. On aproject level, Insufficient information poses challenges in accurately assessing project success,resulting in measurements that fail to cover all strategic objectives. In the context of theportfolio, the absence of project information and uncertainties can lead to a misalignmentbetween the actual prioritization criteria employed in the selection process and the strategicobjectives of the organization. Additionally, it may contribute to a less detailed and formalstrategic plan. Furthermore, the cost associated with adjusting the portfolio is directly linked tothe effort and expenses involved in obtaining project information. Regarding resources,insufficient information on supply and demand creates challenges in considering projectdependencies and synergies during the evaluation of project groups. Moreover, limitedtransparency across functional boundaries within the organization leads to a system wheredecision rules cannot be established at the portfolio level. Instead, it encourages bottom-uppriority decisions. Furthermore, a biased assessment by stakeholders in the functionaldepartments may result in an inadequate screening process, leading to an increased workloadin the portfolio structuring process. Finally, the large variation in project types, coupled withdiverse impact targets spanning individual and multiple functions, makes it difficult to createrelevant project categories for budgeting and portfolio structuring.

<div>In this thesis, the role of location-specific microstructural features in the fatigue performance of the safety-critical aerospace components made of Nickel (Ni)-base superalloys and linear friction welded (LFW) Titanium (Ti) alloys has been studied using crystal plasticity finite element (CPFE) simulations, energy dispersive X-ray diffraction (EDD), backscatter electron (BSE) images and digital image correlation (DIC).</div><div><br></div><div>In order to develop a microstructure-sensitive fatigue life prediction framework, first, it is essential to build trust in the quantitative prediction from CPFE analysis by quantifying uncertainties in the mechanical response from CPFE simulations. Second, it is necessary to construct a unified fatigue life prediction metric, applicable to multiple material systems; and a calibration strategy of the unified fatigue life model parameter accounting for uncertainties originating from CPFE simulations and inherent in the experimental calibration dataset. To achieve the first task, a genetic algorithm framework is used to obtain the statistical distributions of the crystal plasticity (CP) parameters. Subsequently, these distributions are used in a first-order, second-moment method to compute the mean and the standard deviation for the stress along the loading direction (σ_load), plastic strain accumulation (PSA), and stored plastic strain energy density (SPSED). The results suggest that an ~10% variability in σ_load and 20%-25% variability in the PSA and SPSED values may exist due to the uncertainty in the CP parameter estimation. Further, the contribution of a specific CP parameter to the overall uncertainty is path-dependent and varies based on the load step under consideration. To accomplish the second goal, in this thesis, it is postulated that a critical value of the SPSED is associated with fatigue failure in metals and independent of the applied load. Unlike the classical approach of estimating the (homogenized) SPSED as the cumulative area enclosed within the macroscopic stress-strain hysteresis loops, CPFE simulations are used to compute the (local) SPSED at each material point within polycrystalline aggregates of 718Plus, an additively manufactured Ni-base superalloy. A Bayesian inference method is utilized to calibrate the critical SPSED, which is subsequently used to predict fatigue lives at nine different strain ranges, including strain ratios of 0.05 and -1, using nine statistically equivalent microstructures. For each strain range, the predicted lives from all simulated microstructures follow a log-normal distribution; for a given strain ratio, the predicted scatter is seen to be increasing with decreasing strain amplitude and are indicative of the scatter observed in the fatigue experiments. Further, the log-normal mean lives at each strain range are in good agreement with the experimental evidence. Since the critical SPSED captures the experimental data with reasonable accuracy across various loading regimes, it is hypothesized to be a material property and sufficient to predict the fatigue life.</div><div><br></div><div>Inclusions are unavoidable in Ni-base superalloys, which lead to two competing failure modes, namely inclusion- and matrix-driven failures. Each factor related to the inclusion, which may contribute to crack initiation, is isolated and systematically investigated within RR1000, a powder metallurgy produced Ni-base superalloy, using CPFE simulations. Specifically, the role of the inclusion stiffness, loading regime, loading direction, a debonded region in the inclusion-matrix interface, microstructural variability around the inclusion, inclusion size, dissimilar coefficient of thermal expansion (CTE), temperature, residual stress, and distance of the inclusion from the free surface are studied in the emergence of two failure modes. The CPFE analysis indicates that the emergence of a failure mode is an outcome of the complex interaction between the aforementioned factors. However, the possibility of a higher probability of failure due to inclusions is observed with increasing temperature, if the CTE of the inclusion is higher than the matrix, and vice versa. Any overall correlation between the inclusion size and its propensity for damage is not found, based on inclusion that is of the order of the mean grain size. Further, the CPFE simulations indicate that the surface inclusions are more damaging than the interior inclusions for similar surrounding microstructures. These observations are utilized to instantiate twenty realistic statistically equivalent microstructures of RR1000 – ten containing inclusions and remaining ten without inclusions. Using CPFE simulations with these microstructures at four different temperatures and three strain ranges for each temperature, the critical SPSED is calibrated as a function of temperature for RR1000. The results suggest that critical SPSED decreases almost linearly with increasing temperature and is appropriate to predict the realistic emergence of the competing failure modes as a function of applied strain range and temperature.</div><div><br></div><div>LFW process leads to the development of significant residual stress in the components, and the role of residual stress in the fatigue performance of materials cannot be overstated. Hence, to ensure fatigue performance of the LFW Ti alloys, residual strains in LFW of similar (Ti-6Al-4V welded to Ti-6Al-4V or Ti64-Ti64) and dissimilar (Ti-6Al-4V welded to Ti-5Al-5V-5Mo-3Cr or Ti64-Ti5553) Ti alloys have been characterized using EDD. For each type of LFW, one sample is chosen in the as-welded (AW) condition and another sample is selected after a post-weld heat treatment (HT). Residual strains have been separately studied in the alpha and beta phases of the material, and five components (three axial and two shear) have been reported in each case. In-plane axial components of the residual strains show a smooth and symmetric behavior about the weld center for the Ti64-Ti64 LFW samples in the AW condition, whereas these components in the Ti64-Ti5553 LFW sample show a symmetric trend with jump discontinuities. Such jump discontinuities, observed in both the AW and HT conditions of the Ti64-Ti5553 samples, suggest different strain-free lattice parameters in the weld region and the parent material. In contrast, the results from the Ti64-Ti64 LFW samples in both AW and HT conditions suggest nearly uniform strain-free lattice parameters throughout the weld region. The observed trends in the in-plane axial residual strain components have been rationalized by the corresponding microstructural changes and variations across the weld region via BSE images. </div><div><br></div><div>In the literature, fatigue crack initiation in the LFW Ti-6Al-4V specimens does not usually take place in the seemingly weakest location, i.e., the weld region. From the BSE images, Ti-6Al-4V microstructure, at a distance from the weld-center, which is typically associated with crack initiation in the literature, are identified in both AW and HT samples and found to be identical, specifically, equiaxed alpha grains with beta phases present at the alpha grain boundaries and triple points. Hence, subsequent fatigue performance in LFW Ti-6Al-4V is analyzed considering the equiaxed alpha microstructure.</div><div><br></div><div>The LFW components made of Ti-6Al-4V are often designed for high cycle fatigue performance under high mean stress or high R ratios. In engineering practice, mean stress corrections are employed to assess the fatigue performance of a material or structure; albeit this is problematic for Ti-6Al-4V, which experiences anomalous behavior at high R ratios. To address this problem, high cycle fatigue analyses are performed on two Ti-6Al-4V specimens with equiaxed alpha microstructures at a high R ratio. In one specimen, two micro-textured regions (MTRs) having their c-axes near-parallel and perpendicular to the loading direction are identified. High-resolution DIC is performed in the MTRs to study grain-level strain localization. In the other specimen, DIC is performed on a larger area, and crack initiation is observed in a random-textured region. To accompany the experiments, CPFE simulations are performed to investigate the mechanistic aspects of crack initiation, and the relative activity of different families of slip systems as a function of R ratio. A critical soft-hard-soft grain combination is associated with crack initiation indicating possible dwell effect at high R ratios, which could be attributed to the high-applied mean stress and high creep sensitivity of Ti-6Al-4V at room temperature. Further, simulations indicated more heterogeneous deformation, specifically the activation of multiple families of slip systems with fewer grains being plasticized, at higher R ratios. Such behavior is exacerbated within MTRs, especially the MTR composed of grains with their c-axes near parallel to the loading direction. These features of micro-plasticity make the high R ratio regime more vulnerable to fatigue damage accumulation and justify the anomalous mean stress behavior experienced by Ti-6Al-4V at high R ratios.</div><div><br></div>