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Browsing by Subject "Integrity"

Now showing 1 - 4 of 4
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    Explicit Crack Modeling based Approach for Structural Integrity Assessment of Brittle and Quasi-Brittle Structures
    (2015-02) Singh, Gyanender
    There is considerable variation in the fracture properties of brittle and quasi-brittle materials. Due to this large variation, probabilistic models are employed for estimating failure of brittle components/structures. However, due to limitations and shortcomings in the models, the predictions are not accurate. The shortcomings include: inability to handle stress concentrations, dependence of empirical constants on loading conditions, incorrect size-effect predictions and limited applications of the model. Although higher design margins can accommodate the inaccuracy in predictions, the cost of manufacturing increases. The work presented herein is directed towards addressing these issues. An approach based on explicit crack modeling (ECM) for accurately estimating failure in brittle/quasi-brittle components and structures is presented. Factors which govern fracture in a structure (fracture energy, strength of the material, damage behavior of the material, heterogeneity in the material microstructure) are incorporated in the ECM approach. The approach was validated by predicting the failure probability of L-shaped specimens at varying load levels followed by comparison of the predictions with published data. The study showed that the predictions from the ECM approach were not only in good agreement with the published data but were also more accurate than the Weibull model based predictions. The ECM approach can also predict size effect--the dependence of fracture properties and their statistical variation on the size of the specimen. This capability was demonstrated through failure prediction of specimens in tensile and flexural tests. Specimens of different sizes were considered and the predicted fracture properties were in good agreement with those obtained experimentally. The ECM approach for estimating failure of components/structures subjected to complex physical conditions was illustrated through the failure estimation of nuclear reactor graphite components. For modeling stresses in the graphite components subjected to high temperature and neutron irradiation, a constitutive model for evaluating the stresses was constructed and implemented through a user material (UMAT) subroutine in finite element software Abaqus. UMAT was integrated with Extended Finite Element (XFEM) technique for modeling irradiation-induced failure of the components under in-reactor conditions. Component lifetime as well as crack initiation and propagation details were predicted. This type of detailed failure information has the potential to improve design guidelines and standards of brittle components/structures.
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    Exploring the nomological net of trust in leadership: an empirical examination of antecedents, moderators, and outcomes
    (2012-12) Rasch, Rena Lenore
    To fully understand human interactions in the workplace, we must understand the role trust plays. My dissertation is a general investigation of trust between subordinates and leaders within an organizational context. Using a diverse sample of US employees, I examined the relative importance of three key trust determinants: leader benevolence, competence, and integrity. I also examined the role trait trust plays in the trust nomological net. I examined previously posited, yet untested, moderators of the trustworthiness-trust relationship. Lastly, I tested the contextual effects of risk and formal controls on the relationship between employees' trust in leadership and their turnover intentions. I found an individual's propensity to trust seems to affect trust in leadership through perceptions of leader trustworthiness. Leaders can inspire trust by being capable, kind, and honest. Leader integrity is the most important direct determinant of trust in leadership. Despite theoretical arguments, relationship length and job complexity have no bearing on the importance of the direct determinants of trust in leadership. A manager may use trust to influence his/her staff, who are more willing to assume risk on their manager's behalf. Trust may act as a substitute for costly and rigid formal control mechanisms, like legal contracts. Despite theoretical arguments, situational risk in the form of organizational change, whether perceived or actual, does not magnify the importance of trust in leadership to turnover intentions. Still, trust in leadership is important to predicting turnover intentions, even beyond job satisfaction and organizational commitment.
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    Institutional Integrity: Perceptions Of Organizational Legitimacy And Organizational Virtuousness In A Research University Setting
    (2020-05) Slattengren, Erin
    This study examines approaches to managing problems in research by exploring the external factors and internal organizational characteristics that shape the integrity of research at a research university. Two theoretical constructs, organizational legitimacy and organizational virtuousness, frame this analysis of systems, methods, and activities used to ensure integrity at a research university, and explore connections between them. This study is based on twenty interviews with research leaders and faculty researchers in two colleges, one representing an applied research discipline and the other a basic science discipline, at a public research-intensive university. Findings suggest that systems and mechanisms created to ensure organizational legitimacy (public trust, confidence, social responsibility) in research are fundamental to the survival of a research university, in that they convey credibility to external stakeholders. Findings also suggest that the virtues of collegiality, integrity, openness, trust, and purpose are aspirational characteristics of a desirable research environment, and organizations can promote or hinder these characteristics through formal and informal processes. Finally, the interviews indicate that university leaders see connections but not exact alignment between the actions taken to achieve organizational legitimacy and the actions taken to promote organizational virtuousness.
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    RPV/UAV Surveillance for Transportation Management and Security
    (University of Minnesota Center for Transportation Studies, 2008-12) Gebre-Egziabher, Demoz
    This report describes the results of an investigation into some of the technical and operational issues associated with using Unmanned Aerial Systems (UAS) for the application of surveillance in support of transportation infrastructure management and security. As part of this investigation a low-cost, miniature, hand-launched aerial vehicle and supporting ground systems suitable for surveillance of highways and traffic infrastructure were developed. Except for the ground station software, this system was built from off-the-shelf components. The ground station software developed was used to enhance ground station operators' situational awareness and simultaneously allow analysis of the data transmitted from the aerial vehicle. In addition, a key system that was developed was an open-source Guidance, Navigation and Control (GNC) software suite for autonomous operation of small aerial vehicles. The culmination of this work was a series flight tests where the UAS developed was used as a tool to enhance situational awareness over a simulated traffic incident or emergency situation. The test consisted of defining a series of waypoints around the area of the simulated incident and launching the miniature aerial vehicle to autonomously fly from waypoint to waypoint.