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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A model-based safety analysis approach for high-integrity socio-technical component-based systems

Sefer, Edin January 2015 (has links)
Designing high-integrity socio-technical systems requires a thorough understanding of all safety risks of such systems. For many years, safety risk assessment has been conducted separately for hardware, software, human, organizational and other entities in socio-technical systems. Safety risk assessment that does not consider all factors at the same time cannot adequately capture the wide variety of safety risk scenarios that need to be considered. This thesis proposes a model-based analysis approach that allows interpretation of humans and organizations in terms of components and their behavior in terms of failure logic. The proposal is built on top of the tool-supported model-based failure logic analysis technique called CHESS-FLA. CHESS-FLA supports the analysis of the component-based system architectures to understand what can go wrong at a system level, by applying failure logic rules at a component level. CHESS-FLA addresses only hardware and software components and as such it is inadequate for the analysis of socio-technical systems. This thesis proposes an extension of CHESS-FLA based on the preexisting classification (developed within SERA), of failures of socio entities. This extension combines CHESS-FLA and SERA - classification and delivers an approach named Concerto-FLA. Concerto-FLA is fully integrated into the CONCERTO framework allowing an automated analysis to be performed on architectures that contain human, organizational and technical entities present in socio-technical systems. The use of the approach is demonstrated on a case study extracted from the petroleum domain. The effectiveness of the delivered tool is briefly evaluated based on the results from the case study. / CONCERTO project
2

Thermisches Kunststoffnieten - Verfahrensablauf, mechanische Eigenschaften, Versagensverhalten

Brückner, Eric 29 January 2021 (has links)
Bauteilkonstruktionen mit integrierten Kunststoffnietverbindungen nehmen aufgrund der steigenden Anzahl artfremder Werkstoffkombinationen im Rahmen von Hybridbauweisen kontinuierlich zu. Als nicht lösbare und punktuell wirkende Verbindung wird das Kunststoffnieten insbesondere aufgrund seiner kosteneffizienten und einfach anmutenden Prozessführung u. a. für die Herstellung von Elektronik- und Sensorelementen sowie für das Verbinden von Bauteilen im Interieur- bzw. Exterieur-Bereich eingesetzt. Aufgrund der hohen Anwendungs- und Werkstoffvielfalt unterliegt der Kunststoffnietprozess jedoch komplexen Anforderungen, die für eine sichere Prozessanwendung durch ein hinreichendes Prozessverständnis sowie eine zielführende Qualitätssicherung kompensiert werden müssen. Die vorliegende Dissertation befasst sich mit der wissenschaftlichen Analyse der thermischen Nietprozesse Warmumformen und Heißluftnieten. Im Mittelpunkt der Betrachtungen steht die systematische Ausarbeitung der Zusammenhänge zwischen dem Verfahrensablauf, den mechanischen Eigenschaften sowie dem resultierenden Versagensverhalten der Nietverbindung. Die Ergebnisse zeigen, dass bei einer optimierten Prozessführung für beide thermischen Nietverfahren hohe mechanische Eigenschaften erreicht werden können. Als dominierender Faktor offenbarte sich die Anbindungsqualität des Nietkopfes an den Nietzapfen, welche in einem direkten Zusammenhang zum Erwärmungs- und Umformverhalten des Nietzapfens steht. Zudem sind die Verarbeitungseigenschaften und die erreichbare Verbindungsqualität vom eingesetzten Werkstoff abhängig. / Due to the rising number of dissimilar material combinations in the field of hybrid design, components with integrated plastic rivet joints are steadily increasing. Among other things, staking is primary used as a non-detachable and point-acting joint for the production of electronic and sensor elements as well as for the joining of components in the automotive interior and exterior by reason of its cost-efficient and seemingly simple process control. However, due to the high diversity of applications and materials, the staking process is subject to complex requirements, which must be compensated by a sufficient understanding of the process as well as a perfected quality assurance in order to ensure reliable process application. The present dissertation deals with the scientific analysis of the thermal staking processes hot forming staking and hot air staking. The investigations focus on the systematic analysis of the relationships between the procedure itself, the mechanical properties and the resulting failure behavior of the riveted joint. The results show that high mechanical properties can be achieved for both thermal staking processes by having an optimized process control. The most dominant factor revealed to be the bond quality of the rivet head to the rivet pin, which is directly related to the heating and forming behavior of the rivet pin. In addition, the processing properties and the achievable joint quality depend on the material which is used.

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