Chang, Lei (2012)Experimental Data on Fire-Resistance Behaviorof Reinforced Concrete Structures withExample Calculations.[Laurea magistrale], Università di Bologna, Corso di Studio in Civil engineering [LM-DM270]
Gualandi, Gabriele (2012)Crack modeling and crack propagation in structures using damage model and extended finite element techniques.[Laurea magistrale], Università di Bologna, Corso di Studio in Civil engineering [LM-DM270], Documento ad accesso riservato.
Tavano, Matteo (2012)Seismic response of tank-fluid systems: state of the art review and dynamic buckling analysis of a steel tank with the added mass method.[Laurea magistrale], Università di Bologna, Corso di Studio in Civil engineering [LM-DM270]
Altini, Enrico (2012)Tactile perception - Perception of tactile distance changes with body site: a neural network modelling study.[Laurea magistrale], Università di Bologna, Corso di Studio in Ingegneria biomedica [LM-DM270] - Cesena
Monti, Luca (2012)Tactile Perception - Perception of tactile distance on a single skin surface changes with stimulus orientation: a neuronal network modelling study.[Laurea magistrale], Università di Bologna, Corso di Studio in Ingegneria biomedica [LM-DM270] - Cesena
Ricci, Riccardo (2012)Laboratory study of grouted macadams impregnated with mine waste geopolymeric binder.[Laurea magistrale], Università di Bologna, Corso di Studio in Ingegneria civile [LM-DM270], Documento ad accesso riservato.
Mordenti, Andrea (2012)Programming Robots with an Agent-Oriented BDI-based Control Architecture: Explorations using the JaCa and Webots Platforms.[Laurea magistrale], Università di Bologna, Corso di Studio in Ingegneria informatica [LM-DM270] - Cesena
During the production of injection moulded components made of semi-crystalline thermoplastics, the material is locally exposed to different thermal conditions and thermal histories. While in the injection phase the surface layer material that gets in direct contact with the cold mould wall solidifies at cooling rates of up to 700 K/s, the core layer material solidifies at cooling rates of ~1 K/s, especially for thick-walled components. The significant differences of the solidification conditions lead to varying formations of the microstructure and the crystallisation degree across the thickness. Since the thermal conductivity depends on the crystallisation degree, a non-uniform thermal conductivity can be found through the thickness of the material. However, current injection moulding simulations do not take into account the decrease of the crystallisation degree towards the component edges by adjusting thermal conductivity depending on the local thermal history. To characterise the thermal conductivity in experimental tests, differential scanning calorimetry (DSC) analyses can be performed. However, DSC is typically limited to a maximum cooling rate of 0.5 K/s and thus cannot replicate the relevant crystallisation conditions for injection moulding. In contrast the Flash-DSC 2+, Mettler-Toledo, Ohio allows cooling rates up to 5000 K/s and thus covers the full range of injection moulding occurring cooling rates. The presented work will demonstrate a new methodology for the thermal conductivity characterisation using the Flash-DSC 2+. This approach enables the direct measurement of thermal conductivity as a function of the crystallisation degree and provides a more detailed description of the thermal boundary conditions in injection moulding processes and simulations. Initial experimental results show that a stacked test sample consisting of a polymer and a metal with a known and discrete melting point is suitable for measuring the thermal conductivity using the Flash-DSC 2+, analogous to the procedure using a conventional DSC. This methodology is verified in experimental tests with annealed polymer samples of isotactic polypropylene of the type PP505P, Sabic, Saudi-Arabia with a crystallisation degree of about 49 %. Thereby, it was demonstrated that the thermal conductivity is independent of the applied heating rate, which corresponds to the expectation. This allows the stacked test sample to solidify from the melt at any cooling rates and the measurement of thermal conductivity during subsequent re-heating at a high heating rates, which are characterised by a low noise to signal ratio. Since the solidification effects of the metal and the polymer can overlap especially at high cooling rates and a measurement of the crystallisation degree by Flash-DSC 2+ at very low cooling rates cannot be evaluated due to a high noise to signal ratio, the crystallisation degree depending on the cooling rate is empirically modelled by an additional measurement. Thus, for the first time, a measurement of the thermal conductivity as a function of cooling rate, respectively degree of crystallisation for the material is demonstrated here. This enables a more precise description of the thermal conditions within injection moulding simulations.
The production of conventional cross-linked polymer networks and their composites, i.e., thermosets and thermoset composites, was estimated to consume more than 40 billion kg of polymer in 2020. Unfortunately, thermosets cannot be melt-reprocessed into moderate- to high-value products because permanent crosslinks prevent melt flow. Three of many examples include rubber tires, disposed at a rate of ~300 million annually in the U.S. alone, polyurethane (PU) foam, and cross-linked polyethylene, with major economic and sustainability losses resulting because the spent materials are commonly landfilled or burned for energy. Here, I will report on research demonstrating the ability to employ simple one-step or two-step reactions to produce networks and network composites with dynamic covalent crosslinks that are robust at use conditions but allow for melt-state reprocessing at elevated temperature. Unique to our research group, we have developed several approaches that allow for melt-state reprocessing of addition-type polymer networks and network composites, including those synthesized directly from monomers containing carbon-carbon double bonds, such as those used in coatings and flooring, and those synthesized from polymer or combined polymer and monomer with both containing carbon-carbon double bonds, like materials used in tires and in cross-linked polyethylene. All approaches allow for full crosslink density recovery after multiple reprocessing steps. We have also demonstrated for the first time the ability to make PU and PU-like networks, e.g., polyhydroxyurethane and polythiourethane networks, reprocessable with full recovery of crosslink density. An "Achilles' heel" has been identified regarding the application of dynamic covalent networks, i.e., such networks are subject to creep at elevated or sometimes even room temperature, which is often highly undesirable. We have addressed this limitation in two ways. In one case, we add a fraction of permanent crosslinks to dynamic covalent networks. In a second class of systems, we employ dynamic chemistry with a sufficiently high activation energy, allowing for reprocessability at high temperature but with the dynamic chemistry essentially fully arrested well above room temperature, e.g., 70-80 degrees C. Implications of these studies for making major gains in the sustainability of polymer networks and network composites will be discussed.
Regardless of the industrial sector, the identification of components, packaging and entire products is becoming increasingly important. In addition to production-related identification and registration of components, individual labeling is used to meet legal requirements and customer demands for traceability. More flexible and fully automated production and assembly processes are increasing the need for clear identification of components and assemblies. Downstream processes such as lasering, labeling, printing or embossing are state of the art. In order to be able to reduce work steps, cycle-integrated processes such as in-mold decoration are chosen. As part of the KMU innovativ joint project "Plastic packing Unique Device Identification System" (PUDIS), solution strategies for marking components directly in the injection molding process are being developed. In the project a prototypical realization of such a marking system is developed. The marking system consists of a marking module, a control unit, a scanning module and a corresponding user interface. A three-dimensional code is generated via the marking module, which is integrated in the injection mold, and molded directly onto the component during the original molding process in the injection mold. The design of this marking module is subject to various challenges in view of the high temperature and pressure intensities within the cavity of the mold. The overall system ensures clear identification and traceability of the plastic parts produced. A feasibility study carried out with a reduced functional scope was able to confirm the assumptions underlying the project and show that the marking module can withstand the conditions prevailing in the cavity and form a reproducible marking in the part. The project team was able to achieve these successes after implementing the marking module in the injection molding machine on 2 needles. The markings on the injection molded parts were measured tactilely and optically. Needle 1 and 2 cover a distance of about 0.4 mm from the 0-state to the 1-state. It was demonstrated that there is no displacement of the needles despite the high cavity pressure. A database for the decoding algorithms was obtained based on the components produced in the experiments. In the later course of the project, tests are to be carried out with all 25 needles and complete codes generated. The components will then be evaluated and analyzed via the evaluation software. Once all systems are functioning, long-term tests will be carried out to validate the system for series production. The aim of the project is to enable in-situ marking in plastic components. The requirements for the marking module used for this range from the smallest possible installation space to a modular design. Furthermore, a software for the evaluation of the introduced coding is being developed. KOMDRUCK AG, Formconsult Werkzeugbau GmbH and Schmalkalden University of Applied Sciences are involved in the PUDIS project. 2b1af7f3a8