Glas wird mit dem Ziel, die Festigkeits- und Sicherheitseigenschaften zu verbessern, thermisch vorgespannt und zu Verbundglas laminiert. Nur so ist es möglich, Bauteile wie Treppen, Träger und Stützen transparent zu gestalten oder sogar Ganzglaskonstruktionen auszuführen. Gleichzeitig werden an diese Glasbauteile höchste ästhetische Ansprüche gestellt. Diese Ansprüche können aktuell nicht immer erfüllt werden. Aus dem Veredelungsprozess von Verbundglas resultiert ein Kantenversatz zwischen den Einzelgläsern, der die optische Qualität der frei sichtbaren Kanten erheblich beeinträchtigt. Darüber hinaus führt dieser Kantenversatz bei Lasteinleitung über die Kante zu einer ungleichmäßigen und damit ungünstigen Lastverteilung auf die Einzelgläser. Das Nachschleifen der Verbundglaskante ermöglicht, die optische Beeinträchtigung zu beheben und eine ebene Kantenoberfläche zu schaffen. Bei thermisch vorgespanntem Glas verursacht das Nachschleifen allerdings einen mechanischen Eingriff in den thermischen Vorspannungszustand, der sinkende Festigkeiten zur Folge haben kann. Dies stellt ein erhebliches Risiko dar, da das Bauteil unplanmäßig versagen könnte. Eine wissenschaftlich belegte Beurteilung des Versagensrisikos ist derzeit nicht verfügbar. Die europäische Normung schließt das Nachschleifen deshalb vollständig aus. Die vorliegende Arbeit trägt dazu bei, diese Lücke zu schließen und verfolgt das Ziel, den Einfluss des Nachschleifens auf thermisch vorgespannte Gläser zu charakterisieren. Eine Auseinandersetzung mit der Herstellung und Veredelung von Flachglas führt zur Ausgangssituation für das Nachschleifen und den zu berücksichtigenden Einflussgrößen. Das daraus abgeleitete experimentelle Versuchsprogramm beinhaltet die zweistufige Untersuchung von 240 Probekörpern aus Einscheiben-Sicherheitsglas und Teilvorgespanntem Glas mit variierender Glasdicke. Diese wurden in unterschiedlichen Nachschleiftiefen bearbeitet. Zunächst erfolgt die umfangreiche Analyse des thermischen Vorspannungszustands mit Hilfe von spannungsoptischen Messmethoden. Der zweite Schritt beinhaltet Bruchversuche zur Bestimmung der Festigkeit sowie begleitende mikroskopische Untersuchungen des bruchverursachenden Defektes. Die Analyse der Korrelation zwischen den Ergebnissen der thermischen Vorspannung und dem Bruchverhalten erlaubt die Beschreibung des Einflusses des Nachschleifens auf thermisch vorgespanntes Glas. Daraus geht hervor, dass die thermische Vorspannung an der Kante mit steigender Nachschleiftiefe sinkt. Mit den Vorspannungswerten sinkt auch die Beanspruchbarkeit der Gläser. Die verbleibenden charakteristischen Festigkeiten unterschreiten jedoch nicht zwangsläufig die normativ geforderten Grenzwerte. In Abhängigkeit von Glasart und Glasdicke ist das Nachschleifen in definierten Grenzen möglich, ohne ein unplanmäßiges Versagensrisiko hervorzurufen. Aus den Ergebnissen der Probekörper dieser Arbeit geht hervor, dass Teilvorgespanntes Glas, in Abhängigkeit von der Glasdicke, maximal 3 mm nachgeschliffen werden konnte, ohne die in den Produktnormen geforderten Festigkeiten zu unterschreiten. Im Gegensatz dazu lag die Grenze bei Einscheiben-Sicherheitsglas schon bei 1 mm Nachschleiftiefe. Auf dieser Grundlage sowie der Zusammenführung aller Ergebnisse dieser Arbeit erfolgt die Herleitung von konstruktiven sowie verfahrenstechnischen Empfehlungen, die sich positiv auf die nach dem Nachschleifen verbleibende Festigkeit auswirken. Für die Ingenieurpraxis wird zudem ein Nachweiskonzept für thermisch vorgespannte Gläser mit nachgeschliffenen Kanten erarbeitet. Die Erkenntnisse dieser Arbeit zeigen, dass das Potential des Nachschleifens als zusätzlicher Veredelungsschritt von thermisch vorgespannten Verbundgläsern genutzt werden kann. Sie belegen, auf Basis umfangreicher wissenschaftlicher Untersuchungen, dass kein unplanmäßiges Versagensrisiko durch das Nachschleifen entsteht, wenn bestimmte Grenzwerte eingehalten werden. Die aus dem Umfang der Versuche dieser Arbeit abgeleiteten Empfehlungen und das entwickelte Nachweiskonzept eröffnen einen Weg für den zukünftigen Einsatz des Nachschleifens von thermisch vorgespannten Gläsern, um Glasbauteile mit ebenen und optisch hervorragenden Verbundglaskanten schaffen zu können.:1 Einleitung 2 Glasherstellung und -veredelung 3 Thermische Vorspannung 4 Festigkeit und Bruchverhalten 5 Gesamtergebnisse und Empfehlungen 6 Zusammenfassung und Ausblick 7 Literatur / To enhance the strength and safety of glass members, glass is often both thermally toughened and laminated. This enables the realisation of transparent components such as staircases, beams and columns, or even all-glass constructions. Additionally, these glass constructions must meet the demand on high aesthetic quality. Currently, it is not always possible to reach these demand. Processing laminated glass can cause an edge offset between the individual glass panes, which significantly affects the optical quality of visible glass edges. Moreover, in the case of glass components with load introduction into the laminated glass edge, the offset leads to an uneven and adverse load splitting on the individual glass panes. Regrinding laminated glass edges provides the opportunity to remove the optical deficit and establish smooth edges. However, regrinding of thermally toughened glass causes a mechanical intervention into the residual stress state that could lead to a decrease in strength. This poses a considerable risk, as the glass component could fail unexpectedly. Despite this significant risk, there are currently no scientifically established risk assessment methods for the influence of regrinding. Therefore, the European standards exclude the regrinding of thermally toughened glass. Accordingly, this thesis aims to address this deficiency by characterising the effect of regrinding on thermally toughened glass. In this thesis, extensive analysis of flat glass production and processing of glass lead to the influencing variables, which has to be considered in the examination of regrinding. The derived two-stage testing programme includes 240 specimens made of fully tempered glass and heat-strengthened glass of varying thicknesses. Specimens underwent regrinding to varying depths. Firstly, the analysis of the residual stress state is carried out with stress-optical measuring methods. Afterwards, fracture tests are executed to determine the strength. Accompanying studies include microscopic examinations of the defects in the glass causing the fracture. Measured residual stress state and fracture stress are correlated in order to characterise the influence of the regrinding process on thermally toughened glass. The study demonstrated that increasing regrinding depths lead to a decrease in the residual stress at the edge. As a result, the resultant strength also decreases. However, the remaining characteristic strengths are not necessarily below the normatively regulated characteristic strengths. Depending on the glass type and thickness, regrinding is possible within defined limits without causing an unexpected risk of failure. The results of the tested specimens of this thesis indicate that, depending on the glass thickness, regrinding of heat-strengthened glass is possible up to a maximum of 3 mm regrinding depth without a reduction in strength below standardised limits. In contrast, the maximum limit of regrinding fully tempered glass was 1 mm. On this basis, as well as, the combination of all experimental results of this thesis, constructive and procedural recommendations which positively affect the remaining strength after regrinding are derived. In addition, a verification concept for thermally toughened glass with reground edges is developed. Finally, the results of this thesis show that the regrinding process can be implemented as an additional finishing step for thermally toughened laminated glass. Based on comprehensive scientific studies, the outcome verifies that regrinding up to defined limits does not result in risk of premature failure. The derived recommendations and developed verification concept, which results from the examinations of this thesis, establish opportunities for future use of reground laminated thermally toughened glass to create glass components with smooth edges of the highest optical quality.:1 Einleitung 2 Glasherstellung und -veredelung 3 Thermische Vorspannung 4 Festigkeit und Bruchverhalten 5 Gesamtergebnisse und Empfehlungen 6 Zusammenfassung und Ausblick 7 Literatur

Plastic flow in bulk metallic glasses (BMGs) localizes into narrow bands, which, in the absence of a microstructure that could obstruct them, propagate unhindered under tensile loading. In constrained deformation conditions such as indentation and at notch roots, extensive shear band formation can occur. A key issue in the context of fracture of BMGs that is yet to be understood comprehensively is how their toughness is controlled by various state parameters. Towards this end, the change in fracture toughness and plasticity with short term annealing above and below the glass transition temperature, Tg, is studied in a Zr-based BMG. Elastic properties like shear modulus, Poisson's ratio as well as parameters defining the internal state like the fictive temperature, Tf, density, and free volume are measured and correlation with the toughness was attempted at. While the elastic properties may help in distinguishing between tough and brittle glasses, they fail to reveal the reasons behind the toughness variations. Spherical-tip nanoindentation and microindentation tests were employed to probe the size, distributions and activation energies of the microscopic plastic carriers with the former and shear band densities with the latter. Results indicate that specimens annealed at a higher temperature, Ta, exhibit profuse shear banding with negligible changes in the local yield strengths. Statistical analysis of the nanoindentation data by incorporating the nucleation rate theory and the results of the cooperative shear model (CSM), reveals that short term annealing doesn't alter the shear transformation zone (STZ) size much. However, density estimates indicate changes in the free volume content across specimens. A model combining STZ activation and free volume accumulation predicts a higher rate in the reduction of the cumulative STZ activation barrier in specimens with a higher initial free volume content. Of the macroscopic physical properties, the specimen density is revealed to be a useful qualitative measure of enhancement in fracture toughness and plasticity in BMGs. We turn our attention next to the brittle fracture in BMGs, with the specific objective of understanding the mechanisms of failure. For this purpose, mode I fracture experiments were conducted on embrittled BMG samples and the fracture surface features were analyzed in detail. Wallner lines, which result from the interaction between the propagating crack front and shear waves emanating from a secondary source, were observed on the fracture surface and geometric analysis of them indicates that the maximum crack velocity to be ~800 m/s, which corresponds to ~0.32 times the shear wave speed. Fractography reveals that the sharp crack nucleation at the notch tip occurs at the mid-section of the specimens with the observation of flat and half-penny shaped cracks. On this basis, we conclude that the crack initiation in brittle BMGs occurs through hydrostatic stress assisted cavity nucleation ahead of the notch tip. High magnification scanning electron and atomic force microscopies of the dynamic crack growth regions reveal highly organized, nanoscale periodic patterns with a spacing of ~79 nm. Juxtaposition of the crack velocity with this spacing suggests that that the crack takes ~10-10 s for peak-to-peak propagation. This, and the estimated adiabatic temperature rise ahead of the propagating crack tip that suggests local softening, are utilized to critically discuss possible causes for the nanocorrugation formation. The Taylor’s fluid meniscus instability is unequivocally ruled out. Then, two other possible mechanisms, viz. (a) crack tip blunting and resharpening through nanovoid nucleation and growth ahead of the crack tip and eventual coalescence, and (b) dynamic oscillation of the crack in a thin slab of softened zone ahead of the crack-tip, are critically discussed. One way of alleviating the fracture-related issues in BMGs is to impart a microstructure to it, which would either impede the growth of shear bands or promote the multiplication of them. One such approach is through the BMG composites (BMGCs) route, wherein a crystalline second phase incorporated in the BMG matrix. There is a need to study the effects of reinforcement content, size and distribution on the mechanical behavior of the BMGC so as to achieve an optimum combination of strength and ductility. For this purpose, an investigation into the microstructure and tensile properties of Zr/Ti-based BMG composites of the same composition, but produced by different routes, was conducted so as to identify “structure–property” connections in these materials. This was accomplished by employing four different processing methods—arc melting, suction casting, semi-solid forging and induction melting on a water-cooled copper boat—on composites with two different dendrite volume fractions, Vd. The change in processing parameters only affects microstructural length scales such as the interdendritic spacing, λ, and dendrite size, δ, whereas compositions of the matrix and dendrite are unaffected. Broadly, the composite’s properties are insensitive to the microstructural length scales when Vd is high (∼75%), whereas they become process dependent for relatively lower Vd (∼55%). Larger δ in arc-melted and forged specimens result in higher ductility (7–9%) and lower hardening rates, whereas smaller dendrites increase the hardening rate. A bimodal distribution of dendrites offers excellent ductility at a marginal cost of yield strength. Finer λ result in marked improvements in both ductility and yield strength, due to the confinement of shear band nucleation sites in smaller volumes of the glassy phase. Forging in the semi-solid state imparts such a microstructure.

The main subject of the diploma project was to create architecture study for new building of a Gallery for sport aircrafts and their traditions and other equipment that cooperate with this topic. The Gallery is designed in Brno´s Medlanky municipality and it is incorporated on current local sport airport. This project was preceded by studio project on the same area, which included reconstruction and development of this airport area. In this diploma project I was trying to continue with this development and establish a design which would react to my earlier design. The site has a sloped character and it separated from a dense city area. Starting point for the design was to gently touch the landscape and also trying to find certain references directly in the closest surrounding. From the views to surrounding was created the idea to preserve the horizontal lines and with a landscape and constructions demands was created the main idea to continue with the landscape over the spatial structure. The need to cover large-scale exhibit items like aircrafts and other items from this topic led to a starting point of my design. The structure is formed as a spatial truss structure and dominates the exhibition space. Building is connected by program and structure to services and other areas like conference hall, coffee, study room, work room and administration. As a one building it teems mainly from arrival at the airport area when the roofing is an organic, monolithic surface disappearing in surrounding. But gallery itself emerges from the ground and opens towards the aircraft take off and departure area where it is also direction of a main view to the surrounding. The building is also unique for its entering, such as the main entrance through narrow staircase gap in the roof. This entrance should evoke to people an aircraft landing, where while descent plane dive in to the clouds and appear underneath above a whole new landscape. Thus a person sore in to the roof surface a