TY - CONF A1 - Kiefer, P. A1 - Balzer, R. A1 - Behrens, H. A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Deubener, J. T1 - In-situ observation of sub-critical crack growth in water bearing borate glasses N2 - 185 cracks were initiated in a soda-lime-silica glass by Vickers indentation and grown under controlled dry nitrogen atmosphere. Direct observation of subcritical crack growth (SCCG) upon indentation was performed using a video camera with an image acquisition rate of 3 ms. The results show that the validity of K(c) relations used to determine the indentation fracture toughness from a single imprint is questionable. It seems that correlation of crack length to stress intensity necessitate the use of statistical significant data of multiple crack events. T2 - FFAG 7: 7th International Workshop on Flow and Fracture of Advanced Glasses CY - Aalborg, Denmark DA - 02.07.2017 KW - Sub critical crack growth KW - Glass KW - Vickers KW - Water bearing glass KW - Indentation fracture toughness PY - 2017 AN - OPUS4-44211 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kiefer, P. A1 - Balzer, R. A1 - Behrens, H. A1 - Waurischk, Tina A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Deubener, J. T1 - In-situ Beobachtung und statistische Analyse des unterkritischen Risswachstums in Gläsern N2 - Um das Risswachstum in Gläsern zu untersuchen, sind in einer Glovebox 185 Risse ausgehen von Vickers-Eindrücken in Kalk-Natron-Glas initiiert und gewachsen. Die direkte Beobachtung des unterkritischen Risswachstums erfolgte mit einer Hochgeschwindigkeitskamera. Die Ergebnisse zeigen, dass die statistische Auswertung vieler radialer Risse von multiplen Rissevents notwendig ist, um eine Korrelation zum Spannungsintensitätsfaktor ziehen zu können. T2 - Fachausschuss I der Deutschen Glastechnischen Gesellschaft (DGG) CY - Erlangen, Germany DA - 26.09.2017 KW - Risswachstum KW - Glas KW - Vickers KW - In-situ PY - 2017 AN - OPUS4-44215 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kiefer, P. A1 - Balzer, R. A1 - Dietrich, U. A1 - Behrens, H. A1 - Waurischk, Tina A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Deubener, J. T1 - Viscosity of water bearing glasses in the glass transition range – Phosphates vs. silicates and borates N2 - Water has a strong impact on the viscosity and the transition temperature of oxide glasses. It acts as a fluxing agent, reducing viscosity particularly in the glass transition range, and by that flattening the viscosity-temperature curve and decreasing the fragility of hydrous glass melts. This general behavior is found for silicate and borate as well as in borosilicate compositions. However, there is still a lack of data with respect to hydrous phosphate glasses. Here, we study the influence of structural water on the viscosity of Li2O-MgO-(Al2O3-)P2O5 glasses. The glasses were synthesized in an internally heated pressure vessel (IHPV) at a pressure of 0.5 GPa. The selected pressure allows for the synthesis of glass specimens with water contents of several wt.%. The viscosity measurements were carried out in the glass transition range, i.e. log η ≈ 10-13 (η in Pa s), using a sphere penetration viscometer. The measured data agree with glass transition temperatures measured by differential thermo analysis. First results further suggest that the fragility of the analyzed phosphates decreases with increasing water content. T2 - 91. Glastechnische Tagung CY - Weimar, Germany DA - 28.05.2017 KW - Water-bearing glasses KW - Viscosity PY - 2017 AN - OPUS4-40812 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kiefer, P. A1 - Deubener, J. A1 - Waurischk, Tina A1 - Balzer, R. A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Behrens, H. T1 - Statistical analysis of Vickers induced subcritical crack growth in soda-lime silicate glasses N2 - Studies on Vickers induced subcritical crack growth are controversially discussed since the stresses that drive the crack growth are distributed three dimensionally within the material and cannot be retraced by available methods. Hence, empirical approaches are used to calculate mechanical material parameters such as the stress intensity factor KI. However, the results of these approaches show large deviations from those measured by standardized techniques such as double cantilever beam (DCB) or double cleavage drilled compression (DCDC). Yet, small specimen sizes and low specimen quantities can prevent the execution of DCB and DCDC measurements. Here we present an approach that is based on a statistical analysis of Vickers induced radial cracks. For this purpose more than 150 single radial cracks were analyzed. The cracks were generated in a commercial soda-lime silicate glass. The experiments were performed in a glovebox purged with dry nitrogen gas to minimize the influence of atmospheric water on crack growth. The temporally resolved evolution of the radial cracks was monitored in-situ using an inverted microscope equipped with a camera system directly below the Vickers indenter. An automated image analysis software was used to determine the crack length over time. The data show that the crack propagation and thereby the crack velocities are not uniformly but statistically distributed. These findings allow, using the statistical mean value of the distributions in combination with DCB data, a precise formulation of KI for each measured crack length. T2 - 92nd Annual Meeting of the German Society of Glass Technology in Conjunction with the Annual Meetings of the Czech Glass Society & the Slovak Glass Society CY - Bayreuth, Germany DA - 28.05.2018 KW - Crack growth KW - Soda-lime silicate glass KW - Vickers PY - 2018 AN - OPUS4-45703 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kiefer, P. A1 - Deubener, J. A1 - Waurischk, Tina A1 - Balzer, R. A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Behrens, H. T1 - Subcritical crack growth in water bearing soda-lime silicate glasses N2 - The presence of water in the surrounding atmosphere of a propagating crack has a major influence on the subcritical crack growth. While these external phenomena are well understood, there is still a lack of knowledge on the influence of structurally bound water on crack propagation. Thus, our recent study aims on the analysis of crack propagation in water bearing soda-lime silicate glasses with up to 8 wt.% water. The samples were synthesized in an internally heated pressure vessel at 0.5 GPa. Since this preparation route limits the sample sizes, standard test geometries allowing for the determination of stress intensity factors, such as double cantilever beam, are not feasible. Thus, radial cracks in the hydrous glasses were initiated by Vickers indentation and crack growth was simultaneously captured with a camera system. An automated image analysis algorithm was used for the analysis of the crack length of each single video frame. To minimize influences by atmospheric water, all experiments were conducted in a glovebox purged with dry N2. About 150 cracks per glass composition were analyzed to provide statistical significance of the Vickers-induced SCCG. The results show that structurally bound water has a major influence on SCCG by means of crack lengths, growth rates and time of crack initiation. T2 - 92nd Annual Meeting of the German Society of Glass Technology in Conjunction with the Annual Meetings of the Czech Glass Society & the Slovak Glass Society CY - Bayreuth, Germany DA - 28.05.2018 KW - Water speciation KW - Soda-lime silicate glass KW - Crack growth KW - Vickers PY - 2018 AN - OPUS4-45704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kiefer, P. A1 - Balzer, R. A1 - Waurischk, Tina A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Behrens, H. A1 - Deubener, J. T1 - Statistical analysis of subcritical crack growth in water bearing soda-lime silicate glasses N2 - The talk was given at the PNCS-ESG 2018 in Saint Malo and summarizes the actual findings about Vickers induced crack growth in water bearing soda-lime silicate glasses. T2 - 15th International Conference on the Physics of Non-Crystalline Solids & 14th European Society of Glass Conference CY - Saint Malo, France DA - 09.07.2018 KW - Water speciation KW - Vickers KW - Crack growth KW - Soda-lime silicate glass PY - 2018 AN - OPUS4-45707 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kiefer, P. A1 - Deubener, J. A1 - Waurischk, Tina A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Behrens, H. A1 - Balzer, R. T1 - Density, microhardness and elastic moduli of hydrous soda-lime silicate glasses N2 - The effect of structural water on density, elastic constants and microhardness of water-bearing soda-lime-silica glasses of up to 21.5 mol% total water is studied. T2 - 25th International Congress on Glass (ICG2019) CY - Boston, MA, USA DA - 09.06.2019 KW - Elastic constants KW - Soda-lime-silica glass KW - Water content KW - Microhardness PY - 2019 AN - OPUS4-49537 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kiefer, P. A1 - Deubener, J. A1 - Waurischk, Tina A1 - Balzer, R. A1 - Reinsch, Stefan A1 - Müller, Ralf A1 - Behrens, H. T1 - Subcritical crack growth in water bearing soda-aluminosilicate glasses N2 - The subcritical crack growth in water bearing soda-aluminosilicate glasses is compared to the crack growth in a commercial soda-lime silicate glass. The water speciation is shown for comparison of water species in the material. Differences will be discussed in the poster session. T2 - Glastechnische Tagung 2019 CY - Nürnberg, Germany DA - 13.05.2019 KW - Glass KW - Crack growth KW - Vickers KW - Water speciation PY - 2019 AN - OPUS4-48343 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -