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Author: Hessenkemper, Heiko × End date: 2024 × Start date: 2020 × End date: 1999 × Start date: 1990 ×

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Now showing 1 - 4 of 4
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    stress generation modulus as a counterpart of the stress relaxation modulus
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Brückner, Rolf; Hessenkemper, Heiko; Habeck, Andreas; Yue, Yuanzheng
    In order to measure the time dependence of the stress relaxation modulus, E, a stress-strain deformation has to precede which induces a stress within the viscoelastic sample from which the sample relaxes. The generation of stress is characterized by a strain rate-dependent and relaxation rate-dependent portion which exhibits a maximum value, E_max, which is called "stress generation modulus". E_max was called the "maximum stress relaxation modulus" in earlier papers. Meanwhile, however, it turned out that a better verbal distinction should be made in future by the new term "stress generation modulus" because E_max is about one order of magnitude larger than E.
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    Glass conditioning by viscosity controi
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) Roger, Ulrich; Hessenkemper, Heiko; Roth, Peter
    During the forming process of a glass melt the viscosity is the dominant process parameter. Up to now in the industrial Container glass production only temperature-controlled Systems have been used. With these control elements only thermally induced variations of the viscosity are visible. Variations in the composition, the redox State , the water and the SO₃ content in the melting process cause a shift in the viscosity Up to now these changes have not been detectable and therefore, it has not been possible to compensate them. Α measuring device for t he continuous determinadon of the viscosity in the glass was developed and tested for several months in a Container glass plant. All measured variations of the viscosity can now be corrected by the existing control elements for the thermally controlled glass conditioning. Dependent on the posidon of the viscosimeter in the feeder Channel , a feedforward or feedback Controlling concept is practicable.
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    Tracing of primary melt formation and reactions involved in glass batch melting
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Suwannathada, Pichanon; Hessenkemper, Heiko
    The primary melt formation and the reactions involved therein were traced by means of electrical conductivity measurement. After the temperature of the furnace had reached 1200 °C, 700 g of soda-lime-silica glass batches, either with or without carbon addidon, were loosely charged into an induction furnace. An electrical conductivity sensor connected with a thermocouple was put immediately into the batch; then the conductivity in terms of voltage drop and the temperatures were continuously recorded. Not only the changes in t h e reaction atmosphere were detected, but also at least four events leading to the occurrence of the primary melts could be identified. They were the double salt (Na₂Ca(CO₃)₂) with a soda-rich NaCa mixed crystal eutectic, the sodium distilicate-silica eutectic, the double salt melting temperature, and the soda melting temperature. The temperature at which the conductivity curve passed its original baseline is proposed as the primary melt formation temperature. The first highest sodium ion diffusion rate, or hopping region on the conductivity-temperature curve, is also proposed as the primary glass-forming melt temperature.
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    Influence of water dissolved in the structure of soda-lime-silica glass on melting, forming and properties: state-of-the-art and controversial issues Report of the International Commission on Glass (ICG) Technical Committee 14 "Gases in Glass"
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Geotti-Bianchini, Franco; Brown, John T.; Faber, Anne J.; Hessenkemper, Heiko; Kobayashi, Sho; Smith, Ian H.
    The paper summarizes the information available about the water content of soda-lime-silica glass, the factors that influence it and the influence exerted by water in glass on redox and sulphur retention, on fming, on the melting and forming behaviour, workability and the physical and chemical properties of the melt. Such issues were discussed by the authors in their presentations at the first Forum on Water in Glass, organized in 1997 by Technical Committee 14 (TC 14 "Gases in Glass") of the International Commission on Glass (ICG). The present paper reports the conclusions of the final discussion, highlighting the issues on which consensus was reached (IR spectroscopy is suitable to monitor the water content; the water content of conventionally fired Containers is 300 to 400 ppm and daily oscillations are moderate; water, redox and sulphur interact mutually; water lowers the viscosity; the influence of water content variations on the radiative thermal conductivity is moderate) and the still controversial issues (influence of water and hydroxides in the batch on the final water content; influence of water in the batch and atmosphere on the redox State of the glass; influence of oscillations of OH level on the workability; influence of OH level on ease of forming, product quahty and strength).