Browsing by Author "Sedlacek, Gerhard"

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    stress distribution in thermally tempered glass panes near the edges, corners and holes : Part 1. Temperature distributions during the tempering process of glass panes
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Laufs, Wilfried; Sedlacek, Gerhard
    While theoretical and experimental analyses of temper Stresses within the central areas of glass plates, i.e. for the theoretically "infinite plate", have been carried out in the past, the distributions of the induced Stresses near the edges and holes have yet to be examined in order to give a complete description of the stress field in the entire plate. The build-up of temper stresses depends on the temperature distribution as a function of time. For this reason, in part 1 of this paper the two- and three-dimensional cooling phenomena during the tempering process have been studied for all zones of a pane by means of analytical Solutions of the equation of heat conduction as well as by means of a discrete Simulation (Finite Element Method). The latter method allows for studying the temperature distributions in the vicinity of arbitrarily shaped holes. The influence of the tempering parameters (coefficient of heat transfer) and of the material constants on the temperature distribution is described, too. Part 2 of this paper deals with the induced distributions of temper stresses resulting from the thermal history of glass plates as defined in part 1.
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    stress distribution in thermally tempered glass panes near the edges, corners and holes : Part 2. Distribution of thermal stresses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Laufs, Wilfried; Sedlacek, Gerhard
    With temperature profiles during the thermal strengthening process determined in part 1 of this paper, the distribution of thermal stresses for the central area, near the edges and holes of the glass plates are calculated numerically with the help of a fmite-elementsimulation (THERVO PRO) which models the formation of temper stresses with time. Comparison with existing experimental data for the central area (zone 1) shows very good correspondence with numerical results. For zone 2 (edge), at about a distance d away from the edge, a somewhat reduced surface compression due to membrane stresses is observed. At zone 2 and zone 3 (corner) surface compression is found parallel to the edge surfaces, since due to equilibrium requirements there is no thermally induced stress perpendicular to the surfaces. In general, near the edge and corner stress distribution is three-dimensional as well as around zone 4 (hole). The hole with a cone has a certain difference compared with a cylindrical hole: it does not have a reduction of tangential surface compression at some distance from the hole on the cone side.