Breakage Behavior Of Float Glass And Low-E Glass Under Thermal Loading

The breakage of building glass causes great damage under the thermal loading, especially in fire condition. The fracture was influenced by many factors. In order to realise these factors more deeply, an experimental apparatus for studying the breakage behavior of glass under thermal load was established, which can setup many conditions to study the factors effect on fracture.Using this appratus, firstly, the factors screening experiments were carried out to select the significant factors to the glass fracture under thermal loading. Three most important factors(glass thickness, roughness of glass edge, heating rate) and two important factors(plate sides of glass, width of the shaded area) were found. After that, experiments with changing level of a single significant factor were done to get the impact evaluation. Additionally, 2 types of glass (float glass and Low-E glass) were used to compare the results. It was found that:1. Most of the 1st breakage happened in the upper part of the glass, and more frequently occurred in the middle of the upper edge. This phonoment may becaurse of the high temperature air in the enclosed apparatus.2. Condersidering the factor of the glass thickness, the impaction of 5 different thicknesses to the 1st cracking of float glass were studied. It was found that the 1st brekage time, the temperature difference between the center points of glass surface, the average temperature difference of 1st breakage between the surface center point of fire side and the shaded point of ambient side in the glass surface, and the thermal stress of 1st breakage will increase with the glass thickness increase.3. Condersidering the factor of the roughness of glass edge, there are only 2 levels: edging and no edging in the study. It was found that float glass with edging is more heat-resisting than that of no edging float glass.4. Condersidering the factor of the heating rate, the impaction of 5 different heating rates to the 1st cracking of glass were studied. It was found that the 1st brekage time will decrease when the heating rate inrecrease in both float glass and Low-E glass. The temperature difference between the center points of glass surface, the average temperature difference of 1st breakage between the surface center point of exposing fire side and the shaded point of ambient side in the glass surface, the thermal stress of 1st breakage will increase with the increasing heating rate of the float glass, but for Low-E glass, these parameters will increace to a peak value with the heating rate of 15 oC/min and then decrease.5. Condersidering the factor of the width of the shaded area, the impactions of 5 different widths on the 1st cracking of glass were studied. It was found that the width factor is more important to temperature of the point in the shaded surfuce of ambient side, it will decrease with the width increase for the float glass, and it will firstly decrease and then increase for the Low-E glass. But this factor has little influence on the 1st brekage time, the temperature difference between the center points of glass surface, the average temperature difference of 1st breakage between the surface center point of exposing fire side and the shaded point of ambient side in the glass surface and the thermal stress of 1st breakage.Taking the figures from the experiments of float glass and Low-E glass both with the volume of 600×600×6mm3, it was found that the figures are more fit to the Weibull distribution which contain 2 parameters or 3 parameters. And that shows the the Weibull distribution can be used to decribe 4 important parameters in the 1st craking of glass which are the 1st brekage time, the temperature in the center point of fire side surface, the average temperature difference of 1st breakage between the surface center point of fire side and the shaded point of ambient side, the thermal stress of 1st breakage. The function of Weibull distribution, survial probability,failure probability and the probability density function are given in the articl. It was also found from the research of the 4 parameters in statistics that the values of 4 parameters are lower of float glass than that of Low-E glass in the same failure probability, which means Low-E glass is more heat-resisting than float glass.Finally, a software which is based on finite element method and coded with Fortran language is developed by us to simulate the glass breakage and crcak growth. The results are compared with experiments both by us and by other people given in the article. It was found the simulation results are coinciding with the experiments.