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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Prony series spectra of structural relaxation in N-BK7 for finite element modeling
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Prony series spectra of structural relaxation in N-BK7 for finite element modeling

机译：N-BK7中结构弛豫的Prony级数谱用于有限元建模

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摘要

Structural relaxation behavior of N-BK7 glass was characterized at temperatures 20 °C above and below T_(12) for this glass, using a thermo mechanical analyzer (TMA). T_(12) is a characteristic temperature corresponding to a viscosity of 1012 Pa·s. The glass was subject to quick temperature down-jumps preceded and followed by long isothermal holds. The exponential-like decay of the sample height was recorded and fitted using a unique Prony series method. The result of his method was a plot of the fit parameters revealing the presence of four distinct peaks or distributions of relaxation times. The number of relaxation times decreased as final test temperature was increased. The relaxation times did not shift significantly with changing temperature; however, the Prony weight terms varied essentially linearly with temperature. It was also found that the structural relaxation behavior of the glass trended toward single exponential behavior at temperatures above the testing range. The result of the analysis was a temperature-dependent Prony series model that can be used in finite element modeling of glass behavior in processes such as precision glass molding (PGM).
机译：使用热机械分析仪（TMA），在此玻璃的T_（12）之上和之下20°C的温度下，对N-BK7玻璃的结构弛豫行为进行了表征。 T_（12）是对应于1012Pa·s的粘度的特征温度。玻璃先经历了快速的温度下降，然后又保持了长时间的恒温。记录样品高度的指数式衰减，并使用独特的Prony系列方法进行拟合。他的方法的结果是拟合参数图，揭示了四个不同的峰或弛豫时间的分布。随着最终测试温度的升高，弛豫次数减少。弛豫时间并未随温度变化而明显变化;但是，Prony权重项基本上随温度线性变化。还发现，在高于测试范围的温度下，玻璃的结构弛豫行为趋于单指数行为。分析的结果是一个与温度相关的Prony系列模型，该模型可用于精密玻璃成型（PGM）等工艺中玻璃行为的有限元建模。

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