ドライヤー内における湿紙乾燥収縮のシミュレーション

第1報各湿紙水分における収縮応力と弾性係数の測定

抄録

When a wet web dries up in a paper machine dryer section, it shrinks depending on drying conditions. When the shrinkage during drying is larger, the dried web has a tendency to make a more elongation and be less stable when subjected to humid conditions.
The auther has demonstrated in the series of previous papers that there will be a farirly large moisture variation in the cross direction during drying, even when its final moisture profile is rather uniform. This result will suggest that the moisture variation profile in a cross direction during drying, may end up in the variation of shrinkage in a cross direction of the dried web, which may cause an uneven behavior in a cross direction under humid conditions.
In order to investgate this hypothesis, the finite element method will be a good tool. This method, however, requres two physical properties, elastic modulus and stress, which in this case is force generated by drying. Moreover, these two properties vary as a wet web becomes dry.
So, in the Part I of the series, these two properties are measured as functions of a web moisture, using a multi-purpose tensile tester with a procedur edeveloped for this measurement.
W: moisture content g·water/g·fiber
F: drying force kg/(0.1g·water/g·fiber)·mm²E: elastic modulus kg/mm²F=4×10 ^(-4.43×W) (W≥0.07)
F=0.5×10^(9.2×W) (W≤0.07)
E=11×W^-0.740
These data are obtained under the small stress of 0.03kg/15mm.
In the coming report, the web shrinkage variation profile in a cross direction will be discussed by the finite element method using above data.