非牛顿流体拉膜过程中膜厚及自由面的分析

Analysis of film thickness and free surface in non-Newtonian fluid film-drawing process

采用一种特殊夹具装置将基板与旋转流变仪相连,利用旋转流变仪对提拉速度以及浸渍时间进行调控,实现提拉镀膜实验的自动控制;利用高速摄像机对整个提拉镀膜过程进行拍摄记录,并采用流体力学软件对提拉镀膜过程进行数值模拟,从而研究提拉速度对提拉过程中基板的受力、液膜厚度以及自由面形态的影响。结果表明:随着提拉速度的增大,基板竖直方向受力及液膜厚度均逐渐增大,而自由面逐渐降低且动态弯月面区曲率显著减小;相同实验条件下采用数值模拟和分析基板受力的方法求得的膜厚与高速摄像机测得膜厚有很好的一致性,表明两种方法均具有可行性;通过对实验所得数据点进行曲线拟合,发现膜厚与提拉速度的0.68次方成正比。

A special fixture was used to connect the substrate with the rotational rheometer,and automatic control of the film-drawing experiment was realized by using the controllability of the pulling speed and the immersion time of the rheometer.The whole process of film-drawing was recorded with high-speed camera,and numerical simulation of the film-drawing process was carried out by using hydrodynamics software,for purpose of studying the influence of pulling speed on the stress on substrate,the thickness of liquid film and the shape of free surface in the pulling process.Results indicate that,with the increase of the pulling speed,the vertical force on the substrate and the liquid film thickness increase gradually,while the free surface lowered and the curvature of the dynamic meniscus region decreased significantly.Under the same experimental conditions,the film thickness obtained by numerical simulation and force analysis of the substrate was in good agreement with that obtained by high-speed camera,which proved the feasibility of the two methods.Through the curve fitting of the experimental data points,it was found that the film thickness was directly proportional to the 0.68 power of the pulling speed.