Mathematical modeling of the wall effect on drag forces in molding flow using optical fiber sensing data

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• 作者：Lo ; Yu-Lung ; Lai ; Hsin-Yi ; Tsai ; Ming-Hong
• 关键词：Wall effect ; Molding flow ; Drag force ; Optical fiber sensors
• 刊名：Journal of Materials Processing Technology
• 出版年：2000
• 出版时间：January 1, 2000
• 年：2000
• 卷：97
• 期：1-3
• 页码：174-179
• 全文大小：270 K

文摘

This paper studies the wall effect on drag forces in molding flow using optical fiber sensing data. The results indicate that the effect of the wall cavity is significant in the calculation of the drag forces and is required to be considered in molding. The study also shows the effectiveness of the approach in characterizing the behavior of the wire sweep in the encapsulation of semiconductor chips. An in-line fiber etalon (ILFE) sensor is designed and fused in the middle of the optical fiber for accurate strain measurement. This is done by first laying an optical fiber in the mid-plane of a simple rectangular mold cavity, and then measuring the strain at the mid-span of the optical fiber that is subjected to the flow of homogeneous fluid. For a given flow field, several drag force models have been used to calculate the drag forces over the optical fiber. The resulting strain of the optical fiber is estimated analytically first by FEM and then compared with experimental results. To study the wall effect, different sizes of mold cavities are employed for different b/a ratios and used in Takaisi’s model. Subsequently, Takaisi’s model is then modified to comply with the experimental data obtained by using various b/a ratios for comparison with the numerical drag force model computed by Han and Wang. The result indicates that a modified Takaisi model in compliance with the requirement of b/a within the range 20–200 is in good agreement with the numerical model proposed by Han and Wang who had taken effect of the wall cavity into consideration for drag-force calculation. The modified model based on a smaller b/a value is somewhat closer to the numerical model in a higher average cavity velocity. The wall effect of molding flow is concluded to be an important factor for various tests conducted at a greater average cavity velocity or a smaller value of b/a.