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Investigation of the Effect of Voids on the Stability of Webs

Sandesh, Mallya
Webs such as paper or plastic films may have holes of various shapes cut into them as a part of the manufacturing or converting processes. These webs might still have to be transported through the web process machinery for further processing. Handling of such materials becomes difficult as the stress distribution varies across the web at the cross section of the hole. When this variation of stress travels down the web with a hole, it can cause troughs and wrinkles in the web as the web crosses the roller. The goal of this research is to study how these holes affect the web's propensity to wrinkle. It was observed that the void in the web generates a compressive cross machine direction stress in webs passing over rollers. When this cross machine direction stress exceeds the critical value of the compressive stress for a particular material, the web buckles over the roller and generates a wrinkle. It appears that among an elliptical void and a circular hole of comparable dimensions, the elliptical void is worse than a circular hole in terms of generating wrinkles. The effect of voids on instability behavior of webs has been successfully predicted. If the shape of void present in the web is insignificant, the void shape generating least cross machine direction stresses can be used.