Wound roll stress analysis including air entrainment and the formation of roll defects

Abstract

Numerous procedures have been developed to determine the stresses inside wound rolls of film. These typically use factors such as winding tension, film thickness and film properties to calculate the stresses. The calculation presented here includes provisions for entrained air and methods to predict the formation of common roll defects. The entrained air pressure, the air gap and the winding tension are used to fully define the surface boundary condition during winding. Incipient buckling criteria are developed to predict deformations induced by transverse and circumferential stresses. the results include radial pressures, circumferential and transverse direction stresses, buckling defect formation indicators and the entrapped air pressure for the plane-strain case.