Modeling the influence of web thickness and length imperfections resulting from manufacturing processes on wound roll stresses

Imperfection in thickness and length result from web manufacturing processes such as forming and coating. Webs are stored in wound roll form as they await subsequent processing. Herein an axisymmetric nonlinear winding model is developed. Results from this model will show how small imperfections in web thickness and length can lead to substantial residual stress variation in the wound roll. These stress variations can lead to partial or entire loss of the web in the wound roll. The results from the winding model can be used to determine what winding conditions can be used to mitigate the residual stresses. The results can also be used to determine practical limits for web imperfections to prevent residual stresses in the wound roll from producing material loss. Results from the model will be compared to test data on webs wound in the laboratory to verify the model and to generate an awareness of the magnitude of the problem.