Study on the Development of Axial Stresses in Wound Rolls

Abstract

The primary objectives for this thesis were to establish if axial stresses associated with winding are sufficient to cause corrugation failures and verify if a 2-D winding model accurately predicts stresses seen in a roll that were obtained experimentally. In order to validate the model, machine direction and cross machine direction strains were measured experimentally during the winding process. Two different widths of web were tested, a 6 inch and a 24 inch wide web. Model stresses were converted to strains and a comparison was made between experimental strains and model strains. The 2-D model used made a good prediction of machine direction strains when compared with experimental results. This agreement was made possible by adding a negative bending strain value to machine direction strains obtained experimentally. The model was verified with cross machine directions strains for the 24 inch wide web, but not the 6 inch. The 24 inch web was approaching a plane strain condition; therefore the model is verified for conditions where plane strain conditions exist. A conservative critical axial stress equation was used to aid in predicting corrugation failures in the roll. According to the equation, corrugations should have appeared in the 24 inch roll, but not the 6 inch roll. When performing experiments, corrugations were not observed in either width of roll. The critical axial stress equation used did not account for the stiffness of the web material that was supporting the outer layer of the wound roll, explaining why corrugations were not seen.