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Effect of air entrainment in centerwound rolls

Good, J. K.
Holmberg, M. W.
Internal stress models for centerwound rolls have existed for over thirty years but no model to date has accounted for air which is entrained due to the web velocity and the viscosity of air. This paper reports the results of an experimental investigation in which the entrained air thickness was monitored on a centerwinding roll. The results confirmed that the air foil bearing theory was adequate for describing the amount of air entrained to a centerwinding roll. Knowledge of the amount of entrained air allowed the derivation of a reduced radial modulus of elasticity for the wound roll which when used with a wound roll model yielded results which compared well to experimental pressure data.