One-Dimensional Dynamic Impact Model to Predict Hardness of Wound Rolls

Abstract

Wound Roll quality measurement plays a crucial role in predicting defects inside a wound roll. The quality of a wound roll is measured in terms of its hardness. A Rho Meter is one such instrument which measures the hardness of a wound roll in arbitrarily chosen unit called Rho. The Rho Meter works on the principle of impact. The peak force exerted by the striker of the Rho Meter onto the surface of the roll is measured by the accelerometer on top of the striker and is converted into arbitrary units called Rhos. The dependence of the Rho hardness of a wound roll on its radial modulus was studied. The moving components of the Rho Meter were modeled. The wound roll was modeled using a pre-existing code (Roll Compressor) that can predict the deformation response of a wound roll due to an external contact. These sub models were combined to produce a 1-D dynamic model that could predict the maximum deceleration of the Rho Meter striker which could then be converted to Rho units.The model made fairly good predictions of the hardness of the wound rolls. These predictions were validated with experimental results obtained by center winding rolls at constant but varied tensions. Also the case of variation in hardness values with variation of pile heights of wound rolls was studied. The deviation of the hardness values predicted by the 1-D code from the experimental values can be corrected by including the factors such as the dynamically varying pressures, radial modulus, shape of the Rho Meter striker and interlayer slippage at the locality of impact. Also by refining the mesh of the Roll Compressor, better results can be obtained but requires longer computational times.