Determination of wound roll structure using acoustic time of flight measurement

Abstract

Roll structure measurement is presently done with destructive and intrusive measuring devices, such as FSR's or with specially instrumented winders. These methods are generally limited to research and development applications. Prior to this paper, there was no method of non-destructively determining the structure of a roll with unknown winding conditions.

This paper presents a measurement technique that uses thru thickness acoustic time of flight measurements to determine roll structure, an extension of the work done by J. David Pfeiffer [1] and alluded to by L. Eriksson [2] and D.R. Roisum [3]. A measurement is made of the time required for an acoustic wave to travel through the roll. This time of flight measurement is used as an extra degree of freedom in a winding model such as Z. Hakiel's [4] to replace an unknown or questionable model input, such as radial modulus or winding tension. The roll structure is determined by adjusting the model input until the calculated time of flight matches the measured time of flight.

The measurement technique was verified by comparison with two other independent methods. Each method was used to map the radial pressures in the left and right sides of six different wound rolls. Excellent results were obtained with the Acoustic Gage, when winding tension was used as the adjustable parameter. The excessive pressures predicted by winding models, the excellent results obtained by adjusting winding tension in the Acoustic Gage and the indication that stack tests produce accurate radial modulus data, cast doubt on the validity of the hoop stress boundary condition.