On-line continuous measurement of rolls' coefficient of restitution

Abstract

This paper reports on the development of a novel technique to measure on-line rolls' coefficient of restitution or "springiness". The ratio of speed of separation to speed of approach in an elastic collision is termed the coefficient of restitution (Cr). The Cr sensor is based on the concept of an elastic collision of a steel object being freely dropped onto the web, as a roll is being wound, from a known height in the direction normal to the contact surfaces and rebound to a measured elevation. An important feature of this is the relationship between the rebound height and the in-roll stresses. The sensor returns the value of Cr as a function of roll radius. The latter can accurately be calculated from the data acquired via the sensor. The results indicate that the Cr values are complex and produce dramatic changes near the roll core. Further investigations are underway to verify the results and their interpolation in terms of the direct relationship with the in-roll stress and other parameters that may contribute to changing the roll springiness.