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Impact of mandrel support on core Ec

Gerhardt, T. D.
Rykard, D.
Yang, Y.
Over the past 15 years, Sonoco has conducted solid mechanics research focused on structural behavior of spirally wound, paper tubes. The scope of this program has included experimental, numerical, and analytical mechanics approaches as documented in references (1-9). As is well known from published winding models, core outside diameter stiffness (Ec) is incorporated into the analysis through a boundary condition. We have previously published proper Ec values for paper tubes (4) and, at the last OSU International Web Handling Conference, described a method to experimentally measure Ec (9). However, all published Ec data was collected on cores that were supported on the ends, but had minimal radial support in the test zone. In the field, many winding processes utilize an expandable mandrel that supports the core along its entire length. Our recent research suggests that these support conditions can have a significant impact stiffening the core wall and increasing Ec. As Ec is changed, expected stresses in the wound roll are altered. In this paper, we describe a new experimental method capable of measuring Ec data for cores supported by mandrels found in some field applications. To collect this data, we modified the test device described at the last conference. We also present a Finite Element model that quantifies core stiffening from mandrel support.