An analysis to minimize the amount of spring back after coiling of helicalsteam generator tubes

The spring back phenomena occurring in the coiling process of a steam gener ator tube induce dimensional inaccuracy and make the coiling procedure diff icult. In this research, an analytical approach has been carried out to eva luate the amount of spring back for helical steam generator tubes. The mode l was developed on the basis of beam theory and elastic-perfectly plastic m aterial properties. This model was extended to consider the effect of plast ic hardening and the effect of the tensile force on the spring back phenome na. Parametric studies were performed for various design variables of steam generator tubes in order to minimize the spring back in the design stage. A sensitivity analysis has shown that low yield strength, high elastic modu lus, small helix diameter, and large tube diameter result in a small amount of spring back. The amount of spring back can be controlled by the selecti on of adequate design values in the basic design stage and reduced to an al lowable limit by application of a tensile force to the tube during the coil ing process. (C) 2001 Published by Elsevier Science Ltd.