Shear stress peaks in a superconductor cable during the winding of a large toroidal field coil

The paper presents a simplified elastica conductor model (SECM) built by a finite chain of intervals with constant bending moment and curvature. The problem does not allow to linearize the curvature. A bilinear moment-curvature relationship as derived from bending experiments was used to describe the elastoplastic behaviour of the cable under different tension forces acting on the ''free'' end near the supply spool. Due to the geometric and material nonlinearities mentioned no direct solution is possible. The paper describes the discrete model as well as the iterative shooting method which finds the equilibrium shape of the conductor. The distributions of bending moment and shear forces on the D-shaped contour as well as along the conductor are given. They show a pronounced influence of the tension force in the relevant range of 1 to 40 kN. An inconsistency due to compromising model simplifications is shown which occurs at the contour points where the curvature radius suddenly changes. Remarks on the elastic springback of the superconductor observed there conclude the paper