Improvement of the SUPERCOIL system code. Pt. 2

This report describes the part of the NET/84-042/PH contract relating to fatigue problems with TF coils due to the influence of the poloidal magnetic field. A model is developed on the basis of the crack growth rate concept which allows the lifetime of TF coils to be predicted. The stresses induced in the TF coils by the PF magnetic fields are calculated with an analytical model. The first step in the model is to calculate the magnetic force per unit length produced in the TF coil by the poloidal magnetic field. The second step is to calculate the induced stresses by considering realistic lateral support structures. With these additional stresses (additional with respect to the static stresses produced by the TF field), the maximum tolerable number of cycles is determined by the Paris law. Within the analytical model use is made of a further design driterion following from torsional moment yielding shear stresses. The accuracy of the analytical model is tested with finite-element calculations. (orig.)