The mechanical design of coils for generating high magnetic fields. A comparison between analytical results and results obtained by use of finite element methods

The mechanical behaviour of a wire-wound high-field coil was calculated using a finite-element program. If simplified assumptions for the elastic and plastic properties are made, the results for the stresses in the mid plane are identical to those from our earlier (analytical) calculations. The mechanical model used in the finite-element calculations for the elastic properties is based on existing theory for composite materials. The plastic behaviour, however, is directly calculated for the two separate materials. From calculations using more realistic material properties it emerges that the simplified analytical calculations gave conservative estimates of the stresses. Further it appears that the maximum field is not only limited by the strength of the material, but that the maximum strain of the wire has also to be taken into account