Numerical Analysis of Mechanical Behavior for a 9.4-T Whole-Body MRI Magnet

A whole-body high-field MRI magnet is being constructed. A compensation solenoid method was employed to design the coil configuration for the magnet. In order to manage the mechanical stress, we sectioned the long solenoid into six windings, and they were wound on five aluminum alloy mandrels. Four compensation coils were wound outside of the long solenoid windings to compensate the field inhomogeneity of imaging region. Preliminary analysis used by a simplified method has been conducted to estimate the stress levels and coil deformations. Furthermore, a finite-element method (FEM) was used to obtain the stress distribution of the magnet structure fully. The electromagnetic stresses, the sliding behavior, and the quench dynamic stresses were simulated by these FEM models. The cumulative stresses caused by winding pretension and thermal contractions were used as initial stresses to calculate the frictional stresses for the interface contact analysis. The quench-induced stresses and deformations of thermal shields are also discussed. The results are exploited to conduct mechanical design and construction of the magnet.