The quick development of REBCO wires has allowed the construction of High Temperature Superconductor (HTS) insert magnets to reach DC magnetic fields above 30 T. These magnets are operated in liquid helium at 4.2 K to achieve the highest current density benefitting from the weak dependence of the critical current density of the superconductor on the magnetic field at high fields. The 32 T all supercondcuting magnet is such an example of a technology offered to users at the National High Magnetic Field Laboratory in Florida, USA. An other example of such insert magnet is the Little Big Coil (LBC) which holds the world record with the generation of a DC 45.5 T magnetic field. Those achievements mark a new path for devising technologies to reach ultra high DC magnetic fields using 2G HTS technology. However, there are still some challenges to overcome such as field stability and field quality and some issues related to the mechanical degradation of the 2G HTS insert to be addressed to ensure a safe and reliable operation. The mechanical degradation can originate either from the intrinsic dependence of the critical current and n index on the local strain or the low cleavage strength of the material. In both cases, quenches may be triggered at high magnetic field and high curent density leading to the inevitable loss of the magnet physical integrity. In the present work, we recall first the electromagnetic modelling of large scale 2G HTS magnets using the recent T-A formulation in 2D. Using the LBC as case study, a mechanical model coupled to the electromagnetic model is detailed. This new approach include the strain dependence of the critical current density and n index to unveil local degradations that may affect the screening currents ultimately rending the magnet unoperative.

Keywords: 2G HTS wires, Insert magnets, High magnetic field generation, Screening currents