Mechanical Behavior of Impregnated REBCO Pancake Winding Based on Electromagnetic-Thermoelastic Analysis

In this study, the mechanical behavior of an impregnated single pancake wound with a REBCO coated conductor is analyzed in magnetic field after its cooling through finite element (FE) modeling. A two-dimensional axisymmetric FE model with averaged material properties of the impregnated winding is developed. First, the thermal residual stress and deformation accumulated during cooling from 300 K to 4.2 K are analyzed. Using the thermal residual stresses and strains as initial conditions, the mechanical behavior of the impregnated winding under the self-field and background field are subsequently studied. Finally, the contribution of the thermal mismatch stress as well as the Lorentz force under the self-field and background field to the radial stress of the impregnated pancake winding is discussed, and the risk of delamination failure under each situation is evaluated. The results show that the radial stress due to the thermal mismatch increases with the decrease of cooling temperature. As the transport current increases, the radial stress decreases under the self-field, but increases under the background field. The discussion indicates that there is the potential risk for delamination failure during cooling, and the risk increases with the decrease of temperature. If delamination does not appear after cooling, the winding will not be damaged owing to interfacial debonding under self-field. However, the risk of delamination failure increases upon increasing the transport current under a strong background field.