Estimation of the stress state of axially tensioned Bi-2223/Ag tapes

Axial tension test is often used in characterization of superconductor tapes. However, because of the thermal stresses and composite nature of the conductor, the stress distribution in the tape cannot be directly obtained from the measurement. Here, a computational procedure based on two-dimensional finite element method was developed in order to model the multi-axial stress distribution in Bi-2223/Ag tapes during cooling from the annealing temperature to measurement temperature and in axial tension test. In order to increase the compatibility with other codes the method was implemented in Matlab/Femlab environment. Elastic and elasto-plastic material models with temperature dependent Young's modulus and yield strength were used for superconductor filaments and for silver matrix. The uncertainty of Young's modulus of the filaments complicated the computations and made it necessary to perform calculations with several values. With a justifiable choice of the modulus, the results corresponded well with the measured ones. A comparison to the widely used one-dimensional analytical model showed that both models predict principally similar stress curve for the measurement.