EFFECT OF NONUNIFORMITY OF CRITICAL CURRENT DENSITY ON ELECTROMAGNETIC MECHANICAL PROPERTIES OF SUPERCONDUCTING THIN STRIP

Abstract
High temperature superconducting materials have attracted many attentions in the field of science and technology due to their outstanding advantages such as high current carrying capacity and low AC loss, etc. However, a series of electromagnetic mechanical problems in practical applications seriously hinder its development in the field of engineering technology. Thusly, a superconducting thin rectangular strip is considered to transport current. The influence of the inhomogeneous critical current density on the electrical and mechanical properties are analyzed. The critical current density is assumed to distribute nonuniformly along the width of the superconducting thin strip, then the analytical expressions for the induced current and magnetic field in the thin strip are developed. Based on a superconducting critical Bean model, the analytical expression of the flux pinning force is obtained. The plane stress method of the elastic theory is adopted to calculate the flux pinning stress and strain, then the magnetostriction in the superconducting thin strip are obtained. The simulating results show that: the nonuniformity of the critical current density has no influence on the distribution law of the flux pinning force induced in the superconducting thin strip, the same as the flux pinning stress and strain do. However, the nonuniformly distributed critical current density increases the penetration depth of the trapped magnetic flux. The value of the maximum compressive stress is also increased, and its position approaches to the center of the thin strip when the transport current increases. The maximum tensile stress appears in the thin strip when reducing the transport current from its maximum value, and its value decreases with the decrement of the transport current. The shape of the magnetostriction curve changes when the distribution of the critical current density is inhomogeneous, and its maximum value is less to that with homogeneous critical current density. All in all, the influence of the inhomogeneous critical current density cannot be neglected during the study of the superconducting materials.

