Fracture analysis of Arc-shaped interfacial crack between a superconducting cylinder and its functionally graded coating

Superconducting materials have a vast range of applications in several fields courtesy of their distinct properties. The use of these materials, however, is faced with various challenges such as fracture failure among others. Due to this problem, many different studies have been directed on crack analyses, especially in cylindrical superconducting composites. Although their magnetoelastic behaviors have been achieved through pre-existing research works, little is still known about their fracture properties of the interfacial cracks.

Compared with the existing crack problems in superconducting cylinder, it is a challenge for the fracture analysis on an interfacial crack between a homogeneous superconducting cylinder and its functionally graded superconducting coating.

Research conducted at Shijiazhuang Tiedao University in China by Professor Wenjie Feng and his PhD student Zhen Yan was aimed at establishing a novel mechanical model for an arc-shaped crack along the interface between a homogeneous superconducting cylinder and its functionally graded superconducting coating subjected to the action of transport currents along the symmetry axis of the superconducting cylinder. Their work is published in the journal, Composite Structures.

In their paper, by adopting the generalized Irie–Yamafuji model in the cylinder and the newly established extended generalized Irie-Yamafuji model in its coating, both the flux and current density distributions in the composite are given clearly in the processes of both transport current ascent and descent. On the other hand, the stress intensity factors and energy release rates at crack tips are further given in concise forms and numerically calculated by solving a system of linear algebra equations

Feng and Yan successfully uncovered some new phenomena concerning fracture properties that were initially not known to a good number of researchers. For instance, during current transport accent, the crack easily propagates and grows, while in the process of transport current descent, the propagation and growth of the crack come to a halt. Besides, the bigger the crack opening angle is, the easier the crack propagates. Also, either increasing the shear modulus graded index of the superconducting coating or decreasing the introduced critical state model parameters can impede crack propagation and growth.

According to the authors, the study will help in advancing the design, manufacturing, and applications of superconducting composites materials.