Investigation of quality of high-resistive coatings of superconducting wires with acoustic emission method

Monitoring of materials, processes, and technologies by measuring acoustic emission

“…In this connection, the criteria of the unsteadiness for a specimen as a whole (in stretching) and for the external fiber (in twisting) coincide, and it is possible to optimize the structure of the conductor by the results of tensile tests. The vulnerability of the conductor to damage can be evaluated directly in twisting by measuring the AE, whereas the plasticity margin after the twisting can be evaluated by analyzing the strain diagrams and the AE due to stretching the conductor [ 13]. The suggested methods for controlling the damage of conductors in twisting and evaluating the retained plasticity margin in stretching by measuring the AE have been used together with the described results for improving the manufacturing process of composite superconductors.…”

“…The approach developed has been realized in control over the plasticity of multifiber composite superconductors 0.5 -1.5 mm in diameter with 7500 -44,500 niobium fibers in a bronze matrix [13]. The technology of their production is quite complicated and includes repeated cold drawing, twisting, and finishing drawing to the requisite size.…”

“…The measuring of AE together with metallographic, electron microscopic, and fractographic analyses made it possible to determine the main stages of plastic deformation and cracking and estimate the vulnerability of the conductors to damage in various stages of twisting [13].…”

“…The method of acoustic emission has been successfully used for studying the nucleation and propagation of surface cracks in layers with a variable toughness (for example, in carburized layers of steels [I1]) in thin (0.5-3 ~tm thick) layers of chromium protective coatings on superconductors [12], in corrosion cracking of pipes from zirconium alloys under stress [21], in brittle fracture of conductors from HTSC-ceramics [14], and in many other cases.…”

“…In the last 15 years, the Department of Metal Science and Strength Physics of the Moscow Institute of Steel and Alloys headed by M. A. Shtremel' has created methods and means for measuring AE and accumulated a great amount of practical experience in using the rnethod of AE for solving many important problems of metal science, for example, design of sparingly alloyed, cold-resistant, high-manganese steels [1-5], creation of zirconium alloys with a high fracture toughness, improvement of the technology for manufacturing channel and shell pipes from zirconium alloys for nuclear reactors [6][7][8][9][10], increasing the crack resistance of hardened surface layers and protective coatings [11,12], advancement of the technology for manufacturing multivein superconductors for large magnetic systems, and design of the technology for manufacturing superconductors from high-temperature superconducting ceramics (HTSC ceramics) [13,14].…”