Date of Award
Master of Science
Madhu S. Madhukar
Don W. Dareing, John D. Landes
Presently, one of the most promising sources for a future of abundant, low-emission, and efficient energy comes in the form of nuclear fusion. However, in order for it to become a reality, fusion technology must overcome the obstacle of plasma confinement. Utilizing the tokomak based design for magnetic plasma confinement; ITER is currently developing a fusion reactor to prove its commercial viability.
The purpose of this research was to determine the feasibility of pulling toroidal field cable with a press-fit grip sleeve that utilizes friction to generate a gripping force. Such a design is being considered by ITER to integrate (join) 800 m long sections of superconducting cable and conduit for use in toroidal field plasma confinement coil construction. In order to see if friction alone had the potential to withstand the required pulling load, eight grip sleeve samples were subjected to monotonic tensile loading until failure (sleeve slippage) occurred. It was also important that the grip could withstand the variable loading that will likely occur during the pulling process due to friction between the cable and conduit. Therefore, a period of cyclic loading, prior to tensile loading, was incorporated into the testing regimen. Based on the results of each experiment, additional modifications were made until the sleeve’s gripping strength exceeded that of the weld joint used in the design, meaning the physical limitations of the grip sleeve had been reached. Once the design was optimized, additional samples were tested under identical conditions to establish repeatability. In addition, Finite Element Analysis was used to obtain better insight into the deformation behavior of the cable.
Based on the findings of this research, it was determined that a 300 mm long press-fit sleeve with a 25.4mm long reinforcement grip ring is capable of supporting a 116 kN (26,000 lbf) to 126.5 kN (28,500 lbf) tensile load, with little to no adverse effects from fatigue testing. Since this value exceeds the 8,000 lbf load used by a Japanese team to perform this same task, it can be concluded that the press-fit grip design is capable of performing the required cable pull with a generous safety factor.
Hayes, Paul Michael, "Use of a Press-Fit Grip Sleeve for Cable-In-Conduit Superconductor Integration: Effects of Tensile and Fatigue Loading. " Master's Thesis, University of Tennessee, 2010.