Type of Document Dissertation Author Mbaruku, Abdallah Limbunga Author's Email Address email@example.com URN etd-03292006-174521 Title Electromechanical and Fatigue Properties of As-manufactured and Quench Damaged YBCO Coated Conductor Degree Doctor of Philosophy Department Mechanical Engineering, Department of Advisory Committee
Advisor Name Title Justin Schwartz Committee Chair Cesar Luongo Committee Member Peter Kalu Committee Member Peter McLaren Committee Member Simone Peterson Hruda Committee Member Keywords
- Fatigue loading effects
- Quench damage effects
- YBCO coated conductor
- Electromechanical porperties
Date of Defense 2006-03-17 Availability unrestricted AbstractSuperconductors are elements, inter-metallic alloys or compounds that exhibit zero resistance to electrical flow when cooled below their critical temperatures. Applications of these materials were stalled for 50 years after their discovery in 1911 because the physics of superconductivity was misunderstood. During applications, these materials must be operated within the superconducting critical surface to avoid quenching. As with all materials, they must also be operated within respective stress/strain limits to avoid electromechanical failure.
Applications of high temperature superconductors (HTS) have been explored since mid 1980ís. Most research has been done to develop power devices that will replace conventional conductors like copper and aluminum. Devices developed are generators, motors, transformers and superconducting magnetic energy storage systems (SMES). While efforts to develop superconducting power devices are made, manufacturers of the superconductors are working to improve the performance of the conductors.
When quenching occurs on superconductor, it may either cause complete or partial damage to the superconducting material. Furthermore, materials loaded monotonically behave differently when loaded in fatigue mode. This research has studied the effects partial quench damage and fatigue loads on superconducting behavior of YBCO coated superconducting tapes.
For partial quench damage study, a 180 mm long YBCO superconducting tape was subjected to controlled quenching. Prior to the quenching, critical currents (Ic) of known sections of the tape were measured. These are compared to the currents after the quench to identify sections that have damage. Sections with damage and non-damaged were then subjected to stress-strain, strain-Ic, and fatigue-Ic tests. Results from partial quench damaged and non-damaged samples are compared. For fatigue loading study, the YBCO samples were subjected to fatigue tests with strain ratios of 0.2 and 0.5 to 2x105 cycles. Critical current were measured before the start of the fatigue tests, and at some intervals of cycles during the fatigue tests.
This dissertation is about this work. Experimental approach, equipment used and results and conclusions are presented.
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