In applications employing high-temperature superconducting conductors, various cyclic loading (fatigue) conditions produced by mechanical, thermal, or periodic electromagnetic forces are inevitable. Applying coated conductor (CC) tapes under fatigue loading conditions is expected to critically affect the long-term reliability of its superconducting performance. Most studies evaluating the mechanical and electromechanical characteristics use quasi-static uniaxial tensile tests. Few have focused on the characterization of CC tapes under fatigue loading. In this study, the electromechanical property characterization of Cu-stabilized GdBa 2 Cu 3 O y (GdBCO) CC tapes including fatigue behaviors were investigated at 77 K. High-cycle uniaxial fatigue tests were carried out on GdBCO CC tapes 4 and 12 mm in width, and the two were compared in terms of mechanical and electromechanical aspects at a stress ratio of 0.1. The mechanical and electrical fatigue limits of the CC tapes were determined at 77 K. The 4 mm wide CC tapes showed less fatigue limits when compared to the 12 mm wide ones. However, regardless of the CC tape width, the sequence in the obtained characteristic strengths at 77 K was the same: yield strength>irreversible stress limit>mechanical fatigue limit>electrical fatigue limit. Fracture surface morphologies were observed using scanning electron microscopy-energy dispersive x-ray spectroscopy and electron probe micro-analysis to clarify the fatigue fracture mechanism and to examine the influence of the architecture of the CC tapes on fatigue behaviors. Damage along the edges, caused by slitting during fabrication of the 4 mm wide CC tapes, generated a stress concentration, eventually resulting in earlier crack initiation not only on the substrate, reducing mechanical fatigue strength, but also on the superconducting layer, degrading the measured critical current.
Various test techniques have been established to investigate the electromechanical properties (EMPs) of CC tapes under external loads. The most conventional method is to examine variations in critical current, Ic, by repeatedly measuring the V-I curves while intermittently applying a load or deformation to the CC tape. The conventional methods for obtaining EMPs, such as the reversible limits for Ic degradation, require repeated measures of Ic in a loading-unloading scheme, and this entails considerable time and effort therefore, they must be improved for practical and engineering reasons. We recently developed an easy-to-use system that can continuously measure variations in Ic while applying a load or deformation to the CC tape, thereby evaluating its EMPs. The main advantages of the new measurement system are real-time monitoring of Ic behaviors during loading and allowing reduced the test time. While it uses a conventional test configuration, this new system continuously measures Ic through effective feedback control of the electrical-field voltage induced in the CC tape specimen during loading. Through this feedback control system, the Ic degradation behaviors in CC tapes resulting from possible cracking in the superconducting layer during loading are depicted. The reversible limits for Ic degradation were also determined. To assess the effectiveness of this newly developed measuring system, the applicability of the method was identified by evaluating the EMPs of various commercially available CC tapes. By comparing the results with those achieved using conventional testing, we found this to effectively evaluate the EMPs of CC tapes. The results showed that this system provides a simple way of evaluating the EMPs of HTS CC tapes by simultaneously measuring variations in Ic under load or deformation. It is much faster at depicting Ic degradation behaviors, and it elaborately determines the reversible limits of Ic induced in the CC tape during testing.
In order to recognize the allowable bending diameter in coils, the strain as function of diameters is evaluated. The irreversible strain limits of I c in the easy and hard bending modes were measured. Strains were calculated at the coating film in the easy bending and at outer edge or inner edge in the hard bending of the CC tape, respectively. The tape geometry subjected to bending procedures is considered from the current industrial spool winding operation. Through the linear superposition of strain induced in different bending modes regarding the expressions, the appropriate design for critical bending diameter is suggested. Results proved that the existence of buckling resulting from bending in hard direction when applied strain exceeded 0.6% is possible. The depicted results showed that the strain limit as a viable parameter should be considered for future purposes.
The increase in space exploration missions in recent years gave way to the development of a volume-efficient and cost-effective nanosatellite like the cube satellite (CubeSat) which can be developed and fabricated in a relatively short time. With its size and design, CubeSat parts like casings can be produced and assembled through 3D printing to produce inexpensive satellites. Research in this area is undeniably important to maximize the rapid development of CubeSats. While progress has been made, challenges remain in applying 3D printing technology in the development of CubeSats. In this paper, the current status regarding the advancement of 3D printing for CubeSat applications is discussed. First, important issues about the common materials for CubeSat and potentially 3D printing materials for CubeSats are addressed. Second, 3D printing CubeSat parts through the feasible structure design models by combining material and parameter designs are explored from a wide range of references. And also, 3D printing of cube satellite parts by DOST AMCen and STAMINA4Space has also been demonstrated. Lastly, an outlook on the future direction of the 3D printed CubeSat for the Philippines space program is provided.Keywords: Cube satellite, CubeSat, 3D printing, high-performance polymers
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