Flux Pinning-Induced Stress in a Long Hollow Cylindrical Superconductor Restricted by a Metal Tube

End notched flexure (ENF) experiment using three-point bending beam specimen is a very convenient test configuration to evaluate the mode-II fracture toughness of composites. High-temperature superconductor (HTS) tapes are multi-layered composite that have been widely used in magnets and cables. HTS tapes are manufactured at room temperature ([Formula: see text][Formula: see text]300 K) but are used in the liquid-nitrogen temperature (77 K) environment. The large temperature change leads to large shear stress which may cause delamination of HTS tapes. In this paper, a closed-form expression of energy release rate (and therefore the stress intensity factor) for mode-II fracture of HTS tapes with thermal effect is developed based on the end notched flexure specimen. Results show that HTS tapes in working condition are prone to delaminating. Increasing the thickness of Hastelloy layer can reduce the energy release rate of mode-II cracking thus increase the interface strength. In the design of HTS tapes, the silver and copper layers are used to enhance the stretch of the HTS tapes. While silver and copper layers will increase the energy release rate for mode-II crack. This fact indicates that thicker silver and copper layers are not always good from the fracture mechanics point of view. The results of thermomechanical model and fracture criterion model of this research are useful for determining mode-II fracture toughness of superconducting composites for high-temperature applications.

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A double cantilever beam incorporating cohesive crack modeling for superconductors

Wang

et al. 2020

Mod. Phys. Lett. B

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In this paper, a double cantilever beam (DCB) specimen incorporating cohesive crack is developed for superconductors which have potential applications in high temperature superconducting cables in space solar power station. The cohesive interface is introduced along the crack front of the DCB model under electromagnetic force. The load-separation relation (i.e. the crack opening displacement) is used as the fracture mechanics parameter and the corresponding curves during fracture process are obtained and verified by the finite element numerical method. Results show that the presence of tensile electromagnetic force makes crack propagate easily. Superconductors with small cracks have good adaptability to the oscillation of magnetic fields while that with large cracks are easier to fracture during the descent of the magnetic field. In addition, the ductility ratio of the cohesive interface can significantly increase the fracture strength. The length of fracture zone decreases as the crack length increases.

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Flux Pinning-Induced Stress in a Long Hollow Cylindrical Superconductor Restricted by a Metal Tube

Cited by 4 publications

References 19 publications

Numerical modelling and analysis of current induced stresses in REBCO coil stacks

Numerical modelling and analysis of current induced stresses in REBCO coil stacks

An end notched flexure specimen model for mode-II fracture of high-temperature superconductor tapes with thermal effect

A double cantilever beam incorporating cohesive crack modeling for superconductors

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