Fracture analysis of bulk superconductors under electromagnetic force

Self Cite

Single-grain GdBCO bulk superconductors have significant applications potential due to their ability to trap stable and large magnetic fields. The internal fracture of these bulk superconductors caused by Lorentz force and thermal load is a key issue in their practical applications. The aim of this work presented here is to investigate the mechanical behavior of the bulk superconductor during pulsed field magnetization. The H-formulation and heat transfer equation are used to obtain the electromagnetic force and thermal load in the bulk with and without defects. Numerical simulations show strong local enhancement of the electromagnetic load at the crack tips. Moreover, dynamic stress intensity factors at the crack tips are presented based on the two-dimensional state-based peridynamic theory. In addition, the crack propagation path is predicted. Finally, different dynamic crack problems are considered to discuss the influence of crack, void, inclusion, and hole on the mechanical stability of the bulk. Results show that defects increase the risk of damage of superconducting bulks.

Section: State-based Pd Modelmentioning

confidence: 99%

“…Recently, Ru et al [39] proposed a bond-based PD model to study dynamic fracture problems in bulk superconductors when subjected to electromagnetic force. However, they considered Poisson's ratio as = v 1 4 and neglected the thermal loading.…”

mentioning

confidence: 99%

Numerical simulation of dynamic fracture behavior in bulk superconductors with an electromagnetic-thermal model

Yong

Zhou

2019

Self Cite

“…Zeng and Zhou et al [15] studied the pressure distribution of an elliptical hollow cylinder with a single-value magnetic field. Besides, Ru et al [16] employed a 2D model based on Hmethod to simulate the dynamic defect growth of an elliptical hole in an HTS under the strong magnetic field, comparing the results with the magneto-optical experiments in a 2D space. The applied external field was still a uniform field.…”

Section: Introductionmentioning

confidence: 99%

“…As mentioned above, the researchers mainly used analytical methods [11][12][13][14][15] or finite element methods (FEMs) [16][17][18] to study the deformation and stress distribution of an HTS with an elliptical or circular cross-section hole in a homogeneous or static magnetic field. And the models they built are all 2D models.…”

Section: Introductionmentioning

confidence: 99%

Electromagnetic-thermal behaviors of bulk superconductor with cuboid slot under moving magnetic field

Yu¹,

Feng²,

Gu³

et al. 2020

We established a 3D coupled model to study the electromagnetic-thermal behaviors of a levitation system containing a bulk high-temperature superconductor (HTS) with a cuboid slot under the nonuniform magnetic field due to the movement of a permanent magnet (PM), analysing the influences of the geometrical parameters of the slot and inclination angle on the electromagnetic-thermal behaviors, giving the dynamic distribution of the global electromagnetic force density in the HTS. The results show that the longer the length of the slot, the smaller the levitation force, and the greater the loss. As its length takes up 7/10 of the HTS diameter, the loss is 4 times that of the HTS without damage. Due to the homodromous induced current appearing near the slot, the maximum guidance force increases with the length. The levitation force decreases with the increase of the slot depth. Its curve near the maximum becomes blunt and the loss increases significantly. As the depth is 3/5-4/5 of the HTS height, the loss is 300-400 times of that without damage. The guidance force and loss increase with the depth. As the inclination angle rises, the levitation and guidance force both drop. At 30 • , their maximums decrease by 70 % and 90 %, respectively. The lateral stability of the system thus becomes poorer, indicating the inclination angle is one of the important factors for instability. As the PM moves vertically, the guidance force density symmetrically distributes near the both wide sides of the slot. Its side faces with the wide sides will bear the shear force, resulting in that the slot has the tendency to tear along these faces. As the PM reciprocates laterally, the slot is subjected to the lateral shear force, proportional to the displacement.

“…Wu et al studied the mechanical behavior in high-temperature superconductors under PFM [46]. The fracture behavior of the bulk superconductors under PFM was also studied based on different methods, such as the peridynamic and phase-field methods [47][48][49].…”

Section: Introductionmentioning

confidence: 99%

Analysis of mechanical behavior in inhomogeneous high-temperature superconductors under pulsed field magnetization

Yong

Zhou

2020

Self Cite

Melt-textured large, single-grain REBCO (RE: rare earth element or Y) bulk superconductors have growth sector boundaries (GSBs) and growth sector regions (GSRs). The critical current density is dependent on the GSBs and the GSRs, which will influence the electromagnetic field and the temperature field distributions. REBCO bulk superconductors are brittle materials and during the manufacturing process, cracks and inclusions may exist, therefore it is necessary to analyze the mechanical response during the magnetization process. In this paper, the mechanical response of an inhomogeneous cylinder superconductor under electromagnetic stress and the thermal stress during the pulsed field magnetization process is studied. By solving the coupled magnetic and heat diffusion equations in association with a modified E − J power-law relationship, we can obtain the electromagnetic field and the temperature field distributions; then, the mechanical response of the bulk can be determined. The trend shown by our numerical simulation is consistent with the experimental results. Then we study the mechanical behavior of inhomogeneous high-temperature superconductors with and without a flux jump. The case without or with the SUS 304 ring is also analyzed.