Magnetization is of great importance for the application of bulk superconductors. Flux jumps are frequently-encountered challenges during magnetization, leading to sharp temperature rises and material failure, and eventually affecting the field trapping capability of bulk superconductors. Intrinsically, the flux jumps and mechanical failure induced by thermomagnetic instability are coupled with each other, which makes the numerical simulation of the magnetization of bulk superconductors a challenging task. In this paper, a numerical simulation framework is developed based on my previous work (Jing 2020 Supercond. Sci. Technol. 33 075009), which further couples the H-formulation and the phase-field fracture model with the heat diffusion equation to simulate the flux jump and mechanical failure behaviors of bulk superconductors during magnetization. The experimentally observed features of the flux jumps are reproduced, and the corresponding mechanical failure is evaluated. The magnetic field, temperature, stress/strain, and mechanical failure within the bulk sample are presented. It is found that the varying ramp rate of the pulsed field significantly influences the flux jump behaviors of bulk superconductors. The optimum characteristic time t0 of the pulsed field for the final trapped field is predicted through numerical simulations.

中文翻译：

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脉冲场磁化过程中大块超导体的热-磁-机械不稳定性行为的耦合多物理场建模

磁化对于体超导体的应用具有重要意义。通量跳跃是磁化过程中经常遇到的挑战，会导致温度急剧上升和材料失效，并最终影响体超导体的场捕获能力。从本质上讲，热磁不稳定性引起的通量跳跃和机械故障是相互耦合的，这使得体超导体磁化的数值模拟成为一项具有挑战性的任务。在本文中，基于我之前的工作（Jing 2020）开发了一个数值模拟框架超导。科学。技术。 33075009)，它进一步将 H 公式和相场断裂模型与热扩散方程耦合，以模拟块状超导体在磁化过程中的通量跳跃和机械失效行为。重现了通过实验观察到的通量跳跃特征，并评估了相应的机械故障。介绍了散装样品中的磁场、温度、应力/应变和机械故障。发现脉冲场的变化斜坡率显着影响体超导体的通量跳跃行为。最佳特征时间 吨0 通过数值模拟预测最终捕获场的脉冲场的大小。