Based on stress-controlled fatigue tests of 45 carbon steel notched specimens, an in-situ comprehensive evaluation of fatigue damage evolution was accomplished via micromagnetic non-destructive testing techniques, and various magnetic parameters were then determined to describe the actual fatigue state. In general, the characteristics quantities extracted from magnetic hysteresis, Barkhausen noise and incremental permeability measurements exhibited a trend of initial oscillations during the early stages of fatigue, reflecting fatigue softening. As the load cycle increased, the magnetic parameters became stabilized and experienced drastic changes in the final stage before failure. Evidently, the dynamic dependence of fatigue magnetization behavior was related to the progressive accumulation of damage by the cyclic loading. Among those, the magnetic incremental permeability method was highly sensitive to the fatigue damage before a macroscopic crack was initiated. Particularly, the Mean eigenvalues of incremental permeability signals presented a nonlinear increment behavior, starting approximately from the 80 % of fatigue life, which could be used to assess the degree of damage quantitatively. Furthermore, the unique zero-crossing feature of Mean value at 94.2 % lifetime can serve as a warning for imminent fatigue failure of the component.

中文翻译：

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基于多微磁无损检测熔融法的中碳钢疲劳损伤早期检测与监测

在对 45 个碳钢缺口试样进行应力控制疲劳试验的基础上，通过微磁无损检测技术完成了疲劳损伤演变的原位综合评价，然后确定了各种磁性参数来描述实际疲劳状态。一般来说，从磁滞、Barkhausen 噪声和增量磁导率测量中提取的特性量在疲劳的早期阶段表现出初始振荡的趋势，反映了疲劳软化。随着负载循环的增加，磁参数变得稳定，并在失效前的最后阶段经历了剧烈的变化。显然，疲劳磁化行为的动态依赖性与循环载荷损伤的逐渐积累有关。其中，磁增量磁导率法对宏观裂纹开始之前的疲劳损伤高度敏感。特别是，增量磁导率信号的平均特征值呈现非线性增量行为，大约从疲劳寿命的 80% 开始，可用于定量评估损伤程度。此外，94.2% 使用寿命时的平均值的独特过零功能可以作为组件即将发生疲劳失效的警告。