铁磁性材料拉/压疲劳磁记忆信号研究

为探索金属磁记忆信号变化的物理本质,研究不同类型的疲劳载荷对磁信号的影响,首先利用金属磁记忆的基本原理对磁信号的产生过程进行分析和预测,然后对低碳钢Q345分别进行拉伸和压缩疲劳试验,比较不同循环周次下的磁信号法向分量曲线;分析不同检测点在拉伸、压缩疲劳循环中的磁记忆信号变化规律;并从磁畴和位错的角度解释了磁信号在整个疲劳阶段的变化情况。结果表明:在1个循环周次的作用下,检测线的磁信号发生了很大变化;随着加载循环周次的增加,磁信号法向分量Hp(y)整体上保持顺时针旋转,拉伸试件在接近断裂时的磁信号幅值急剧增大;对拉伸及压缩疲劳试件,均可通过磁信号法向分量平均值Hp(y)ave表征应力集中和疲劳损伤程度大小,并且损伤积累参数ΔHN可以用来判断试样所处的损伤阶段。

Research on magnetic memory signal of ferromagnetic material under tensile and compressive fatigue loading

To investigate the physical mechanism of metal magnetic memory signal variation,the impact of different fatigue loads on the magnetic signal was discussed.The excitation process of magnetic signal was analyzed and pre-dicted by relative fundamentals.The low carbon steel Q345 was tested under the tensile and compressive fatigue load,the magnetic signal curves under different loading cycles were compared,and the magnetic signal variation during the fatigue process was analyzed and explained in the view of magnetic domain and dislocation.Results show that magnetic signal on the scanning lines changed greatly after one cycle,and the curve of magnetic signal main-tained clockwise rotation on the whole during the fatigue tests.When the specimen is about to fracture,the magnet-ic signal amplitude increases sharply.The mean value of magnetic signal normal component Hp(y)ave can be used to indicate the stress concentration and the fatigue damage degree of the specimen under both the tensile and com-pressive fatigue loading,and the value of accumulative damage parameterΔHNcan be used to predict the phase of fatigue crack growth.