【摘要】 通过对优质碳素钢做疲劳拉伸实验,研究在交变应力作用下,铁磁材料的表面磁场强度垂直分量的变化.实验研究表明:磁场强度垂直分量过零点不能完全表征应力集中位置.磁场强度梯度的变化与疲劳循环次数有一定关系.随着加载及应力循环次数的增加,沿试件轴线方向各点的磁场强度出现一定的规律性变化,前期各点变化趋势基本一致,当试件出现微小裂纹时,以裂纹点为分界出现相向变化,在远离裂纹的测点也存在同样的趋势.扩展成宏观裂纹时,裂纹处及端面达到磁饱和状态,产生较强的漏磁场,磁场强度在裂纹两侧出现正负两个区域,出现过零点.更多还原

【Abstract】 This paper presents the research on the change of the vertical component of surface magnetic field of ferromagnetic materials observed during the tensile fatigue experiment of high quality carbon steel.Our experiments show that the stress concentration point cannot completely be determined by the zero point of the vertical component of the magnetic field.However,it has been observed that the magnetic filed strength gradient is related to the frequency of the fatigue load cycle.When increasing the load and frequency,the values of magnetic field strength along the axis of the sample show regular changes.The change of magnetic field strength at each sampling point displays basically the same trend during the initial stage.When tiny crack begins to form in the sample material,the magnetic field strength around each crack shows significant change.The trend of such change can even be observed from those sampling points far away from the cracks.As soon as a macro crack has formed from the tiny cracks,the magnetic field reaches saturation at the crack and on its surfaces,which results in the leakage of magnetic field.The strength of magnetic field has a zero point at the crack,and a region of positive strength on one side of the crack and a region of negative strength on the other side.更多还原