金属磁记忆检测技术是一种可早期检测铁磁构件应力集中程度的新方法,但进一步定量评价和广泛应用的瓶颈问题是复杂的应力磁化反转特征.对40Cr钢圆棒试件在不同最大拉力下进行反复加载-卸载拉伸试验,测定试件表面某确定点处漏磁场与拉应力的关系.试验结果表明,当试件处于弹性变形阶段时,漏磁场强度与拉应力的变化规律为线性关系;当试件受力超过屈服强度时,漏磁场强度与拉应力的变化规律变为折线,表现为先减小后增大再减小的应力磁化反转现象.随着最大拉力的增大,应力磁化反转极值点位置向较高拉应力方向移动,漏磁场强度最大变化量△Bmax也逐渐增大.
Metal magnetic memory testing is a novel method which can early detect stress concentration level of ferromagnetic components,but the bottleneck problem of further quantitative evaluation and widely application is the complex stress-magnetism reversal characteristic.A repeated loading-unloading tensile test was applied to round bar specimens made of 40Cr steel under different maximum tensile and the relation between the leak magnetic field at certain point on the surface and tensile stress was measured.The results show that the law of the change between the surface leak magnetic field at certain point and tensile stress is a linear relation in elastic deformation stage.When tensile exceeds yield strength,the law of the change between the surface leak magnetic field at certain point and tensile stress is a polygonal line,appearing a stress-magnetism reversal phenomenon:decreasing firstly,then increasing and decreasing again.With the increase of the maximum tensile,the extreme point of stress-magnetism reversal moves to higher tensile stress and maximum variation △Bmax of leak magnetic field increases as well.
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