构件低周疲劳损伤的金属磁记忆检测试验研究

对18CrNi4A钢缺口试件在三级应力水平下进行了低周疲劳试验和磁记忆信号检测,研究应力集中、疲劳损伤及疲劳应力对磁信号的影响规律。结果表明,利用磁信号Hp(y)曲线突变特征和磁信号梯度K曲线异变峰特征可表征试件损伤位置;采用H′p(y)=Hp(y)N-Hp(y)0的磁信号处理方式,磁信号H′p(y)曲线过零点与试件断裂位置重合,处理后的磁信号过零法可更有效的表征试件损伤位置;磁信号梯度Kmax值随疲劳损伤程度的增加而逐渐增加,反映了构件疲劳损伤程度,可表征试件疲劳损伤程度;磁信号与疲劳应力水平存在强烈的相关性,应力水平越大,磁信号值也越大。

Test Research on Low-Cycle Fatigue Damage of Parts by Metal Magnetic Memory Methods

Low-cycle fatigue tests of notched 18CrNi4A steel specimens were carried out under three different fatigue stresses, and metal magnetic memory (MMM) signals were detected. The effects of stress concentration, fatigue damage and fatigue stress on the MMM signals were investigated. The results show that fatigue-damaged locations can be predicated effectively according to the mutational characters of the MMM signal H_p(y) curve and K curve. It is found that the zero-crossing points of the MMM signal H′_p(y) curve(H′_p(y)=H_p(y)_N-H_p(y)_0) have the same positions as the fracture points, so it can be concluded that fatigue-damaged locations can be predicated more effectively by zero-crossing points. The absolute value of the MMM signal feature parameter K_(max) increases with the aggravation of the fatigue damage. The fatigue damage can be assessed effectively by the value of K_(max). In addition, there is an inherent relationship between the fatigue stress and the MMM signal feature parameters H_p(y)max, H_p(y)_(min) and H_p(y)_(sub); the larger the fatigue stress is, the larger the absolute values of the feature parameters are.