激光熔覆试件疲劳过程磁记忆检测试验研究

运用金属磁记忆检测技术对激光熔覆试件进行应力评价。对激光熔覆试件进行疲劳试验,检测不同疲劳周次试件表面的磁记忆信号法向分量H_p(y)和切向分量H_p(x),观察不同疲劳周次的磁记忆信号特征,分析法向分量梯度偏离程度R随着疲劳周次N增加的变化规律。结果表明:随着N的增加,H_p(y)曲线均呈顺时针旋转,R值先缓慢增加、后迅速陡增;运用R值作为参量将熔覆试件的损伤程度划分为三个等级,确定试件的安全阈值分别为2.82和9.4。当R值达到9.4的阈值时,试件处于临界断裂状态,应及时干预,确保其安全服役。基于磁弹性效应和裂纹扩展磁机械效应探讨了熔覆试件应力的磁记忆评价机理。

Experimental study of laser cladding specimen during fatigue by magnetic memory methods

For achieving the stress evaluation of laser cladding specimen based on metal magnetic memory testing technology,Fatigue tests of laser cladding specimen are carried out.Meanwhile,the magnetic signal is measured through the fatigue tests.The normal component of magnetic signal Hp(y),the tangential component of magnetic signal Hp(x),changing with fatigue cycle time are investigated.The magnetic memory signal characteristics of different fatigue cycles were observed.Analyze the changing law of the degree of gradient deviation of normal component,R,with the increase of fatigue cycle.The results indicate that,As N increases,the Hp(y) curve rotates clockwise,The R value increases slowly at first and then rapidly.The damage degree of laser cladding specimen was divided into three grades by using R value as the reference quantity.The safety thresholds of laser cladding specimen were determined to be 2.82 and 9.4.When R value reaches the threshold of 9.4,the specimen is in critical fracture state,and timely intervention should be made to ensure its safe service.The mechanism of stress evaluation of laser cladding specimen is discussed from viewpoint of the magnetoelastic effect and magneto-mechanical effect of crack propagation effect.