含缺陷承载门式刚架的金属磁记忆检测试验研究

Experimental study on metal magnetic memory testing of carrying gable frame with defects

以门式刚架拟静力试验为基础,采集并分析了含缺陷刚架的梁和柱在不同荷载等级下的法向磁信号H p(y)值,研究试件未退磁状态下法向磁信号H p(y)值随荷载变化的规律,以及预制缺陷与磁信号的对应关系.结果表明:试件初始剩磁场强度较大,试件表面的磁信号在数值上虽然会随着荷载的变化而变化,但磁信号曲线在形状上会保持初始剩磁场的分布状态,直至外应力能够克服残余应力的影响;试件到达临界状态时,即试件刚度急剧退化、屈服或者失稳时,法向磁信号H p(y)值会发生突变或反转;磁信号曲线在节点、缺陷附近由于应力集中表现出波峰波谷.因此,可以通过磁信号的突变、反转、波峰、波谷、过零点反演试件的受力状态、应力集中和缺陷的位置.

Based on the pseudo-static test of the defected gable frame,collecting and analyzing the beams and columns′normal magnetic signals of H p(y)value under different load levels.The specimen is not demagnetization,the law of H p(y)value changing with load and the relationship between prefabricated defects and magnetic signals were studied.The results show that the initial residual magnetic field strength of the specimen is large,and the magnetic signal on the surface of the specimen will change with the changing of load in value,but the magnetic signal curve will maintain the distribution of initial residual magnetic field in shape until the external stress can overcome the influence of residual stress.When the specimen reaches the critical state,such as the stiffness of the specimen is sharply degraded,yielding or unstable,the H p(y)value of the normal magnetic signal will be mutated or reversal.The magnetic memory signal curve at the node and near the defect shows the peak and trough due to the stress concentration.Therefore,the stress state,stress concentration and defect location of the specimen can be retrieved by means of magnetic signal mutation,inversion,wave peak,trough and zero crossing point.