中碳钢疲劳试验的磁记忆检测

金属磁记忆检测技术是无损检测领域新兴的检测手段,由于其具有独特的检测理念,被期望能够在铁磁性金属构件早期损伤阶段即进行准确的无损检验工作,但是该技术仍处于发展初期,需要开展大量基础性研究工作来探究其机理和应用范围.通过不同加载方式的疲劳试验,研究疲劳载荷作用下中碳45钢试件磁记忆信号的变化情况.研究表明:指定疲劳方式下试件磁记忆信号随疲劳循环次数增加呈现规律性变化;磁记忆检测高载疲劳损伤的能力优于低载疲劳损伤,对含缺陷试件疲劳损伤的判别强于无缺陷试件.分析磁记忆现象的成因,认为疲劳作用促使试件受载薄弱区域位错应力场形成和成长,使该区域磁畴分布明显异于正常区域,进而以特殊磁信号形式表现出来.试验表明:磁记忆检测技术有助于评判金属材料的损伤情况,但评判的准确性会受到加载条件和试件形貌等多种因素的影响.

MAGNETIC MEMORY TESTING FOR MEDIUM CARBON STEEL UNDER THE CONDITION OF FATIGUE EXPERIMENT

Metal magnetic memory testing technology is a new kind of testing method in the field of nondestructive testing. With special testing concept,it is expected to accomplish veracious nondestructive testing job for ferromagnetic metal work pieces in the early damage phase.Owing to the immature development of metal magnetic memory testing technology,a lot of basic researches about theory and application range of this new technology need to be carried out.The change of magnetic memory signals for medium carbon 45 steel is studied by a variety of fatigue experiments.The research shows that magnetic memory signals varies regularly in the special fatigue mode.The magnetic memory,testing technology can test the high-load fatigue damage better than it can do for the low-load one.It has better ability of testing defect specimens than that of testing the smooth ones.Furthermore,the cause of formation of magnetic memory phenomenon is analyzed.It is deduced that it is the fatigue action that results in the formation and development of dislocation stress fields in the weak region of loaded specimens and arises obviously different distribution of magnetic domains between these weak regions and normal regions,and these special regions can be found by special magnetic signals.Experiments reveal that,magnetic memory testing technology is useful to judge damage state of metal materials,but the judge veracity may be influenced by a variety of factors,such as the condition of loading and specimen shape.