X80管线钢不同缺陷类型的磁记忆检测试验研究

为探究X80管线钢不同缺陷类型的力磁耦合特性,设计了平板试件与穿孔、边缘切槽3种不同试件,通过金属磁记忆检测方法对X80管线钢试件不同缺陷类型的磁记忆信号特征进行了试验研究.采用材料试验机对试件导入不同程度的塑性损伤与应力集中,通过光学应变测量系统获取试件表面的实时应变情况,同时采用磁记忆检测仪对试件表面诱发磁场的法向分量与切向分量进行卸载离线检测.结果表明:随着塑性损伤程度的增加,无缺陷试件的磁记忆信号法向分量与切向分量从平缓趋向波动,但未出现明显的峰值;含穿孔与切槽试件磁记忆信号法向分量在缺陷处出现过零点与反对称双峰,切向分量出现单峰值,并且渐趋明显.初步探究了X80管线钢塑性损伤与磁记忆信号之间的关联性,为油气管道塑性损伤程度的无损定量评价奠定了基础.

Experimental investigation on metal magnetic memory testing of different defects in X80 pipeline steel

In order to investigate magneto-mechanical coupled effects of different types of defects in X80 pipeline steel, characteristics of metal magnetic memory signals of three kinds of specimens under different loads (i.e., plate specimen, perforated specimen, and grooved specimen) were experimentally studied. Different levels of plastic strain were introduced to specimens through multiple loading times. Strain distribution of specimens was measured through opt ical measurement system, and the normal and tangential components of magnetic memory signal were off-line detected by magnetic memory detector after unloading. The experimental results indicate that the magnetic memory testing signal of the plate specimen tended to fluctuate with increasing plastic strain, but no peak occurred. While zero crossing point and anti-symmetric peaks appeared in the normal components of the signals of the perforated and grooved specimens, and the tangential component had a single peak at the position of defects. These features became more obvious with the increase of plastic strain. This research preliminarily investigated the correlation between plastic strain and magnetic memory signal, which lays a foundation for the nondestructive quantitative evaluation of plastic strain in X80 pipeline steel.