磁记忆检测技术在压力容器上的应用

Application of Magnetic Memory Testing Technology on Pressure Vessel

针对磁记忆检测技术在压力容器检验应用过程中存在的信号识别混乱、易误判等问题,分析了在载荷作用下,表面缺陷、埋藏缺陷等不同缺陷类型以及点状、面状和体积型等不同缺陷性质的磁记忆信号产生规律,并且分析了典型缺陷的磁记忆信号特征。结果表明:面状缺陷可以通过磁记忆信号的梯度值、幅值和曲线特征来进行定位和判断,其他类型缺陷的识别度较低。在载荷作用下,磁记忆信号随缺陷扩展端的应力状态而变化;在缺陷扩展期间,磁记忆信号的梯度值和幅值与应力值呈单调递增关系,缺陷扩展端应力释放后,磁记忆信号也随之下降。结合不同检测方法的结果比对,建立了以梯度值、幅值、峰峰值及环境磁场值为参数的磁记忆信号评价方法,明确了磁记忆检测技术在压力容器上的适用范围和检测对象为活性缺陷和应力集中区域的检测。

Magnetic memory testing（MMT）technology has been wildly used in metal component on stress concentration and defect detection.In order to resolve the problem that it is difficult to identify the damage MMT signal and the misinformation often appears,the rules of magnetic memory signal of different types（including surface defects and inner defects）and different nature（including punctuate,planar and volumetric defects）while being under different load conditions according to the actual pressure vessel operation have been studied.The characteristics of typical defects magnetic memory signal are analyzed.The results show that the planar defects can be identified and located by the gradient,amplitude and the curvilinear character of magnetic memory signal,whereas the other types of defect is hard to distinguish.The magnetic memory signal changes with the stress situation of the defect extended edge under loads.The gradient and amplitude of magnetic memory signal increase monotonically with increasing stress value during the defect extending and fall after the stress released.Compared with the results of different NDT method,the evaluation method of magnetic memory signal of typical defect is put forward by the appraisal parameters with reference value,and the appraisal parameters including the gradient,amplitude,the peak value and the environmental magnetic field value.The application scope and object of MMT in pressure vessel are defined and limited to inspect the active defects and stress concentration zone.