摘要
随着科学技术的快速发展,人们对产品质量的要求越来越高,构件的质量检测由常规的宏观缺陷检测发展到缺陷源的早期诊断。国外学者经过潜心研究,于二十世纪九十年代提出一种新的检测技术—磁记忆检测技术。与常规检测技术相比,磁记忆检测技术具有快速、无外加磁场及检测成本低等优点。但由于该技术发展历史短暂,从技术原理到检测装备研发,再到实际应用,还有许多问题尚待研究。本文结合中国南方机车车辆集团公司科技项目“磁记忆技术在铁道车辆重要件检测中应用研究”(2004 NCK 057),对磁记忆检测技术原理、装备研发及实际应用中的若干关键技术进行了理论与实际应用研究,深化了对磁记忆技术的理解和认识,开发了磁记忆检测装备和磁记忆检测数据分析系统软件,为磁记忆检测技术的实际应用提供了技术保证。
磁记忆检测的原理实际上是磁弹性和磁机械效应共同作用的结果。依据铁磁学原理,探讨了地磁效应使铁磁构件产生磁性的机理,研究了铁磁构件在磁弹性及磁致伸缩效应的共同作用下产生磁记忆效应的机理。解释了磁记忆技术能够检测、确定构件缺陷及应力集中部位的原因。研究认为磁记忆检测技术是对铁磁构件进行早期诊断唯一行之有效的无损检测方法。
基于磁记忆检测技术原理,设计了磁记忆检测装置的工作原理及内部结构组成。提出了既可以检测记录Hp (y)值,也能够记录漏磁场梯度变化|Kσ_Z|值的设计思路,方便了检测人员对检测构件的分析判断。另外,对检测装置的硬件电路和软件系统及检测探头分别进行了分析研究和设计,特别是对检测探头的关键组成——磁敏传感器进行了详细分析研究,最终设计制造出了磁记忆检测装置,并成功实现了产品化。
结合磁记忆检测技术数据记录特征,并根据VB编程语言理论,开发了基于Microsoft Windows的迅速、简便、功能全面的磁记忆检测数据处理软件系统。该数据处理系统可以将数据记录导入特定的数据库,对数据记录进行方便的管理,还可以与通用的excel进行交互,最终将数据记录以直观形象的方式进行多种图表类型的显示,并可以进行一些数学的分析,为深入研究磁记忆技术的实际应用提供了科学工具,具有很大的实际应用价值。
通过试验及实际应用研究、分析,认为对于特定构件,一定存在判断该构件存在缺陷或存在应力集中及潜在缺陷的漏磁场梯度|Kσ_Z|值,提出了以漏磁梯度|Kσ_Z|值作为判据来判断构件存在缺陷或应力集中及潜在缺陷的新方法。
在对部分试样的应力状态进行ANSYS有限元分析后,进行了拉伸试验和磁记忆检测试验。并在不同缺陷试件、不同检测路径、不同检测方向、不同材质钢材对磁记忆检测影响的试验研究的基础上,归纳出了一些对实际应用非常有指导意义的结论,并对结论进行了理论分析研究。通过分析,认为构件的应力集中与应变会导致所在部位的漏磁场出现规律性的变化,即应力集中处漏磁场的梯度具有最大值,而且塑性较差、屈强比较高的材料更容易在缺陷处产生大的漏磁场梯度值|Kσ_Z|。另外,随着轴向拉伸力F的增大,试样缺陷处漏磁场的法向分量的最大值Hp(y)max减小,最大漏磁梯度|Kσ_Z|值减小,塑性变形后下降趋缓,但更为稳定。
通过磁记忆技术在铁道机车车辆车轮辐板孔、钩体、钩舌、钩尾框等重要构件及焊缝检测中的应用研究,并与磁粉探伤、X—射线探伤及解剖结果进行了对比,建立了磁记忆检测与磁粉探伤、X—射线探伤检测结果对应关系。研究表明,当KσZ值分别≧50和≧100时,采用磁记忆技术检测辐板孔和车钩,其检测结果的准确度和可信度优于常规磁粉探伤方法;当|Kσ_Z|≧50时,采用磁记忆技术检测焊缝,其检测结果的准确度和可信度优于常规X—射线探伤方法,并对其进行了验证。同时验证了磁记忆检测技术在铁磁构件检测中的适用性。
As the development of the science and technology, the quality of products become more and more important. The focus of the inspection goes from the macroscopic imperfection to its source prediction. After the diligent study of the scholars from abroad, as a new detective technology, the Metal Magnetic Memory Testing (MMMT) was found in the 1990s of 20th century. Compared to the normal detective technologies, the MMMT has many advantages such as high-speed, non-externally applied magnetic field and low cost. However, because of the short development history, not only equipment but also the practical application of the MMMT need to be further studied. In the background of the project titled“The application research of the MMMT on the important components of the railway vehicle(2004 NCK0 57)”supported by China South Locomotive and Rolling Stock Industry (group) Corporation, the mechanism, equipment and application of MMMT are studied in this dissertation. The data processing system(DPS) is also developed. Then, the technology support for the practical application was provided.
The cooperative action of the magnetostriction and the magneto-mechanical effect makes the mechanism of the MMMT. The geomagnelic effect, magnetostriction and the magneto-mechanical effect on ferromagnetism items were analysed based on the theory of ferromagnetism. The reason why the MMMT can find the defects and stress concentration zone was explained. The investigation shows that the MMMT is the only effective method which can give the early diagnosis of the ferromagnetism items.
The components of the MMMT equipment were designed based on the basis of the mechanism. It makes smoothly for the operators to analyze the results by measuring the Hp(y) and its gradient change |Kσ_Z|. In addition, the hardware circuit, system software and the detector are studied and designed. Specially, the the magnetic sensor which considered to be the most important component of the MMMT detector is analyzed thoroughly and studied. After the research and design of the all parts, the MMMT equipment was manufactured.
The data processing software system which based on the Microsoft Windows of the MMMT was developed. The DPS have many advantages such as high-speed, easy to use and powerful function. The system can not only keep track of the date but also analyze it by the present data processing method such as Excel. It also can give many displays in vary kinds chart and carry some mathematics calculation and analysis. All in all, the DPS provides a scientific tool for the MMMT and have a important value for the practical application.
The experiment and the analysis of the MMMT with differernt component were carried out. The result shows that the |Kσ_Z| on the defects and stress concentration zone were unique. The new method using gradient change of magnetic leakage field |Kσ_Z| as criterion is used to determine the defects and stress concentration zone in this dissertation.
Some useful conclusions were sumed up after analyzing the effects of MMMT signals of samples with different notches, scanning route, geomagnetic field direction and the different steels. Thorough the analysis, the regular change of the |Kσ_Z| was found follow the change of the stress concentration zone. The maximum of the |Kσ_Z| appeared on the most stress concentration zone. The plastic and pliable materials were consideed to have the less |Kσ_Z|. Over and above, both the normal component of the magnetic leakage field (Hp(y)max) and the |Kσ_Z| became smaller in contrast to the increase of the F in axial direction.
The relation between the magnetic particle testing, X-ray testing, destruction testing and MMMT was found out through the application research on wheels, bridge, bolster guide of the railbound vehicles and the welding seam. The results showed that the accuracy of the MMMT was better than the normal magnetic particle testing in the testing of the radials holes and the coupling gears when the |Kσ_Z| surpassed 50 and 100 respectively. The accuracy and credibility of the MMMT was also better than the X-ray testing in the testing of welding seam when the |Kσ_Z| surpassed 50. In short, the application of the MMMT was confirmed to be suitable in the engineering field.
引文