裂纹的交流电磁场检测与反演研究

【作者】 胡书辉；

【导师】 张世昌；

【作者基本信息】 天津大学 ， 机械电子工程， 2004， 硕士

【摘要】 本文探讨了交流电磁场检测技术（ACFM）起源、技术原理和研究现状，通过实验的方法测定了裂纹缺陷上方电磁场的分布情况。在建立ACFM数值模型时考虑了影响磁场的众多因素，并对ACFM的数值模型进行了理论验证，该模型可以对裂纹进行数据仿真计算。在对ACFM研究的基础上，探讨了电流的强度、频率、材料的磁导率和提离对检测磁场信号的影响，通过研究得出结论，交流电磁场检测技术与其它检测技术相比多种因素对ACFM检测结果均不敏感，这为产品的开发和应用奠定了基础，提供了依据。通过对大量不同尺寸的半椭圆形裂纹的模拟计算和实验结果相比较对模拟计算进行了实际验证。在大量检测数据的基础上得出裂纹上方磁场分布与裂纹尺寸形状之间关系的规律，以此规律为基础，采用查表和插值的方法，构造出裂纹尺寸的反演算法。最后本文借助于Bx磁场信号的畸变形状与裂纹形状之间的相似性，推出了工件二维表面裂纹形状的反演算法，该算法简单易行，并且克服了一般反演问题中常见的不适定问题。更多还原

【Abstract】 This paper discusses the origion and theory of the alternating current field measurement and constructs numerical model through the numerical simulation method with the three-dimensional finite element analysing software ANSYS, which has stong ability in finite element analysis. At first,in order to get magnetic distribution in the vicinity of the any crack the general numerical model of ACFM is built using a low-frequency formulation software developed by ANSYS, which can obtain the with irregular shape. Then, in order to offer some suggestions on production design and use, the study on the effects due to lift-off, material properties , intensity and frequency of current on the measurements are discussed based on this model, which shows that, compared with the others testing methods, ACFM is not sensitive to the above factors. Through a large number of testing result semi-elliptical cracks,the rules of magnetic signals and crack size are concluded. Furthermore, an inversion algorism to evaluate the surface-breaking crack size is put forward based on above rules using the interpolating method. At last, the inversive algorism of 2-D surface crack shape reconstruction is put forward according to the similarity between spatial distributing of magnetic field and surface-breaking crack shape, which is simple and avoids the ill-posedness of general inversion problems.更多还原