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传统的漏磁检测是经磁化后测量试样表面漏磁场的垂直分量再对拾取的信号量进行分析研究的方法,然而这种仅通过单一垂直分量特性来判定缺陷的方法易出现漏检、误判。针对该方法的不足,本研究采用了一种在测量漏磁场垂直分量的同时又提取并分析水平分量特性的二维检测方法,考虑到水平分量易受干扰信号影响,运用了矢量合成法提取水平分量,通过联合利用漏磁场的垂直分量存在过零点和水平分量具有最大值特性的方法来判断缺陷,并选取多种标准与自然试样进行试验研究。试验结果表明:采用漏磁二维检测可有效实施铁磁构件的缺陷检测,提高检测可靠性,可望有很好的实际工程应用前景。 相似文献
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This paper describes analytical expressions for the magnetic leakage field of two types of internal defects: two dimensional rectangular and elliptical defects as functions of the applied magnetic field strength, the defect size and the distance below the surface. In this study, the magnetic image effects from the spatial boundary and the defect boundary are taken into consideration. That is, the leakage field of rectangular-like defects or elliptically shaped defects ‘below the surface’ are derived by using the modified dipole model and image theory. The profiles and strengths of leakage fields calculated from the proposed analytical forms are presented under various conditions and compared with experimentally measured ones. 相似文献
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以激光对接焊的焊接缺陷为对象,研究基于数值模拟的焊接缺陷漏磁场的分析方法. 建立对接焊焊接缺陷检测的三维模型,利用漏磁场理论对比分析不同几何缺陷与漏磁场信号之间的关系规律,并用试验进行验证. 结果表明,裂纹的深度越深,磁感应强度越大,未熔合、凹坑分别随着角度、宽度的增大而磁感应强度减小,并且验证漏磁场信号可以作为焊接缺陷检测的依据. 采用RGB分割法对磁光图像进行分割并提取几何特征,用模糊C-均值聚类(FCM)对不同焊接缺陷进行识别,有良好的识别率. 相似文献
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测试分析新型电磁搅拌器内螺旋磁场和旋转磁场的磁感应强度、分布和作用规律,研究螺旋磁场对Pb-80%Sn过共晶合金凝固组织影响的作用机理,并与无磁场和旋转磁场条件下合金凝固组织的形貌特征及成分分布进行对比分析。结果表明:螺旋磁场相比于旋转磁场可以在铸锭内部更大区域内形成均匀搅拌,更易于破碎和细化枝晶组织,既能促进椭球或球状晶的生成,又能更好地改善宏观偏析;在频率一定的情况下,初生相晶粒尺寸随着励磁电流的增大而减小;当励磁电流为125A时,旋转磁场和螺旋磁场细化晶粒的效果最好;继续增大电流,晶粒产生粗化;螺旋磁场可基本消除成分偏析,并在较小励磁电流(100A)下达到采用旋转磁场(125A)时的最佳搅拌效果。 相似文献
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基于金属磁记忆检测方法,用实验室静态拉伸模拟无缝钢轨的缺陷的产生,利用EMS-2000金属磁记忆诊断仪对PD3无缝钢轨进行漏磁效应研究,获得PD3无缝钢轨在不同载荷下表面漏磁场强度法向分量Hp(y)和其梯度值K的分布情况。研究发现,随着载荷的增加,试样测量线上磁场强度及其梯度值呈规律性的变化。Hp(y)过零点与梯度K的极值点能够较好地表征样品应力集中位置的特征,Hp(y)幅值和梯度K的变化能反映样品应力集中程度。该试验表明金属磁记忆检测技术可以有效地应用于无缝钢轨应力集中位置和程度的判断。 相似文献
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M. Shamonin T. Beuker P. Rosen M. Klank O. Hagedorn H. Dtsch 《NDT & E International》2000,33(8):547-553
We investigate the feasibility of using rare-earth iron garnet films grown on (111)-oriented substrates as magneto-optic indicator films for the visualization of magnetic leakage fields in non-destructive evaluation. In most cases the leakage field of the defect has a strong component in the film plane. The influence of this in-plane dc magnetic field on the image formation is investigated. It is shown that the presence of a strong in-plane magnetic field allows one to extend the dynamic range of the out-of-plane field imposed by the uniaxial anisotropy field HA. On the other hand, an in-plane field reduces the sensitivity. The guidelines for selecting parameters of magneto-optic indicator films are given. 相似文献
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Magnetic flux leakage technique is used for defect detection inside a magnetically permeable bar by measuring the leakage fields outside the bar. Defects of varying sizes in a magnetically permeable bar have been modelled as localized anti-dipoles with different moments. These defect locations and moments have to be determined based on the measurement of the leakage fields in the presence of random noise. Multiple Signal Classification (MUSIC) approach has been used to identify the defect locations and the moments of these defects. After finding the location of the first dipole representing the larger defect, using orthogonal projection of the measured magnetic field data away from the first defect location, location of the next dipole is identified by MUSIC. This process is continued until all the defects are exhausted. The leakage fields from three deeply buried defects were simulated by direct forward calculation and the resulting data were utilized for inversion using this approach. It has been possible to identify the number of defects and their locations by this approach even in the presence of reasonable levels of additive noise. 相似文献
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A. D. Razmyshlyaev S. V. Yarmonov P. A. Vydmysh M. V. Ageeva 《Welding International》2016,30(6):463-466
The design of equipment for generating the transverse magnetic field in arc welding can be optimised by modelling the direct magnetic field produced by the device for generating (GD) the transverse magnetic field (TMF) by the electric field of the current flowing in flat models made of electrically conducting materials. The lines of force of the electric field in the flow of the current in the modelling medium correspond to the lines of force (induction lines) of the magnetic field generated by GD TMF. Using these modelling methods, it is shown that to obtain the maximum values of the transverse component of the induction of the magnetic field in the zone of the welding arc of the electrode droplet and liquid metal of the weld pool, the optimum design of GD TMF is the one in which the angle of inclination of the bars to the vertical is equal to 45° and the end surfaces have chamfers parallel to the plane of the welded sheets. 相似文献
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连铸空心管坯内置行波磁场对凝固组织的影响 总被引:1,自引:0,他引:1
利用低熔点Sn-3.5%Pb合金进行了空心管坯内置行波磁场的静态模拟实验研究。结果表明:管坯内置行波磁场可以引起金属熔体内部纵截面上的大环流,减小了熔体凝固前沿的温度梯度,降低了金属熔体的冷却速率,抑制了熔体的枝晶生长,从而促进了晶粒的球化,改善了管坯的凝固组织。 相似文献
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目的提高磁性磨具表面光整加工技术对30CrMnSi高强度结构钢表面的加工效率,解决以往永磁式磁性磨具光整加工中磁场强度弱、磁能利用率低的问题。方法首先对30CrMnSi导磁工件的材料去除机理进行分析,探讨了磁感应强度B对工件材料去除的重要性。然后基于海尔贝克阵列(Halbach Array)进行了磁场的设计,通过理论计算和仿真分析,确定了永磁单元尺寸和磁场布置方案。最后以自制粘接性磁性磨料,对30CrMnSi板材进行单因素光整加工实验。结果根据磁场计算和仿真结果,确定了Halbach Array永磁阵列两个周期为最佳的磁场布置方案,并获得了理想的磁场强度和最佳的磁场分布。对30CrMnSi板材的加工实验表明,粗糙度下降百分比(%ΔRa)随着磁极转速和磨粒目数的增大而增大;磁性磨料中铁磁相与磨粒相质量比为3∶1、磁极转速为500 r/min、磨粒目数为240目时,加工效果最好,获得了Ra=0.129μm的表面,粗糙度最大下降百分比为90.74%。结论使用HalbachArray的方法对永磁场进行设计,可以增大加工区域的磁场强度并改善磁场分布,从而提高对30CrMnSi高强度结构钢表面的加工效率。 相似文献