共查询到19条相似文献,搜索用时 46 毫秒
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通过试验确定了不同材质钢管的磁致伸缩曲线,得到了不同材质钢管缺陷检测的电磁超声传感器(EMAT)直流电磁铁的励磁电流与超声波幅值的关系,确定了最佳励磁电流,并得出其变化规律与磁致伸缩曲线变化趋势一致的结论。为电磁超声传感器设计和开发提供了依据。 相似文献
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磁致伸缩传感器技术探测钢管隔热层下腐蚀缺陷的研究 总被引:1,自引:0,他引:1
介绍西南研究院在磁致伸缩传感器技术用于钢管隔热层下腐蚀缺陷探测研究工作的进展,包括实验设施,实验结果和讨论,总结和建议。 相似文献
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磁致伸缩和磁记忆问题研究 总被引:9,自引:1,他引:9
从铁磁性材料的基本特性和最小自由能原理出发,探讨了应力和外磁场对磁性材料磁化状态的不同影响,讨论了磁致伸缩现象的规律和特点。用磁致伸缩方程组详细研究了磁记忆现象产生的条件和规律,分析了应力和地磁场在磁记忆现象中的不同作用。结论认为应力可改变材料的磁特性,地磁场则可改变材料的压磁性,两者共同作用产生净磁场,磁记忆现象不仅与应力和材料的磁特性有关,而且还与工件在空间的位置和方向有关。 相似文献
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对电磁铸造圆形感应器产生的磁场在金属熔体内的电磁作用力进行了理论分析和实验研究。指出导体中电磁作用力仅存在于径向及轴向方向上。电磁作用力的大小不仅与磁感应强度有关,还与磁感应强度的分布梯度有关;电磁有旋力是由于磁场分布不均匀造成的,其旋度方向在柱坐标系的周向方向上。试验研究分析了感应器结构、电流等工艺参数对电磁场分布的影响。 相似文献
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对电磁超声换能器法的发展历史沿革进行了回顾;在理论上对(?)值估算公式的推导过程进行了完善;最后指出了该技术目前所存在的问题。 相似文献
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在许多情况下,只应用一种NDT技术存在不足,这就迫使NDT操作人员使用一种以上的技术以保证检测出危害被检物使用寿命或功能的缺陷。但分别实施多种技术的检测,就会延长检验时间。介绍了一种新的NDT设施,采用两种不同的非接触无损检测技术进行互补,即电磁声换能器(EMAT)和脉冲涡流(PEC)探头。检测结果表明,脉冲涡流和电磁声换能器因是非接触,所以可应用于材料生产过程中的自动在线检验,也可用于在役检验。 相似文献
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电磁超声检测技术由于无需媒介以及与被测物体非接触,不但可提高检测效率,而且可将超声检测技术的应用扩展到高温、高速和在线检测。根据电磁超声传感器的工作原理,建立了基于有限元的电磁超声无损检测数值分析方法,开发了相应的计算程序,验证了其有效性。应用开发的电磁超声数值模拟程序,研究了不同激励方式对电磁超声波的影响,得到了相应超声波在均匀各向同性金属介质中的传播过程。该计算方法和程序为实际电磁超声检测中缺陷的定量和探头优化提供了手段。 相似文献
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Electromagnetic Acoustic Transducers (EMATs) are widely used in Nondestructive Evaluation (NDE) of metals, including the inspection of ferritic steels. Optimization of EMATs in ferromagnetic materials is often accomplished using computational simulations that account for the three main types of transduction mechanism, namely the effects of Lorentz forces, magnetization forces, and magnetostriction. The extensive literature on the Lorentz and magnetization mechanisms of EMATs has been historically scattered with alternative notations causing conflicting interpretations of the fundamental governing equations that often led to erroneous implementations of these equations in computational simulations. The purpose of this paper is to clarify this issue. The confusion is caused by the arbitrary nature of the separation of electromagnetic transduction force into Lorentz and magnetization components. This paper shows that apparently contradicting models are actually equivalent if the Lorentz and magnetization forces are chosen to correctly match each other, while mixing otherwise acceptable but mutually incompatible terms leads to unacceptable modelling errors. This paper also provides guidelines for the implementation of these transduction mechanisms in computational models for EMATs. 相似文献
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It this study, omni-directional shear-horizontal wave transduction is performed using a specially configured magnetostrictive patch transducer in a ferromagnetic plate. For a ferromagnetic plate, unavoidable magnetic flux leakage into the plate not only results in poor transduction efficiency but also generates unwanted waves within the plate. These problems must be overcome to inspect ferromagnetic plates using the transducer. Therefore, we investigate the reasons for the poor performance and propose a method to improve its performance. The effectiveness of the proposed method was validated through simulations and experiments. 相似文献
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Optimization of an excitation signal is proposed for long-range inspection of thin steel wires by ultrasonic waves. Due to its sensitivity to flaws normal to the axial direction, a longitudinal wave is a useful tool for flaw detection of wires. We can launch and detect longitudinal waves at arbitrary positions on the wire by using electromagnetic acoustic transducers. The broadband pulse is suitable for achieving high spatial resolution in locating flaws. However, the dispersion of the longitudinal wave distorts the waveform, and consequently decreases the apparent signal amplitude. If the effect of the dispersion is removed, the signal to noise ratio can be expected to be improved and the high flaw detectability can be obtained. In this study, we suggest using the optimum excitation signal, which has been modified to compensate for the dispersion during the propagation of the assumed path length. It is possible that the flaw, which occupies 10% of the cross-sectional area of the wire, can easily be detected from a distance of 10 m. 相似文献
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针对电力架空线路上金具球头挂环失效断裂原因,用不同热处理方式制备了一组显微组织不同的对比试件。提出直接用LCR测量仪测量探头线圈电感值来区分复杂形状铁磁构件显微组织的检测方法。确认了探头对不同显微组织球头挂环的分选能力,研究了检测频率对测量结果的影响。检测结果表明,提出的检测方法简单可行,测量结果可靠。 相似文献