三角度磁巴克豪森测量平面应力方法研究

为了提升磁巴克豪森（magnetic Barkhausen noise,简称MBN）应力测量效率,提出了一种三角度磁巴克豪森测量平面应力的方法,分析了角度选择对精度的影响。为了减小标定的不确定性,提出了一种基于多维特征重构不确定性度量空间的贝叶斯标定方法。实验结果表明,当应力大于50 MPa时,采用相互间隔60°的3个角度,可实现主应力值测量误差不大于±10 MPa、方向测量误差不大于±5°。贝叶斯标定模型进一步将幅值误差降低到±5?MPa以下,并将方向测量的±5°误差带扩展到40 MPa的低应力区。该研究方法为工程中采用磁巴克豪森高效、准确测量平面应力奠定了基础。     

U型磁轭励磁时磁巴克豪森噪声信号分布规律研究

磁巴克豪森噪声是材料性能和应力状态检测的重要技术之一,材料磁化时磁巴克豪森噪声信号发射分布状况以及信号接收器的位置直接决定着所获取原始信号结果,进而对后期结果评判具有非常重要的影响。研究得到了U型磁轭励磁方式不同励磁条件下材料表层磁巴克豪森噪声信号的发射强度分布。试验使用缠绕于磁芯上的线圈作为接收器,采用逐点测试方法获取Q235材料表面磁巴克豪森噪声信号分布图。通过这些信号分布图,得了材料磁化强度与巴克豪森噪声信号发射强度分布的关系,以及信号接收器位置对接收信号的影响。     

磁巴克豪森噪声重构磁滞参数的硬度测定方法EI北大核心CSCD

针对铁磁性材料硬度指标的快速、定量、无损检测的实际需求,揭示了材料微观结构变化对磁巴克豪森噪声信号的影响机理,提出了采用磁巴克豪森噪声重构磁滞参数作为无损定量评价材料力学性能硬度指标。采用不同热处理制度对45钢试件进行处理,得到一组具有硬度梯度的标定试件;通过比较标定试件上不同激励电压对磁巴克豪森检测系统灵敏度的影响,选择最佳激励电压;采用磁巴克豪森噪声检测技术对不同热处理标定试件进行检测,对检测信号数据进行后处理,得到磁巴克豪森噪声能量滞后周期循环曲线,即重构磁滞回线。计算不同热处理45钢标定试件4种重构磁滞参数,构建材料力学性能硬度指标、微观结构及4种重构磁滞参数之间的映射关系,得到磁巴克豪森噪声重构磁滞参数评价45钢硬度的标定模型,并对标定模型进行验证,标定模型预测硬度误差基本满足工程应用10%的指标要求。     

磁巴克豪森噪声重构磁滞参数的硬度测定方法

针对铁磁性材料硬度指标的快速、定量、无损检测的实际需求,揭示了材料微观结构变化对磁巴克豪森噪声信号的影响机理,提出了采用磁巴克豪森噪声重构磁滞参数作为无损定量评价材料力学性能硬度指标。采用不同热处理制度对45钢试件进行处理,得到一组具有硬度梯度的标定试件;通过比较标定试件上不同激励电压对磁巴克豪森检测系统灵敏度的影响,选择最佳激励电压;采用磁巴克豪森噪声检测技术对不同热处理标定试件进行检测,对检测信号数据进行后处理,得到磁巴克豪森噪声能量滞后周期循环曲线,即重构磁滞回线。计算不同热处理45钢标定试件4种重构磁滞参数,构建材料力学性能硬度指标、微观结构及4种重构磁滞参数之间的映射关系,得到磁巴克豪森噪声重构磁滞参数评价45钢硬度的标定模型,并对标定模型进行验证,标定模型预测硬度误差基本满足工程应用10%的指标要求。     

剪切式力与称重传感器的力学基础

本文介绍了剪切式力与称重传感器的主要特点及其所采用的对剪应力所引起的扩应力进行测量的间接测量原理，从分析平面应力状态下斜面上的应力，主应力平面五主剪应国平面的关系，主应力方向以及主应变与剪应变的关系入手，论述了剪切式力与称重传感器的力学基础，并简要的推导了矩形，工字形，圆截工字形，长方形和正方形空心截面的剪应力求解公式，给了了分析结果。     

磁巴克豪森噪音(MBN)法对产品厚度测量的影响

本文试图说明通过变化被测产品横截面和标定试块的厚度做出依据巴克豪森噪音法测量产品残余应力的结论。将测量和比较不同试块厚度获取的RMS值和巴克豪森脉冲的整体数目作为巴克豪森噪音参数,间接有效地反映了试块各种横截面厚度对巴克豪森噪音电平的影响。文中还分析了磁化频率和磁化电流对灵敏度的影响。     

基于磁巴克豪森噪声的S136钢表面硬度定量预测模型对比

表面硬度是铁磁性材料制造质量评价的重要指标,其无损定量检测是该领域的研究热点。为将磁巴克豪森噪声技术用于S136表面硬度的无损定量检测,利用实验室研制的磁巴克豪森噪声检测装置对60块具有不同表面硬度的S136试件进行重复性测试,统计测得多项磁参量的变异系数,结果表明检测装置具有良好的重复检测精度。为实现表面硬度的磁学定量表征,分析磁巴克豪森噪声和切向磁场强度检测信号的6项特征磁参量与硬度的关系,重点对比研究基于一元、多元线性回归和BP神经网络模型的表面硬度定量预测方法。研究结果显示:采用6项磁参量作为输入的BP神经网络模型对表面硬度的预测精度最高,对300个案例的平均预测误差仅为2.14%,最大误差约为11.74%,274个案例的预测误差小于5.00%。研究成果为实现钢板表面硬度的磁巴克豪森噪声无损定量检测提供了方法借鉴。     

巴克豪森噪声在电站用铁磁材料疲劳寿命评估领域的研究现状

介绍了国内外应用巴克豪森噪声检测技术在电站用铁磁材料疲劳寿命评估中的研究状况。分析、总结巴克豪森噪声与显微结构特征的内在关系以及巴克豪森噪声疲劳寿命预测曲线的研究进展,并指出该技术存在的问题和今后发展的方向。     

测量一个主应力方向动应力的组合应变计

本文介绍适用于平面应力状态一个主应力方向动应力测量的两种组合应变计的原理、使用方法和数据处理,以及忽略横向效应系数时组合应变计测得应力值的误差。     

基于磁性方法的集成无损检测装置研究

为了对铁磁性材料的残余应力、微裂纹等缺陷进行快速检测,设计了基于AMR传感器的集成无损检测装置。该装置集成了磁记忆检测技术、漏磁检测技术和磁巴克豪森噪声检测技术,并对含残余应力带与不同方向预制裂纹的45#钢试件进行检测实验。结果表明:该集成装置既可以检测试件中的残余应力,又可以识别不同角度的微裂纹缺陷,并且可以对残余应力进行定量化评价,实现了铁磁材料残余应力、微裂纹等损伤状态的综合评估。     

Study of surface integrity of ground bearing steel using Barkhausen noise technique

An experimental study was undertaken to compare the role of process parameters on the grindability of bearing steel (unhardened and hardened) in conventional grinding domain with particular emphasis on surface integrity. Surface residual stress on the ground specimens has been assessed using X-ray diffraction technique and Barkhausen noise analysis. The aim of this article was to compare the applicability of Barkhausen noise analysis technique to assess the state of residual stress with simultaneous change in microstructure along with the formation of white layer, microhardness, the incorporation of plastic deformation, etc. The results indicate a significant effect of downfeed and work speed on surface integrity parameters like residual stress, microstructure, and microhardness. Residual stress varied in the present work over a domain of 50–700 MPa. Despite simultaneous variation in the microhardness, microstructure, and residual stress during grinding, a linear correlation could be established between Barkhausen noise parameters and residual stress.     

基于主动磁化的钢板应力测量性能提升方法研究

提出一种提高基于磁弹效应的钢板应力测量灵敏度和一致性的方法。 从力磁耦合理论模型出发,分析强磁化和弱交流 磁化对力磁耦合所起的作用:强磁化能通过降低初始磁导率和统一力磁耦合参数,提高应力测量的灵敏度及一致性;弱交流磁 化提供小幅振荡磁场,能有效消除干扰磁场影响。 开展了基于磁弹法的钢板应力测量有限元仿真研究,表明当初始相对磁导率 较低时,应力作用下的钢板法向磁感应强度变化率较大,即应力测量灵敏度较高。 开展了不同强磁化条件下不同厚度钢板的拉 伸试验,测量其法向磁感应强度变化。 实验结果表明:与未磁化相比,强磁化后钢板应力测量灵敏度有数十倍提升,一致性有数 倍至百倍提高。 其中,3 mm 厚度钢板采用单磁铁移动磁化方式的应力测量灵敏度和一致性参数提高至 1. 665 mGs/ MPa 和 2% ;5 mm 厚度钢板采用双磁移动磁化方式的应力测量灵敏度提高至 1. 41 mGs/ MPa,采用单磁铁移动磁化方式的一致性参数 提高至 0. 2% ;7 mm 厚度钢板采用双磁铁移动磁化方式的应力测量灵敏度和一致性参数提高至 1. 2 mGs/ MPa 和 1. 8% 。     

Barkhausen noise as a function of grain size in non-oriented FeSi steel

The Barkhausen noise was measured in non-oriented steel with different grain size. The change of the grain size was achieved by application of respective thermo-mechanical treatments to the investigated steel. The measurement results of the Barkhausen noise parameters for the sine magnetic flux density is presented and the influence of grain size on the Barkhausen noise is discussed. We explored the noise upon the whole hysteresis loop and not only the average statistical properties of the noise. To clarify different measurement results shown in literature, we explained the influence of the grain size on the Barkhausen noise using two different processes – change of the mean correlation domain volume and change of the number of domains. These two effects can be distinguished by each other by calculating the root mean square value of the Barkhausen noise only for the second half of the magnetizing process and considering only the high frequency spectrum of the noise.     

最小区域球度误差评价的弦线截交方法

最小区域球度误差评价是精密测量技术中的一个非常重要并且复杂问题。针对笛卡儿坐标系下球体形状误差评价,介绍一种利用弦线截交关系求解最小区域球度误差评价方法。通过构建笛卡儿坐标系下球度误差测量模型,提出基于一般二次曲面理论的最小二乘球心计算方法。根据最小区域球度误差模型分类,利用弦线截交关系建立起最小区域球度误差评价的2+3和3+2模型,最后通过截交几何模式产生了虚拟中心,从而准确确定球度误差评价模型的最大弦线与最大截面,达到快速精确构建模型的目的。测试数据和实例应用表明,基于弦线截交关系的最小区域球度误差评价方法具有更高的计算效率,且测量空间不受测量坐标系和零件几何形状误差的影响,并显著提高了整体评价的精度与准确性。     

Pre-sliding Behaviour of Single Asperity Contact

The pre-sliding and static friction force behaviour at asperity level between a smooth ball and a smooth flat surface at different normal loads, as well as friction behaviour during full slip has been studied. The normal load dependence of the friction force and the preliminary displacement is discussed when the mean contact pressure is kept under 100 MPa. The theoretical model to calculate the shear stress and the preliminary displacement in the contact is discussed and the experimental data were used to verify the model. The results show that for low applied normal loads the adhesion force has an influence on the friction force measurements. Furthermore, the results for the friction force and preliminary displacement show good agreement with the theoretical trends. The experiments along with the model can be used to analyse the tangential traction in the contact and the behaviour of the stick–slip area. The measurement results along with the model were used to calculate the maximum shear stress at the point of sliding for different applied normal loads. It is also shown that at low applied normal loads the shear stress is not constant as compared to relatively high applied normal loads due to the presence of adhesion force.     

Ultrasonic measurement of tie-bar stress for die-casting machine

In die casting, the real-time measurement of the stress of the tie-bar helps ensure product quality and protect the machine itself. However, the traditional magnetic-attached strain gauge is installed in the mold and product operating area, which hinders the loading and unloading of the mold and the collection of die castings. In this paper, a method for real-time measurement of stress using ultrasonic technology is proposed. The stress variation of the tie-bar is analyzed, and a mathematical model between ultrasonic signal and stress based on acoustoelastic theory is established. Verification experiments show that the proposed method agrees with the strain gauge, and the maximum of the difference square is only 1.5678 (MPa)². Furthermore, single-factor experiments are conducted. A higher ultrasonic frequency produces a better measurement accuracy, and the mean of difference squares at 2.5 and 5 MHz are 2.3234 and 0.6733 (MPa)², respectively. Measurement accuracy is insensitive to probe location and tonnage of the die-casting machine. Moreover, the ultrasonic measurement method can be used to monitor clamping health status and inspect the dynamic pulling force of the tie-bar. This approach has the advantages of high precision, high repeatability, easy installation, and noninterference, which helps guide the production in die casting.     

A new high-cycle fatigue criterion applied to out-of-phase biaxial stress state

A new multiaxial high-cycle fatigue criterion based on the so-called critical plane approach is presented. According to such a criterion, the critical plane orientation is proposed to be correlated with the averaged principal stress directions deduced through the weight function method. Then the fatigue failure assessment is performed by considering a nonlinear combination of the maximum normal stress and the shear stress amplitude acting on the critical plane. The proposed criterion is applied to a general sinusoidal biaxial stress state, for which analytical formulae can be derived. The theoretical results calculated according to the present criterion, together with those of other common critical plane criteria, are compared with experimental data related to different brittle (hard) metals under in-phase or out-of-phase sinusoidal biaxial normal and shear stress states.     

Extraction of Barkhausen noise from the measured raw signal in high-frequency regimes

This paper deals with extraction of pure Barkhausen noise from the raw signals received in high-frequency regimes. The raw Barkhausen noise signals measured in high-frequency regimes contain components which cannot be attributed to the interaction of Bloch Walls with pinning sites and stress states such as the thermal noise of the sensor and the mechanical vibrations of the sensor-exciting core. Due to the variable ratios of thermal noise to Barkhausen noise as well as distortion of the signal due to vibrations, the raw signal as received and the pure Barkhausen noise signal can differ remarkably, thus making signal interpretation a debatable issue. For this reason, the post-processing method of the measured signal is presented here. In addition, the properties of μScan 500 device are analysed in detail.     

扫描电子束铝合金表面处理应力场仿真与试验验证

研究扫描电子束铝合金表面处理应力场的分布规律,对了解残余应力的形成机理具有十分重要的理论及实际意义。在热弹塑性理论的基础上建立电子束表面处理应力场的有限元模型,分析高温热力学参数对电子束表面处理应力场的影响;通过仿真与试验验证相结合的方法确定材料的高温热力学参数,得到铝合金电子束表面扫描后的应力分布规律。随着弹性模量和切变模量的增加,ADC12铝合金材料表面的变形量和最大应力均成非线性增加。经电子束表面处理后试样表面扫描带附近为拉应力,而在其他位置为压应力;最大拉应力出现在扫描带的内侧边缘处,外侧边缘次之,而扫描带中间的拉应力最小;最大表面应力为127.6 MPa,变形量为1.8 mm。     

磁光阱异面空间角度测量及测量不确定度评定

随着空间几何量精密测量技术在装备制造工业的制造与装配过程中应用越来越广泛,角度计量正在从平面角度向空间角度发展。针对磁光阱的异面空间角度进行测量,使用平行平晶作为标准平面引出待测面法向量,并将其空间角度有效的划分成水平投影角和竖直投影角两个平面角度进行测量,保证了空间角度的可溯源性,得到磁光阱各待测面法向量间的空间角度偏差最大值为0.286 0 mrad;然后通过蒙特卡洛法评定该方法的测量不确定度为0.095 9 mrad;最后与三坐标测量机法比对结果中偏差最大值为0.184 2 mrad,在考虑待测面平面度指标为±0.145 4 mrad时,二者的一致性良好。目前该方法已在NIM5铯原子喷泉钟物理真空子系统的研制中进行了应用,证明了该方法能够满足测量的准确度要求。