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Caution to Apply Magnetic Barkhausen Noise Method to Nondestructive Evaluation of Plastic Deformation in Some ferromagnetic materials

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Chinese Journal of Mechanical Engineering 2019年第6期32卷 85-91页

作者： Manru He Takanori Matsumoto Tetsuya Uchimoto Toshiyuki Takagi Hongen Chen Shejuan Xie Zhenmao Chen Shannxi Engineering Research Center for NDT and Structural Integrity Evaluation State Key Laboratory for Strength and Vibration of Mechanical StructuresSchool of AerospaceXi’an Jiaotong UniversityXi’an 710049China Institute of Fluid Science Tohoku UniversitySendai 980‑8577Japan

Magnetic Barkhausen Noise(MBN) method is known as an effective nondestructive evaluation(NDE) method for evaluation of residual stress in ferromagnetic materials. Some studies on the feasibility of the MBN method for NDE of residual strains were also conducted and found applicable. However, these studies are mainly focused on the state of residual strains which were introduced through a one-cycle-loading process. In practice, however, structures may suffer from an unpredictable and complicated loading history, i.e., the final state of plastic strain may be induced by several times of large loads. Whether the loading history has influences on MBN signals or not is of great importance for the practical application of the MBN method. In this paper, several ferromagnetic specimens with the same final state of residual strain but of different loading history were fabricated and inspected by using a MBN testing system. The experimental results reveal that the loading history has a significant influence on the detected MBN signals especially for a residual strain in range less than 1%, which doubts the feasibility to apply the MBN method simply in the practical environment. In addition, micro-observations on the magnetic domain structures of the plastic damaged specimens were also carried out to clarify the influence mechanism of loading history on the MBN signals.

关键词： Plastic damage Deformation history MBN method ferromagnetic materials

Current and Shot Noise in a Quantum Dot Coupled to ferromagnetic Leads in the Kondo Regime

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Chinese Physics Letters 2007年第1期24卷 195-198页

作者：吕嵘刘志荣 Center for Advanced Study Tsinghua University Beefing 100084 Ludwig-Maximilians- Universitat Theresienstr. 37 80333 Mfinchen Germany Max Planck Institute for Metals Research Heisenbergstrasse 3 D-70569 Stuttgart Germany

Using the Keldysh nonequilibrium Green function technique, we study the current and shot noise spectroscopy of an interacting quantum dot coupled to two ferromagnetic leads with different polarizations in the Kondo regime. General formulas of current and shot noise are obtained, which can be applied in both the parallel （P） and antiparallel （AP） alignment cases. For large polarization values, it is revealed that the behaviour of differential conductance and shot noise are completely different for spin up and spin down configurations in the P alignment case. However, the differential conductance and shot noise have similar properties for different spin configurations in the P alignment case with the small polarization value and in the AP alignment case with any polarization value.

关键词： SPECTRUM analysis ferromagnetic materials KONDO effect

Phase Transitions of ferromagnetic Potts Models on the Simple Cubic Lattice

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Chinese Physics Letters 2014年第7期31卷 41-45页

作者：王顺谢志远陈靖 Bruce Normand 向涛 Institute of Physics Chinese Academy of Sciences Beijing 100190 Department of Physics Renmin University of China Beijing 100872

We investigate the 2- and 3-state ferromagnetic Ports models on the simple cubic lattice using the tensor renorrealization group method with higher-order singular value decomposition （FIOTRG）. HOTRG works in the thermodynamic limit, where we use the Zq symmetry of the model, combined with a new measure for detecting the transition, to improve the accuracy of the critical point for the 2-state model by two orders of magnitude, obtaining Tc = 4.51152469（1）. The 3-state model is far more complex, and we improve the overall understanding of this case by calculating its thermodynamic quantities with high accuracy. Our results verify that the first-order nature of the phase transition and the HOTRG transition temperature benchmarks the most recent Monte Carlo result.

关键词： PHASE transformations (Physics) ferromagnetic materials CUBIC crystal system CRYSTAL lattices SINGULAR value decomposition

Kink Structures of Spin-Polarized Electrons due to Electron-Magnon Scattering in ferromagnetic State

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Chinese Physics Letters 2007年第12期24卷 3516-3519页

作者：马磊 National Laboratory of Solid State Microstructures and Department of Physics Nanjing University Nanjing 210093 Department of Physics and Electronic Engineering Zaozhuang University Zaozhuang 277160

We propose a model composed of spin-polarized itinerant electrons and bosonic spin-wave excitations, and study renormalization of the spin-polarized itinerant electron bands due to electron-magnon scattering. Spin-polarized kink structures are predicted in the normal state quasiparticle dynamics of ferromagnetic superconductor as UGe2. It is suggested that the angle-resolved photoemission experiment may be helpful in this respect.

关键词： BAND theory of magnetism SPIN waves ferromagnetic materials SCATTERING (Physics)

Critical Behaviour of the One—Dimensional ferromagnetic t—J Model

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Chinese Physics Letters 2002年第1期19卷 108-110页

作者：杨赋王玉鹏 TechnicalInstituteofPhysics&Chemistry ChineseAcademyofSciencesBeijing100080 InstituteofPhysicsandCenterforCondensedMatterPhysics ChineseAcademyofSciencesBeijing100080

The one-dimensional super-symmetric ferromagnetic t-J model is studied via the thermal Bethe ansatz. Analytic expressions of the free energy for T → 0 are obtained. A new critical behaviour beyond the universal class... 详细信息

关键词： ferromagnetic materials

Effect of Barrier Width on Bias-Dependent Tunnelling in ferromagnetic Junctions

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Chinese Physics Letters 2004年第11期21卷 2271-2274页

作者：李飞飞肖明文李正中胡安许望 DepartmentofPhysics NanjingUniversityNanjing210093

We present a finite temperature theory for bias-dependent tunnelling in ferromagnetic tunnelling junctions. The effects of the barrier width d on the tunnelling magnetoresistance (TMR) and its sign change behaviour are discussed with this theory. Numerical results show that both the zero-bias TMR and the critical voltage Vc at which the TMR changes its sign decrease with the increasing barrier width for a considerably thick barrier junction. Furthermore, it is found that a minimum exists in the curve of Vc versus d if a composite junction is under oxidized.

关键词： ferromagnetic materials

Mechanism study on electromagnetic acoustic transducer for ultrasonic generation in ferromagnetic material

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Journal of Southeast University(English Edition) 2004年第3期20卷 309-314页

作者：雷华明阙沛文张志钢黄晶上海交通大学自动检测研究所上海200030

Based on the proper assumptions and approximations, the coupling mechanism of the electromagnetic acoustic transducer (EMAT) for ultrasonic generation within ferromagnetic material was studied by analyzing the eddy current distribution, Lorentz force, magnetostriction force and magnetization force. Some useful numerical calculations are presented to explain the EMAT behavior with general geometric arrangements. It is indicated that for the ferromagnetic material the magnetostriction effect dominates the EMAT phenomenon for ultrasonic wave generation in low magnetic field intensity, while the material does not reach its magnetizing saturation. But, with the increase of the bias magnetic field and saturation, the magnetostrictive terms will make no contributions to the ultrasonic generation and the Lorentz force becomes the only exciting mechanism. It is important to determine both the Lorentz and magnetostriction forces and select the appropriate working manner for achieving an optimized design.

关键词： Calculations Eddy currents ferromagnetic materials Magnetization Magnetostriction Ultrasonic waves

Study on magnetic memory signals of medium carbon steel specimens with surface crack precut during loading process

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Rare Metals 2006年第z1期25卷 431-435页

作者： DONG Lihong XU Binshi DONG Shiyun YE Minghui CHEN Qunzhi Basic Department Ordnance Engineering College Shijiazhuang 050003 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China Basic Department Ordnance Engineering College Shijiazhuang 050003 China Beijing Aeronautical Technology Research Center Beijing 100076 China

Static tensile test and tensile-tensile fatigue test of medium carbon steel sheet specimens with surface crack precut were performed on MTS810 hydraulic testing machine to clear the meaning of the point of Hp(y) value zero. Magnetic memory signals were measured during the test process. The results show that only one point of Hp(y) zero value exists in all measured magnetic signal curves during the loading process, which should be a sign of intersection of positive-negative magnetic poles after magnetic ordered state appears and does not indicate the position of surface crack precut. The analysis shows that the surface crack precut can not interrupt the magnetic ordered state occurred during the test completely, hence its Hp(y) value is not zero. However, the crack extending to a penetrated defect at the instant of specimen′s fracture leads to the discontinuance of magnetic ordered state.

关键词： metal magnetic memory ferromagnetic materials surface crack precut Hp(y) zero value magnetic ordered state

An Anomalous Kerr Loop of LaBaMnO Thin Film

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Journal of materials Science & Technology 1998年第4期14卷 371-373页

作者： Hou, BH Xu, QL Ji, SZ Zhang, TP Peng, P Shang, CH Wang, YJ Xu, L Zhang, Y Univ Sci & Technol China Dept Phys Hefei 230026 Peoples R China Chinese Acad Sci Inst Phys State Key Lab Magnetism Beijing 100080 Peoples R China Chinese Acad Sci Inst Nucl Phys Shanghai 201800 Peoples R China

An anomalous Kerr loop was observed in an oriented LaBaMnO film annealed in oxygen. Many tiny crystal columns were observed with scanning tunneling microscope and magnetic force microscope. The magnetic moment m in the column is perpendicular outward to the surface, which forms a surface phase with spin pinning state. This spin pinning results in the obvious asymmetrical Kerr loop of magneto-optical effect when the magnetic field is in the two opposite directions vertical to the surface.

关键词： ferromagnetic materials