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 Wysłany: Pon 19:42, 20 Gru 2010 Temat postu: ed hardy clothing Improved detection of metal magn |
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Improved method of metal magnetic memory testing of
nalundertheloadsof26kNindrivemagneticfield value and the rate of change, as shown in Figure 4 and Figure 5. Analysis 4 (1) The arrangement of atoms in the sample surface within the specimen is different, its yield limit is less than the yield limit of the sample as a whole. Therefore, the overall sample to yield before the sample reaches the yield surface has already been there, if the time unloading the sample surface in a certain degree of residual stress. 141 from the literature shows that the sample reached its law before yielding to the magnetic field strength decreased slightly. (2) According to the literature [5] shows that,[link widoczny dla zalogowanych], when the sample entered the cross-section yielding, the material inside the proliferation of dislocations, dislocation density increases. Because the presence of dislocations, to produce the elastic strain energy of dislocations, due to changes in internal energy, the existence of dislocations will affect the static magnetic domain structures and domain wall movement, a dislocation stress field pinning defects similar to role l_6], so specimens were unloaded after yielding to, normal magnetic field strength significantly improved. (3) The process of dislocation in the slip resistance should be the role of all, when the dislocation slip is prevented by obstacles, they are obstacles along the slip plane in the pileup in front of them, and in the pileup front group created a high degree of stress concentration. When the sample into the yield, the dislocation density increases as the load increases, dislocation slip dislocation generated a corresponding increase in volume, so normal magnetic field through zero also increases. And in the process of plastic deformation, the dislocation pileup continue to be a breakthrough, but also the continuous generation of new dislocation pileup, resulting in a different load, zero-crossing method to the magnetic field is not exactly the same. If the pileup of dislocations is not 186 �� Iii by cross slip or climb over obstacles, leaving stress relaxation down, it will lead to crystal fracture, here is the last seen location of necking. 5 Conclusion Because the mechanism of magnetic memory signal generator has not been generally accepted explanation, the author uses electromagnetic effects artificially added to the external magnetic field excitation, for different magnetic field on the metal magnetic memory signals of a preliminary study found that: (1) in the natural magnetic field, the magnetic memory signal is a bit confusing, especially over the yield limit, there has been more than normal magnetic field component of the crossing point, therefore, according to the zero crossing has been difficult to determine the damage location. (2) in the artificial magnetic field, the magnetic signals show apparent regularity,[link widoczny dla zalogowanych], and in a different load, there is only too obvious zero, and the zero crossing as the load increases quickly at the necking approximation,[link widoczny dla zalogowanych], therefore, according to the crossing point can damage would appear to prejudge the position, enabling the detection of early damage components. References: [1] Lin Junming,[link widoczny dla zalogowanych], et al. A magnetic memory based on nondestructive testing [J]. NDT, 2000,22 (7) :297 - 299. [2] of Jilin, et al. Metal magnetic memory testing technique [J]. NDT, 2001,23 (4) :154-156. [3] of Jilin, Lin Junming. Metal magnetic memory testing technique [M]. Beijing: Electric Industry Press, 2000. [4] Wan Defu, Luo Shihua. Magnetic Physics [M]. Beijing: Electronic Industry Press, 1987. [5] Geng-Xiang Hu, Qian rhizosphere. Metallurgy [M]. Shanghai: Shanghai Science and Technology Press, 1980. [6] Li Qiang. Theory and Application of Magnetoelastic study [z]. Northern Jiaotong University, PhD thesis, 1995. [7] Zhou Junhua, according to mine silver. Ferromagnetic materials, the theoretical analysis of magnetic memory phenomenon [A]. Eighth National Conference on NDT and International Seminar on NDT, destructive testing power system of the Ninth Conference Proceedings [C]. Suzhou: 2003. [8] Zhang Jing, Wei-ping, et al. Fatigue testing of components [J]. TESTING A physical volumes, 2003,39 (9): 45O a 453. [9] Liu Hongwen. Mechanics of Materials [M]. Beijing: Higher Education Press,[link widoczny dla zalogowanych], 1992. (Continued from page 182) [41BaiCL, WangzH, DaiCC, eta1. MicrostructuresofNanosizeHydrogenatedCrystallineSiliconStudiedbyScanningTunnelingMicroscopy [J]. JVacSciFechnol, 1994, (12) :1823-1825. [5] He Yuliang, et al. A transmission mechanism of nanocrystalline silicon films [J]. Physics, l997, 46 ( :1637-1644.
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