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 Wysłany: Nie 16:33, 19 Gru 2010 Temat postu: ugg milano Analysis of nuclear damage rail imports |
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Analysis of rail imports of nuclear damage
To injury form. Nuclear damage with a smooth fracture surface area. The shape of stone. Sometimes was bright silver. Said the white core, see Figure 1; sometimes dark brown, Mi nigra. Nuclear injury is the railway works departments commonly known form of such damage. The fact is the fatigue damage. Black core is extended to the outcrop of fatigue crack, crack surface was dark brown due to oxidation. Identification of a nuclear injured 40 rail tracks are located on the curve, in which R 300m curve l1 root (all the shares). The total weight of 0.4 meter by 0.7 million tons. Chemical analysis 2 test 2.1 Chemical analysis of rail results are listed in Table 1. Can be seen from the table, C, si partial lower limit. Mo, V content is less than 2.2 provides the mechanical properties of tensile test of rail failure. The results are shown in Table 2. Shows the tensile strength, elongation minimum deviation,[link widoczny dla zalogowanych], which is lower than the tensile strength of a pull rod technical requirements, 2.3 Macro Analysis of fracture cracks found in the ultrasonic testing of rail human open, shown in Figure 1. The original smooth surface on the fracture surface crack, the rest is man-made sections. Rail with vertical and horizontal cracks both along the longitudinal crack open after the tensile test results in Table 2 fracture surface shown in Figure 2. The fatigue cracks are cracks, there are longitudinal and transverse fatigue crack fatigue crack. Longitudinal effect of fatigue cracks in the wheel and rail tread of about 1Omm Department, there are linear fatigue source, and to extend the side rails. Longitudinal crack growth to a certain extent, to the longitudinal crack is the source for nuclear damage cross rail loop 1 cross-sectional aspect of macro morphology of 0.9 loop 2 forms to the macro-crack surface rail 2.2x Table 1 Chemical composition () * 36 * TESTING A physical volumes Vo1.33No. 4 (1997) to the fatigue growth; horizontal expansion began, first with the vertical crack into the 10. ~ 3O. Point of view, roughly perpendicular to the vertical post. 2.4 Microscopic analysis of fracture using scanning electron microscopy and energy dispersive x-ray inspection fracture, vertical linear source at the microscopic characteristics of fatigue shown in Figure 3, the photo shows the dual-magnification photographs, the figure on the right half-size box to the left of the zoom region, where there are dense black like substance. Type of x-ray with 1SIS EDS, black-like substance is alumina type inclusions, the X-ray spectroscopy analysis shown in Figure 4. Longitudinal and transverse fatigue crack microscopic characteristics shown in Figure 6 Figure 5 is very smooth morphology, have experienced a lot of stress cycles, the relatively rough topography in Figure 6. Therefore, relatively speaking, horizontal expansion is faster than the vertical. 2.5 Metallographic examination under light microscopy, failure pearlite rail organizations; longitudinal fatigue crack next to the long and thin inclusion, inclusion level two. Crack next to the plastic deformation characteristics of organizations, and the white phase appears,[link widoczny dla zalogowanych], the longitudinal linear microhardness Figure 3 inclusions at the fatigue source dual larger photo Left: 18X Right: 128 ×. E k ... eV can be spread at the source of fatigue at the Figure 4 spectrum of inclusions 6 horizontal circle morphology of fatigue crack extension 625 × Figure 7 next to the vertical crack and plastic deformation of martensite fi00 × measured results show that the white phase martensite,[link widoczny dla zalogowanych], shown in Figure 7.3 Analysis and Conclusion scroll wheel on the rails (possibly accompanied by sliding), rail rolling stock and cargo by all the load, especially in the small radius curve, the Rail of the lateral side of the centrifugal force also role. Scroll wheel on the rail, the maximum compressive stress is the role of wheel and rail tread surface, but the maximum shear stress in a certain distance away from the tread sub-surface. Noted in the data reported to consider the elastic contact straight track to axle load 22t, truck wheels wheel diameter 840mm estimate wheel-rail contact width of 6.7mm,[link widoczny dla zalogowanych], the maximum contact stress of 1】 ~ TMPa,[link widoczny dla zalogowanych], maximum shear stress of 353MPa, the maximum shear stress location in the next 7 ~ 8ram tread at the fact, due to the small radius curve of the heavy elements and electric locomotives, the maximum shear stress location in the tread of about] 0mm Department. Estimated by the tensile yield strength, yield shear stress limit of the rail is about 480MPa. Alumina Inclusion caused the stress concentration, and by the trains run on the curved rail when the role of the centrifugal impact, resulting in maximum shear stress exceeds the yield limit, causing the Department of inclusion plastic deformation around the metal matrix, the crack initiation to and development of alumina Inclusion source of the actual role of initiation. Under the tread at about 10ram tissue uniformity is essential to avoid rail contact fatigue. In summary, the Austrian imports of alumina inclusions in the rail is the main reason for nuclear damage, bend the rail service first longitudinal loading conditions determine the way after the horizontal crack. Figure 5 Longitudinal contact fatigue crack fatigue growth characteristics of 600 × Il Received Date] Hu :1996-09-20
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