Metallographic examination Lll low magnification inspection of the cross section of the oil extraction chamber to do low-fold test, found that there are coarse crystals on the test surface, and the low double streamline on the sample is exposed along the parting surface.
7. Go to page 39 and ask if it no longer exists and achieve good social results.
7 Conclusion The fracture failure property of the exhaust rocker arm belongs to the one-way bending stress and high cycle fatigue fracture; the geometry and shape design of the rocker arm are unreasonable, and the technical requirements do not meet the national standards; the quality and working conditions of the locomotive type 0 locomotive and the southwest region The poor road conditions increase the stress of the rocker arm; the unreasonable geometry and shape of the basic rocker arm accelerates the time of early fracture failure; the staff and managers of the various processes of the rocker arm manufacturing lack the necessary professional Knowledge is the main reason why the rocker arm is in a dangerous working state for many years, causing continuous machine breakage.
Today, today and now, today, today and now, today, present and modern, present and modern, present and modern, today, present and modern, today, present and modern, today, today, today, today, 36. The metallographic samples were taken on the parts for high-strength gold examination, and the microstructure was not over-burned.
2 Test result analysis According to the above analysis, the crack is a fatigue crack, and the crack originates from the thread undercut in the oil discharge chamber. Since the parting surface is the weak part of the forging, and the machining quality of the internal thread undercut is not good, there is obvious machining tool mark, so in the circulating hydraulic test, it is easy to cause stress concentration at the machining tool mark, resulting in parts Exposure along the parting surface of the parting surface will inevitably lead to the reduction of the fatigue resistance of the material. The smaller the grain size, the higher the fatigue strength and the longer the life of the crack formation period. On the contrary, the larger the grain size, the lower the fatigue strength and the life of the crack formation period. The shorter. Therefore, under the action of external force, the crack propagation speed is increased until the final breakage and oil leakage.
3 Conclusion This two-way hydraulic lock is broken due to fatigue.
4 It is recommended to improve the processing quality of parts and meet the accuracy requirements; change the forging method, improve the distribution of low-current streamlines; improve the manufacturing process and control the grain size.
Zhang Dong and so on. Practical analysis of mechanical failure. National Defense Industry Press, Shu Delin. Metal mechanical properties. Mechanical Industry Press, 198; 7.
Hu Shiyan, Jin Heling, Tian Yongjiang. Aircraft parts break failure spectrum. Aerospace Editorial Department, 1984.
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