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The main processing conditions of the test gears in Table 1 are divided into several types, mainly considering the bending fatigue strength test of the austempered ductile crankshaft timing gear in the current production, and the reliability of the test, while studying the austenitic ball gear root The influence of the presence or absence of the decarburization layer on the bending fatigue strength of the gear and the tolerance of the inner diameter of the gear, that is, the influence of the actual interference amount of the gear after being hot-sleeve on the crankshaft on the bending fatigue strength of the gear; in addition, in order to further improve the austempered ductile iron The bending fatigue strength of the gear is studied. The effect of the shot peening of the Aube ductile iron gear and the different shot peening strength on the bending fatigue strength is studied.
Fatigue test The hardness value of the austempered iron gear is shown in Table 12, which meets the hardness requirements specified in the drawings: 28 to 35 HRC. Fatigue Test The metallographic structure of the core of the Aube ductile iron gear is shown in Fig. 13 and Fig. 14, and is a residual austenite of +10% to 20%.
It can be clearly seen from Table 2 to Table 11 and Figure 3 to Figure 12 that firstly, the bending fatigue test strength of the Austempered ductile iron gear produced by the current process can fully meet the requirements of the 6DF1 diesel engine, and its 50% probability base. The ultimate tangential force fatigue load is 10.474kN, which is greater than the base tangential force load of the gear design calculation of 2.9392kN, which is 3.56 times; the bending fatigue test strength of the austempered ductile iron gear tested in other schemes is also fully capable. Meet the requirements of the 6DF1 diesel engine.
Secondly, we can see from the test results that the state (2) is higher than the ultimate fatigue load of the state (1), and the state (4) is higher than the ultimate fatigue load of the state (3), that is, the gear hole size is appropriately increased, and the gear heat jacket is reduced. The surplus is conducive to increasing the ultimate fatigue load of the Aobei ductile iron gear, which is in line with the normal law, but the effect is not very obvious.
The state (1) is higher than the ultimate fatigue load of the state (3), and the state (2) is higher than the ultimate fatigue load of the state (4), that is, the root decarburization layer is not worn away and is higher than the tooth root decarburization layer, but The estimated results are just the opposite and the results are more obvious. Why is this? After in-depth analysis, the author believes that the bending fatigue failure process of the gear is a process of crack generation and crack propagation, and the crack generation has a greater effect on the gear fatigue failure. The austempered ductile iron gear which is not ground by the decarburization layer of the tooth root, the base body is austempered ductile iron, has high strength and certain plastic toughness, is not easy to be deformed, and the ferrite decarburization layer of the surface layer has low strength. However, the plasticity is very good, so during the bending fatigue test, the tensile stress generated by the test load at the root of the tooth firstly causes the ferrite decarburization layer of the surface layer to produce a rounded corner of the root of the tooth - the root of the tooth is rounded - the root of the tooth Angle-to-tooth root rounding--tooth root rounding--tooth root rounding--discussion on the leakage of the number of cycles in the cracked part of the tooth root.