Test And Analysis Of Fatigue Crack Propagation Of Low Speed Heavy Duty Gears

Low-speed heavy-duty gears are widely used in machinery,metallurgy,mining,and other equipment.When the load exceeds the fatigue limit of the material during use,fatigue cracks will occur and gradually expand.When the remaining part is unbearable,it will cause broken teeth,which will cause casualties and economic losses.It is necessary to test and analyze the fatigue crack growth of low-speed heavy-duty gears.In order to study the fatigue cracking of low-speed heavy-duty gears,a compact tensile specimen was first made from 42 Cr Mo steel.After the heat treatment,type I crack growth test was performed on the fatigue tester using stress ratios of 0.1 and 0.6.Then the fatigue crack growth of the compact tensile specimen was simulated using ABAQUS.Comparing the experiment with the simulation results,it is proved that the experiment and the simulation are consistent.Next,the bending fatigue test of the designed and processed 1ow-speed heavy-duty gear on a bending fatigue tester with different stress levels was carried out,and the relationship between fatigue life and stress levels under different reliability estimates and the fatigue limit of the gear were obtained.Finally,the fatigue fracture was observed under a scanning electron microscope.The results show that the small stress ratio is more likely to cause the initiation and expansion of fatigue cracks,the equivalent stress at the crack tip is greater,and the area of the plastic zone is larger;under the same stress ratio,a larger stress range is more likely to cause fatigue failure,resulting in shorter fatigue life of the gear.Under micro conditions,the crack initiation stage occupies a small proportion of the fatigue life.The stable expansion stage is an important stage of fatigue crack propagation,and the fracture form is cleavage fracture.The gear teeth are fractured instantaneously during the rapid expansion stage and the fatigue fracture is the shape of a tearing dimple.The location of material defects makes it easier to initiate cracks and affect fatigue lifeFigure 31;Table 8;Reference 78...