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Minimum safety factor of contact strength: Smin=1SH=HLimH=686466=1.473>1 Contact fatigue strength meets the safety factor requirement. Bending fatigue strength check calculation F1=F1KAKVKFBbmCosmYYF1YYO=50.42MPa Where: bending stress, MPa; circumferential force at F1 index circle, kg; KFB tooth load distribution coefficient is 1.25; Y tooth width influence coefficient is 1.18; YF1 tooth shape The coefficient is taken as 2.03; the Y helix angle coefficient is taken as 0.70; the YO cutter diameter influence coefficient is 0.91; the M modulus is taken as 6; the m helix angle is taken as 1530.
Where: YF2 tooth profile is taken as 2.41; YF1 tooth profile is taken as 2.04. The bending fatigue limit of test gear fLim=362.97MPa is calculated as: fLim=fLimyNyX=246.82MPa where: yN bending strength has a life factor of 1; yX The size factor is 0.69; the minimum safety factor of bending strength: SFLim=1. The safety factor of bending strength: SF2=FLimF2=250.4559.56=4.025>1SF1=FLimF1=250.4559.56=4.967>1 The bending fatigue strength meets the requirements.
Hardness and material analysis The hardness test results of the active gear teeth show that the hardness of the tooth surface is HRC56-58, the hardness of the core is only HRC30-32, and the hardness gradient of the surface layer is too steep, and the hardness of the core of the driving wheel is low, which increases. The ratio of shear stress to shear strength produces a high residual tensile stress at the interface between the surface layer and the core. Therefore, the additional stress of the working load easily causes cracks at this interface and expands due to fatigue. The steep gradient not only accelerates the formation of cracks in the transition zone, but also causes deep spalling and accelerates the early failure of the gear.
After the lubrication analysis was disintegrated, it was found that both gears had rust, and the lubricating oil contained particulate impurities and moisture. In addition, some metal grinding debris generated during the gear meshing process, the aging of the rubber oil pipe makes the oil circuit not smooth, and the oil supply is insufficient. Under the action of the driving wheel 1495r/min speed and impact load, the tooth surface temperature is too high due to insufficient lubrication, which seriously affects the contact fatigue characteristics of the friction pair and promotes plastic deformation of the tooth surface metal surface. The scratch groove is formed along the sliding direction of the tooth surface, and the flying thorn is formed on the tooth side, which causes surface deformation and wear.
Conclusion and measures analysis results (1) improper heat treatment method, so that the hardness gradient between the surface layer and the core is too steep. (2) The gear machining accuracy is not high and the tooth surface roughness level is low. (3) Vibration and impact overload occur during meshing. (4) Poor lubrication.
Corrective measures (1) Strengthen the control of the quality of materials and the quality of heat treatment. (2) Guarantee the machining accuracy of the gear, improve the grade of the surface roughness of the tooth surface, spray the shot root, and properly shape the shape to improve the load bearing capacity. (3) Regularly check the quality of the lubricating oil to ensure the smooth flow of the oil system.