Experimental study on bending fatigue of 42CrMo heavy equipment transmission gear

Cracks will first appear at the tooth root of the gear, because when the gear is running, the meshing other gear will give normal load to the tooth surface. At this time, the stress concentration phenomenon will appear at the tooth root of the gear. This failure is fatigue failure. Under the periodic loading condition of fluctuating load, fatigue failure is the main failure mode of transmission gear of heavy equipment.

When designing gears, it is very important to consider the influence of fatigue failure on gear life. Because the cumulative damage theory is intuitive for fatigue propagation under random load, the cumulative damage theory can be used to estimate the fatigue life of components under sinusoidal load. However, due to the inherent scattering type of fatigue phenomenon, the cumulative damage theory may not be very accurate. Therefore, it is necessary to determine the fatigue life of components under random load by experiment and establish a theoretical model. Through the gear bending fatigue test, the service life of the gear is obtained by the lifting method and group method under the set load and constant frequency, and the results are calculated to obtain the P-S-N curve of the gear.

Through the bending fatigue test of the self-designed and manufactured transmission gear of heavy equipment, and then the analysis and processing of the test data by mathematical statistics, the P-S-N fitting curve relationship is obtained and the P-S-N curve of fatigue test is drawn. The results show that the fatigue limit of the test gear is 14.271kn under the condition of 50% reliability. When the reliability is increased from%% to 99%, the fatigue limit is not greatly reduced, and it is concentrated around 12.5kn, indicating that the fatigue life of the gear is higher when the maximum load is around 12.5kn during use. When the load is greater than this value, the fatigue life of the gear is shortened.

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