Fatigue Failure Mechanism Analysis And Key Technology Research Of Cross Shaft Based On Universal Joint

The Universal Joint Cross shaft is the main part of the cross shaft type universal joint.The main function of the cross shaft universal joint is to form the transmission shaft assembly and transmit the power output from the engine to the drive axle through the transmission shaft assembly,thus driving the wheel to achieve rotational movement.Because of its working characteristics,the universal joint cross shaft is prone to fatigue failure,such as wear,crack and even fracture,therefore,how to reduce the probability of cracking,improve the fatigue strength and prolong the service life of the universal joint cross-shaft has become an urgent problem to be solved.In view of the fatigue failure of the Universal Joint Cross shaft produced by a factory,through the mechanism analysis and test of the fatigue life test design of the cruciform universal joint and the key technical aspects such as the effect of grease properties on its fatigue failure,the results are as follows:(1)the best combination of material hardness and fatigue wear resistance can be achieved when the hardness of the Cross Shaft is 62HRC;Through the measurement of the effective carburizing layer of the cross shaft,it is concluded that only when the ratio of carburizing layer depth to total carburizing layer depth in high hardness zone(HV ≥550)is more than 50%,the fatigue resistance of the material can be improved fundamentally The analysis results of metallographic experiment show that too high quenching temperature or too long quenching time will cause the inner grains of the alloy to be coarser due to excessive heat,and oxide will be formed along the grain boundary,which will lead to the decrease of grain boundary adhesion and fatigue crack failure.(2)through the fatigue life assembly test of the cruciform shaft universal joint,according to the test data and results,the internal clearance of the cruciform shaft bearing should be designed with the compensation of temperature taken into account,and the clearance should be controlled within 0.1 mm ~ 0.4 mm;The needle roller isdesigned with full convexity,and the fatigue failure or even fracture of the needle roller end caused by stress concentration can be avoided to a great extent by increasing the curvature of the needle roller.The test results show that the improved needle roller improves the overall fatigue life of the cross shaft by 74%.(3)Through the analysis and research on the fatigue performance of the grease used in the cross shaft,it can be seen that the use of different types of extreme pressure anti-wear agents in a certain proportion and added to the grease can significantly improve its anti-wear extreme pressure performance,thus Can greatly improve the fatigue life of the universal joint cross shaft;Due to the temperature resistance of the grease,the maximum and minimum temperature of the lubricated part of the cross shaft must also be considered when selecting the grease to avoid its discomfort due to the temperature resistance of the grease Fatigue failure caused by the phenomenon;grease must also be compatible with the sealing rubber to prevent the rapid aging of the rubber to lose the seal,resulting in the loss of grease or impurities,which leads to the failure of the journal and bearing wear.