Fatigue Life Prediction And Finite Element Analysis Of High Contact Ratio Helical Gears In Air Compressor

Statistical data both at home and abroad show that fatigue failure of mechanicalequipment in the project amounted to60~90percent. So fatigue damage is the mostcommon form among total mechanical destroy. In air compressor, helical gear pairconnect the motor and the impeller., so it is the key part of an air compressor, whichdetermines the machine’s service life and trouble-free working hours. Traditionaldesigns are often based on the static strength design method to increase the allowablesafety factor or reduce the allowable stress to improve its reliability without an anti-fatigue design, therefore it often can’t guarantee the reliability and safety of its run,helical gear pair mainly subjected to cyclic loading, once fatigue failure and brokenteeth occurs, it will not only affect the normal operation of equipment, but also bringsgreat economic losses. Therefore, according to working conditions of the gears, makeaccurate stress analysis to get the distribution of stress and strain, study the failure law,and estimate the fatigue life, which can provide the necessary data for the inspection,repair and maintenance of air compressors.Therefore, this paper takes the helical gears of the air compressor as the researchobject, integrated use the finite element theory of elastic contact theory, tooth profilemodification, multi-body dynamics theory, the theory of fatigue damage and modalanalysis theory, the gear pair finite element analysis of the tooth profile modification,dynamic simulation, fatigue life prediction and modal analysis, which has greatreference value for the anti-fatigue design of air compressor. The research includes thefollowing aspects:①The meshing finite element model of helical gears is established in ANSYS.Then we adopt profile modification to decrease meshing impact, the results show thatthe maximum stress is673.627MPa, and the adoption of tooth profile modificationeffectively reduces the engagement of the addendum impaction. At last the coefficientof friction, modification height, and the length of the modification addendum how effectthe tooth peak stress is discussed in this paper.②Virtual prototype model of the helical gear pair is established in dynamicsanalysis software ADAMS. Then, the collision is added between two gears, the solutionparameters are set, and the dynamic meshing force is obtained.③According to material data, the approximate S-N curve of material is fitted. And combined with the stress results and load spectrum, fatigue life of helical gear pair ispredicted based on fatigue damage theory. The result shows that: safety factor is greaterthan1, ignored very minority of low life points, can reached64.17years,which is greaterthan design requirements of20years, can meet the research requirement.④Modal analysis of gear pair is done to extract the top6-order natural frequencyand vibration mode. The results show that meshing frequency6078.25Hz is much largerthan the former6-order natural frequency, and the fundamental frequency is greater thanthe master-slave gear goes, so the system will no resonate occurs and it has gooddynamic properties.