Gear Fatigue Life And Pitting Reliability Of Wind Turbine Gearbox

Gear drive depends on the contact of gear tooth profile to transmit power.It has lots of advantages such as heavy load capacity,wide transmission power range,high transmission efficiency and so on.Therefore,it’s widely used by most mechanical equipment.In recent years,with the increasing demand for high-speed,heavy-duty and large torque gears,the fatigue life and reliability of gears have been the key of current research.It’s reported that tooth surface damage cause most of the gear fatigue.Especially,fatigue pitting exerts huge influences on the fatigue of gear surface.This paper mainly discuss the third stage(high-speed output stage)gear of a 2.5MW wind turbine gearbox transmission system and study the stress intensity,fatigue life and fatigue reliability under the pitting condition of the helical gear.The main work of the contents and results are as follows:1)The third stage helical gear transmission model is established.This paper studies a current 2.5MW gearbox of the certain gearbox company and establishes the ideal helical gear and the helical gear model with pitting corrosion by ANSYS APDL programming.2)The load spectrum is obtained by fitting the measured torque frequency diagram,and the stress spectrum is achieved through the finite element calculation.According to the "stress-time" history of the gear’s maximum stress point,the mean value of stress and stress amplitude are obtained by rain flow counting method.Then,the function expression of stress mean and stress amplitude is obtained.Besides,based on the Goodman formula and probability and statistics theory,the probability density function can be derived to find out the life of the gear.Compared with the life calculated by the nominal stress method,it is found that the former is more reliable.3)As for the wind gear surface pitting,under the effect of the torque spectrum,the stress spectrum is calculated in different pitting conditions and the reliability of helical gears with different pitting diameters and numbers is obtained.The results show that the reliability of gear declines with the increase of pitting diameter.When the diameter increases to a certain extent,the stress concentration decreases and the reliability declines slowly.With the increasing number of pitting corrosion,the stress concentration is obvious.At the same time,the reliability is remarkably declining.