Analysis And Research On Gear Profile Modification Based On Thermal-Fluid-Solid Coupling Method

Gear transmission is the most important part of the helicopter transmission system.However,the vibration is easily generated during engagement due to the external factors such as actual processing,installation errors and the elastic deformation of the gear under the applied loads.This causes a large stress and reduces the reliability of gear engagement.The profile modification technology can effectively decrease the contact stress of tooth surface,make the process of engagement more stable and promote the reliability of gear system.At present it is usually only considered that the lubricating oil can cool down the entire gear transmission,and at the same time improve the lubrication performance of the gear meshing,which doesn't consider the effect of lubricating oil on the temperature field and stress field.Therefore,to explore the profile modification technology by using thermal-fluid-solid coupling method has certain engineering application value.In this paper,parametic modeling of the gearbox system was carried out.Under the premise of considering the influence of lubricating oil on temperature field and stress field,the finite element model of the gearbox without profile modification was built.The distribution of lubricating oil,pressure field,temperature field and stress field were discussed.Then the three basic elements of profile modification were explored and the optimal modification scheme was obtained.Finally,the influence of the position of the modified gear was researched by carring out the profile modification on the gear and pinion gear under the condition of the optimal modification scheme.The numerical simulation on thermal-fluid-solid coupling analysis method of the gearbox system without profile modification showed that the volume fraction of the lubricating oil at the tooth end of the gear meshing region was larger,while the tooth root was smaller after the system was stabilized;the maximum pressure inside the gearbox was continuously decreasing,and the maximum pressure appeared at the gear meshing,where the maximum positive pressure appeared at the entrance of the meshing area and the maximum negative pressure appeared at the exit of the meshing area;the temperature rise mainly occured at the gear meshing,and the temperature rise on the pinion gear was relatively small than the gear;the stress was mainly concentrated at the root of the pinion gear and the gear.The numerical simulation on thermal-fluid-solid coupling analysis method of the gearbox system with profile modification showed that the optimal modification scheme was obtained when the modification curve b=1.22,the maximum amount of modification Amax-0.06 mm and the modification length L=3.9 mm.At this time,the gear end had the strongest oil-bearing capacity and the ability to form an oil film at the gear meshing was superior to other combination modification schemes so that the optimal lubrication effect was obtained.After the system was stabilized,the variance of pressure inside the gearbox,the temperature rise and the value of maximum stress at the gear meshing was the smallest.No matter what kind of profile modification elements were selected,the stress concentration of the gear root could be significantly improved,the temperature rise of gear surface could be reduced,and the performance at gear meshing could be optimized.In addition,the tooth profile modification on the pinion gear should be considered priority in engineering.