FE Analysis Of Double Helical Gears With Modifications,Machining And Assembly Errors

As a core component of heavy aircraft,large-sized ship and energy equipment,double helical gears train has a lot of advantages such as the large bearing force and the small axial force.The meshing transmission precision,mechanical efficiency,contact stress of tooth surface,bending stress of tooth root,contact area of herringbone gears directly affect the working performance of gears,such as working life,bearing capacity,vibration,transmission noise,even reduce the quality of the whole machinery and equipment.Many key factors are neglected in traditional gear stress calculation based on formula,which may cause unsatisfactory result.In this paper,the contact stress and bending stress of double helical gears have been calculated with the method of FE analysis,which has the advantages of high calculation accuracy and adaptability.The major study context in this paper includes those:the precise geometric models of double helical gears are built in the three-dimensional modeling software based on the meshing theories of gears.The static and dynamic meshing characteristics of double helical gears have been studied.The effect of machining errors,assembly errors on contact and bending stress has been analyzed.The double helical gears with tooth profile modification and lead crowning within a certain range has been investigated.The main contents can be summarized as follows:(1)Based on the generative machining principle,the precise geometric models of double helical gears and modified gears were built.Then a finite element model has been established in the finite element analysis software.Static contact analysis and dynamic loading contact analysis of a pair of double helical gears were made.The contact area,contact and bending stress of tooth root were obtained.(2)The double helical gear consists of two helical gears with the same helix angle in opposite spiral direction.Therefore,the left and the right helical gear will be not symmetrical in the process of meshing,which could cause unbalanced loads in tooth surface.Therefore,the effect of machining errors,assembly errors on loading capacity and transmission error of a pair of double helical gear has been investigated.The effect of different machining errors and assembly errors on surface contact stress and bending stress has been compared and analyzed.(3)The research on tooth modification has been made.Finite element models in different tooth profile modification and lead crowning conditions have been established,and contact pressure before and after modification has been compared and analyzed.The most suitable modification value in the model has been found.It was found that tooth modifications could reduce the stress concentration in the meshing process of a pair of double helical gears.Finally,the tooth modifications and assembly errors were combined to observe the change of the meshing performance of a pair of double helical gear.