Effect Of Frictional Force Between Teeth On The Gearing Root Bending Stress

The gear bending strength analysis is a foundation in research, such as gear power capacity rating, profile correction, as well as vibration and noise of gearing. In view of accurate model, it is significant to investigate the deflection and stresses of engaging teeth precisely.The main research subject of this article is an involute cylinder spur gear. Friction between teeth was currently neglected when designing gearing bending fatigue strength. In fact, even if the gear transmission is working under the state of lubricating , the meshing tooth will have frictional force unavoidably . But can it be neglected? The model of the current paper is the driving gear meshing at teeth top, which was analyzed by mumerical calculation theoretically and the finite element model to probe the effect of friction between teeth on the bending fatigue stress at the root of gear tooth .The different calculation methods of gear root stresses were researched and compared at first, then applied prospect of FiniteElement Method(FEM) in the field is emphasized. And then the calculation formula and frictional force influence factor of the tooth root bending stress was derived theoretically considering inclusive of frictional force. Some principal techniques of accurate modeling in FEM for gear failures are developed systematically. Chief studies are conducted as follows: According to fundamentals of engagement of tooth profiles, exact curve of meshing teeth profiles are derived, which is composed of involute and isometry curve; Geometrical model of gear teeth with complex boundary is established by with PRO/E Parameter modeling, when model is changed, we only need input some parameters, so tooth root bending stress with different parameters gears are analysed easily; the gear models with one or three teeth are analysed by FEM, using Solid95 and Solid92element types, gaining different stress values.At last on contrast of the results of calculation in theory and FEM, it is unanimous basically to receive tooth root bending stress changed with the gear tooth number and the coefficient of friction, It has been found that the friction effect is related to both the frictional coefficient (f)and the teeth number. When/ > 0.07, fatigue bending stress increase by more than 5% due to friction; when f > 0.15, it increase and is up to 10% . This shows , while calculating the crooked fatigue intensity of the gearing, the frictional force can't be ignored. While considering the impact frictional force on bending stress of tooth root, it is multiplied by friction influence factor on the basis of existing bending stressconveniently, obtain the result of calculation.