| With the development of the domestic automobile industry,many enterprises are actively carrying out the independent research and development of auto parts.It’s a very important issue for car manufacturers to consider whether the strength,stiffness and fatigue life of their products meets the requirements.As an important part of the automobile transmission system,the driving axle plays an important role in reducing the speed,increasing the torque,changing the direction of torque transmission and achieving differential.Its reliability has important influence on the vehicle’s dynamic,stability and safety.The hypoid gears have a large working load and a long working time,which are often the weakest parts in the drive axle assembly.Based on this background,the purpose of this paper is to establish a method of calculating the bending fatigue life of the hypoid gear and study on the influence of the gear mounting error on the bending stress and fatigue life.Firstly,according to the meshing principle and processing method of hypoid gear,a three-dimensional model of hypoid gear is established in CATIA software based on the principle of virtual machining.Secondly,two fatigue test standards(QC/T533-1999 and FPT MTD014)of hypoid gears are selected,and the finite stress analysis of hypoid gears is carried out according to the experimental load of these two standards.In the finite element analysis process,a number of analytical steps are set up to solve the problem that the hypoid gear stress calculation is not easy to converge.The result shows that the change of the tooth root stress with the meshing time is in accordance with the meshing regularity of the hypoid gear,and the correctness of the gear three-dimensional model and the finite element simulation method is proved.Then,a uniaxial fatigue life analysis method and a multiaxial fatigue life analysis method based on FEMFAT software were used to predict the bending fatigue life of the hypoid gear.Uniaxial fatigue analysis only considers the influence of the first and third principal stresses,while the multiaxis fatigue analysis takes the stress tensor of the tooth root node as a fatigue load in the whole process to calculate the fatigue damage parameters on the critical plane.The result shows that multiaxial fatigue life is much smaller than uniaxial fatigue life,and the difference between the two results is directly related to the Degree Of Multiaxiality(DOM)of the stress state.Then,the influence on the bending stress and fatigue life of the pinion axial installation error(H error),the gear axial installation error(G error),the offset error(V error),and the axial angle error(g error)are analyzed.H error,G error and gerror will lead to a large change in gear bending stress and fatigue life,in which the large decrease in multiaxial fatigue life of the pinion caused by negative G error needs to be pointed out.G error or V error will leads to the tooth root stress peak point or the minimum fatigue life point position changes along the tooth width direction,while the V error effects significantly.Finally,the fatigue test of the driving axle under the QC/T533-1999 and FPT MTD014 standard is carried out by using the electric control system of the electric motor powertrain.The result shows that the uniaxial fatigue life is too large,and the multiaxial fatigue life is in good agreement with the experimental result.The reliability of the method for predicting the bending fatigue life of the hypoid gears in this paper is verified,which can provide a reference in the gear designing process and shorten the designing time. |
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