Study On Fatigue Similarity Of Transmission Mechanical Components

Because of its excellent working performance and stability,universal coupling has been regarded as an important transmission mechanism component in aerospace field,such as aircraft steering,wing flap control,fuel drive,door mechanism and so on.As for the components of large-scale transmission machine,it is bound to face some problems such as heavy weight and insensitive operability.In the process of fatigue strength test,if a specific position that needs improvement is found,it will face the problem of secondary design of experimental parts,which will inevitably lead to a waste of time,manpower and material resources,resulting in high research and development costs.Therefore,the sample can be reduced according to a certain proportion,and the fatigue strength test of the testing machine can be carried out with small samples,which can effectively eliminate the waste of resources.Although small samples are widely used because of their simple structure and low cost,there are great differences between small samples and actual parts in terms of geometry,size and working conditions,so it is impossible to accurately characterize the fatigue characteristics of actual parts,which will lead to greater errors.In view of the above problems,the specific research work of this paper is as follows:(1)Based on the scale model similarity theory,the fatigue strength similarity of large transmission mechanical components is studied.In the process of studying the similarity coefficient of mechanical components,the advantages and disadvantages of power exponential gradient method,The Critical Distance(TCD)theory,stress field strength method and high stress volume method are analyzed.Finally,the combination of high stress volume method and finite element method is the main research method in this paper.(2)Then,this research combines SOLIDWORKS software to select the transmission mechanism of multi-axis multi-rotor aircraft,and establishes the finite element model.After that,the original model and the scaled model of the mechanical components of the transmission mechanism are compared and analyzed by ANSYS Workbench software,and the data set simulated by the scaled model is fitted by its corresponding theoretical formula,and the fatigue strength similarity relationship is studied and the errors are analyzed.(3)Finally,under the comprehensive influence of notch coefficient,size coefficient and S-N curve,the fatigue strength similarity coefficient of large-scale structural parts is studied,and the relationship of fatigue strength similarity coefficient is deduced.Then,the relationship of fatigue strength similarity coefficient is verified and analyzed by using the data in the simulation experiment,and then the S-N curve of the scale model is modified by using the fatigue strength similarity relationship to obtain the S-N curve of the scale model component.The fatigue life is calculated and analyzed by simulation test,and the relationship of fatigue life similarity coefficient is deduced,and the derived formula is fitted and analyzed with the fatigue life data obtained in simulation test,thus verifying the accuracy of the relationship of fatigue life similarity coefficient.Therefore,this paper establishes a new expression of fatigue strength similarity coefficient and fatigue life similarity coefficient under bending-torsion cycle,which can be used to conveniently obtain the fatigue strength of large mechanical components under bending-torsion action,draw the corresponding S-N curve,and predict the fatigue life of large mechanical components,providing an important basis for fatigue evaluation.