Investigation On Mechanism And Prediction Method Of Fretting Wear In Aero-engine Involute Spline Coupling

Involute spline coupling is one of the key parts in transmission system of aviation,marine and so on,and its wear characteristics and life time play decisive role in the safety of power transmission system.According to the latest statistics,in the failure of the helicopter transmission system,the failure caused by spline couplings accounts for about 10%~20%,and the failure caused by fretting wear in spline coupling accounts for more than 90%.Since the fretting wear mechanism of spline couplings has not been fully mastered,it is still impossible to control or prevent the failures of wear of spline couplings effectively,which greatly restricts the improvement of the life and reliability of the aero drive system.Thus,the research on fretting wear mechanism and prediction method of involute spline couplings not only has a great demand for engineering background,but also has important theoretical significance.In this paper,the fixed aero-spline couplings were studied.By carrying out the friction and wear experiment of spline`s materials,the mechanism and prediction method of fretting wear were explored,and it was verified by an aviation involute spline coupling.Meaning while,in order to minimize the fretting wear,the best crowning method was proposed.It not only can provide a basic for designing the involute spline couplings which have good resistance,long service life and high reliability,but also provide a reference for the aviation maintenance cycle of involute spline couplings.The main research contents and innovation points of this paper are:1.The friction and wear characteristics of the aircraft spline materials were studied,and the friction and wear performance parameters of the material were obtained.For 18 Cr Ni4A and 32Cr3 Mo VA widely used in aviation,the friction coefficient,wear coefficient and wear depth of 18 groups of these material specimens were tested by using multifunctional friction and wear tester.The effect of materials,loads,rotation speed and surface treatment on friction coefficient,wear coefficient and wear depth were investigated.It provides the basis for choosing the material of the aviation spline pairs,and provides the material characteristic parameters for the analysis of the wear mechanism and the prediction of the wear amount of the follow-up spline couplings.2.An experimental scheme for simulating the fretting wear mechanism of a spline coupling by a plane spline coupling was put forward,the simulation experiment of fretting wear of spline coupling was carried out.According to the aviation involute spline coupling`s parameters,the fretting wear test of plane spline coupling was designed.Andthen,with high frequency vibration tension compression fatigue testing machine,the fretting wear mechanism was got that the spline wear mechanism was three kinds of mixed wear mode which was composed of abrasive wear,adhesive wear and oxidation wear.Based on the results of experiment,the three kinds of wear forms of participation were given,and the prediction method of fretting wear in a spline coupling was established.3.The nonlinear dynamic model and its solution method for the dynamic load analysis of the involute spline couplings were established.The dynamic load between spline couplings of teeth under different working conditions is obtained,and the dynamic model and the dynamic equations of spline couplings were established.The actual contact tooth number was calculated by step-wise loading method.Meaning while,the dynamic parameters were calculated and the dynamic load characteristics under different working conditions were analyzed.At the same time,the law of load sharing and axial load distribution in the spline couplings was revealed.It provides the dynamic load characteristics for calculating the fretting wear of spline couplings.4.The fretting wear mechanism of aviation involute splines was explored.The wear mechanism of fixed helicopter spline couplings with micro amplitude vibration in the process of transmitting is fretting wear.It is mainly composed of abrasive wear,adhesive wear and oxidations wear.And then,based on the wear mechanism the fretting wear of an involute spline coupling is predicted by using the rack fretting wear prediction model.5.The detection research on the fretting wear of aviation involute spline couplings was carried out.Scanning electron microscope was used to observe the surface morphology of involute spline in a helicopter transmission system,and the composition of the local spline tooth was studied using EDS,the fretting wear mechanism of the aviation spline was got.It provides a reliable experimental basis for wear mechanism in this work.Finally,by using the weighing method and the 3D Sensofar surface profile measurement,the fretting wear of the spline coupling was measured,and the reliability of the proposed method was verified.6.The measures to reduce the fretting wear of the aviation involute spline couplings were analyzed.The optimum modification method was put forward.Some improvement measures on how to prevent the fretting wear in spline couplings were presented.And the optimal repair curve,the optimal repair amount and the optimal repair center were determined based on numerical method.Finally,the optimal repair method was validated by numerical examples.The study on fretting wear mechanism,fretting fatigue and fretting testing not only can optimize the design,but also have significant reference value for investigating on themechanism of fretting wear on similar spline couplings.