Research On Failure Mechanism Of Face-Gear Drive Under Boundary Lubrication Conditions

Face-gear drive with cylindrical gear and bevel gear wheel meshing,is a new-type gear drive. It has many advantages, such as high coincidence degree,strong bearing and steady working,etc. Based on its unique shunt performance,it has been gradually applied in the main reducer of the armed helicopter. Based on its flexible performance, the armed helicopter can realize the control of the super low altitude areas in the war,and due to the features of the war region,it is also vulnerable to attack from the ground and air. When the armed helicopter is shot and the oil begins to leak, its transmission system will experience extreme lubrication conditions, including starved lubrication, boundary lubrication,dry friction,which is a serious threat to the safety of man-machine. Boundary lubrication is an especial loss-oil lubrication condition,which has a great influence on regular work of drive system. In order to predict the survival ability of face-gear drive under boundary lubrication,failure analysis of face-gear drive under boundary lubrication was carried out in this paper,the main contents are as follows:1)Based on the theory of boundary lubrication,Physical Chemistry and formation mechanism of boundary film,temperature is treated as the failure criterion of lubrication, and the critical failure temperature equation of face-gear drive under boundary lubrication was derived with activation energy, meanwhile,the influences of different activation energy and gear rotational speed on critical failure temperature were discussed.2)Based on the loaded tooth thermal contact analysis,contact trace,contact load and the relative sliding speed on tooth surface were calculated during the whole engagement period,and friction coefficient and frictional heat flow at the contact points were derived. According to the theory of heat transfer and meshing performance of face-gear,the heat conduction differential equation of transient thermal analysis for face-gear drive under boundary lubrication was given,and boundary conditions of all tooth areas were determined.3) The thermal finite element model of face-gear drive was formulated. The loading of moving heat and heat loss of tooth during each meshing period were simulated by means of APDL,and transient temperature field of face-gear under boundary lubrication was solved. According to the calculation results of the finite element analysis and critical failure temperature model,the life of face-gear under boundary lubrication was determined,and the influence on the life of different geometric parameters and gear rotational speed were discussed, finally, optimal gear rotational speed of face-gear drive under boundary lubrication condition was obtained.4)The face-gear for experiment was produced,and the contact trace on tooth surface and the temperature rising trend of tooth were tested,which were compared with the result of finite element simulation analysis,and the conclusion that theoretical results are reasonable was obtained.