Study On Fatigue Life Of Spring Clutch And Optimization Of Structural Parameters

Spring clutch plays an important role in the process of helicopter high-speed because of its compact structure and high applicable working speed.The variable cross-section spring,the key part of the spring clutch,is a flexible structure.It is easy to excite dynamic response in different working conditions of the helicopter,which can cause fatigue failure of the spring clutch.By analyzing the influence of clutch structure parameters on fatigue performance,the fatigue life of spring clutch is predicted,and the structure parameters are optimized to improve the fatigue life of spring clutch.At the same time,a more reliable and simple fatigue life prediction and evaluation method of spring clutch is provided.The specific research contents are as follows:(1)The statics theory is used to analyze the force of the variable cross-section spring.The structural parameters are designed and selected according to the operating conditions of the clutch.The finite element model of the clutch is established to study the influence of different structural parameters on the stress distribution of the spring.The results show that the maximum Mises stress occurs at the edge of the inner ring of the 14th ring(from the number of input ends)spring,and the stress of the inner ring is significantly higher than that of the outer ring.When the spring fails,it is easy to expand along the direction of the maximum circumferential tensile stress action surface.(2)Based on the results of clutch stress analysis,the fatigue life and dangerous position of spring clutch are predicted by Fe-safe fatigue analysis software,and the influence of different structural parameters on the fatigue life of clutch is studied.The results show that under the given working condition,the fatigue life of the spring clutch is 3.277×10~5 times,and the fatigue dangerous position appears in the inner ring of the 14th ring.The chamfering treatment will significantly increase the fatigue life of the clutch,and the increase of interference and clearance will reduce the fatigue life of the clutch.The oil tank treatment and preload have little effect on the fatigue life of the clutch.(3)Taking the fatigue life of the spring clutch as the objective factor,the orthogonal test was designed to optimize the structural parameters of the clutch.The results show that the influence of clearance,chamfer and mandrel interference on the fatigue life of clutch is extremely obvious,obvious and relatively obvious,respectively.The maximum combination of fatigue life is chamfer of 0.4 mm,mandrel interference of 0.15 mm and spring clearance of 0.4 mm.At this time,the number of fatigue life is8.011×10~6 times.(4)The fatigue performance test was carried out on the spring clutch fatigue test bench,and the fatigue life and failure location of the spring clutch were obtained.The results show that the variable cross-section spring breaks at the inner corner of the inner ring of the 14th ring,and the number of cycles before fracture is 2.688×10~5 times.The cracks propagate along the thickness direction and diameter direction of the spring section.The fatigue failure area has a good correspondence with the simulation results.The number of test life is smaller than the simulation results,and the error is 17.97%,which verifies the accuracy of fatigue life prediction results.