| In the firing process,the heavy parts of the automatic mechanism are subjected to the impact of high impact,strong vibration,high bore pressure and other complex cyclic loads,and the fatigue fracture of the heavy parts of the automatic mechanism has occurred repeatedly in the domestic small and medium caliber artillery automatic mechanism.The design usually adopts the increase of safety factor to meet the strength requirements,and the structure of the heavy parts is not optimized enough and the stress concentration is high,which causes the problems of repeated system design,high cost and long period.To address the above-mentioned problems,this paper takes the durability of the rotating locking mechanism of 35 mm artillery automatic mechanism under the action of cyclic impact load as a traction,and reveals the main factors affecting its durability and its influence mechanism by studying the failure mode effect and criticality analysis of the rotating locking mechanism.The study also takes the impact load applied to the locking mechanism and the stress redistribution of the structure on the durability of the rotating locking mechanism as the research object,and further verifies and optimizes the durability influence law by combining the durability test of the rotating locking mechanism simulated parts and BP neural network algorithm,so as to provide basic technical support for improving the durability of the heavy parts of the automatic mechanism.The main research contents are as follows:(1)The typical faults of the rotating locking mechanism of artillery automatic mechanism in active service were sorted out,and the failure mode,effects and criticality were analyzed.To fill in FMECA work sheet and draw criticality matrix,it summarizs the main factors affecting the durability of the rotating locking mechanism.(2)The load factor and structural parameter factor among the main factors affecting the durability of the rotating locking mechanism were quantitatively processed.By means of the plane axisymmetric model composed of pill cylinder,breechblock and barrel,the influence law of different friction coefficients between pill cylinder and pill chamber and different axial initial clearance on the impact load on the breechblock is analyzed.Combined with the impact load change curve,the orthogonal test method was used to simulate the structural parameters of the locking mechanism and the surface processing quality,etc.On the premise of unchanging the basic dimensions of the components,the influence of the reasonable layout of the structure on the durability of the structure was investigated,and the simulation results were analyzed by the extreme difference analysis method to obtain the primary and secondary influence of each factor on the durability of the locking mechanism.The durability of the locking mechanism is influenced by the change in the root angle of the locking tooth of the gun breech..(3)The durability tests of the rotating locking mechanism were conducted on the original design scheme and the design scheme in the orthogonal test,and the results of the orthogonal test were verified.The fatigue durability life of the simulated parts used in the test is basically consistent with the results of the real structure simulation calculation,and the fracture location of the simulated parts is basically consistent with the fatigue crack sprouting location of the real structure simulation calculation.(4)Using BP neural network algorithm,the neural network model of fatigue durability life of rotating locking mechanism is established,and the level of influencing factors in the orthogonal test is further refined.The orthogonal test method preferred results compared with the original design scheme durability life improvement rate of 2.56 times;while the BP neural network algorithm,with higher optimization efficiency,calculated a better level of influence factors scheme,compared with the original design scheme durability life improvement rate of2.78 times. |
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