The Fatigue Reliability Design Analysis Of The Key Parts Of Firearms

In this paper,the pin and extractor which are the key parts of a gun were taken as the research object,the local stress and strain distribution of the key parts based on the finite element and the agent model are analyzed,and the reliability of the life of the pin and extractor under the fatigue failure is studied.Finally,the reliability analysis and parametric optimization of the pin are carried out by the probability-interval mixed variable.This thesis mainly analyzes and researches the following questions:(1)Considering the main influencing factors in the firing process of bullet,the pin and extractor were taken as the research object,the factors which have a smaller influence are neglected or simplified when modeling.Based on the geometric shape,load characteristics and finite element analysis of the gun model,the finite element method is used to establish the simulation model and analyze the influence of important boundary conditions and material parameters on the local stress and strain.(2)The real physical performance model is often complicated for complex components such as the pin and extractor of automatic weapons,and the explicit function relationship between the target performance and the design variables can not be output.In this paper,the Kriging interpolation model is established by analyzing the result of stress and strain simulation,and the stochastic input variables are defined from the parameters such as the size,the material constant and the initial condition of the above two important parts,without taking down the model precision.Finally,the relationship between the equivalent stress of the stopper interface and the random input variable is obtained.(3)Through the finite element simulation analysis,the stress-time course curve of the joints at the critical interface is obtained,and the stress spectrum is used to deal with the rain flow.The local stress-strain analysis of the critical nodes is carried out according to the Neuber formula.Finally,the fatigue life of the pin and extractor is estimated according to the Miner damage accumulation model.The reliability analysis and prediction of the fatigue life of the pin are carried out by using the degenerate data statistical method.The distribution functions of the fatigue damage of the pin and extractor are fitted and the reliability of the pin and extractor are evaluated by the degradation data analysis.(4)For the defects of the traditional reliability analysis must be based on the theory of probability and statistics,and the probability theory requires a large sample or event with reproducibility to describe the probability parameters,interval variables are introduced to describe some parameters of the complex parts due to lack of samples,a fatigue reliability analysis method based on probability-interval mixed variable is proposed.Finally,combined with the theory of uncertainty and optimization methods,the pin was taken as an example,the reliability optimization design method with uncertainties is studied.