Research On The Performance Degradation Modeling Methods Of Key Components And Automatic Mechanism Of Light Caliber Cannon

Generally speaking,from entering the forces to remediation and decommission,automatic gun always experiences a series of different performance degradation processes.If the gun performance degradation can be monitored,it would be possible to make proper maintenance strategy,so not only abnormal failure can be prevented but also service efficiency can be maximized.Automatic gun performance degradation modeling and assessment is proposed as an active maintenance technology based on the above envision.It focuses on the performance degradation assessment through the whole lifetime of equipment,and is totally different from existing fault diagnosis theory and method.Therefore,It has great significance of research and development of automatic gun performance degradation modeling and evaluation method,which could improve equipment service efficiency and prevent catastrophic failure.Based on the comprehensive analysis of research status at home and abroad,this paper takes a certain light caliber automatic gun as the object of study.By analyzing various factors that lead to automatic gun performance degradation,the research on performance degradation modeling methods of component and automatic gun is carried out under the framework of equipment performance degradation assessment.The main contents are as follows:First of all,in view of the problem that the present method of constructing finite element(FE)model of tube is complicated,parametric and high precision generation algorithms for the barrel and wear tube FE model is proposed.Based on the idea of parametric modeling,a Piecewise-Connection algorithm is presented to construct the geometric model of barrel and its FE model.Based on the above basis,a more efficient and general method:Direct Writing algorithm,is elaborated for generation of tube’s FE model.Based on the measured data of bore with wear,a Node-Offset algorithm is put forward for generation of the FE model of bore with arbitrary degrees of wear.The establishment of FE model of tube with different wear degrees could be helpful for the further research of automatic gun performance degradation.Secondly,aiming at the problem that current projectile-barrel coupling analysis has too much assumptions and leads to larger computation error,the computation method of projectile-barrel coupling analysis is improved and the coupling process between barrel and projectile is studied.By summarizing and analyzing research state of thermo-mechanical coupling analysis,the relationship between physical parameters,material parameters and temperature during engraving process of bearing band and interior ballistic process is determined.The thermo-mechanical coupling FE model of engraving process of bearing band and interior ballistic process is established.Aiming at the problem that coefficient of secondary work is set to constant and inaccurate calculation results is obtained when using the classical interior ballistic model,a calculation algorithm of the coefficient is put forward.On the basis of above algorithm,the impact of extracting bullet force on the engraving process and interior ballistic process is also studied.The method of calculating wear volume increment of tube with wear is put forward.and the degradation characteristics of projectile dynamics and interior ballistic parameters after bore wear are further analyzed by using above thermo-mechanical coupling FE model.Then,in the light of lacking accurate damage and degradation model for stranded wire helical spring(SWHS),the nonlinear damage model and degradation model is constructed respectively,and efficient and high accuracy identification algorithm of model parameters is studied.Based on static and dynamic test results of SWHS,a generalized modified normalized Bouc-Wen model(generalized BW model),which considering impact velocity,is proposed.An adaptive unscented Kalman filter algorithm(AUKF)with adaptive noise statistics estimator is proposed to identify model para,meters of SWHS,and the influence of measured noise level on the stability of AUKF is also analyzed.After conducted 6000 times impact testing for 4 automatic gun springs,the change characteristics of non-linear response model parameters of SWHS after performance degradation are analyzed,and definition of performance degradation of SWHS is proposed.The performance degradation model of feeding slide spring and counterrecoil spring of a small caliber machine gun is established.Aiming at the poor accuracy of AUKF in identification of SWHS damage model parameters,an improved opposition-based differential evolution algorithm(WODE)is proposed and numerical method is used to prove its effectiveness.When the SWHS is damaged,the dynamic response characteristics of damage model are analyzed and a separation method of atypical damage component is proposed.Besides the Slip-Lock damage unit which based on the Bouc-Wen-Barber-Noori(BWBN)model,two damage element models for spring are constructed based on the general establishing method for atypical hysteresis model.Finally,performance degradation model of gas-operated automatic gun is established.and degradation process is studied.The multi-rigid body model of automatic mechanism and basic computation equations of interior ballistic and gas-operated device which consider the effects of heat loss are derived based on aerodynamic and thermodynamics.The influence of different spring response models on the speed,displacement and theoretical rate of automatic transmission frame are analyzed.Based on the performance degradation model of SWHS,the influence of spring performance degradation on the automatic mechanism is investigated.The subroutine frame of interior ballistic model,gas-operated device and SWHS is put forward.And the simulation model framework of whole gun firing dynamics with considering of the projectile-barrel coupling process is also presented.After calculation and modification,the effectiveness of simulation model is verified,and the influence of interior ballistic performance degradation on the motion characteristic of gas-operated automatic mechanism is analyzed.The dynamic and kinematic degradation characteristics of automatic gun under two degradation factors is studied by combining the SWHS degradation model and the interior ballistic performance degradation model,and degradation law of automatic gun theoretical firing rate is obtained.The current research results are of great theoretical and practical value for the coupling analysis between gun and projectile,the analysis and fault prediction of automatic mechanism.The key technologies and research ideas can also provide reference for performance evaluation and life prediction of other equipment.