Study On Transfer Law Of Launch Load And Structural Optimization Of Large Caliber Guns

The development trends of modern artillery include large power,high mobility and high precision,and there are requirements of guns with higher rigidity,strength,velocity and precision.The mechanical characteristics of launching load which transmit along the key components of guns are needed to be captured.The transfer law of launch load should be controlled by structural optimization methods.The traditional design theory of guns is unsatisfied with this development.Therefore,it is of great importance to carry out the research on the launch load transfer law and structural optimization technology for large caliber guns.In the current work,nonlinear finite element methods and modern optimization design methodology were used to study the structural optimization,nonlinear finite element modeling,launch load transfer law and structural dynamic response optimization of guns.The stiffness and strength of artillery key components under different firing conditions were studied by using the finite element method,and the weak links in the structure were identified.Improvements were made to the cradle,which effectively improved the stiffness and strength of the cradle.Aiming at improving the stiffness of the top carriage of guns whose recoil length changes with elevation,a structural topology optimization method was presented,and the optimization under multiple firing conditions was conducted.The best outline and the optimal stiffener layout of the top carriage were obtained.The size optimization design method was applied to detailed design of the top carriage,and a structural optimization scheme was acquired.The stiffness and strength of the optimized top carriage were improved significantly.The launch dynamics model of the large caliber gun was established based on nonlinear finite element method.Finite element modeling methods for nonlinear connection relationship of the components in the gun,including contact impact relations between barrel and liners,between elevating gear and elevating gear arc,as well as between base plate and ground,were studied.The modal analysis of the gun was then carried out by using the finite element method,which was validated by the test results.The dynamic responses of the gun during launch,including recoil displacement,angular velocity of muzzle,and cradle strain,were calculated by the implicit integration algorithm.The finite element model of the gun was validated by comparing the numerical results with the experimental data.The mechanical characteristics of launch load which passed through key components such as liners,elevating gear arc and trunnions were studied by the nonlinear finite element method.The results from the finite element analysis and the traditional method were compared,and the shortcomings of traditional method were indicated.The dynamic stress variation and distribution of the gun under different firing conditions was studied,and the results show that the stiffness and strength of the gun satisfy the design requirements.The general contact algorithm and multi linear isotropic hardening elasto-plastic material model were adopted to establish the finite element model of the saddle ring,which considering the large-scale contact/impact between the raceway and rollers.A comparison between the elastic and elasto-plastic dynamic responses of the saddle ring were conducted.The distribution and variation of stress,contact stress and contact force in the saddle ring were obtained.The effects of structural arrangement of recoil mechanism and overall structural parameters on muzzle vibration were investigated.The muzzle vibration responses among the cases of different fixed forms and locations of recoil mechanism were compared,and the effects of structural arrangement of recoil mechanism were assessed.By conducting the sensitivity analysis of overall structural parameters on muzzle vibration,the effects of the mass eccentricity of recoil parts,the mass of muzzle brake,and the position of the front liner were evaluated.The sample data of muzzle vibration were obtained by using the optimal Latin hypercube design of experiments and the nonlinear finite element dynamic analysis.The Polynomial response surface model,Kriging model,BP neural network model and RBF neural network model of the gun were established,respectively,and the adaptability among different approximate models was compared.It was shown that the BP neural network model had higher prediction accuracy.The objective function of muzzle vibration optimization was established.The structural dynamic response optimization of the gun was achieved by using the BP neural network model and genetic algorithm,and the muzzle vibration was considerable decreased.The muzzle vibration of the optimized gun,calculated by nonlinear finite element method,was in good agreement with the result calculated by BP neural network model,which indicats that the presented approach is effective and feasible.