| Nitroguanidine gun propellant has high energy and low ablation performance.It has been widely used in large and medium artillery.But at modern times,the extrusion process of the gun propellant and the design of the mold depend mainly on trial and error,which cannot meet the need of precision manufacture of gun propellant.In order to solve these problems in the production process of the gun propellant,the researches on the rheological law,the extrusion process and the optimization design of the flow channel of the gun propellant mold have been done.It's propitious to improve the precision manufacturing level of the gun propellant and shorten the process of mold design cycle.The rheological behavior of nitroguanidine gun propellant which has different formulation,temperature and solvent ratio is studied by capillary rheological test.It is indicated that the gun propellant is a typical non-Newtonian pseudoplastic fluid.The constitutive equation of the flow model of the gun propellant can be described accurately by the Power model.The mathematical model of the extrusion process is established by means of numerical simulation method.The influence of nitroguanidine gun propellant formulation on the pressure field,velocity field and shear rate field distribution in compression process is analyzed,and the simulation sizes have been obtained.Compared with the actual size,the simulation result is close,and the error of the parameters of outside diameter,inner diameter,and outer arc thickness are less than 10%.Based on these above researches,the flow models of the 11/7 mold channel with different shrinkage angles and forming length are established.The numerical simulation method is used to analyze the effects of the shrinkage angle and the length of the forming section on the shear rate field,pressure field and velocity filed in the extrusion process.With the simulation result,the optimal shrinkage angle of mold channel is 45°and the length of forming section is 30mm. |
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