摘要
Abstract
In order to explore the causes of perforation deviation after the extrusion of seven-perforated gun propellant,and seek a solution to improve the perforation deviation problem,the control method of perforation deviation towards the ideal di-rection was studied based on the fluidity of the propellant in the mold during extrusion.The internal flow channel model was es-tablished on the basis of the geometric model of propellant grain,and the Bird-carreau law model was used for simulation analy-sis,including the numerical prediction of the shape and size of the extruded grains.Then,the extrusion process was inversely simulated,the shape of die was designed,and the flow field distribution and pressure distribution of the extrusion process were analyzed.The designed die was used to simulate the extrusion,and the feasibility of inverse design of die was verified theoreti-cally.The results show that the uneven flow velocity,not the pressure or shear rate,is one of the key factors associated with the perforation deviation phenomenon.According to the velocity distribution of the cross-section at the inlet of the mold during the extrusion process,it can be seen that the inlet flow velocity distribution is different.It reveals that the flow velocity near the wall is low,while the flow velocity between the needles is about 1.5 times higher.After leaving the die,the flow velocity in most areas decreases.The sectional area of the fast flow region increases due to the decrease of the flow velocity,on the contrary,the area of the slow flow region decreases due to the increase of the flow velocity.The results reveal the redistribu-tion of the velocity causes the deformation of the free surface of extruded propellant.The inverse extrusion simulation can com-pensate for the perforation deviation in the propellant.The extrusion verification test of the inverse design of the die shape is carried out,and the perforation shape of the extrudate is more regular than before.Therefore,it is expected that the yield of propellant can be improved by designing the mold shape based on inverse extrusion design.关键词
流体力学/Polyflow/流变模型/逆向挤出/七孔发射药/口模设计Key words
fluid mechanics/polyflow/the rheological model/inverse extrusion/seven-hole propellant/mouth die design分类
军事科技
