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RESEARCH FOR A PROJECTILE POSITIONING STRUCTURE FORSTACKED PROJECTILE WEAPONSQiao Luo*, Xiao-bing Zhang**Nanjing University of Science and Technology, Nanjing, ChinaThe stacked projectile weapon system functions as an automatic, high rate of fire, firearm wherebyit may be used as a close-in ship-board defense against bombs, missiles or attack aircraft as it launchesa large numbers of projectiles within a short period of time. Its characteristic is that a plurality ofprojectiles are axially disposed within the barrel and serially launched. One of the key technologies ofserially launching is the projectile positioning. Improper positioning causes the movement of the latterprojectile, the volume change of the powder chamber, even fragmentation of the propellant. What?smore, the latter projectile may be launched prematurely, and it may bring about catastrophic accidents.Therefore, the projectile structure and positioning technology should be well designed and optimized.The present projectile positioning structures have respective advantages and shortcomings, a newstructure based on the self-locking principle is put forward in this paper.The structure is verified as feasible by static analysis if the proper material and structuralparameters are chosen. And the condition of reliable positioning is get, which is the maximum staticfriction coefficient between the contact surfaces of the positioning ring and the barrel must be greaterthan the maximum static friction coefficient between the contact surfaces of the positioning ring andthe projectile. It is very important for the choice of the material.In order to check the strength and verify the feasibility of the structure in launch conditions, themulti-body contact finite element model of the projectile, the positioning ring and the barrel isestablished, coupled with dynamic load in the interior ballistic cycle. The dynamics equations of theelastic body can be solved by step-by-step integration method. The interior ballistic model is a systemof ordinary differential equations, it can be solved by a fourth-order Runge?Kutta method. According to calculations and discussion, the conclusions are as follows:(a) projectile positioning structure is feasible, shown in Fig. 1(a);(b) strength of the projectile and the positioning ring can meet the strength requirement for launchconditions, shown in Fig. 1(b);(c) increase in the maximum static friction coefficient between the contact surfaces of the positioningring and the barrel improves the positioning performance, as well as decreases in the maximum staticfriction coefficient between the contact surfaces of the positioning ring and the projectile;(d) increase in the upper thickness and height improves the positioning performance, as well asdecreasing in lower thickness. Lower thickness affects positioning performance more greatly, shown inFig. 2.
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11975(a) the axial displacement contours of the ring and barrel (b) the von-miss stress contours of the projectFig. 1. The axial displacement contours of the ring and barrel and the von-miss stress contours of the project.0.040.080.120.160.160.200.240.280.320.36Structure 1stStructure 2ndStructure 3rdf1lower limit off 2Fig. 2. The results of the three structures.