Study On Dynamic Characteristics Of Mechanical Fuze For A Small Caliber Projectile

In order to provide reference for design of shear pin safety device design in fuze, simulation software LS-DYNA was used to study the shear pins safety device arming in slip shooting, the safe pin hit bottom and rebound insurance. Using LS-DYNA numerical simulation method to study safe pin safety device go down to fuze chamber bottom wall and rebound process, the relative upward movement of the seat with safe pin and the maximum displacement between whether having the spacer or not, the base materials, safe pin diameter, safe pin travel, spacer materials and spacer thickness. Spacer can be increased to effectively prevent the rebound of the safe pin; with smaller elastic modulus of base materials, the relative upward movement maximum displacement of the safe pin and the seat was smaller; with smaller diameter of safe pin materials, the relative upward movement maximum displacement of the safe pin and the seat was larger; with smaller travel of safe pin, the relative upward movement maximum displacement of the safe pin and the seat was smaller; with larger elastic modulus of spacer materials, the relative upward movement maximum displacement of the safe pin and the seat was bigger in general; with the increase of the thickness of the spacer material, the relative upward movement maximum displacement of the safe pin and the seat was bigger.In order to study the material selection which is preferable for clip ring, LS-DYNA finite element software was used to study shock response of the clip ring comprising different materials (beryllium bronze, lead brass,20 steel) in fuze respectively and projectile fall under 1.5 m conditions,target board was consists of steel, wood and concrete, clip ring drop azimuth elected as opening mouth of clip ring rotated 9° (at this moment, torque on the clip ring got its maximum in theory),10°,11°,12° and 13° along the vertical direction, analysis the data found:the clip ring located 9° had maximum peak minimum; clip ring material was preferably should choose high elastic copper alloy materials; drop target board material softer clip ring undertaken smaller overload; fuze alone down to the target board clip ring had larger displacement than projectile down to the target board.To study the warhead fuze ballistic flight unscrewed outside possibility, classical exterior ballistic theory was used to estimate drag coefficient and polar damping coefficient of projectile, applying Workbench Fluent modules to complete projectile aerodynamic simulation and get the drag coefficient and polar damping coefficient and the effect of changing in mach number, rate, the angle of attack on the drag coefficient and polar damping coefficient. Pass kinetic analysis of high-rate rotating fuze and quantitative analysis of centrifugal force torque, friction torque and polar damping torque, the following conclusions was got:fuze will not be unscrewed; fuze be unscrewed was determined by drag coefficient and polar damping coefficient, the possibility of fuze be unscrewed proportional to polar damping coefficient while inversely proportional to drag coefficient; the possibility of fuze be unscrewed at initial trajectory was lager than at end trajectory.LS-DYNA software was used to research various factors effect on shear effect of shear pin.Based on the regularity degree of shear pin fracture, following conditions was got: clearances between shear pin, safe pin with supporting seat are smallest possibly in easy assembly conditions; the two sides clearances between safe pin with supporting should be much the same; Making rounded corner but not making fillet to remove burrs in the edges and corners of shear pin pores in aiming pin and supporting seat. The best materials of safe pin, shear pin and supporting seat respectively are 45 steel, HPb63-3Y copper alloy and 7A04 aluminum alloy. Shear pin safety device is suitable for launch environment which has short duration load.