Analysis And Research On The Status Difference Of An Automatic Rifle Heat Gun

Firearm Deviation Under Cold and Hot Condition and Firearm Heat Dissipation refer to the phenomenon that the precision of fire is inconsistent when firearm is under cold and hot condition.Precision of fire inconsistency is mainly showed in two aspects,accuracy of fire inconsistency and density of fire inconsistency.Nowadays,firearm is extremely required to be with high precision;research of firearm’s characteristics when in cold and hot state,can provide a basis for in-depth understanding of the mechanism of Firearm Deviation Under Cold and Hot Condition and Firearm Heat Dissipation,and has important practical significance to ensure the accuracy of fire.This paper firstly studies the mechanical properties difference of barrel,when they are in cold and hot state.The barrel is a part of a small caliber automatic rifle,which is the research object.Tensile tests are done to barrel at different temperatures by universal testing machine.By doing the tests,four mechanical properties(yield strength,tensile strength,modulus of elasticity and elongation)of these two parts are obtained.Based on testing result,empirical models of main mechanical properties are established via fitting method.Secondly,a finite element model for the barrel of the small caliber automatic rifle is built,after the establishment of boundary condition and initial condition of inside and outside barrel wall based on internal ballistic theory and thermoelastic coupling theory.In addition,powder gas temperature and convective coefficient of barrel in three different periods of shooting are established also;then physical and mechanical properties parameter of steel material and chromium material are determined when barrel is under different temperature.Based on the established barrel finite element model,Multiphysics module in ANSYS software and APDL language programming are employed to calculate the transient temperature field and strain field at different times in the process of 150 rounds automatic firing.Furthermore,temperature,radial displacement,axial displacement,these three items vary with the shooting numbers.Analysis on the change and distribution of these three items in different position of the barrel with different shooting numbers is showed in this paper.The outer diameter of barrel is changed to study its effect on transient temperature field and strain filed.In addition,barrel under cold and hot condition with 10 rounds firing is simulated by finite element analysis,the change of three items listed above in different position of barrel is analysed,when barrel is under cold and hot condition.Lastly,shooting tests are done to an automatic rifle.Temperatures in different positions of the muzzle and projectile dispersion under cold and hot condition are measured.The testing results provides the basic data for in-depth understanding of the mechanism of Firearm Deviation Under Cold and Hot Condition and Firearm Heat Dissipation.