Numerical Simulation Research On The Effect Of Aerodynamic Heating On Charge Quality And Penetration Stability

Aerodynamic heating has always been the main factor restricting the development of supersonic or hypersonic weapons.Long-term aerodynamic heating puts a severe impact on the stability of warhead charges during flight and high-speed penetration.In order to study the effect of aerodynamic heating on the charge quality and penetration stability,this paper takes a simplified model of a warhead as the research object,and carries out a numerical simulation of the effect of aerodynamic heating on the charge quality and penetration stability.LLM-105 based PBX heat resistant explosive was selected as the warhead charge.In order to accurately describe the finite element model of the charge in different states,the specific heat capacity,thermal conductivity,linear expansion coefficient and other material properties of the charge were accurately measured out.The two-dimensional finite element model of the warhead and the outer field was established,with the Spalart-Allmaras turbulence model and the fluid-structure coupling method,using FLUENT fluid simulation software,numerical simulations were carried out to simulate the effects of different flight speeds,different charge densities,different shell wall thicknesses,and different thickness of the buffer layers on the charge temperature.The temperature distribution of the charge obtained in the FLUENT fluid simulation software was used as the load condition,and the ABAQUS finite element simulation software was used to carry out the numerical simulation of the influence of the above-mentioned different working conditions on the thermal stress and displacement of the charge.The two-dimensional finite element model of the warhead penetrating the two-layer 921A target plate was established,with the constitutive equation of the material,using ANSYS/LS-DYNA explicit dynamics software,numerical simulation regarding the high temperature environment on the penetration stability of the charge was carried out.Studies have shown that:(1)The increase of the flying Mach number will lead to a sharp increase in the temperature of the charge,and will cause an increase in the thermal stress and thermal displacement of the charge,and at the same time will increase the Von-Mises of the charge during the penetration process.When the flying Mach number is 5Ma,the maximum temperature of the charge is 662K(389℃),in which the charge has already been thermally ignited.As the flying Mach number increases from 2Ma to 4Ma,the maximum thermal stress value of the charge increases from 0.125MPa to 0.155MPa,and the maximum thermal displacement increases from 0.314mm to 0.736mm.The maximum Von-Mises that the charge bore during penetration process also increased from 0.087MPa to 0.548MPa.(2)The temperature and thermal stress of the charge have an inverse correlation with the change of the charge density as the same as the Von-Mises stress change during the penetration process.When the charge density is 2000kg/m~3,the maximum temperature of the charge during the aerodynamic heating process drops to 405K(132℃),the maximum thermal stress and thermal displacement of the charge reduced to 0.135MPa and 0.481mm,respectively.The maximum Von-Mises stress during penetration is also reduced to 0.508MPa.(3)The increase of the wall thickness of the warhead shell and the thickness of the buffer layer can protect the charge to a certain extent,and the maximum temperature of the charge reduced by 7.11%and 23.83%respectively during aerodynamic heating.At the same time,the Von-Mises suffered by the charge during the penetration process has also been correspondingly reduced.