改性双基推进剂非线性本构模型及其数值实现

In order to analyze the mechanical response of modified double-base (CMDB) propellant under complex loads,a nonlinear viscoelastic constitutive model of CMDB propellant with damage variables was established.In view of the tensile-compression asymmetry of CMDB propellant,the key parameters in the constitutive model were obtained by uniaxial tensile,uniaxial compression and corresponding relaxation tests.The nonlinear mechanical behavior of CMDB propellants can be accurately described when the damage variable negatively correlated with strain rates was characterized by means of a double exponential form with strain and strain rate. At the same time,volume strain was introduced as the determinant variable of tensile and compression conditions, and a numerical implementation method of nonlinear constitutive model based on UMAT subroutine was developed.The constitutive model considering tensile-compression asymmetry and its numerical implementation method were applied to the mechanical response analysis of the gas-generator grain under ignition impact load,and the analysis results were compared with those of single tensile parameters.The results show that when tensile-compression asymmetry is considered, the equivalent strain and damage variable of the structure are significantly different from the analysis results using single tensile parameters.Therefore,it is of great significance to judge the tensile and compressive state of the structure and select the correct parameters.