HTPB复合固体推进剂粘弹性应变能及非线性本构模型

Viscoelastic strain energy and nonlinear constitutive model for HTPB composite solid propellant

为了准确表征HTPB复合固体推进剂在有限变形条件下的力学性能,针对推进剂粘弹性应变能及本构模型进行研究。提出了推进剂粘弹性应变能函数和非线性本构方程的一般形式,并通过一元非线性回归方法拟合不同应变率下的拉伸试验数据,得到了材料参数关于应变率的函数,并由此建立了推进剂单轴拉伸变形下的应变能函数和本构方程,预测了不同应变率下的应力曲线,与试验结果和已有模型的预测结果进行了对比。结果表明,材料参数与应变率之间呈现幂函数关系;推进剂应变能密度随变形量的增大呈非线性单调增长,同一变形条件下,应变率越高,推进剂的应变能密度越大;本构方程可准确描述推进剂拉伸变形的应力应变关系,且尤其适用于表征低应变率下,材料在有限变形内的粘弹特性。

To characterize the mechanical property of HTPB composite solid propellant under finite deformation condition, vis- coelastic strain energy and nonlinear constitutive model were studied in this paper. The general forms of strain energy function（SEF） and nonlinear constitutive model were proposed, and the tensile test data were fitted by unitary nonlinear regression analysis. As a consequence, the material parametric function of strain rate was obtained, and on this basis the uniaxial tensile SEF and constitutive equation were established. The nominal stress curves at different strain rate were predicted, furthermore, they were compared with experimental results and prediction resuhs of existing models. The results show the power function relationship between material pa- rameters and strain rate, and the strain energy density proves to rise nonlinearly with strain, the higher the strain rate is, the larger the strain energy density will be at the same deformation. Moreover, the constitutive equation was demonstrated to be accurate on describing the tensile stress-strain relation of propellant, especially on representing the viscoelastic behavior at finite deformation and low strain rate.