中应变率下HTPB推进剂压缩力学性能和本构模型研究

Mechanical Properties and Constitutive Model for HTPB Propellant under Intermediate Strain Rate Compression

关键词:  HTPB推进剂  中应变率  压缩力学性能  本构模型

Key words:  HTPB propellant  Intermediate strain rate  Compressive mechanical properties  Constitutive model

摘要:

为研究固体推进剂在中应变率条件下的压缩力学性能，在高应变率液压伺服试验机上开展了单轴压缩实验，并获取了温度范围为-40 ~ 25℃及0.40 ~ 85.71s-1应变率下HTPB推进剂的应力-应变曲线。结果表明，本文的实验方法是有效的，温度和应变率对HTPB推进剂的压缩力学性能影响显著。随温度降低和应变率升高，应力-应变曲线特性变得更加复杂，并与准静态下的应力-应变曲线特性有明显区别。压缩模量[E]和压缩应力[σ0.17]随温度的降低和应变率的升高而逐渐增加，且均与应变率具有相对较好的线性双对数关系。在低温和较高应变率的双重作用下，-40℃，85.71s-1条件下的压缩模量[E]和压缩应力[σ0.17]分别为25℃，0.40s-1条件下数值的10.64倍和4.25倍。基于时温等效原理，得到了HTPB推进剂的压缩力学性能主曲线，该主曲线能够对低温较宽应变率范围内推进剂的压缩力学性能进行预测。在朱-王-唐非线性粘弹性本构模型的基础上，构建了考虑温度和应变率效应的固体推进剂中应变率压缩本构模型，并采用遗传算法拟合了本构参数。通过不同温度和应变率下预测结果与实验数据的比较，验证了模型的有效性。所建模型能够较好地描述0.17应变以内HTPB推进剂的压缩变形，可为低温中应变率下固体火箭发动机药柱的结构完整性分析提供理论基础。

Abstract:

To investigate the compressive mechanical properties of solid propellant at intermediate strain rates，uniaxial compressive tests were carried out by using the servo-hydraulic testing machine，and the stress-strain curves of HTPB propellant were obtained in a wide range of temperatures(-40 ~ 25℃) and strain rates (0.40 ~ 85.71s-1). The results indicate that the proposed test method is effective and the effects of temperature and strain rate on the compressive mechanical properties of HTPB propellant are significant. As the temperature decreases and strain rate increases，the characteristics of stress-strain curves for HTPB propellant are more complex and are obviously different from those under static conditions. Meanwhile，both compressive modulus [E] and compressive stress [σ0.17] increase as a linear-log function of strain rate at different temperatures. Because of the coupled effects of low temperature and high strain rate，the values of the compressive modulus [E] and compressive stress [σ0.17] at -40℃ and 85.71s-1 are 10.64 and 4.25 times of their values at 25℃ and 0.40s-1，respectively. The mechanical properties master curves for HTPB propellant were obtained based on the time-temperature superposition principle and can predict the compressive mechanical properties of HTPB propellant over a considerable range of strain rates at low temperature. Based on the Zhu-Wang-Tang model，a nonlinear viscoelastic constitutive model considering the effects of temperature and strain rate was developed for intermediate strain-rate compression of solid propellant. The constitutive parameters were identified by the GA-based optimization method. The overlap between experimental results and predicted results for HTPB propellant are good at strain lower than 0.17 under the test conditions，which confirms that the developed constitutive model is valid and can provide the theoretical basis for further analyzing the structural integrity of propellant grain at low temperatures and intermediate strain rates.