构建AP-HTPB固体推进剂松弛模量主曲线的不同方法（英文）

Different Methods for Developing Relaxation Modulus Master Curves of AP-HTPB Solid Propellant

分析了建立高氯酸铵-端羟基聚丁二烯(AP-HTPB)固体推进剂松弛模量主曲线的三种不同方法(Williams-Landel-Ferry(WLF)方法、Arrhenius方法和基本的时间-温度叠加(TTS)方法)。通过不同温度(-40,+20,+76℃)和10%常应变下1380s的应力松弛试验得到了复合固体推进剂松弛模量。通过评估松弛模量,给出转移因子和松弛模量主曲线,最后通过确定系数(R^2)得出了最佳的拟合方法。结果表明,基本TTS方法可给出最佳拟合曲线,因为该方法不依赖外部材料常数和应用中的经验方程,而且该方法可以适用于任何黏弹性材料。但是,在应用有限元软件时,经常要求用材料常数来定义非线性黏弹性材料模型,这种情况下,目前研究结果表明,当给出合适的常数后,WLF和Arrhenius两种方法均可给出满意的结果,而且WLF方法更为准确,因此在AP-HTPB固体推进剂有限元分析中倾向于采用这种方法。

A comparative assessment of three different methods used for estimating and generating the relaxation modulus master curves of ammonium perchlorate-hydroxyl-terminated polybutadiene （AP-HTPB） solid propellant was carried out. These methods are the Williams-LandeI-Ferry （WLF） method, the Arrhenius method, and the basic time-temperature superposition （TTS） method. The experimental data of the relaxation modulus for composite solid propellant were gathered by performing stress relaxation tests at constant strain level 10% for 1380 s at several temperature （ -40, ＋20, ＋76 ℃）. The procedures and steps for evaluating the three methods was based on the same experimental data obtained for relaxation modulus to estimate the shift factors and then to generate the master curves of relaxation modulus and finally comparing the best fit method through the deter- mination coefficient （ R2 ）. The corresponding results indicate that the basic TTS method generated the best fit curve relative to the experimental data because this method is independent of external material constants and empirical equations in its application and it can be generally applicable to any viscoelastic material. However, in the applications of finite element software, the material constants are usually required to define the non-linear vis- coelastic material model, in this case, the result of the present work demonstrates that both WLF and Arrhenius methods can produce satisfactory re- sults, when appropriate constants are used, and the WLF method has proven to be more accurate and would be preferred in finite element analysis of AP-HTPB solid propellant.