聚醚亚酰胺PEI树脂论文高分子材料时相关棘轮行为的本构描述.doc

聚醚亚酰胺(PEI)树脂论文：高分子材料时相关棘轮行为的本构描述 【中文摘要】高分子材料日益广泛的应用,使其时相关棘轮效应在结构安全和寿命评估方面具有越来越重要的作用。近年来,高分子材料循环变形行为方面的实验已相继开展,有关其理论模型也在建立过程中。然而,就已有的实验研究和理论进展来看,表现出两点不足：第一,专门就其棘轮行为进行的实验研究尚欠系统性,尤其对其时间相关特性的揭示还不够细致；第二,高分子时相关棘轮行为的理论模型亟待建立,已有的本构模型也须进一步改进和发展完善。为此,本论文开展了如下三方面工作：1.在室温下,对聚醚亚酰胺(PEI)树脂进行了较为系统的单轴时相关非对称应力循环加载实验。调查了不同平均应力,不同应力幅值,不同应力率以及不同峰值应力保持时间对该树脂棘轮行为的影响,为建立时相关棘轮行为本构模型提供了实验基础。2.将Schapery模型用于描述聚醚亚酰胺(PEI)树脂在非对称应力循环下的时相关棘轮行为。通过与实验结果的比较,表明了Schapery模型可以用来模拟PEI树脂的时相关棘轮行为,从而推广了该模型的应用范围。3.为进一步考证Schapery模型对聚醚亚酰胺(PEI)树脂时相关棘轮行为的模拟能力,还对拉伸-拉伸循环和拉伸-压缩循环下的棘轮行为模拟结果进行了比较,结果表明：原模型不能对两种工况做出统一的描述。通过对参数方程进行合理的改进,使得修正的Schapery模型能够同时兼顾两种工况的模拟,并通过与实验的比较得到了较为满意的结果。 【英文摘要】Time-dependent ratcheting of polymer materials is of great importance in the safety design and life assessment of structures. In recent years, the cyclic deformation of polymer materials including ratcheting behavior presented during the asymmetrical stress-controlled cyclic loading was extensively studied by many researchers experimentally, and the theoretical models were constructed. However, as for the obtained experimental and theoretical results, there are still two shortcomings. First, there are few researches on the ratcheting behavior of polymer materials, especially for the time-dependent ratcheting. Second, the new models for the time-dependent ratcheting of polymer materials need to be further constructed and the existed models also should be extended.Therefore, there are three aspects of contributions in this work as follows:1) The time-dependent ratcheting of a Polyetherimide (PEI) resin is experimentally investigated under the uniaxial stress-controlled cyclic loading with non-zero mean stress at room temperature. The main attention is paid on the effects of different mean stresses, stress amplititudes, stress rates and holding-times at peak stress on the ratcheting of the PEI polymer. Some significant conclusions useful to construct a cyclic constitutive mod