【摘要】：涂層織物膜材料是一種典型的高分子復合材料,具有明顯的非線性、非彈性、各向異性、黏彈性特性,其材料力學性能受外界環(huán)境、荷載水平、加載歷史等因素的影響顯著。在實際膜結構工程中,隨著時間的推移,徐變和應力松弛會使膜面預張力減小,導致膜面松弛和結構剛度降低,因此十分有必要系統(tǒng)研究膜材的黏彈性性能,這對研究膜結構長期使用性能、保證結構的安全性能具有重要的意義。本文以PTFE涂層織物膜材為研究對象,進行了一系列應力松弛性能、蠕變性能和循環(huán)拉伸性能的試驗研究,討論了拉伸速率、加載次序、溫度、應力水平等因素對膜材黏彈性力學性能的影響規(guī)律,推導了基于各向異性的膜材料黏彈性本構方程。主要的研究內容如下:(1)進行了不同條件下的應力松弛和蠕變試驗,分析了溫度、應力水平、初始拉伸速率等因素對膜材經、緯向松弛應力和蠕變應變的影響規(guī)律。推導了應力松弛-蠕變的轉換關系式。采用幾種常用的黏彈性模型對上述試驗曲線進行了擬合,分析比較了各類模型的擬合精度,得到了用于描述涂層織物膜材黏彈性行為的本構關系模型。(2)進行了不同條件下的單軸循環(huán)拉伸試驗,得到了加、卸載彈性模量、棘輪應變、滯回環(huán)面積等參數(shù),分析了偏軸角度、拉伸速率、加載應力幅等因素對膜材料棘輪行為的影響規(guī)律,將膜材料的應變進行了分解處理,采用修正的Burgers模型對膜材料循環(huán)拉伸曲線進行了預測。(3)進行了一系列偏軸試驗,包括循環(huán)拉伸試驗、應力松弛試驗和蠕變試驗,系統(tǒng)地研究了膜材料的各向異性�；趶秃喜牧险桓飨虍愋岳碚�,推導得到了膜材料彈性模量、松弛模量和蠕變柔量與偏軸角度的關系式。由各向異性材料塑性理論及流動法則,通過引入蠕變勢函數(shù)、等效應力及等效蠕變率等表達式,得到了PTFE涂層織物膜材各向異性本構方程。
[Abstract]:The coated fabric membrane material is a kind of typical polymer composite material, which has obvious nonlinear, inelastic, anisotropic and viscoelastic properties. The mechanical properties of the coated fabric are significantly affected by the external environment, load level, loading history and other factors. In the actual membrane structure engineering, creep and stress relaxation will reduce the pretension of membrane surface with time, resulting in the relaxation of membrane surface and the decrease of structural stiffness. Therefore, it is necessary to study the viscoelastic properties of membrane materials systematically. It is of great significance to study the long-term service performance of membrane structure and ensure the safety performance of the structure. In this paper, a series of experimental studies on the stress relaxation, creep and cyclic tensile properties of PTFE coated fabric membrane were carried out. The tensile rate, loading sequence, temperature and tensile rate were discussed. The influence of stress level on the viscoelastic properties of membrane materials was studied. The viscoelastic constitutive equation of membrane materials based on anisotropy was derived. The main research contents are as follows: (1) stress relaxation and creep tests under different conditions are carried out, and the effects of temperature, stress level and initial tensile rate on warp, zonal relaxation stress and creep strain are analyzed. The relationship between stress relaxation and creep is derived. The experimental curves are fitted with several common viscoelastic models, and the fitting accuracy of these models is analyzed and compared. A constitutive relation model for describing viscoelastic behavior of coated fabric membrane is obtained. (2) uniaxial cyclic tensile tests under different conditions are carried out, and parameters such as loading, unloading elastic modulus, ratchet strain, hysteresis loop area and so on are obtained. In this paper, the influence of axial angle, tensile rate and loading stress amplitude on ratchet behavior of membrane material is analyzed, and the strain of membrane material is decomposed. The modified Burgers model is used to predict the cyclic tensile curves of membrane materials. (3) A series of biaxial tests including cyclic tensile tests stress relaxation tests and creep tests are carried out. The anisotropy of membrane materials is systematically studied. Based on the orthotropic theory of composite materials, the relationship between elastic modulus, relaxation modulus and creep compliance of membrane materials and the axial angle is derived. Based on the plastic theory and flow rule of anisotropic materials, the anisotropic constitutive equation of PTFE coated fabric membrane was obtained by introducing creep potential function, equivalent stress and equivalent creep rate.
【學位授予單位】：中國礦業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU599

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本文編號：2168327