面向不同应力比的复合材料拉—拉疲劳寿命能量预测法研究

发布时间：2018-01-10 15:30

本文关键词：面向不同应力比的复合材料拉—拉疲劳寿命能量预测法研究　出处：《南京航空航天大学》2016年硕士论文　论文类型：学位论文

【摘要】：以试验方法获取不同应力比下复合材料的疲劳寿命,所耗费的时间和经济成本太高,因此一直以来,研究人员都关注于研究能够降低试验成本的快速预测复合材料疲劳寿命的理论和实验方法。能量方法是研究疲劳的重要方法之一,但现有的疲劳能量理论还存在许多难点和不足。为此,本文对复合材料疲劳的能量过程进行研究,并尝试建立一个能够预测复合材料寿命的能量方法。复合材料疲劳过程中,输入的机械功以多种能量形式向外界耗散,其中绝大部分转化为耗散能和非弹性变形能。输入功可以用循环滞回能表示,且与疲劳载荷条件和循环加载次数有关;热耗散是能量耗散的主要形式,其变化与温度的变化相似;非弹性变形能是导致复合材料从裂纹萌生、扩展直至发生疲劳断裂破坏的能量,它与材料的损伤状态是直接相关的。为探究复合材料疲劳过程中的能量变化规律,本文对玻璃纤维复合材料层合板进行了静拉伸试验以及疲劳试验,试验的同时用高精度的红外热像仪记录了疲劳过程中的温度变化,并对一些典型的试验现象和结果进行了分析和规律总结。对复合材料拉-拉疲劳载荷下迟滞回能的变化规律研究发现,疲劳过程中应变变程和对数迟的迟滞回能占应变能密度比值都随循环次数线性增加的,进而建立了对循环滞回能量化描述的模型,并对所建模型进行了验证,结果与试验值吻合较好。从复合材料疲劳过程循环滞回能、热耗散和非弹性变形能之间的关系,结合材料温度的变化得到了非弹性变形能的定量描述;而复合材料受单一形式的拉-拉疲劳载荷时,疲劳破坏的非弹性变形能与疲劳寿命之间存在一一对应的关系,且此关系是材料自身的力学属性可通过疲劳试验获得。综合了以上的研究内容,结合所作复合材料疲劳试验,建立了复合材料疲劳寿命的能量法预测模型。并对所建寿命预测模型进行了验证,从结果看模型对疲劳寿命的预测比较准确。
[Abstract]:The fatigue life of the composites under different stress ratios is obtained by the test method, the time and economic cost are too high, so it has been all along. Researchers have focused on the theory and experimental methods of fast prediction of fatigue life of composite materials which can reduce the test cost. Energy method is one of the important methods to study fatigue. However, the existing fatigue energy theory still has many difficulties and shortcomings. Therefore, the energy process of composite fatigue is studied in this paper. An energy method is established to predict the life of composite materials. In the fatigue process of composite materials, the input mechanical work is dissipated to the outside world in a variety of forms. Most of them are transformed into dissipative energy and inelastic deformation energy. The input work can be expressed by cyclic hysteresis energy, which is related to fatigue load condition and cyclic loading times. Heat dissipation is the main form of energy dissipation and its variation is similar to that of temperature. Inelastic deformation energy is the energy that leads to crack initiation, propagation and fatigue fracture failure. It is directly related to the damage state of the material. In order to investigate the energy change law of the composite during fatigue, the static tensile test and fatigue test of glass fiber composite laminates are carried out in this paper. At the same time, the temperature change during fatigue was recorded by high precision infrared thermal imager. Some typical experimental phenomena and results are analyzed and summarized. The ratio of hysteresis energy to strain energy density increases linearly with the number of cycles during fatigue. A model for describing the energy of cyclic hysteresis is established and verified. The results are in good agreement with the experimental data. The quantitative description of inelastic deformation energy is obtained from the relationship among cyclic hysteresis energy, heat dissipation and inelastic deformation energy during fatigue process. When the composite is subjected to a single form of tensile and tensile fatigue load, there is a one-to-one relationship between the inelastic deformation energy of fatigue failure and the fatigue life. This relationship is the mechanical properties of the material itself can be obtained through fatigue tests. Combined with the above research content, combined with the fatigue test of composite materials. The prediction model of fatigue life of composite materials by energy method is established, and the prediction model of fatigue life is verified. The results show that the model is accurate in predicting the fatigue life of composite materials.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB33

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