基于疲劳理论和能量分析的机械设备寿命预测方法研究

发布时间：2018-03-08 04:16

本文选题：状态监测　切入点：振动能量　出处：《郑州大学》2013年硕士论文　论文类型：学位论文

【摘要】：近年来,科技的进步正带动着现代机械设备向大型化、精密化、复杂化、连续化、高速化的方向发展,而工作环境越来越复杂的机械零件和工程构件,也同样受到长期、持续的交变载荷的作用。交变载荷容易造成机械设备的疲劳问题,疲劳破坏是在工程中造成构件失效最重要的原因之一。因此,无论是工程实际还是在理论研究上,疲劳学都是研究的热点问题。早在19世纪,疲劳问题开始进入世界各地学者们研究的领域,且在很长一段时间内,取得了很多丰硕的成果。虽然如此,寿命预测依然面临诸多问题。如果用一种确定性的方法去预测,所得的疲劳寿命都是一个确定的值,但结构的疲劳是一种非常复杂的现象,它受到诸多不确定因素的影响。现有的预测理论主要分为基于力学的寿命预测和基于概率统计的寿命预测理论,这些理论是基于构件的应力幅值和平均应力值等静态特征值进行估算,忽略了系统的动态变化,造成估算误差,而状态监测能够得到系统的动态参数。基于以上考虑,将传统的疲劳理论和系统动态状态监测这种信息技术联系起来进行机械设备的寿命预测是非常必要的。本文首先通过求解一个单自由度振动系统在简谐激励作用下的响应来引入振动能量,阐述振动能量的基本概念和意义,以及在寿命预测中的可行性分析,结合疲劳理论,推导出基于振动能量的疲劳寿命公式,最后使用健康度的概念,对机械设备的剩余寿命进行预测。本文的主要内容如下所示： 1.对一单自由度系统进行在简谐激励作用下的振动分析,从中得到单频率的振动功率和振动能量,判断两个特征量是否能全面的反应系统信息,并揭示振动能量与疲劳寿命的关系。最后根据传统的谱估计方法,得到振动能量谱的表达式。 2.对振动能量谱在状态监测和故障诊断中的作用进行分析研究,利用振动能量谱能够全面反应系统信息的优势,并结合全矢谱进行双通道的信息融合,得到全矢振动能量谱,对转子系统进行故障诊断,能有效的解决转子故障诊断中的误诊和漏诊状况,更加准确有效的识别转子故障。 3.分别通过理论和实例证明疲劳寿命在外部激励不变的情况下与振动能量的近似线性关系,并探讨疲劳寿命与激振频率和应力之间的关系,说明振动能量能够全面反应系统信息,可用于疲劳寿命预测。 4.结合疲劳寿命预测中的线性累计损伤理论,利用时间历程下的瞬时振动能量的改变和振动能量的累计,推导疲劳寿命预测公式,并画出振动能量一时间的疲劳寿命曲线,通过仿真分析验证。 5.结合疲劳寿命中健康度的概念,提出能量健康度概念。通过同等激励下瞬时能量得到健康度指数,并求出剩余振动能量,再根据振动能量一时间曲线,得到系统的剩余寿命。
[Abstract]:In recent years, the progress of science and technology is driving the development of modern machinery and equipment towards the direction of large-scale, precision, complexity, continuity and high speed, while the more and more complex working environment of mechanical parts and engineering components, also suffered a long period of time. The function of continuous alternating load. The fatigue problem of mechanical equipment is easy to be caused by alternating load. Fatigue failure is one of the most important causes of component failure in engineering. As early as 19th century, fatigue began to enter the research field of scholars all over the world, and in a long time, a lot of achievements have been made. Life prediction still faces many problems. If a deterministic method is used to predict the fatigue life, the obtained fatigue life is a certain value, but the fatigue of the structure is a very complicated phenomenon. It is influenced by many uncertain factors. The existing prediction theories are mainly based on mechanics and probability statistics. These theories are based on the static eigenvalues such as the stress amplitude and the average stress value of the component, ignoring the dynamic changes of the system, resulting in the estimation error, and the dynamic parameters of the system can be obtained by state monitoring. It is necessary to combine the traditional fatigue theory with the information technology of system dynamic state monitoring to predict the life of mechanical equipment. In this paper, the vibration energy is introduced by solving the response of a single degree of freedom vibration system under simple harmonic excitation, and the basic concept and significance of vibration energy are expounded, as well as the feasibility analysis in life prediction, combined with fatigue theory. The formula of fatigue life based on vibration energy is derived. Finally, the residual life of mechanical equipment is predicted by using the concept of health. The main contents of this paper are as follows:. 1. The vibration analysis of a single degree of freedom system under simple harmonic excitation is carried out, from which the vibration power and vibration energy of a single frequency are obtained. The relationship between vibration energy and fatigue life is revealed. Finally, the expression of vibration energy spectrum is obtained according to the traditional spectrum estimation method. 2. The function of vibration energy spectrum in state monitoring and fault diagnosis is analyzed and studied. By using vibration energy spectrum, the system information can be fully reflected, and the whole vector energy spectrum can be obtained by combining the full vector spectrum with dual channel information fusion. The fault diagnosis of rotor system can effectively solve the misdiagnosis and missed diagnosis in rotor fault diagnosis and identify rotor fault more accurately and effectively. 3. The approximate linear relationship between fatigue life and vibration energy under constant external excitation is proved by theoretical and practical examples, and the relationship between fatigue life and exciting frequency and stress is discussed. The results show that the vibration energy can fully reflect the system information and can be used to predict the fatigue life. 4. Combining with the linear cumulative damage theory in fatigue life prediction, using the change of instantaneous vibration energy and the accumulation of vibration energy under the time course, the fatigue life prediction formula is derived, and the fatigue life curve of vibration energy and time is drawn. It is verified by simulation analysis. 5. Combining the concept of health degree in fatigue life, the concept of energy health degree is put forward. The index of health degree is obtained by instantaneous energy under the same excitation, and the residual vibration energy is obtained, and then the residual life of the system is obtained according to the time-curve of vibration energy.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TH114

【参考文献】