Fatigue Life Prediction Of Mechanical Equipment Based On Energy Analysis And Fatigue Theory

For the past few years, the development of science and technology takes modem mechanical equipment toward the maximization, precision, complication, continuous, and high-speed. So the working condition of machinery parts and engineering structures is more and more complication, they are working under alternate loading over a long period of time. Alternate loading frequently takes fatigue of mechanical equipment, and fatigue damage is the most important element to the lose efficacy of engineering structures. For this reason, not only in theory, but in engineering, fatigue is a hot topics. From early19th century, the question of fatigue was taken into account and studied by many scholars all over the world,and they have reaped many fruits of research in a long time; However, the scholars still can not explain many phenomena about fatigue life attracting the scholars to study. If the determination methods are used to analyze fatigue, the fatigue life is determinate. But the fatigue of structure is a very complicated phenomenon which affected by many uncertainties. The current ways of fatigue life prediction mainly include mechanics or probability statistics, those ways all based on static parameter,for example stress amplitude or mean stress value and so on, but ignore the dynamic change of system, so the result has a little error. Besides, state monitor can get dynamic parameter of mechanical equipment. Above all, So it is necessary to combine traditional fatigue with state monitor for the fatigue life prediction of mechanical equipment.1. Analyse the vibration energy of single freedom vibration system under the harmonic excitation, get the vibration energy and vibration power under a single frequency from this, the results show that the vibration energy can comprehensively reflect the influence of amplitude and frequency on the system. And then combine with traditional signal analysis methods in order to get vibration energy spectrum and vibration power spectrum which can fully reflect the influence of amplitude and frequency of the signal on the system.2. On the vibration energy spectrum in condition monitoring and fault diagnosis of the role analysis research, the use of vibration energy spectrum can comprehensive response system information advantage, and connecting with the full vector spectrum for dual channel information fusion, get full vector vibration energy spectrum, counter rotating subsystem of the fault diagnosis, can effectively solve the rotor fault diagnosis of misdiagnosis and missed diagnosis condition, accurate and effective identification of rotor fault.3. Respectively through the theory and proved in the external incentive fatigue life under the condition of constant with the vibration energy of the approximate linear relationship, and discusses the fatigue life and vibration frequency and stress, the relationship between the vibration energy that can be comprehensive reaction system information, and can be used for fatigue life prediction.4. Combined with fatigue life prediction of the linear cumulative damage theory, using the time history of the transient vibration energy change and vibration energy is accumulated, fatigue life prediction formula, and draw the vibration energy-time fatigue life curve, through the simulation analysis and testing.5. Combined with the fatigue life of the concept of health degree, this paper puts forward the concept of healthy energy. Through the same excitation instantaneous energy get health index, and get the residual vibration energy, then according to the vibration energy-time curve, get the residual life of the system.