Research On Condition Diagnosis Of Sliding Bearing Based On Acoustic Emission Detection Method

Sliding bearing is one of the pivotal parts in large power machine, and it has an essential influence on the operating safety and reliability of the whole unit. With traditional monitoring and diagnosis methods of sliding bearing, the relationship between the fault type and the characteristics parameters can't be build, therefore, in this dissertation, acoustic emission technology is used to monitor and analyze the operations of the bearings to find out the qualitative or quantitative relationship between the bearing and operating conditions, and to determine the state of sliding bearing.First, the AE characteristics and mechanism of sliding bearings in rotating machinery are studied from the theory perspective, and it can be found that the energy of acoustic emission signals mainly comes from friction between oil and pad. Thus, one of the sliding bearings of a simulated rotor test bench of 300MW turbo-generator unit serves as the calculation example in this thesis, and the loss of power (AE signal energy) under different status is simply calculated. The result is that with the temperature increases, the loss decreases, with the load increases, the loss increases, and with the amount of the lubricating oil decreases, the losses increases.By analyzing the AE signal characteristics of sliding bearing, wavelet decomposition and reconstruction method are adopted to obtain friction signal of sliding bearing. Based on this the cross-correlation analysis and the traditional parameters analysis are used to analyze the friction signal of sliding bearing, to establish the relationship between the status of bearing running and the characteristics parameters of acoustic emission.Through the experiments study in the spot test and laboratory experiments conditions, the sliding bearings AE parameters, such as energy rates, central frequency, the maximum correlation are founded to identify the operation condition of sliding bearing, and a new parameter - the instability degree of energy spectrum is also presented. Besides the relationship between the acoustic emission signals characteristics parameters and the operation condition in the process of speeding up or down, the relationship between process of change the status and the process of failure is obtained; and what's more the qualitative relationship between the acoustic emission signals characteristics parameters and the operation condition is established. At the end, the standards to identify the operation condition and the fault status are found in this dissertation.