Time-frequency Analysis And Research On Vibration Signal Of Hydraulic Pipe Crack Fault

The vibration of hydraulic system is ubiquitous in engineeringpractice. As one of the most important part of hydraulic system, pipe plays a key rolein the safety and stability of hydraulic system and even the whole engineeringstructure. It is not only connected with the hydraulic system components, ensure thenormal work, but also has the function of energy transfer in system.So the reliabilityand stability of the whole hydraulic system is influenced by the vibration of pipe.In this paper,hydraulic pipe vibration testing system is build through the VisualBasic programing software based on NI Measurement Studio platform to get controlof USB-6009data acquisition and other hardware to acquire vibration signal of steelpipe under normal and crack condition in experience. Then the acquired vibrationsignal is analysed, compared and judged under a series of traditional and modernsignal analysis theories, like Fourier transform, Wavelet, Wavepocket andHilbert-Huang transform to detect the feature of crack fault in pipe. Based on theseanalysis, structure crack identification methods like linear frequency responsefunction and Nonlinear Output Frequency Response Function,which is put forward inrecent years, is used under the established simulation model in ANSYS finite elementsoftware in structure to detect and locate the pipe crack in different position.Research shows that: the wavelet analysis, wavepocket decomposition andHilbert-Huang transform signal analys is method is effective and feasible in theanalysis of hydraulic pipe crack fault vibration signal, and every methods have itsrespective superiority. With time-frequency multi-resolution characteristics, Waveletanalysis of signal decomposition and reconstruction by orthogonal waveletsin different frequency channels improve the precision of analysis. Wavepockettransform optimizes the decomposition of high frequency and gets more fine. With agood self-adaptability for local signal analysis, Hilbert-Huang transform makes up thedefects of Wavelet. Research on effect of parameter variation on the structure of thesystem in frequency domain, Linear frequency response function method is easy tocalcul-ate and has a higher precision. Through it, the stability and fault of the systemcan be jud-ged easily. For the nonlinear vibration,which is widely exist in engineeringpractice, Nonlinear Output Frequency Response Function method of structural crackidentification in dealing with fault diagnosis of nonlinear system is very simple andefficient. With a very good practical significance, it opens a new way for the faultdiagnosis of hydraulic pipe.