Application And Research Based On The Fractal Theory Of Aviation Hydraulic Tube Vibration Crack Fault Diagnosis

With the rapid development of modern economy,the technology of aeronautics is widely applied to various fields.The plane's engine as a driving force components,their normal work is vital to guarantee the safe operation of the aircraft.Engine fault is mostly caused by the hydraulic piping vibration.So the hydraulic pipeline vibration problem is particularly important to ensure the safe operation of the aircraft.In this paper,regard hydraulic pipe crack fault as research object.In order to diagnose the crack of hydraulic pipe and analyze the state of crack propagation,a fractal theory diagnosis method is put forward.Therefore,fractal theory is taken as the theoretical basis,and hydraulic pipeline vibration experiment is taken as experimental means.Then,the crack of hydraulic pipe is analyzed and studied.Firstly the finite element analysis method is used to establish model of the hydraulic pipe.The fluid-structure coupling analysis is carried out for the normal hydraulic pipe and the cracked hydraulic pipe respectively.And the analysis result is introduced into the modal analysis.Then the relationship between the crack frequency and the natural frequency of the hydraulic pipe is analyzed.It can be seen that with the continuous expansion of the hydraulic pipe crack,the natural frequency of the hydraulic pipe is not obvious,and it can not be identified the crack failure and the state of expansion of hydraulic pipe.Secondly,the vibration test of the hydraulic pipe with cracks or not is carried out by using the hydraulic pipe vibration test bed.The cracks of the selected hydraulic pipe are simulated by laser cutting.The vibration test is carried out to get the the time domain vibration signal of hydraulic pipe whether there is crack.The fractal theory is used to calculate the fractal dimension of the vibration signal.The Renyi dimension spectrum and Renyi dimension vary with the crack generation and propagation rule.Spectra can identify the pipe crack failure and crack expansion.Finally,according to the fractal characteristics of the hydraulic pipe,set up the Renyi dimension,the Renyi dimension spectrum and the sensitive dimension as the model space sample bank.And the local linear recognition method is used to diagnose the hydraulic pipe crack.The results are in agreement with the actual crack length of the hydraulic pipe and the result is accurate.The feasibility and validity of the fractal theory method for the crack diagnosis of the hydraulic pipe are verified by the analysis of the signal to be detected and the simulation of the crack length.The above analysis provides a basis for the analysis of the fault diagnosis of hydraulic pipe.