Ultrasonic-based Detection Of Gas Leak For The Unclosed Components Of Aircraft

At present,air-leakage detection is one of the most important part in the assembly stage of unclosed components in large aircraft.A series of leakage detecting method is always carried out after the final assembly.There are no effective methods in part assembly.In order to figure out these problems,an air-leakage detecting system with ultrasonic technique was set up,as well as a series of experiments.Major research work as following:(1)In order to figure out the problem of defect detecting of leakage caused by bad seal after riveting,bonding and welding in aircraft assembly,a method and detection system of leak detection for aircraft components applied in unbind working condition was brought forward based on the principle of leaking ultrasonic caused by negative pressure.(2)Two kinds of test piece of hole pattern and crack were designed to represent typical leak points of micropore and crack.The mathematical models of leakage sound pressure with detecting distance and aperture,and leakage rate with system pressure and leakage area were established.In addition,the leakage quantitative relationships between geometry characteristics of leak points and sound pressure,and leakage rate were obtained.(3)A method of dealing with two kinds of ultrasonic signal by wavelet packet decomposition was put forward.Results showed that leakage form can be distinguished by different energy distribution existed in multiple frequency bands of leakage signal of micropore and crack.Besides,the regularity of distribution has nothing to do with aperture and leakage area.