Research On Technology Of Borescope And Eddy Current Integrative In-situ Nondestructive Testing For Key Components Of Aeroengine

In-situ nondestructive testing avoids disassembling and assembling equipment or structures, so it saves plentiful time and cost. By integration both the volume of equipment is reduced and advantages of many methods are full used, so the defects detection precision is improved. In-situ nondestructive testing and integration are all important research directions in general measuring field. It has very important significance to exploit related research for building up maintenance support of our legionary aero equipments.This paper is based on the engineering practical requirement of the ninth level labyrinth disc and aeroengine blade in-situ nondestructive testing, and the thought of borescope inspection and eddy current testing integrated is proposed. The comprehensive research including nondestrctive testing system design, borescope and eddy current integrative sensor, ninth level labyrinth disc and aeroengine blade in-situ testing, integrative testing informationi fusion are presented. The primary results and conclusions are listed hereafter.(1) The embedded system technique is introduced to nondesturctive testing field. The embedded borescope and eddy current integrative nondestructive testing system is developed. The electronic borescope based on CMOS image sensor is designed. The borescope inspection image enhancement processing methods is researched. And the image quality is enhanced. The research of the power signal generator with broad bandwidth and accurate frequency, the orthogonal lock-in amplifier for eddy current testing weak signal, and and otherwise, is done. The hardware design of eddy current testing is achieved. The real time embedded inspection software is exploited using modularization design thought. The testing system is powerful, intelligent and accorded with integration development request. Compared with the traditional nondestructive testing instrument, it has excellent characteristics of small bulk, light weight, convenience for manipulation, portable design, etc. So it meets the requirements of in situ nondestructive testing for aeroengine.(2) This paper aims at the problem that the structure and performance of the existing eddy current sensors can't satisfy the requirement of in-situ nondestructive testing for the ninth level labyrinth disc of an aeroengine, and an especial structural eddy current sensor is proposed. Its excitation coil and pickup coil are orthogonal in space. The parameters of the eddy current sensor are optimized using finite element simulation method. The eddy current sensor is very sensitive and has little lift-off effect to detect defects of the the ninth level labyrinth disc, and the cracks depth can be evaluated quantitatively. The eddy current sensor is combined with electronic borescope probe. A borescope and eddy current integrative sensor for the ninth level labyrinth disc in-situ testing is designed. The experiment results show borescope and eddy current integrative testing can in-situ detect cracks of the the ninth level labyrinth disc, and the defects detection precision and reliability are very high.(3) At present, the borescope inspection results are estimated artificially not automatically and the inspection efficiency is low. So an approach is propsed for aeroengine blades damage automatic estimation. The shape and texture characteristics of blades damage are extracted using digital image processing. A classifier based on support vector machine is designed for damage automatic estimation. The experiment results show the correct recognition ratio reaches 85%.(4) In order to improve the borescope inspection effect for cracks of aeroengine blades, based on integration thought, firstly a uniform eddy current sensor is designed using finite element emulational method, which has little lift-off effect, and can evaluate the crack length and depth quantitatively. Then, the uniform eddy current sensor is combined with electronic borescope properly, and a borescope and eddy current integrative sensor is designed for aeroengine baldes. The experiment results show the integrative sensor can in-situ detect defects of blades, and and the defects detection precision and reliability are high.(5) A method of borescope and eddy current integrative testing information fusion is proposed using D-S theory of evidence for aeroengine blades. The model of information fusion is established. Th belief assignment function is constructed. The decision-making rule is constituted. The integration of borescope and eddy current testing in information layer is carried out. It improves the correct flaw detection ratio of nondestrctive testing system.The main research results of this paper have been used in aeroengine for daily maintenance and periodic inspection, which reduces maintenance man's workload availably and inspection time in field and the inspection efficiency is improved.