1、XX大学毕业设计文献翻译与原文毕设题目：铝锋窝结构腐蚀的脉冲涡流检测研究 学 院： 测试与光电工程学院专业名称： 测控技术与仪器 班级学号： 11081336学生姓名： 迟文升指导教师： 付跃文二Oxx年 四 月 Non-destructive testing of low-energy impact in CFRP laminates and interior defects in honeycomb sandwich using scanning pulsed eddy current1. IntroductionIn recent decades, there has been an i
2、ncreasing interest in the use of composite materials and structure, like carbon fibre reinforced plastics (CFRP) and sandwich honeycomb structure in many industrial fields, because of the low weight and improved mechanical properties compared with metals. On one hand, random porosity or undesirable
3、material may appear in composite structures during manufacturing process. On the other hand, outside impacts may result in delamination or disbonding when structures are in service. These undesirable inclusions or defects affect the structure and its mechanical properties. In order to check the inte
4、grity of the composite structures, these defects have to be detected and evaluated after manufacturing and monitored during in-service operation. To accomplish this, non-destructive testing (NDT)techniques are investigated, such as ultrasonic testing, X-ray, eddy current (EC), microwave, electrical
5、resistivity measurement, acoustic emission, flash thermography, and shearography.Eddy current, widely used for detecting defects in metallic components, can be used in detection of conductive composite material, like CFRP and metalmatrix composites. EC testing offers a number of advantages compared
6、to other NDT techniques: it enables detection of surface and subsurface damage in contrast to dye penetrant inspection; it can be applied to non-magnetic metallic items in contrast to magnetic flux leakage; it does not require an acoustic couplant as is the case for ultrasonic inspection,and it is m
7、ore economical, easily applied, and less hazardous than radiography. Pulsed eddy current (PEC) technique is an important advance over other EC methods, which has been proved as an effective tool for flaw detection and corrosion detection in metals. In previous works, various features are selected an
8、d usedto represent the conductivity change by stress in aluminium and permeability variation in steel corrosion. In this paper,scanning PEC is applied in detection and evaluation of defects in CFRP laminates and honeycomb sandwich panels, and appropriate features are extracted to characterise the su
9、rface impact defects and inner delamination.Over the past twenty years, optical methods have gradually appeared and are now being applied to NDT field. The major advantage of optical methods over other NDT techniques is that optical methods are able to inspect a large area in a relatively short time
10、. Flash thermography is commonly used for metallic samples and composite material, which can reveal many defects: impact damage, delamination, disbonding, etc. Shearography derived from speckle interferometry is a new method, which is used to determine the strain field of a given specimen. Delaminat
11、ion, disbonding or wrinkles can be detected using this method. However,these optical methods are not yet used on an industrial level because the results are relatively hard to analyse, and there is also a lack of both standardization and operator training. In this work, for comparing characteristics
12、 and verifying the effectiveness of scanning PEC, the same samples are tested using flash thermography and shearography.The aim of the present study is firstly to inspect the various specific aeronautical specimens (sandwich honeycomb with inner defects and CFRP with impact damage). The second aim i
13、s to verify the effectiveness of applying scanning PEC to detect defects. The rest of the paper is organized as follows. Firstly, specimens are introduced in Section 2. Then, scanning PEC system and related features are introduced in Section 3, which is followed by experimental studies of defect cha
14、racterisation in honeycomb sandwich panels and CRFP laminates in Section 4. Finally, the conclusions and further work are outlined in Section 5.2. Specimen description2.1. Honeycomb sandwich structureHoneycomb sandwich structures are used extensively on both civil and military aircraft due to their
15、high stiffness and low weight. They also provide a material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties. In the service life of a sandwich panel, impacts are caused by debris during aircraft takeoffs and landings, dropping tools during
16、 maintenance, or even collisions by birds, etc. Visual inspection may reveal little damage, but significant damage (e.g. delamination, disbonding) may occur between the impacted facesheet and the core.In this subsection, two honeycomb sandwich panels (sample 1 and sample 2) with artificial insert defects simulating inside delamina
