Corrosion in Aircraft Fuselage Lap Joints

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Student Name: Masimuddin Mohammed
Student ID: 2008 21 003

Instructor: Joan Macleod
Submission Date: 26th December 2010

Course Title: English 102
Section 1

Title: Corrosion in Aircraft Fuselage Lap Joints

Word Count: 4063

Abstract
Corrosion and fatigue cracks are hidden around the lap joints which in fact create critical problems by affecting the structural integrity of the fuselage. During inspection, large areas have to be examined in a small time period and mostly access is limited to a single side of the structure therefore the airline companies do not consider this inspection as a major issue. Disregarding such inspection resulted to an aircraft crash of Aloha Airlines Flight 243 which was caused by the crack and corrosion in aircraft fuselage lap joint, which is very difficult to detect such defects using the naked eye. Non Destructive Inspection (NDI) techniques, Eddy current array and Ultrasonic phased array were established to detect such defects and researches conducted experiment to prove the reliability of the techniques. Experiment was conducted on various aluminum samples by causing the damage to the samples by chemical etching and electrical discharge machining. The experiment was performed using 16 element Eddy current array probe and 64 element Ultrasonic phased array probe and the images were retrieved by RD Tech Omniscan MX equipment. A line graph is shown after the experiment which shows the reduction in aircraft accidents that were caused due to structural failure after the use of above mentioned techniques. The results from both techniques prove that using Eddy current array can detect damage on the inner layer and all the damages on the upper layer at a small amount of time and by using Ultrasonic phased array it can only detect damage on the upper layer in detail. This suggests that detection can be made early in fuselage lap joints which can be made possible by using both the above techniques. Both the results are compared and discussed to make further improvements in the techniques so operation can be made easier.

Table of Contents

1Introduction 5
2Methodology 6
3Key Terminology
3.1 Ultrasonic phased array 7
3.2 Eddy current array 8

3 Findings
4.3 Case study of Aloha Airlines Flight 243 10
4.4 Experiment of Eddy current array and Ultrasonic phased array 11

5Discussion 14
6Conclusion and Recommendation 23
References 24
Appendix

Fig. 1 - Internal working of Ultrasonic Phased Array| 7|
Fig. 2 - Eddy current flow| 8|
Fig. 3 - Showing Single coil: slow scan and Multiplex coil: fast one line scan| 9| Fig. 4 - Aloha Airlines Flight 243, April 28, 1988| 11|
Fig. 5 - Omniscan MX equipment| 12|
Fig. 6 - Eddy Current Array probe with encoder| 12|
Fig. 7 - Ultrasonic phased array probe| 13|
Fig. 8 - Eddy current array result and Ultrasonic phased array result| 15| Fig. 9 - Eddy current array result and Ultrasonic phased array result| 16| Fig. 10 - Eddy current array result and Ultrasonic phased array result| 17| Fig. 11 - Eddy current array result and Ultrasonic phased array result| 18| Fig. 12 - Eddy current array scan result of top of the bottom damage| 19| Fig. 13 - Eddy current array scan result for top of the bottom damage| 20| Fig. 14 - Eddy current array scan result of top of the bottom damage| 21| Fig. 15 - Showing aircraft crashes due to corrosion before and after NDI techniques (1930-1999)| 22| Table 1 - Dimensions of corrosion and crack damage| 13|

1 Introduction

The process of involuntary degradation of substances such as metals and mineral building material due to the environment is defined as corrosion (Revie 2000). All types of materials are susceptible to degradation which is the main reason behind certain accidents. Corrosion sometimes exists as protective as well as...
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