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CHAPTER 1
INTRODUCTION
Corrosion is one of the serious problem affecting airforce and other aviation industries. It affects the aircraft on its wings, surface, between joints and fasteners. The presences of corrosion underneath the paints of surface and between joints are not easy to be detected. The unnoticed presence of corrosion may cause the aircraft to crash leading to human and money loses. To detect the corrosion present on the metal surface, various methods and tests are used. These tests conducted should be such that it does not destroy or disassemble the plane to parts or damage its surface. Hence for the further use of the plane, Non-destructive tests (NDT) are carried out.
Non-destructive tests
Non-destructive testing as the name suggests is testing procedure without any damage to the part being tested. The various non-destructive testing methods used are:
1) Visual inspection
2) X-ray inspection
3) Die (liquid) penetration inspection
4) Magnetic particle inspection
5) Eddy current inspection
6) Ultrasonic inspection
1.1 Objective
The main objective in detection of corrosion by ultrasonic technique is to develop a global NDT procedure To outline speed and efficient of inspection of corrosion and to find corroded parts easily through introducing imaging interpretation
1.2 Report review
Here in this seminar we are discussing about the detection of corrosion using ultrasonic inspection it is most faster and highly efficient way detection of corrosion. In this chapter 2 deals with the detection of corrosion by guided ways. Chapter 3 deals with the equipment and instruments used. We here use Tektrend’s PANDA guided way system in that various hardware (sensors) and software modules are used in ultrasonic inspection. The chapter 4 deals with the inspection setup. The two technique we discussed here are Pulse echo technique and pitch catch technique. The chapter 5 deals with the various inspection results on layer corrosion on controlled thinning of area, corrosion detection in lap and splice joint, under fasteners of wing skin structure. Chapter 6 deals with the advantages and disadvantages of the ultrasonic detection of corrosion. Chapter 7 shows the conclusion of the inspection
CHAPTER 2
CORROSION DETECTION WITH GUIDED WAVES
Guided Lamb modes are dispersive waves and their velocities are a function of the frequency thickness product. Therefore, any material changes such as corrosion/exfoliation or lack of adhesion between two layers will affect the propagating mode amplitude, velocity, frequency spectrum and its time of flight.
RF waveforms from guided modes going through a corroded area have a relatively low transmitted signal amplitude and time of flight shift, while noncorroded areas are associated with stable time of flight and high received signal amplitude.
Lamb waves also known as plate waves are based on plate wave natural resonant modes. Lamb waves are two dimensional stress waves are guided by the geometry of the plate-like structures whose surfaces are free of stresses. They can propagate in plate-like structures that are only a few wavelengths thick (d<=3l) where l represents the incident wavelength.
Particle displacements and stresses in the Lamb waves occur throughout the thickness of the plate. Their propagation properties depend on the density, the elastic properties and geometrical structure of the inspected object and are also influenced by the thickness of the material and the wave cyclic frequency
Fatigue cracks and exfoliation under the shadow of fastener heads in aircraft skin structures can be detected using ultrasonic guided waves. Guided modes are selected and launched from outside the exfoliated and hidden area to interrogate the interested rivets.
we used Lamb wave because they offer an improved inspection potential due to their:
 variable mode structure and distributions
 multimode character
 sensitivity to different type of flaws
 propagation for long distances
 guiding character which enables them to follow curvature and reach hidden and/or buried parts
Wave structure of guided wave mode represent the ensemble of particles displacement, stresses and the density flux energy distributions.The wave structure is important for the determination of interaction of Lamb waves with defect in a structure. From wave structure, we can determine the eventual interaction of mode with a specified defect

this site is awesome ... thnks for the report .can u giv me the ppt of ultrasonic detection of corrosion in aircraft.