Final Project Presentation - COMPREHENSIVE ANALYSIS OF CORROSION ON THE INTERNAL SURFACES OF...
Transcript of Final Project Presentation - COMPREHENSIVE ANALYSIS OF CORROSION ON THE INTERNAL SURFACES OF...
General Sir John Kotelawala Defence University
Final Year Research Project Presentation:Group-06
COMPREHENSIVE ANALYSIS OF CORROSION ON THE INTERNAL SURFACES OF
AIRCRAFT METAL FLUID LINES USING NDT METHODS.
By:-HMV Dissanayake (ENG/AE/12/0002)
SFMF Marikkar (3883)
AMDN Atapattu (ENG/AE/12/0011)
LLY Srimal (ENG/AE/12/0044)
Supervised By:-
Wg Cmdr. DJK Lokupathriage
Head of the Department
Department of Aeronautical Engineering
Faculty of Engineering
Kotelawala Defence University 1
OUTLINE
• Introduction
• Time Plan
• Objectives
• Research Background
• Methodology
• Results
• Causes
• Root Causes
• Recommendations & Limitations
• Conclusion
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INTRODUCTION
• PT-06 Aircraft – Used for training purposes
• Aluminium pneumatic lines - located between distribution and solenoid valves
• Repeated failures soon after major inspections – Bursts
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TIME PLAN
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Task 2014 2015
Au
g
Sep
Oct
No
v
Dec
Jan
Feb
Mar
Ap
r
May
Refer Reference Material
Gather Background Information
Obtain Test Specimen
Perform The Test And Gather Results
Compilation Of Results
Report Writing
Monitoring Recommendations
Preparation of Report
Finalization Of Report
OBJECTIVES
• Completely analyze corrosion on the internal surfaces of the aircraft metal fluid
lines using NDT methods
• Find root causes for such corrosion
• Make recommendations for alternations in maintenance practices of aircraft
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RESEARCH BACKGROUND
• Non-destructive testing methods
• Types of Corrosion
• Detection of Corrosion
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RESEARCH BACKGROUND cont...
NON-DESTRUCTIVE TESTING METHODS
• Why Non-Destructive Testing methods are used?
• Contrast between Destructive and Non-Destructive Testing methods
• Benefits of Non-Destructive Testing
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RESEARCH BACKGROUND cont...
NON-DESTRUCTIVE TESTING METHODS
• Liquid Penetrant Testing (PT)
• Magnetic Particle Testing (MT)
• Radiographic Testing (RT)
• Ultrasonic Testing (UT)
• Acoustic Emission Inspection (AE)
• Guided Wave Testing (GW)
• Laser Testing (LT)
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RESEARCH BACKGROUND cont...
NON-DESTRUCTIVE TESTING METHODS
• Holographic Testing
• Laser Profilometry
• Laser Shearography
• Magnetic Flux Leakage (MFL)
• Thermal / Infrared Testing (IR)
• Visual Testing
• Eddy Current Testing (ET)
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RESEARCH BACKGROUND cont...NON-DESTRUCTIVE TESTING METHODS
Eddy Current Testing Method
• Eddy Current Testing instruments are usually small and portable.
• The method is used only on electrically conductive materials
• Only a small area can be inspected at a time.
• An energized electromagnetic coil induces an AC magnetic field into the tested specimen.
• The fluctuating magnetic field generates a circulating electric eddy current.
• The presence of a flaw increases the resistance to the flow of eddy currents.
• This is indicated by a deflection on the measuring instruments.
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RESEARCH BACKGROUND cont...
NON-DESTRUCTIVE TESTING METHODS
Testing of Tubes using Eddy Current Inspection
• The Reflection Method
• The Transmission Method
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RESEARCH BACKGROUND cont...
TYPES OF CORROSION
• Uniform Attack
• Galvanic or Two Metal Corrosion
• Crevice Corrosion
• Pitting Corrosion
• Intergranular Corrosion
• Erosion Corrosion
• Stress Corrosion
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RESEARCH BACKGROUND cont...
DETECTION OF CORROSION
• Transient Eddy Current Method
• Pulsed Eddy Current Method
• Other Methods
• Single Layer Corrosion Detection
• Two Layer Corrosion Detection
• The Limited Penetration Method
• Dual Frequency Method
• Variable Frequency Method
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METHODOLOGY
• Examine the chemical composition of test specimen
• Perform a Three Dimensional Eddy Current inspection on the specimen
• Perform a comparison between corroded and non-corroded specimens using a
3D Eddy Current inspection.
• Perform a micro and macro structural examination (Metallography)
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METHODOLOGY cont.…
EXAMINING THE CHEMICAL COMPOSITION OF TEST SPECIMEN
• Sampling
• Sample Preparation
• Chemical Analysis
• Interpretation of Results
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METHODOLOGY cont.…
PERFORMING A THREE DIMENSIONAL EDDY CURRENT INSPECTION ON THE SPECIMEN
• Appropriate probes were selected• 2 MHz 90 degree surface probe
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PERFORMING A THREE DIMENSIONAL EDDY CURRENT INSPECTION ON THE SPECIMEN
• The gain and phase were set accordingly
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METHODOLOGY cont.…
PERFORMING A THREE DIMENSIONAL EDDY CURRENT INSPECTION ON THE SPECIMEN
• The probe was balanced.
• The test was performed.
• The results were recorded.
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METHODOLOGY cont.…
METHODOLOGY cont.…
PERFORM A COMPARISON BETWEEN CORRODED AND NON-CORRODED SPECIMEN USING A THREE DIMENSIONAL EDDY CURRENT INSPECTION
• Two samples of equal dimensions were prepared out of the original specimen.
• Specimen dimensions obtained through Vernier caliper
• Length: 7.9 cm
• Outer diameter: 6mm
• Inner diameter: 4mm
• Thickness: 1mm
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PERFORM A COMPARISON BETWEEN CORRODED AND NON-CORRODED SPECIMEN USING A THREE DIMENSIONAL EDDY CURRENT INSPECTION
• Paint and other applied coatings were removed from the surfaces of the specimens.
• One specimen were dipped in a high concentrated solution of sodium chloride and kept for a week.
• A 3D eddy current test was carried out to check for cracks inside the tubes, following the aforementioned procedure.
• Here, a 2 MHz surface probe and a 200kHz surface probe were employed.
• The results were compared for both specimens.
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METHODOLOGY cont.…
METHODOLOGY cont.…
PERFORMING A MICRO AND MACRO STRUCTURAL EXAMINATION
(METALLOGRAPHY)
• The samples were sectioned
• Then, the samples were mounted
• Coarse grinding was carried out
• Then, medium and fine grinding was carried out
• The samples were mechanically polished
• After that, the samples were etched
• Microscopic Examination was carried out employing a microscope
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RESULTS
• CHEMICAL ANALYSIS
Element % By Mass
Al 96.55%
Mg 2.84%
Mn 0.25%
Fe 0.16%
Ni 0.04%
Si 0.09%
Cr 0.01%
Ti 0.04%
Mo 0.02%
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RESULTS cont.…
THREE DIMENSIONAL EDDY CURRENT INSPECTION ON THE SPECIMEN
Indicated undue liftoffs
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RESULTS cont.…
COMPARISON BETWEEN CORRODED AND NON-CORRODED SPECIMEN USING A THREE DIMENSIONAL EDDY CURRENT INSPECTION
• The probe:
• 2MHz Surface probe
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RESULTS cont.…COMPARISON BETWEEN CORRODED AND NON-CORRODED SPECIMEN USING A THREE DIMENSIONAL EDDY CURRENT INSPECTION
• Corroded and non-corroded test specimen results – 2 MHz Surface probe
Non-corroded Corroded
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COMPARISON BETWEEN CORRODED AND NON-CORRODED SPECIMEN USING A THREE DIMENSIONAL EDDY CURRENT INSPECTION
• The probe:
• 200kHz surface probe
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RESULTS cont.…
COMPARISON BETWEEN CORRODED AND NON-CORRODED SPECIMEN USING A THREE DIMENSIONAL EDDY CURRENT INSPECTION
• Comparison between corroded and non-corroded test specimens – 200 kHz Surface probe
Non-corroded Corroded
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RESULTS cont.…
Original test specimen Macrostructural view of the specimen2824/02/2016
RESULTS cont.…
MACROSTRUCTURAL ANALYSIS OF THE PNEUMATIC SPECIMEN
ROOT CAUSES
• Salinity of the atmosphere
• High turbidity in seawater
• High pH value in seawater around the operating airfield
Caustic Embrittlement - A type of stress corrosion, which occurs due to:
• A susceptible material (aluminum alloy)
• A specific chemical species (a hydroxide)
• Tensile and compressive stresses (acting radially in and out)3124/02/2016
RECOMMENDATIONS & LIMITATIONS
RECOMMENDATIONS
• Charge the pneumatic bottles one hour prior to flight.
• To test the metal fluid lines follow the given procedure below:
• For visual examination, perform a Bore-scope test.
• To detect internal and external defects and flaws such as corrosion, perform an eddy current test
using an encircling probe.
• For a thorough examination, proceed with an x-ray photographic testing.
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RECOMMENDATIONS & LIMITATIONS
LIMITATIONS - EDDY CURRENT TESTING
• Only conductivity probes, surface probes and bolt-hole probes are available in SL.
• The aforementioned probes cannot be used to test small diameter due to higher lift off errors caused
by the unevenness of the surface.
• Also the probe does not fully align with axis of the tube.
• Length of the bolt hole probe is insufficient to go inside the metal tube and cannot be inserted into
curved tubes.
• Expensive encircling probe.
• Costly experiments
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RECOMMENDATIONS & LIMITATIONS
LIMITATIONS – MICRO AND MACRO STRUCTURAL ANALYSIS
• Erroneous interpretations resulted while determining the cause of failure.
• Damages due to grinding and preparing of the sample, being
misinterpreted as flaws and defects.
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CONCLUSION
• The PT-06 aircraft in question was operated near a high saline area around China Bay,
Trincomalee.
• Repeated failures were observed on aluminum pneumatic lines.
• A failed line specimen and a non-failed line specimen were compared.
• Micro and Macro structural analysis were performed to determine the cause of failure.
• High pressure in the tubes leads to moisture formation, which acts as an electrolyte.
• Fluctuating corrosion and moisture results stress corrosion. 3524/02/2016
CONCLUSION cont.…
• For inspection for corrosion using NDT methods the following methods
were suggested.
• Bore-scope for visual inspection
• Eddy current testing using an encircling probe
• It is evidently impractical to spend so much money when there is no
mention of such maintenance activity in the aircraft maintenance manuals.
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