10th International Symposium on NDT in Aerospace

1 License: https://creativecommons.org/licenses/by-nd/4.0/

Eddy Current Array for Aircraft Engine

Component Inspection

André LAMARRE 1 1 Olympus Scientific Solutions Americas, Quebec City, Canada

Contact e-mail: andre.lamarre@olympus-ossa.com

Abstract

Components of aircraft engines are submitted to very high stresses and temperatures during

operation. Consequently, to assure the safety of the public, the integrity of these components

must be ensured with reliable inspection methods. While the use of remote visual and dye

penetrant inspection is widespread, the aircraft engine manufacturing and maintenance

industries now benefit from recent developments in magnetic methods, namely eddy current

array.

Eddy current testing (ECT) has long been considered the technique of choice to detect

and size cracks on the surface of aircraft engine components. Unfortunately, inspections

using single-coil eddy current probes can be slow with results that vary from operator to

operator. In these and other respects, eddy current array (ECA) technology has advanced the

technique significantly. The use of arrays helps to rapidly achieve full coverage of inspected

zones while maintaining a high resolution. Portable eddy current electronics enable the use

of large arrays and the image resulting from the software’s data processing helps the operator

perform a reliable analysis. Probe holders and mechanical supports are continuously being

developed to address the different applications of ECA for engines.

Today, eddy current arrays are used by major aircraft engine manufacturers and

maintenance companies for the assessment of engine components, such as dovetails, blade

attachments, and turbine discs. This presentation will review how eddy current array

technology contributes to public safety.

Olympus Scientific Solutions Americas | Andre LAMARRE

Eddy Current Array for Aircraft Engine Component Inspection

1. Eddy Current Array (ECA) Technology

2. ECA Equipment

3. Engine Applications

4. Conclusion

Agenda

Eddy Current Array Technology

Eddy Current Array Principles

� ECA is a technology based on the ability to electronically drive several eddy current sensors

placed side-by-side in the same probe assembly

� Data acquisition is performed by multiplexing the eddy current sensors

� Most eddy current probes and techniques (absolute, reflection, etc.) for flaw detection can be used with eddy current array probes

Eddy Current Array—Advantages

� Provides larger coverage in a single probe pass while maintaining high resolution

� Improves flaw detection and sizing with C-scan imaging

� Enables inspection of complex shapes with probes customized to the profile of parts

ECA – Signal Representation

ECA probe over a flaw Each coil produces asignal

Color-coded signal amplitude displayed in the C-scan

ECA – Signal Representation

� The C-scan can display either the vertical or horizontal component of the signal in the impedance plane.

� In the example below, only the vertical component of the signal (Y axis) is displayed on the C-scan, ensuring that all defects are clearly shown. The phase of the signal was adjusted so the liftoff signal is in the horizontal plane (X axis).

Liftoff signal

Defects

Eddy Current Array Equipment

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General Hardware Features

OMNI-P-ECT4

− Conventional ECT only

− 4 input channels

− Frequency ranges from

20 Hz to 6 MHz

− Dual frequency operation

− 2 encoder inputs

− 3 alarm outputs

− 1 analog output

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ECA Probes

� Can be optimized for

different applications

� Can be shaped to the

part to inspect

ECA — Probe Parameters

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� Frequency (f)

� Number of elements (n)

� Resolution (r) (also depends on the coil configuration)

� Coverage (C)

Example of an absolute bridge probe

C

r

12

Inside an ECA Probe

• Hard coils

• Many wires

• A lot of soldering

• Labor intensive

SW1

Diapositive 12

SW1 I would call this soldering and not welding.Sarah Williams; 2018-05-28

ECA Hard Coiled Array VS Printed Circuit Board (PCB) Array

Traditional hard coil sensors� Pros:

� Different type and size of coils

� Cons:

� Time consuming

� Repeatability and coil matching

� Expensive

Flexible array on PCB film

� Pros:

� Excellent repeatability and coil matching

� Versatility, i.e., can be attached to holders of different shapes

� Affordable price

� Cons:

� Price/time for the initial film

Engine Applications

Dovetail Slot Inspection — Current Method

� Manual tooling

� Scanner with eddy current pencil probe

� The operator must perform 40 line scans

� Time consuming

� Operators complain of discomfort

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Engine Disk Dovetail Slot Semiautomated Inspection

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� 32 coils cover critical zones � Probe mounted on portable scanner � Scanner in position

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� C-scan displaying EDM and calibration notches in the calibration standard

EDM DEFECTS

CALIBRATION LINES

ECA Engine Disk Dovetail Results

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C-scan of an EDM notch: 1.5 × 0.7 × 0.1 mm

ECA Engine Disk Dovetail Results

New Engine Disk Slot Inspection System

Scanner improved with OmniScan®

flaw detector remote control

Engine Fan Blade Inspection

Stage 2: Semiautomated inspectionStage 1: Manual inspection

Engine Fan Blade Inspection Solution — Development Process

� 2 passes:

– 1 convex side

– 1 concave side

� Wire encoder

� Single pass, convex and concave sides

� Encoded scanner

Semiautomated Fan Blade Inspection Solution

Conclusion

ECA Advantages for Aircraft Engine Inspection

� ECA probes cover large areas in a single pass

� Improved Probability of Detection due to full coverage and C-scan imaging

� Probes can be adapted to the complex shapes of components

� Flexible ECA can be used interchangeably with probe holders of different shapes

� Can be used on-site for aircraft engine component inspection during maintenance

� Referenced in procedures for aircraft and engine maintenance