Building Calibration Standard for Remote Field Eddy Current - - PowerPoint PPT Presentation

▶
building calibration standard for remote field eddy
SMART_READER_LITE
LIVE PREVIEW

Building Calibration Standard for Remote Field Eddy Current - - PowerPoint PPT Presentation

Sep 12, 2022 452 likes •1.01k views

Innovative Materials Testing Technologies, Inc. Building Calibration Standard for Remote Field Eddy Current Technique Detecting Deeply Hidden Corrosion in Aircraft Structures Yushi Sun Innovative Materials Testing Technologies, Inc. 2501 N.

slide-1
SLIDE 1

Building Calibration Standard for Remote Field Eddy Current Technique Detecting Deeply Hidden Corrosion in Aircraft Structures

Innovative Materials Testing Technologies, Inc.

Yushi Sun Innovative Materials Testing Technologies, Inc. 2501 N. Loop Drive, Suite 1610, Ames IA, 50010

  • Tel. 515-296-5328 Fax. 515-296-9910 Email. Suny@iastate.edu

Zhongqing You & XXXX Magnetic Analysis Corporation 535 S. 4th Avenue, Mt. Vernon, NY 10550-4499

  • Tel. 800-463-8622
slide-2
SLIDE 2

Innovative Materials Testing Technologies, Inc.

Outline

  • Introduction
  • Distinguishing Features of RFEC Technique
  • Building Calibration Standards for RFEC Technique
  • Exploiting Fundamental Features of RFEC Technique
  • Location (Remaining Thickness) to Signal Phase Angle Relation
  • Corrosion Depth to Signal Magnitude Relation
  • Corrosion Depth to Signal Y Relation
  • Estimation of Corrosion Shapes
  • Correction Factor in Estimating Small-Sized Corrosion
  • Summary and Future Work
slide-3
SLIDE 3

Innovative Materials Testing Technologies, Inc.

Introduction

  • 1. Early detection of hidden corrosion in aircraft

becomes big public, manufacturer and government concern for economy and safety.

  • 2. Currently deeply hidden corrosion remains

undetectable unless aircraft components are disassembled that is costly and time consuming.

  • 3. A number of new techniques are currently under
  • development. The Remote Field Eddy Current

Technique is among the tops.

slide-4
SLIDE 4

RFEC Phenomenon in Metallic Tubes

Direct energy coupling path Indirect energy coupling path

ΦRF

Excitation coil Pick-up coil

Φ

Indirect energy coupling path

Phenomenon: Signals received by pick-up coils are sensitive to changes in wall thickness, conductivity, and permeability.

.

Innovative Materials Testing Technologies, Inc.

slide-5
SLIDE 5

Underlying Physics:

  • 1. Direct energy coupling is restricted by EC in the

wall.

  • 2. Pick-up coil signal, ΦRF, is dominated by the energy

diffusing along the indirect coupling path that traverses the wall twice.

  • 3. Changes in the phase of ΦRF are directly

proportional to the thickness of the wall.

RFEC Phenomenon in Metallic Tubes

Innovative Materials Testing Technologies, Inc.

slide-6
SLIDE 6

RFEC Phenomenon in Metallic Tubes

Innovative Materials Testing Technologies, Inc.

Typical RFEC signals: double-peak signal Time Signals Real Component, X Imaginary Component, Y

slide-7
SLIDE 7
  • 2. RFEC Phenomenon In Flat Geometries

RFEC Probe Drive Coil Pickup Coil Direct Coupling Path Indirect Coupling Path

  • 1. In the absence of a test part, only direct coupling from the

drive coil is detected, i.e., No RFEC signal is present

  • 2. The RFEC probe is designed to minimize signal from direct

coupling and focuses on the indirect coupling path

Innovative Materials Testing Technologies, Inc.

slide-8
SLIDE 8

Distinguishing Features of RFEC Technique & SSEC System Compared to Commercial ECT:

  • Higher sensitivity: capable of detecting SCC.
  • Deep penetration: capable of detecting deeply hidden

corrosion & cracks.

  • Simple to use: similar to a conventional ECT system.
  • Lower power requirement Current drive power is ~ 0.4 [Ampere-

Volt]

  • Capable of accommodating alternative, non-coil, types of

magnetic sensors

  • Capable of driving multi-phase traveling/rotating

magnetic wave probes.

Innovative Materials Testing Technologies, Inc.

slide-9
SLIDE 9

Examples from Two RFEC Probes

RF-4 mm V.3

Footprint: 0.85” x 2.15”

RF-2 mm V.3

Footprint: 0.3” x 0.62”

Innovative Materials Testing Technologies, Inc.

slide-10
SLIDE 10

RF4mm V. 3 – Three Typical Examples

In Detecting Deeply Hidden Corrosion

It detects (in multi-layer Aluminum Structures) :

  • Φ 0.75” Spherical Metal Loss with Maximum Depth of

0.025” that is 0.600” below Surface. ~ 4.2% thinning.

  • 0.5”×0.5”×0.040” chemical thinning 0.603” below surface

(CNDE Specimen). ~ 6.6% thinning.

  • 0.5”×0.5”×0.006” chemical thinning 0.373” below surface

(CNDE Specimen). ~ 1.6% thinning.

Innovative Materials Testing Technologies, Inc.

slide-11
SLIDE 11

0.125” 0.500” 0.125”

RFEC Probe Rf4mm

Innovative Materials Testing Technologies, Inc.

Φ 0.75” Φ 0.75”

  • Max. Depth = 0.075”
  • Max. Depth = 0.025”

Example 1: 3 Layer 7075 T6 Specimen, 0.125” + 0.5” + 0.125” Total Thickness = 0.750” Spherical-Shaped Corrosion on Bottom of 2th Layer Location = 0.600” Location = 0.575” #1 #2

Location Location

slide-12
SLIDE 12

Innovative Materials Testing Technologies, Inc.

Example 1.1 Φ 0.75” Spherical-Shaped Corrosion Max. Depth = 0.025” On 2nd Layer Bottom Side, f=200Hz Total Thickness = 0.750”, Remaining Thickness = 0.600”

slide-13
SLIDE 13

Innovative Materials Testing Technologies, Inc.

Example 1.2 Φ 0.75” Spherical-Shaped Corrosion Max. Depth = 0.075” On 2nd Layer Bottom Side, f=200Hz Total Thickness = 0.750”, Location = 0.575”

slide-14
SLIDE 14

Innovative Materials Testing Technologies, Inc.

Example 2.1: 5 Layer 2024 T3 Specimen 0.1” + 0.1” + 0.19” +0.19” + 0.063” Total Thickness = 0.643” Corrosion on Bottom of 5th Layer Location = 0.603”

0.100” 0.100” 0.063” 0.190” 0.190”

0.040” deep corrosion A Scan Direction

RFEC Probe Rf4mm Location = 0.603”

slide-15
SLIDE 15

Corrosion Sample #15

CNDE Specimen #15 (0.063” thick) 3.0” × 3.0” × 0.040" chemical thinning on the bottom side 0.5” × 0.5” × 0.040" chemical thinning on the bottom side

Innovative Materials Testing Technologies, Inc.

slide-16
SLIDE 16

Innovative Materials Testing Technologies, Inc.

EXAMPLE 2.1.1 3” × 3” × 0.040” 5th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.603”

slide-17
SLIDE 17

Innovative Materials Testing Technologies, Inc.

EXAMPLE 2.1.2 0.5” × 0.5” × 0.040” 5th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.603”

slide-18
SLIDE 18

Example 2.2 5 Layer 2024 T3 Specimen 0.1” + 0.1” + 0.19” +0.063” + 0.19” Total Thickness = 0.643” Corrosion on Bottom of 4th Layer Location = 0.413”

0.100” 0.100” 0.063” 0.190” 0.190”

0.040” deep corrosion

Remaining Depth = 0.413”

Innovative Materials Testing Technologies, Inc.

RFEC Probe Rf4mm

slide-19
SLIDE 19

EXAMPLE 2.2.1 3” × 3” × 0.040” 4th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.413”

Innovative Materials Testing Technologies, Inc.

slide-20
SLIDE 20

EXAMPLE 2.2.2 0.5” × 0.5” × 0.040” 4th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.413”

Innovative Materials Testing Technologies, Inc.

slide-21
SLIDE 21

Example 3 3 Layer 2024 T3 Specimen 0.26” + 0.05” + 0.063” Total Thickness = 0.373” Corrosion on Bottom of 3rd Layer Location = 0.333”

0.260” 0.063” 0.050”

0.5” × 0.5” × 0.006” corrosion

Remaining Depth = 0.413”

Innovative Materials Testing Technologies, Inc.

RFEC Probe Rf4mm

0.333”

slide-22
SLIDE 22

Corrosion Sample #5

CNDE Specimen #5 (0.063” thick) 0.5” × 0.5” × 0.006" chemical thinning on the bottom side

Innovative Materials Testing Technologies, Inc.

slide-23
SLIDE 23

Innovative Materials Testing Technologies, Inc.

EXAMPLE 3 0.5” × 0.5” × 0.006” 3rd Layer Bottom Side Corrosion, f=500Hz Total Thickness = 0.373”, Location = 0.333”

slide-24
SLIDE 24

RF2mm V. 3 - Two Typical Examples

In Detecting Deeply Hidden Corrosion

It detects (in multi-layer Aluminum Structures):

  • 0.5”×0.5”×0.002” chemical thinning 0.193” below surface

(CNDE Specimen). ~1.1% thinning. (in multi-layer Titanium Structures)

  • 0.5”×0.5”×0.006” chemical thinning 0.157” below surface

(CNDE Specimen). ~4.0% thinning.

Innovative Materials Testing Technologies, Inc.

slide-25
SLIDE 25

Example 4 4 Layer 2024 T3 Specimen 0.05” + 0.05” + 0.032” + 0.063” Total Thickness = 0.195” Corrosion on Bottom of 4th Layer Location = 0.193”

0.050” 0.063” 0.032”

0.5” × 0.5” × 0.002” corrosion

Innovative Materials Testing Technologies, Inc.

RFEC Probe Rf4mm

0.193”

0.050”

slide-26
SLIDE 26

Innovative Materials Testing Technologies, Inc.

Corrosion Sample #1

CNDE Specimen #5 (0.063” thick) 0.5” × 0.5” × 0.002" chemical thinning on the bottom side

slide-27
SLIDE 27

Direction for Scanning & Probe Orientation Corrosion Area Detecting a 0.5”x0.5”x0.002" thinning 0.192” below surface 1.1% Thinning

Innovative Materials Testing Technologies, Inc.

slide-28
SLIDE 28

Innovative Materials Testing Technologies, Inc.

Example 5 3 Layer 2024 T3 Specimen 0.05” + 0.05” + 0.063” Total Thickness = 0.163” Corrosion on Bottom of 3rd Layer Location = 0.157”

0.063”

0.006” deep corrosion

0.050” 0.032”

0.157”

0.050”

Rf2mm Probe

slide-29
SLIDE 29

Corrosion Sample #5

CNDE Specimen #5 (0.063” thick) 0.5” × 0.5” × 0.006" chemical thinning on the bottom side

Innovative Materials Testing Technologies, Inc.

1.0” × 1.0” × 0.006" chemical thinning on the bottom side

slide-30
SLIDE 30

EXAMPLE 5.1 1” × 1” × 0.006” 4th Layer Bottom Side Corrosion, f=2.0 kHz Total Thickness = 0.163”, Location = 0.157”

Innovative Materials Testing Technologies, Inc.

slide-31
SLIDE 31

EXAMPLE 5.2 0.5” × 0.5” × 0.006” 4th Layer Bottom Side Corrosion, f=2.0 kHz Total Thickness = 0.163”, Location = 0.157”

Innovative Materials Testing Technologies, Inc.

slide-32
SLIDE 32

Innovative Materials Testing Technologies, Inc.

Building Calibration Standards

Basic Corrosion Parameters We Need to Find out:

  • 1. Corrosion Depth, D.
  • 2. Location, L. Or, which layer? Top or Bottom Surface?
  • 3. Size and Approximate Shape.

D L

slide-33
SLIDE 33

Innovative Materials Testing Technologies, Inc.

Building Calibration Standards

Two Major Challenges: 1. Location & Depth Estimation – Knowing signal magnitude isn’t enough to tell anything, because it is a function of both Depth and Location. Phase angle is what used in ECT to tell a defect location. However, the relation is not straightforward. How the phase angle of an RFEC signal behaves? 2. Size & Shape Estimation – It is known, from RFECT for tube inspection, that RFEC probe gives a two-peaks signal when it passes a single defect and is difficult to be used for defect shape

  • characterization. Does an RFEC Probe for Inspection Flat

Geometry Objects (FG RFEC probe) tell defect shape information?

slide-34
SLIDE 34

Innovative Materials Testing Technologies, Inc.

Exploiting Fundamental Features of RFEC Technique Several experimental studies have been carried. They show:

1. For Location & Depth Estimation –

Signal phase angle obtained from a FG RFEC probe is a monotonic function of defect location.

2. For Size & Shape Estimation –

A FG RFEC probe does give a single-peak signal from defect if the defect is located at certain depth from the inspection surface. Therefore, the shape & size can be estimated from signal image.

slide-35
SLIDE 35

Innovative Materials Testing Technologies, Inc.

Location to Signal Phase Relation (1)

0.100” 0.040” 0.063” 0.032” 0.190” 0.040” 0.063” 0.032” 0.190” 0.000”, 0.010” or 0.02” 0.100” 0.040” 0.040” 0.063” 0.032” 0.100” 0.040” 0.190” 0.063”

L = 0.353” L = 0.163” L = 0.063”

Case 0.353” Case 0.163” Case 0.063”

slide-36
SLIDE 36

Remaining Thickness to Signal Phase Relation (2)

Innovative Materials Testing Technologies, Inc.

slide-37
SLIDE 37

Innovative Materials Testing Technologies, Inc.

Corrosion Depth to Signal Imaginary, Y, Relation

slide-38
SLIDE 38

Suggested Calibration Standard for Location & Depth

Innovative Materials Testing Technologies, Inc.

slide-39
SLIDE 39

Innovative Materials Testing Technologies, Inc.

A Single-Peak Signal from RF4mm V.3 Opt. 3 Probe

Varying # of layers & Location, D Material Break with air-gap length, G= 0.00”

F = 200Hz Corrosion Size & Shape Estimation

slide-40
SLIDE 40

Innovative Materials Testing Technologies, Inc.

Magnitude Imaginary, Y Phase Angle At L = 0.06”, it is a double-peak signal Drive coil passes Pickup coil passes Corrosion Size & Shape Estimation

slide-41
SLIDE 41

At L = 0.160”, it becomes a single-peak signal Magnitude Imaginary, Y Phase Angle

Innovative Materials Testing Technologies, Inc.

Corrosion Size & Shape Estimation

slide-42
SLIDE 42

Innovative Materials Testing Technologies, Inc.

At L = 0.54”, signal peak approaching the defect position Magnitude Imaginary, Y Phase Angle Corrosion Size & Shape Estimation

slide-43
SLIDE 43

Innovative Materials Testing Technologies, Inc.

A Single-Peak Signal from A FG RFEC Probe

Varying # of layers & Location, L Material Break with air-gap length, G= 0.15”

To go deeper we use f = 100Hz & Air-gap Length = 0.15” Corrosion Size & Shape Estimation

slide-44
SLIDE 44

Innovative Materials Testing Technologies, Inc.

When f = 100 Hz signals when L ≥ 0.54 L = 0.54” L = 0.64” L = 0.73” Corrosion Size & Shape Estimation

slide-45
SLIDE 45

Innovative Materials Testing Technologies, Inc.

For shallow corrosion shape distortion decreases with increase of frequency RF4mm 200 Hz L=0.105” D=0.02” RF4mm 2 kHz L=0.105” D=0.02” Imaginary Y 0.32*Ymax Contours Corrosion Edges Corrosion Size & Shape Estimation

slide-46
SLIDE 46

Innovative Materials Testing Technologies, Inc.

Shape distortion can be minimized with small-sized probe Rf2mm 2 kHz L=0.123” D=0.003” Corrosion Size & Shape Estimation Rf2mm 2 kHz L=0.060” D=0.003”

slide-47
SLIDE 47

Innovative Materials Testing Technologies, Inc.

About Shape Factor “0.32” RF2mm Probe Corrosion Size & Shape Estimation

1”×1”×0.006”, L=0.157” 0.5”×0.5”×0.006”, L=0.157” 0.5”×0.5”×0.002”, L=0.192”

slide-48
SLIDE 48

Innovative Materials Testing Technologies, Inc.

About Shape Factor “0.32” - RF4mm Probe Corrosion Size & Shape Estimation

0.5”×0.5”×0.006”, L=0.413” 0.5”×0.5”×0.006”, L=0.413”

slide-49
SLIDE 49

Innovative Materials Testing Technologies, Inc.

About Shape Factor “0.32” - RF4mm Probe Corrosion Size & Shape Estimation

0.5”×0.5”×0.006”, L=0.603” 0.5”×0.5”×0.006”, L=0.603”

slide-50
SLIDE 50

Innovative Materials Testing Technologies, Inc.

Enhanced Edge in RFEC Signal Due to Designed Probe Structure Corrosion Size & Shape Estimation Φ 0.75 × 0.003”, L = 0.060” Φ 0.75 × 0.003”, L = 0.123”

slide-51
SLIDE 51

Summary and Future Work

  • 1. Corrosion defects can be calibrated based on the

following features of RFEC probe signals:

  • a. Monotonic relation of signal phase to defect

location, L;

  • b. At a given L imaginary,Y value increases with

increase of defect depth, D; c. An RFEC signal becomes of single-peak when L is greater a certain value.

Innovative Materials Testing Technologies, Inc.

slide-52
SLIDE 52

Innovative Materials Testing Technologies, Inc.

Summary and Future Work

  • 2. A possible calibration process has been suggested. It

consists of three steps:

  • a. Determine location L, or on which layer and top
  • r bottom surface, the defect is located;
  • b. Estimate corrosion depth, D, based on the

determined L and signal Y. c. Estimate defect size and shape based on the image of signal Y of a defect.

slide-53
SLIDE 53

Summary and Future Work

  • 3. The accuracy of size & shape estimation depends on:
  • a. Defect size/probe size ratio;
  • b. Frequency and defect location.
  • 4. The enhanced edge feature of current probes creates

error in defect size & shape estimation. Therefore, new probes with less edge enhancement need to be developed.

  • 5. Application of the suggested calibration process to

aircraft applications.

Innovative Materials Testing Technologies, Inc.