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

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. 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. 4 th Avenue, Mt. Vernon, NY 10550-4499 Tel. 800-463-8622

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

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.

Innovative Materials Testing Technologies, Inc. RFEC Phenomenon in Metallic Tubes Indirect energy coupling path Direct energy coupling path Φ RF Φ Excitation Pick-up coil coil 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. RFEC Phenomenon in Metallic Tubes Underlying Physics: 1. Direct energy coupling is restricted by EC in the wall. 2. Pick-up coil signal, Φ RF , is dominated by the energy diffusing along the indirect coupling path that traverses the wall twice. 3. Changes in the phase of Φ RF are directly proportional to the thickness of the wall.

Innovative Materials Testing Technologies, Inc. RFEC Phenomenon in Metallic Tubes Typical RFEC signals: double-peak signal Signals Real Component, X Time Imaginary Component, Y

Innovative Materials Testing Technologies, Inc. 2. RFEC Phenomenon In Flat Geometries RFEC Probe Drive Coil Direct Coupling Path Pickup Coil 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. 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. Examples from Two RFEC Probes RF-4 mm V.3 RF-2 mm V.3 Footprint: 0.85” x 2.15” Footprint: 0.3” x 0.62”

Innovative Materials Testing Technologies, Inc. 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. Example 1: 3 Layer 7075 T6 Specimen, 0.125” + 0.5” + 0.125” Total Thickness = 0.750” Spherical-Shaped Corrosion on Bottom of 2 th Layer RFEC Probe Rf4mm 0.125” Location Location 0.500” 0.125” Φ 0.75” #1 Φ 0.75” #2 Max. Depth = 0.075” Max. Depth = 0.025” Location = 0.600” Location = 0.575”

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

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

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 5 th Layer Location = 0.603” A Scan Direction RFEC Probe Rf4mm 0.100” 0.100” Location = 0.603” 0.190” 0.190” 0.063” 0.040” deep corrosion

Innovative Materials Testing Technologies, Inc. Corrosion Sample #15 3.0” × 3.0” × 0.040" chemical thinning on the bottom side CNDE Specimen #15 (0.063” thick) 0.5” × 0.5” × 0.040" chemical thinning on the bottom side

Innovative Materials Testing Technologies, Inc. EXAMPLE 2.1.1 3” × 3” × 0.040” 5 th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.603”

Innovative Materials Testing Technologies, Inc. EXAMPLE 2.1.2 0.5” × 0.5” × 0.040” 5 th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.603”

Innovative Materials Testing Technologies, Inc. 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 4 th Layer Location = 0.413” RFEC Probe Rf4mm 0.100” 0.100” Remaining Depth = 0.413” 0.190” 0.063” 0.190” 0.040” deep corrosion

Innovative Materials Testing Technologies, Inc. EXAMPLE 2.2.1 3” × 3” × 0.040” 4 th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.413”

Innovative Materials Testing Technologies, Inc. EXAMPLE 2.2.2 0.5” × 0.5” × 0.040” 4 th Layer Bottom Side Corrosion, f=200Hz Total Thickness = 0.643”, Location = 0.413”

Innovative Materials Testing Technologies, Inc. Example 3 3 Layer 2024 T3 Specimen 0.26” + 0.05” + 0.063” Remaining Depth = 0.413” Total Thickness = 0.373” Corrosion on Bottom of 3 rd Layer Location = 0.333” RFEC Probe 0.260” 0.050” Rf4mm 0.333” 0.063” 0.5” × 0.5” × 0.006” corrosion

Innovative Materials Testing Technologies, Inc. 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. EXAMPLE 3 0.5” × 0.5” × 0.006” 3 rd Layer Bottom Side Corrosion, f=500Hz Total Thickness = 0.373”, Location = 0.333”

Innovative Materials Testing Technologies, Inc. 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. Example 4 4 Layer 2024 T3 Specimen 0.05” + 0.05” + 0.032” + 0.063” Total Thickness = 0.195” Corrosion on Bottom of 4 th Layer Location = 0.193” 0.050” 0.050” 0.032” RFEC Probe 0.193” Rf4mm 0.063” 0.5” × 0.5” × 0.002” corrosion

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

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

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 3 rd Layer Location = 0.157” Rf2mm Probe 0.032” 0.050” 0.050” 0.157” 0.063” 0.006” deep corrosion

Innovative Materials Testing Technologies, Inc. Corrosion Sample #5 1.0” × 1.0” × 0.006" chemical thinning on the bottom side CNDE Specimen #5 (0.063” thick) 0.5” × 0.5” × 0.006" chemical thinning on the bottom side

Innovative Materials Testing Technologies, Inc. EXAMPLE 5.1 1” × 1” × 0.006” 4 th Layer Bottom Side Corrosion, f=2.0 kHz Total Thickness = 0.163”, Location = 0.157”

Innovative Materials Testing Technologies, Inc. EXAMPLE 5.2 0.5” × 0.5” × 0.006” 4 th Layer Bottom Side Corrosion, f=2.0 kHz Total Thickness = 0.163”, Location = 0.157”

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. L D