Electromagnetic Testing Chapter 3- Electromagnetic Testing

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Paintbrush array probes are popular because they cover a broad band of material in one placement. Consecutive placements are usually overlapped to guarantee complete coverage of the test area. When used in automatic scanning systems, they usually contain a position encoder to provide feedback on scanning speed, defect size, and location. Pick-and- lace arrays cover rectangular areas and are often used with programmed robotic manipulators. Test results for probe arrays are often displayed as false-color contour maps of the inspection area. Windows-based software simplifies analysis and display functions. The field induction coil typically operates at 5 kHz with standard probes and 50kHz with special high- frequency probes. The 50 kHz high-frequency probes are typically used to obtain higher test sensitivity for nonmagnetic conductive materials. TSC Inspection Systems has a wide range of AMIGO probes designed for use with the AMIGO ACFM Crack Microgauge. Standard probes include weld, minipencil, and micropencil types with several variations and orientations. Figure 3.48 is a flowchart selection guide for common AMIGO probes. Charlie Chong/ Fion Zhang
Figure 3.48 Flowchart selection of common AMIGO probe types. Courtesy of TSC Inspection Systems. Charlie Chong/ Fion Zhang
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Electromagnetic Testing Chapter 3-
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Submarine Applications Charlie Chon
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Fion Zhang at Shanghai 6th April 20
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IVONA TTS Capable. Charlie Chong/ F
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Chapter 3. ELECTROMAGNETIC TESTING
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Barkhausen effect The Barkhausen ef
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Barkhausen Noise Charlie Chong/ Fio
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Figure 3.1 Eddy current principle.
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Figure 3.2 Schematic diagram of bas
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Figure 3.3 The effect of conductivi
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Figure 3.3 The effect of conductivi
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Another important influence on coil
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If the conductivity of the material
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Figure 3.5 The effect of a crack on
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FIGURE 8-49 Conductivity curve: (a)
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So far, we have described how eddy
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Figure 3.6 The effects of (a) condu
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3.1.2 Limiting Frequency f g of Enc
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Figure 3.7 The effect of degree of
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Charlie Chong/ Fion Zhang
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Eddy Current Heating Charlie Chong/
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Eddy Current Heating Charlie Chong/
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Eddy currents weaken the original m
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3.2 MAGNETIC FLUX LEAKAGE THEORY Wh
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3D Magnetic Field Charlie Chong/ Fi
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3D Magnetic Field Fig.1 THE PRINCIP
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Based on what we have learned about
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Charlie Chong/ Fion Zhang Figure 3.
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Magnetic Field - Simple Semi Ellipt
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Flux leakage sensors have small dia
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The frequency of the alternating fi
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Figure 3.14 Rotating magnet arrange
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3.3 EDDY CURRENT SENSING PROBES For
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As the probe moves over the defect,
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Figure 3.17 Differential surface co
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Figure 3.19 shows an encircling coi
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The application of eddy current sen
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Baffles and tube sheets. Charlie Ch
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Another important consideration for
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3.4.1 Induction Coils For an induct
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If the diameter of a surface coil i
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3.4.2 Hall Effect Sensors Hall effe
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Figure 3.21 illustrates the Hall ef
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Hall voltage Charlie Chong/ Fion Zh
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Since a 1 gauss (G) field produces
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Figure 3.22 Effect of magnetic fiel
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3.5 FACTORS AFFECTING FLUX LEAKAGE
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Defect & Flux Distribution Charlie
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The distance between adjacent defec
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3.6 SIGNAL-TO-NOISE RATIO The signa
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With flux leakage testing, signal-t
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As shown in Eq. (3.6), test frequen
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The characteristic frequency for a
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Charlie Chong/ Fion Zhang
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Figure 3.23 Magnetization or magnet
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By taking the product of B and H fo
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The rate of change of the opposing
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Figure 3.25 Encircling coils establ
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Figure 3.27 DC-MFL sensor illustrat
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Fill factors apply only to encircli
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For best results with encircling co
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3.11 INSTRUMENT DESIGN CONSIDERATIO
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TABLE 3.2. Comparison of Instrument
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Some general categories of equipmen
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Figure 3.29 UniWest-454 EddyView mu
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Scanner operation uses a separate c
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Figure 3.30 E-Lab model US-450 full
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3.12.3 ETC-2000 Scanner Because of
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ETC-2000 scanner features include:
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3.13 INSTITUT DR. FOERSTER Institut
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It is possible to provide 100% eddy
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Figure 3.33 ET testing of hot coppe
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For maximum sensitivity, the Circog
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3.14 MAGNETIC FLUX LEAKAGE TESTING
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ASTM E 570 describes magnetic flux
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Applications involving physical par
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Page 179 and 180: 3.17.1 Introduction In 1911, Dr. He
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Page 187 and 188: Figure 3.38 A comparison of Barkhau
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Page 225 and 226: Other applications include: • Ins
Page 227 and 228: Eddy Current Testing at High Temper
Page 229 and 230: Good Luck Charlie Chong/ Fion Zhang
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Electromagnetic Testing Chapter 3- Electromagnetic Testing

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