Eddy Current Inspection Training Course Syllabus

Eddy Current Inspection Training Course Syllabus - Level I

1. INTRODUCTION TO ELECTROMAGNETIC TESTING (EDDY CURRENT / FLUX LEAKAGE)
a. Brief history of testing
b. Basic principles of testing

2. ELECTROMAGNETIC THEORY
a. EDDY CURRENT THEORY
     1) Generation of Eddy Currents by means of an AC field
     2) Effect of fields created by Eddy Currents (impedance changes)
     3) Effect of change of impedance on instrumentation
     4) Properties of Eddy Current
          - Travel in circular direction
          - Strongest on surface of test material
          - Zero value at centre of solid conductor placed in an alternating magnetic field
          - Strength, time relationship and orientation as functions of test-system parameters and test-part

            characteristics
          - Have properties of compressible fluids
          - Small magnitude of current flow
          - Relationship of frequency and plane with current in coil
          - Effective permeability variations when induced in magnetic materials.
          - Effect of discontinuity orientation
          - Power losses

b. FLUX LEAKAGE THEORY
     1) Terminology and units
     2) Principles of magnetization
          - B - H curve
          - Magnetic properties
          - Magnetic field
          - Hysteresis loop
          - Magnetic permeability
          - Factors affecting permeability

3) Magnetization - Electromagnetism theory
a. Oersted's Law
b. Faraday's Law
c. Electromagnetics

4) Flux leakage theory and principle
a. Residual
b. Active
c. Tangential leakage
d. Normal leakage fields

3. READOUT MECHANISM
a. Calibrated or Uncalibrated meter
b. Null Meter with Dial Indicator
c. Oscilloscope
d. Alarm, Lights, etc.
e. Numerical Counters
f. Marking System
g. Sorting Gates and Tables
h. Cut-off Saw or Shears
i. Automation and Feedback
j. Strip-chart Recorder

4. TYPES OF EDDY CURRENT SENSING ELEMENTS
a. Probes
     1. Types of arrangements
          - Absolute
          - Differential
     2. Lift-off
     3. Theory of operation
     4. Applications
     5. Advantages
     6. Limitations
b. Through, encircling or annular coils
     1. Types of arrangements
          - Absolute
          - Differential
     2. Fill factor
     3. Theory of operation
     4. Applications
     5. Advantages
     6. Limitations
c. Factors affecting choice of sensing elements
     1. Type of part to be inspected
     2. Type of discontinuity to be detected
     3. Speed of testing required
     4. Amount of testing (percentage) required

5. TYPES OF FLUX LEAKAGE SENSING ELEMENTS
a. Principles of magnetic-measurement techniques
b. Inductive-coil sensors
     1. theory of electromotive force (emf) induced in coil
     2. Various constructions and designs of coils
     3. Coil parameters affecting the flux leakage response
     4. Sensing-coil systems and connections (single and multi-element probes)
c. Semi-conductor sensing elements
     1. Hall-effect probes
     2. Magneto resistors
     3. Magneto diodes
     4. Magneto transistors
     5. Magnetic and electric characteristics of semi-conductor sensing elements
d. Other methods of magnetic leakage field detection
     1. Magnetic-tape system
     2. Magnetic powder
     3. Magnetic-resonance sensor

6. APPLICATION OF EDDY CURRENT TECHNIQUE

7. PRACTICAL EXPERIMENTS
a. Flaw detection
b. Sorting for properties related to conductivity
c. Sorting for properties related to permeability
d. Thickness evaluation

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