This document provides an overview of magnetic particle testing (MPT). MPT can detect both manufacturing defects and in-service damage in ferromagnetic materials. The basics involve magnetizing a test specimen, which causes discontinuities to distort the magnetic field and produce indications. Iron particles coated with dye are applied and cluster at these indications. The procedure involves pre-cleaning, magnetizing the specimen, applying particles, and interpreting any visible indications of discontinuities. MPT can be done with dry or wet particles and produces indications of cracks and defects.

1. Module-2 Surface NDE Methods
Lecture 4 of 5 - Basics of Magnetic Particle Testing
Prepared by
Mr.M.Mani Vannan
Assistant Professor
Department of Mechanical Engineering 1

2. Introduction
Magnetic particle inspection can detect both production
discontinuities (seams, laps, grinding cracks and quenching
cracks) and in-service damage (fatigue and overload cracks)
Basics of Magnetic Particle Testing 2

3. Basics of Magnetic Particle Testing
1.A ferromagnetic test specimen is magnetized with a strong
magnetic field created by a magnet or Special equipment.
2.If the specimen has a discontinuity, the discontinuity will
interrupt the magnetic field flowing through the specimen
and a leakage field will occur.
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4. Basics of Magnetic Particle Testing
3.Finely milled iron particles coated with a dye pigment are
applied to the test specimen.
4.These particles are attracted to leakage fields and will
cluster to form an indication directly over the discontinuity.
5.This indication can be visually detected under proper lighting
conditions.
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5. Basic Procedure of MPT
1. Component pre-cleaning
2. Introduction of magnetic field
3. Application of magnetic media
4. Interpretation of magnetic particle indications
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6. Pre-cleaning
Contaminants such as oil, grease, or scale may not only
prevent particles from being attracted to leakage fields, they
may also interfere with Interpretation of indications.
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7. Introduction of the Magnetic Field
The required magnetic field can be introduced into a
component in a number of different ways.
1.Using a permanent magnet or an electromagnet that
contacts the test piece
2. Flowing an electrical current through the specimen
3. Flowing an electrical current through a coil of wire around
the part or through a central conductor running near the part.
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8. Application of Magnetic Media
(Wet Versus Dry)
1.MPI can be performed using either dry particles, or particles
suspended in a liquid.
2.With the dry method, the particles are lightly dusted on to
the surface. The dry method is more portable.
3.With the wet method, the part is flooded with a
Solution carrying the particles. The wet method is
generally more sensitive since the liquid carrier gives the
magnetic particles additional mobility.
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9. Dry Magnetic Particles
1.Magnetic particles come in a variety of colors.
2.A color that produces a high level of contrast against the
background should be used.
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10. Wet Magnetic Particles
1.Wet particles are typically supplied as visible or fluorescent.
2.Visible particles are viewed under normal white light and
fluorescent particles are viewed under black light.
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11. Interpretation of Indications
1.After applying the magnetic field, indications that form must
interpreted.
2.This process requires that the inspector distinguish
between relevant and non-relevant indications.
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Basics of Magnetic Particle Testing

12. Crane Hook with Service Induced Crack
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13. Gear with Service Induced Crack
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14. Drive Shaft with Heat Treatment Induced
Cracks
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15. Splined Shaft with Service Induced Cracks
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16. Threaded Shaft with Service Induced
Crack
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17. Large Bolt with Service Induced Crack
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18. Crank Shaft with Service Induced Crack
Near Lube Hole
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Basics of Magnetic Particle Testing

19. Lack of Fusion in SMAW Weld
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20. Toe Crack in SMAW Weld
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21. Throat and Toe Cracks in Partially Ground
Weld
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22. THANK YOU
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