Magnetic Particle Testing ppt

7/13/2019 Magnetic Particle Testing ppt

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MAGNETIC PARTICLE

TESTING


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Magnetic particle inspection can

detect both production

discontinuities and in-service

damage


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INTRODUCTIONTOMAGNETISM

Magnetism is the ability of matter to attract other

matter to itself.

Objects that possess the property of magnetism are

said to be magnetic

magnetic pole is a point where the a magnetic line

of force exits or enters a material


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FERROMAGNETICMATERIALS

A material is considered ferromagnetic if it can bemagnetized

Ferromagnetic materials are made up of magnetic

domains

Magnetic domains point randomly in demagnetizedmaterial, but can be aligned using electrical current

Demagnetized Magnetized


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HOWDOESMAGNETICPARTICLE

INSPECTIONWORK?


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HOWDOESMAGNETICPARTICLE

INSPECTIONWORK? (CONT.)


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BASICPROCEDURE

Basic steps involved:

1 Component pre-cleaning

2 Introduction of magnetic field

3 Application of magnetic media

4 Interpretation of magnetic particleindications


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PRE-CLEANING

The parts surface should be clean and dry before

inspection

Contaminants being attracted to leakage

fields, they may also interfere with interpretation of

indications.


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INTRODUCTIONOFTHEMAGNETIC

FIELD

magnetic field can be introduced into a component

in a number of different ways.

A. Using a permanent magnet or anelectromagnet

B. Flowing an electrical current through the

specimen

C. Flowing an electrical current through a coil ofwire


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DIRECTIONOFTHEMAGNETICFIELD

Two general types of magnetic fields:

1) longitudinal magnetic field

2) circular magnetic field


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IMPORTANCEOFMAGNETICFIELD

DIRECTION

detection of defects occurs when the lines of

magnetic force are established at right angles to the

longest dimension of the defectFlux Leakage

No Flux Leakage


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Longitudinal (along the axis) Transverse (perpendicular the axis)

Kinds of defect


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PRODUCINGALONGITUDINAL

MAGNETICFIELDUSINGACOIL

placing the part near the

inside or a coils annulus.This produces magnetic

lines of force that are

parallel to the long axis of

the test part


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PRODUCINGALONGITUDINALFIELD

USINGPERMANENTOR

ELECTROMAGNETICMAGNETS


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CIRCULARMAGNETICFIELDS


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DRYMAGNETICPARTICLES


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WETMAGNETICPARTICLES


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Indications


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DEMAGNETIZATION

Possible reasons for demagnetization

include: May interfere with welding and/or machining

operations

Can effect gauges that are sensitive to magneticfields if placed in close proximity.

Abrasive particles may adhere to componentssurface and cause and increase in wear toengines components, gears, bearings etc.


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DEMAGNETIZATION

Magnetized

Demagnetized


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ADVANTAGESOF

MAGNETICPARTICLEINSPECTION

Can detect both surface and near sub-surface

defects

Precleaning of components is not critical

Fast method of inspection and indications are

visible directly

low cost compared to many other NDT methods

Is a very portable inspection


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LIMITATIONSOF

MAGNETICPARTICLEINSPECTION

Cannot inspect non-ferrous materials

Inspection of large parts may require use of

equipment

Some parts may require removal of coating

Limited subsurface discontinuity detection

Post cleaning, and post demagnetization is often

necessary


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TH NKYOU

Magnetic Particle Testing ppt

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