This document discusses magnetic particle testing (MPT), a non-destructive testing method used to detect surface and near surface flaws in ferromagnetic materials. It describes the basic principles and procedure of MPT, which involves magnetizing a component and applying iron particles that cluster at locations of flux leakage indicating defects. The document also outlines various magnetization methods including using permanent magnets, electromagnetic yokes, prods, and stationary equipment. It discusses the types of equipment used like Hall effect meters and pie gauges to determine magnetic field properties and different magnetic particle types for inspection.

1. M.KARTHIKEYAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI
karthikeyan@aaacet.ac.in
OML751 TESTING OF MATERIALS

2. UNIT III NON DESTRUCTIVE TESTING
1. Visual inspection
2. Liquid penetrant test
3. Magnetic particle test
4. Thermography test
5. Radiographic test
6. Eddy current test
7. Ultrasonic test
8. Acoustic emission
Principles, Techniques, Methods, Advantages and Limitations,
Applications.

3. MAGNETIC PARTICLE TESTING
PRINCIPLE:

4. INSPECTION PROCEDURE:
 Magnetize the component
 Leakage field will be formed at the surface defects area
 Iron particles either in a dry or wet suspended form are
applied to the surface of the component.
 Now the iron particles will be attracted and cluster at the flux
leakage fields.
 Finally the inspector will easily identify the crack.

5. ADVANTAGES:
 High sensitivity
 Indication are produced directly on the surface of the
component
 Minimal surface preparation
 Portable
 It is quick and relatively uncomplicated
 The method can be adapted for site or workshop use
 It is inexpensive compared to radiography
 Large or small objects can be examined
 Less training requirements.

6. LIMITATIONS:
 Only surface and near surface defects can be detected
 Only non-porous surface can be inspected
 Only applicable to ferromagnetic materials.
 Need a supply of electricity
 Parts must be demagnetized and cleaned after inspection.

7. INSPECTION MATERIALS
MAGNETIZATION EQUIPMENT [or METHODS OF MAGNETIZATION]
1. Permanent magnet
2. Electromagnetic yokes
3. Prods
4. Stationary magnetic particle inspection equipment]
EQUIPMENT USED IN DETERMINATION OF MAGNETIC FIELD
STRENGTH AND DIRECTION
1. Hall effect or gauss meter
2. Pie gauge
3. Quantitative quality indicator [QQI]
MAGNETIC PARTICLES
1. Wet magnetic particles
2. Dry magnetic particles

8. MAGNETISATION METHODS
1. Magnetization using permanent magnet
2. Magnetization using electromagnet
3. Magnetization using prods
4. Magnetization using circular magnetic field [stationary
magnetic particle inspection equipment]

9. MAGNETIZATION USING PERMANENT MAGNET
 Permanent magnets like bar magnets or horse shoe magnets,
can be used for magnetic particle inspection.

10. MAGNETIZATION USING ELECTROMAGNET
Electromagnets only exhibit a magnetic
flux when electric current is flowing
around the soft iron core
High portability can be achieved by
using an electromagnetic yokes.
Many yokes have adjustable legs to
facilitate various inspection area profiles

11. MAGNETIZATION USING PRODS
Prods are handheld electrodes that are pressed against the
surface of the component to be tested.
The current passing between the prods creates a circular
magnetic field around the prods, which is used to detect the
defects.
Prods are provided with a trigger switch to control the current
supplied.

12. MAGNETIZATION USING CIRCULAR MAGNETIC FIELD
[stationary magnetic particle inspection equipment]
In this type, a circular magnetic field can be produced in a
cylindrical components.
The part is placed between the headstock and tailstock and
gripped by pneumatic chuck to permit current to flow, thereby
producing a circular magnetic field.

13. INSPECTION MATERIALS
MAGNETIZATION EQUIPMENT [or METHODS OF MAGNETIZATION]
1. Permanent magnet
2. Electromagnetic yokes
3. Prods
4. Stationary magnetic particle inspection equipment]
EQUIPMENT USED IN DETERMINATION OF MAGNETIC FIELD
STRENGTH AND DIRECTION
1. Hall effect or gauss meter
2. Pie gauge
3. Quantitative quality indicator [QQI]
MAGNETIC PARTICLES
1. Wet magnetic particles
2. Dry magnetic particles

14. HALL EFFECT OR GAUSS METER
 The Hall Effect Meter is a digital meter for measuring the
strength and direction of an applied magnetic field.
 Meter provides a reading of field strength in Gauss, Tesla, or
amp/meters, .
 Tangential probe – senses across the field
 Axial probe – senses parallel to the field

15. PIE GAUGE
 The Pie Gauge is a tool for verifying the direction of magnetic flux on
a surface.
 The pie gauge is a disk of highly permeable material divided into eight
sections by non-ferromagnetic material.
 The divisions serve as artificial defects to provide indications in all
directions

16. QUANTITATIVE QUALITY INDICATOR [QQI]
 Quantitative Quality Indicators (QQI) are magnetic particle test
pieces with artificial defects used to verify field direction

17. INSPECTION MATERIALS
MAGNETIZATION EQUIPMENT [or METHODS OF MAGNETIZATION]
1. Permanent magnet
2. Electromagnetic yokes
3. Prods
4. Stationary magnetic particle inspection equipment]
EQUIPMENT USED IN DETERMINATION OF MAGNETIC FIELD
STRENGTH AND DIRECTION
1. Hall effect or gauss meter
2. Pie gauge
3. Quantitative quality indicator [QQI]
MAGNETIC PARTICLES
1. Wet magnetic particles
2. Dry magnetic particles

18. DRY MAGNETIC PARTICLES
 Dry magnetic particles are available in red, black, gray, yellow
and several other colors so that a high level of contrast can be
achieved.
 Fine particles are needed to identify the leakage fields from
very small discontinuities.
 Coarser particles are needed to identify large discontinuities
 The mix of globular and elongated particles will give good
results

19. WET MAGNETIC PARTICLES
Magnetic particles are also supplied in a wet suspension such as
water or oil.
 The wet magnetic particle testing method is generally more
sensitive than the dry because the suspension provides the
particles with more mobility.

20. INSPECTION MATERIALS
MAGNETIZATION EQUIPMENT [or METHODS OF MAGNETIZATION]
1. Permanent magnet
2. Electromagnetic yokes
3. Prods
4. Stationary magnetic particle inspection equipment]
EQUIPMENT USED IN DETERMINATION OF MAGNETIC FIELD
STRENGTH AND DIRECTION
1. Hall effect or gauss meter
2. Pie gauge
3. Quantitative quality indicator [QQI]
MAGNETIC PARTICLES
1. Wet magnetic particles
2. Dry magnetic particles

21. PART - A
1. Classify the magnetizing techniques?
2. Write down the basic steps in Magnetic Particle testing
procedure?
PART - B
1. With a neat diagram explain about the principle of Magnetic
particle Testing with its advantages and disadvantages. (13
marks)
2. With a neat diagram explain about the magnetisation methods
in order to inspect the materials (15 marks)
QUESTIONS