02-01-2013, 11:53 AM
Non-destructive Testing
1Non-destructive.ppt (Size: 6.89 MB / Downloads: 269)
Definition of NDT (NDE)
The use of noninvasive
techniques to determine
the integrity of a material,
component or structure
or
quantitatively measure
some characteristic of
an object.
Why Nondestructive?
Test piece too precious to be destroyed
Test piece to be reuse after inspection
Test piece is in service
For quality control purpose
What are Some Uses of NDE Methods?
Flaw Detection and Evaluation
Leak Detection
Dimensional Measurements
Structure and Microstructure Characterization
Estimation of Mechanical and Physical Properties
Stress (Strain) and Dynamic Response Measurements
When are NDE Methods Used?
There are NDE application at almost any stage in
the production or life cycle of a component.
To assist in product development
To screen or sort incoming materials
To monitor, improve or control manufacturing processes
To verify proper processing such as heat treating
To verify proper assembly
To inspect for in-service damage
Magnetic Particle Inspection (MPI)
Introduction
A nondestructive testing method used for defect detection. Fast and relatively easy to apply and part surface preparation is not as critical as for some other NDT methods. – MPI one of the most widely utilized nondestructive testing methods.
MPI uses magnetic fields and small magnetic particles, such as iron filings to detect flaws in components. The only requirement from an inspectability standpoint is that the component being inspected must be made of a ferromagnetic material such as iron, nickel, cobalt, or some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level that will allow the inspection to be affective.
The method is used to inspect a variety of product forms such as castings, forgings, and weldments. Many different industries use magnetic particle inspection for determining a component's fitness-for-use. Some examples of industries that use magnetic particle inspection are the structural steel, automotive, petrochemical, power generation, and aerospace industries. Underwater inspection is another area where magnetic particle inspection may be used to test such things as offshore structures and underwater pipelines.
Basic Principles
In theory, magnetic particle inspection (MPI) is a relatively simple concept. It can be considered as a combination of two nondestructive testing methods: magnetic flux leakage testing and visual testing.
Consider a bar magnet. It has a magnetic field in and around the magnet. Any place that a magnetic line of force exits or enters the magnet is called a pole. A pole where a magnetic line of force exits the magnet is called a north pole and a pole where a line of force enters the magnet is called a south pole.
Diamagnetic, Paramagnetic, and Ferromagnetic Materials
Diamagnetic metals: very weak and negative susceptibility to magnetic fields. Diamagnetic materials are slightly repelled by a magnetic field and the material does not retain the magnetic properties when the external field is removed.
Paramagnetic metals: small and positive susceptibility to magnetic fields. These materials are slightly attracted by a magnetic field and the material does not retain the magnetic properties when the external field is removed.
Ferromagnetic materials: large and positive susceptibility to an external magnetic field. They exhibit a strong attraction to magnetic fields and are able to retain their magnetic properties after the external field has been removed.
Magnetic Particle Inspection
The magnetic flux line close to the surface of a ferromagnetic material tends to follow the surface profile of the material
Discontinuities (cracks or voids) of the material perpendicular to the flux lines cause fringing of the magnetic flux lines, i.e. flux leakage
The leakage field can attract other ferromagnetic particles
Result presentation
The impedance plane diagram is a very useful way of displaying eddy current data. The strength of the eddy currents and the magnetic permeability of the test material cause the eddy current signal on the impedance plane to react in a variety of different ways.
1Non-destructive.ppt (Size: 6.89 MB / Downloads: 269)
Definition of NDT (NDE)
The use of noninvasive
techniques to determine
the integrity of a material,
component or structure
or
quantitatively measure
some characteristic of
an object.
Why Nondestructive?
Test piece too precious to be destroyed
Test piece to be reuse after inspection
Test piece is in service
For quality control purpose
What are Some Uses of NDE Methods?
Flaw Detection and Evaluation
Leak Detection
Dimensional Measurements
Structure and Microstructure Characterization
Estimation of Mechanical and Physical Properties
Stress (Strain) and Dynamic Response Measurements
When are NDE Methods Used?
There are NDE application at almost any stage in
the production or life cycle of a component.
To assist in product development
To screen or sort incoming materials
To monitor, improve or control manufacturing processes
To verify proper processing such as heat treating
To verify proper assembly
To inspect for in-service damage
Magnetic Particle Inspection (MPI)
Introduction
A nondestructive testing method used for defect detection. Fast and relatively easy to apply and part surface preparation is not as critical as for some other NDT methods. – MPI one of the most widely utilized nondestructive testing methods.
MPI uses magnetic fields and small magnetic particles, such as iron filings to detect flaws in components. The only requirement from an inspectability standpoint is that the component being inspected must be made of a ferromagnetic material such as iron, nickel, cobalt, or some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level that will allow the inspection to be affective.
The method is used to inspect a variety of product forms such as castings, forgings, and weldments. Many different industries use magnetic particle inspection for determining a component's fitness-for-use. Some examples of industries that use magnetic particle inspection are the structural steel, automotive, petrochemical, power generation, and aerospace industries. Underwater inspection is another area where magnetic particle inspection may be used to test such things as offshore structures and underwater pipelines.
Basic Principles
In theory, magnetic particle inspection (MPI) is a relatively simple concept. It can be considered as a combination of two nondestructive testing methods: magnetic flux leakage testing and visual testing.
Consider a bar magnet. It has a magnetic field in and around the magnet. Any place that a magnetic line of force exits or enters the magnet is called a pole. A pole where a magnetic line of force exits the magnet is called a north pole and a pole where a line of force enters the magnet is called a south pole.
Diamagnetic, Paramagnetic, and Ferromagnetic Materials
Diamagnetic metals: very weak and negative susceptibility to magnetic fields. Diamagnetic materials are slightly repelled by a magnetic field and the material does not retain the magnetic properties when the external field is removed.
Paramagnetic metals: small and positive susceptibility to magnetic fields. These materials are slightly attracted by a magnetic field and the material does not retain the magnetic properties when the external field is removed.
Ferromagnetic materials: large and positive susceptibility to an external magnetic field. They exhibit a strong attraction to magnetic fields and are able to retain their magnetic properties after the external field has been removed.
Magnetic Particle Inspection
The magnetic flux line close to the surface of a ferromagnetic material tends to follow the surface profile of the material
Discontinuities (cracks or voids) of the material perpendicular to the flux lines cause fringing of the magnetic flux lines, i.e. flux leakage
The leakage field can attract other ferromagnetic particles
Result presentation
The impedance plane diagram is a very useful way of displaying eddy current data. The strength of the eddy currents and the magnetic permeability of the test material cause the eddy current signal on the impedance plane to react in a variety of different ways.