The magnetic particle test method of Non-Destructive Examination was developed in the USA, in the 1930s, as a way to check steel components on production lines. The principle of the method is that the specimen is magnetised to produce magnetic lines of force, or flux, in the material.
What is a magnetic particle test used for?
Magnetic Particle Testing (MPT), also referred to as Magnetic Particle Inspection, is a nondestructive examination (NDE) technique used to detect surface and slightly subsurface flaws in most ferromagnetic materials such as iron, nickel, and cobalt, and some of their alloys.
What is the basic magnetic principle?
All magnets have a north pole and a south pole. Like poles repel but opposite poles attract each other. … The magnetic force flows from the north pole to the south pole of the magnet. Connecting the north pole to the south pole of a different magnet (or vice versa) makes all the electrons spin in the same direction.
How do you test magnetic particles?
Magnetic Particle Inspection is performed in four steps:
- Induce a magnetic field in the specimen.
- Apply magnetic particles to the specimen’s surface.
- View the surface, looking for particle groupings that are caused by defects.
- Demagnetize and clean the specimen.
What is MPT in NDT?
Magnetic particle testing, or MPT, is a very sensitive, nondestructive testing method used on rigid materials like iron, cobalt, nickel and their alloys. It’s one of the fastest, most cost-efficient ways to ensure that critical elements like pipes or pipe welds are safe and ready to be used.
What materials can you use for magnetic particle inspection?
Because this method relies on a magnetic field to produce results, it works best on ferrous materials, like nickel, iron, cobalt, and some alloys. Components like billets, bars, castings, forgings, fasteners, weldments and extrusions are also commonly tested using magnetic particle inspection.
What is PT test in welding?
Liquid Penetrant Testing (PT) is used to detect casting, forging and welding surface defects such as hairline cracks, surface porosity, leaks in new products, and fatigue cracks on in-service components.
What are the two basic laws of magnets?
A basic law of magnetism is that unlike poles attract each other. Two bar magnets can illustrate this. One is hung so that it swings freely. A pole of the second is brought, in turn, near each of the two ends of the hanging magnet.
What are the four properties of magnets?
They are: Attractive Property – Magnet attracts ferromagnetic materials like iron, cobalt, and nickel. Repulsive Properties – Like magnetic poles repel each other and unlike magnetic poles attract each other. Directive Property – A freely suspended magnet always points in a north-south direction.
How magnetic field is created?
Any current (movement of electrical charge) will create a magnetic field. Certain materials are capable of realigning the angular momentum of their electrons, and iron is one of them. When the angular momentum of electrons gets aligned, an external magnetic field is created.
What are the limitations of magnetic particle testing?
Disadvantages of the Magnetic Particle method of Non-Destructive Examination are:
- It is restricted to ferromagnetic materials – usually iron and steel, and cannot be used on austenitic stainless steel.
- It is messy.
- Most methods need a supply of electricity.
When would you use the coil to magnetize?
The use of coils and solenoids is a third method of indirect magnetization. When the length of a component is several times larger than its diameter, a longitudinal magnetic field can be established in the component.
What is a Magnaflux?
Mag·na·flux | ” Definition of Magnaflux (Entry 2 of 2) —used for a method of testing a ferrous metal for defects by magnetizing the material and observing the patterns assumed by iron powder applied either dry or in liquid suspension.
How does eddy current NDT work?
Eddy current testing is based on the physics phenomenon of electromagnetic induction. In an eddy current probe, an alternating current flows through a wire coil and generates an oscillating magnetic field. … This in turn affects the movement of electrons in the coil by varying the electrical impedance of the coil.
What is eddy current testing in NDT?
Eddy Current Testing (ET) is a versatile NDT method that can be used to detect (near) surface defects in conductive materials without removing the coating. An electromagnetic inductor is used to generate a magnetic field.
Which material Cannot be tested by MPI?
Which material can’t be tested by MPI? Explanation: Mg is non-ferromagnetic material. So it can’t be tested by MPI. Co, Fe and Ni are ferromagnetic.