Magnetic particle NDT

Question 1

What is the basic principle behind magnetic particle NDT?

Answer 1

It it based on the formation of a magnetic flux scattered in the workpiece. Any inhomogenity will cause discontinuity in the flow of lines of the magnetic field. A flux leakage are located between the edges of the discontinuity and can be detected.

Question 2

How is the testing procedure in magnetic particle NDT?

Answer 2

• Create a magnetic field
• The magnetic flux penetrates under the surface
• Material is sprinkeled with a dust of metal oxides with ferromagnetic charecteristic
• A localizrd thickening of the particles allong the edges of discontinuities will be visualized due to the flux leakage

Question 3

What are some of the limitations of magnetic particle NDT?

Answer 3

• Material examined must be ferromagnetic
• Can only reveal surface and subsurface defects
• Method is orientation sensitive since only defects favorably oriented with respect to the magnetuc field can produce flux leakage
• Need to induce a homogenous pattern of magnetic flow, can not be done to complex geometries.

Question 4

What are the two ways magnitization can be obtained?

Answer 4

• Electrical system
• Magnetic system

Question 5

What are some advantages of magnetic NDT techniques?

Answer 5

• Not very expensive
• Quick
• Does not reqire special pre-cleaning of workpiece
• Can be preformen alsmost everywhere, does not require a laboratory
• Can examine painted surfaces