14-05-2012, 01:25 PM
MAGNA FLUX
MAGNA FLUX.pptx (Size: 2.42 MB / Downloads: 44)
INTRODUCTION
ABOUT MAGNA FLUX TESTING:
Magna flux is non destructive type of testing.
It is also known as magnetic particle testing.
The test is conducted mostly on ferromagnetic materials.
The test is mainly used in detection of surface and sub surface cracks.
PRINCIPLE
When a ferromagnetic material is magnetized upto its saturation , a discontinuity at the surface of substance will cause leakage of magnetic flux.
There is formation of new magnetic poles at this discontinuity which are miniature (very small).
If the leak is detected the discontinuity is also detected.
The leak is detected using magnetic particles.
SIGNIFICANCE
Metal parts when they are machined and/or welded can become stressed during those processes. Those stresses can reveal themselves in the form of small fissures or cracks in the metal joints. These stress fractures at times may be difficult to see with the human eye. A method of employing small magnetic particles and a fluorescent dye was implemented to highlight any abnormalities of the machining and joining those metal parts.
IMPORTANCE OF CRACK ORIENTATIONS
The direction of defect plays important role in detection of defects in ferromagnetic materials.
When the magnetic lines of force are established per-
pendicular to the longest defect the defect detection is easy.
The defect orientation creates large disturbance in the
magnetic field flowing through that defect, and hence
the flux leakage at this part takes place.
Two general types of magnetic field can be established in the specimen, that are as follows: