Particulate Radiation:

Particulate Radiation:
There are three types of Particulate Radiation and they are of little concern to the average radiographer.
Particulate Radiation is different from X and Gamma Rays they have mass and do not travel at the speed of light.
However, Particulate Radiation will penetrate matter, will case ionization and cannot be detected by human senses.
Alpha Radiation as discussed in Lesson 4 has a positive charge and is slow and heavy.
Alpha Particles ionize atoms by removing electrons as they pass but they do not penetrate deeply.
Beta Particles (High Speed Electrons) have a negative charge and because they are lightweight, they are not as ionizing alpha particles.
Neutron Radiation has peculiar penetrating qualities. It penetrates many heavy elements with ease and is absorbed readily by many lighter elements, particularly Hydrogen.

Magnetic Particle Testing

  • When a ferromagnetic material is magnetised the flux lines flow inside the component

  • When there is a discontinuity in the material there is flux leakage

  • The leaking flux attracts a magnetic medium resulting in an indication.

What is magnetic particle testing?

What is magnetic particle testing?

This method is used for the detection of surface and near-surface flaws in ferromagnetic materials and is primarily used for crack detection. The specimen is magnetised either locally or overall, and if the material is sound the magnetic flux is predominantly inside the material. If, however, there is a surface-breaking flaw, the magnetic field is distorted, causing local magnetic flux leakage around the flaw. This leakage flux is displayed by covering the surface with very fine iron particles applied either dry or suspended in a liquid. The particles accumulate at the regions of flux leakage, producing a build-up which can be seen visually even when the crack opening is very narrow. Thus, a crack is indicated as a line of iron powder particles on the surface.