Introducing Non-Destructive Testing Tools

"Two MPT variations exist: wet magnetic particle testing (WMPT) and dry magnetic particle testing (DMPT). Both initiate by applying magnetic current to the component. Material voids in the form of cracks or defects will interrupt current flow. Magnetism then disperses the particles to create a “flux leakage field” at the flaw location, visually providing its approximate size and shape."

Not sure what to make of that (my emphasis).

I second your sentiment... (not a very well researched-or-written piece).

The blurb regarding PT (penetrant testing) mentions only the fluorescent technique (without bothering to touch on the necessity for UV illumination, together WITH the exclusion of visible white light, for THAT technique)... not bothering to mention the visible dye penetrants that are available. At the same time, allusion is made that inspections cannot be performed on hot materials, while, in fact, there are "wax-crayon-type" penetrants that are made to be used on fresh welds.

And, "shame on the author", for suggesting that for VT, all that is needed is the "naked eye" (when that eye is totally and completely useless if the brain that it feeds is not thoroughly trained as to what-all it needs to "catch").

Likewise, for MT the allusion is suggested that surface preparation for inspection is minimal...(tsk-tsk).

John is spot-on , in that the "mechanisms-at-work" in MPT are very poorly delineated (even for a "nutshell" description). Wet and dry are NOT the "only two" variations that exist. Both a.c. and d.c. currents can be utilized, with the a.c. technique being best for detection of surface-breaking-only discontinuities (discontinuity being a key-NDT word not found in THIS article)... AND, a.c. magnetization affords the advantage that subsequent "demagnetization" is not necessary (when performed properly to begin with).

A strategically-placed link-or-two, OR even a proper graphic could have spoken MUCH more eloquently than the equivocation pertaining to the TOFD technique (of the ultrasonic Method)... likewise with the eddy current technologies.

[Regrettably, I could not bring myself to read-on any further....]