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Originally Posted by Tim Corcoran

HF Eddy current is only applicable to aluminum it is not used on iron, steel or other metals. Ultrasonic is usually used on composite materials to determine if there is delamination or voids. Radiography (x-ray) is very expensive, requires very expensive equipment and would cost a lot of money to have an engineer write a test plan to inspect an automotive crankshaft it, would cost more than the price of my new engine will. Dye penetrant will detect surface discontinuities and cracks not normally visible to the human eye. Mag particle (magnaflux) can detect surface and sub surface discontinuities, there are two basic types wet and dry. Most machine shops use the dry method using a dry magnetic dyed powder and applying a current through a set of prods to the test article. The dry mag inspection is only as accurate as the operator is trained and is not the most accurate method and can miss a lot or give inaccurate results. Wet mag particle is much more accurate but requires more specialized equipment and training and these inspections should only be performed by a level II certified technician. The type of dye penetrant that would be used in a machine shop is simple but is very accurate and does not require a lot or training or skill just follow the procedure that comes with the kit. I have been trained and certified a level II in magnetic particle, Radiography, dye penetrant and HF Eddy Current. I would leave it up to a level III to determine if dry mag or dye penetrant was a better test method to inspect for crack in a crankshaft.

WHERE did I say eddy current a ferrous component? You left out magnesium and titanium as metals that can be subjected to eddy current inspection. In case you are not aware the FAA mandated ultrasonic inspection of the primary turbine blades on the CFM56 turbofans after the fatal in-service failure of a primary fan blade on a Southwest Airlines 737s. The primary fan blades used in the CFM56 engines are titanium forgings. Additionally, the FAA MANDATES magnetic particle inspection of ALL ferrous engine components of aircraft reciprocating engines and has for decades. The AERA ( Automotive Engine Re-manufacturers Association) and strongly advises their members to utilize magnetic particle inspection when checking ferrous engine components for cracking and other anomalies. Pratt and Whitney MANDATES magnetic particle inspection of ALL ferrous components of their piston reciprocating and gas turbine engines. Cummins, Detroit Diesel, CAT, Navistar, etc. mandate magnetic particle inspection of ALL of the internal ferrous components of their engines during overhaul. The ONLY time we utilized dye penetrant for NDT in my nearly thirty years in aircraft maintenance was on cast aluminum turbocharger housings or on cast aluminum/ cast magnesium wheel halves ( until we started using eddy current). We also used dye penetrant on cast iron turbocharger exhaust housings per the ADs( we would confirm the results through magnetic particle inspection). In my years as an ASE master engine machinist for JET we used dye penetrant to crack check aluminum engine blocks and aluminum heads, but subjected hundreds of cranks, cams and connecting rods to magnetic particle inspection every week. It your chit, so do what you want to. I’ll stick with my forty years of experience AND the over one hundred years of experience of the men who mentored me over the years. Guess the FAA has no idea as HOW to perform NDT on ferrous metals….BTW, ultrasonic testing on cylinder walls is not only for judging thickness; it is also use to establish the amount of internal corrosion and voids in the internal cylinder walls. It’s pretty smart when engine machinists use ultrasonic inspection before attempting to bore a block with substantial internal corrosion.