Non Destructive Testing Queries - Richard??

[Charles Warner]

I received the following questions regarding the NDT involved in an old atlantic. Way above my pay grade. Can someone provide guidance?

Thanks,

I'm in the process of resurrecting a long-dormant March 80A, and was wondering if I could trouble you for a bit of advice. I plan to have the uprights and the wheel centers crack tested, but have a few questions about the processes involved.
1/ should the parts be prepared with Al oxide or glass bead?
2/ is dye penetrant testing sufficient, or would you recommend x-ray or other methods. What testing is required in the Historic F1 series? I'm concerned most about some wheels that have been exposed to humid conditions and may have been affected by corrosion.
3/ should the bearings be removed prior to testing the uprights?
4/ one of my wheel sets is made by Gotti. The centers of the front wheels seem to have many designed-in stress risers in the form of sharp edges. Are these wheels known for cracking? I will be adding radii to most of these edges if they pass inspection.

[carl correll]

Indycar practice was to have one-piece wheels x-rayed.

You must remove everything from upright castings to get a good look by either die penetrant (dye and developer) or Zyglo (better, flourescent penetrant/developer/UV light inspection).

I never liked the idea of bead blasting before a penetrant check. I'm told it's dumb to think that you will close up surface cracks. I still don't like the idea.

[Steve Demeter]

Do not blast the castings with anything tougher than possibly glass beads.

Sand or grit will immediately remove metal.

I would suggest one of the places that is around that uses walnut shells. Very easy on the metal and will not close up cracks.

[suzrm121]

walnut blasting if your just trying to clean them up a little.

I have parts x-ray or dye penetrate inspected a few times a week, The sharp edges of the uprights can help to hide internal cracking from the dye so I would go with x-ray. A little more $$ but a whole lot more piece of mind braking at 130mph.

[Gmretired]

Charles,

Here is a link to MB racing wheels out of the UK. They list only aluminum oxide for the media. I am using 220 grit for my wheel centers. It's hard to find, I got my media from local aircraft supply. It takes a while but everything is visable. I would use only glass beads on steel parts. Walnut shells only on non structural stuff. I am using the Magnaflux developer kit non UV. They also tell you what chemicals you need to Chromate. You can do it yourself, but make sure you dispose of the waste at a proper landfill waste manage facility.
Dave
http://www.mb-racingwheels.com/magnesium_protection.htm

[beachguy12]

Here are the basic prep rules for an aircraft level penetrant inspection. Strip paint with solvent or chemical strippers and rags. Do not wire brush, wire wheel, sand, sand blast, walnut shell blast, period. This could give you a false negative finding.

Penetrant inspection is to check for cracks at the surface, where all cracks start. Any working of the metal surface can smear metal over the crack opening. The softer the metal or the more agressive the cleaning process the more likely you are to cover the crack and hide it. Depending on the sensativity of the penatrant, incomplete cleaning can also hide the crack by smearing dirt or foregin matter into the crack.

[LeeR]

Thanks everyone for the advice. I'm the guy who originally contacted Charles with the questions. The amount of expertise on this site never ceases to amaze me!

Thanks,
Lee

[La Scuderia Raggi]

Pretty good advice here-in regarding NDT. I would not recommend any bead blasting prior to dye penetrant or magna-fluxing. With respect to X-ray, it is not always the best method for determining cracks. The cracks must be in the correct orientation relative to the beam to be detected (i.e. in line, not perpendicular to the beam). It is perfect for finding internal defects like porosity in a casting. Thanks for bringing me back to my NDT days when I "used" to be a metallurgical engineer. Find yourself a reputable lab in the yellow pages and discuss with them what you are looking for.