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#7613 - 10/28/06 10:18 PM Re: Damascus barrels and magnafluxing question [Re: Dick_dup1]
tanky Offline
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Registered: 05/17/06
Posts: 276
Loc: New Jersey
I can assure you that if a mag particle test or a dye penetrant test were performed on a damascus barrel that it will not show the welds between the ribbons unless they were not fused. It will only show where a flaw is such as a crack or lack of fusion between the welds. These two tests can be used on a damascus barrel but can only tell you if flaws exist where the barrel is visible. You cannot check between the ribs. One way to check the barrels with the dye penetrant method is to dye the inside of the barrels, let the dye penetrate,clean off the dye and then spray the developer on the outside of the barrels. If you get some red indications on the developer it means that you have a porous spot in your barrel. This may be a crack,lack of fusion, or a small hole. There is a test method called an eddy current that can be used to test tubing but it's probably used by seamless tubing manufacturers in the quality control process. You should be able to look in your phone book and look for a testing company in your area. The more industry you have around you the more you will find. If you live way out in farm country they may be a bit scarce. I'd bet that there are some really suitable test methods available in this computer age that I am not aware of that could be used to get a really good test on some old damascus barrels. Xray has sum limitations and probably would only have limited use in this application.

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#7644 - 10/29/06 06:42 AM Re: Damascus barrels and magnafluxing question [Re: tanky]
smlekid Offline
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Registered: 01/04/02
Posts: 411
Loc: Australia
the amount of times I have Magnafluxed things that have been welded you always see the edge of the weld regardless of the qaulity of work I will have to take my H Grade Lefever barrels to work and try it and see what it looks like I would imagine a series of radial marks following the twist I will have to try it this week and report back
dont forget with a crack test you have to apply the charge across the crack it will show up on a parrell charge but it works much better across it at least in my field of work (engine reconditioning)

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#7649 - 10/29/06 07:31 AM Re: Damascus barrels and magnafluxing question [Re: smlekid]
Marc Stokeld Offline
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Registered: 01/05/02
Posts: 674
Loc: North Shore, Louisiana
I am not an NDE technicain, but at one time did have a low-level certification in NDE/NDT. I have taken courses on it and managed NDE folks in several countries, so I have seen a lot of it "up close and personal."

one little pet peave-people involved in NDE/NDT (non-destructive evaluation/non-destructive testing) never use the term "magnaflux." At least I have never met one who did. Instead they refer to "mag-particle testing," usually just called "mag particle" or they say they will "mag" a part. It is kinda like calling a Parker a Fox. Minor pet peave.

What NDE shows you is an "indication," not a crack. A good magparticle technician can examine a set of barrels and find abnormal indications, usually indicationd a "crack," "slag inclusion," and whatnot. They can also give you a qualified opnion on how likely the indication is to cause problems later on. They can find these inside the wall of the tubes, not just on the surface. If it were me and I wanted some testing to give me a warm and fuzzy about my tubes, I would "wet mag" the barrels and be happy with that. In this case, you acutally use a liquid that holds suspended paricles. I would also use the liquid requireing a black light to see the florescent indications. I think this would give the best of finding menaingful indications in the tubes for the least cash outlay. Most "bang for oyur buck," if you will.

If all you are worried about is surface indications, then a good visual inspection or PT (dye-penetrant testing, or "dye checking") will reveal indications quite nicely, quickly, and cheaply. Without going into detail, there are several different ways to MT and PT.

Also, a good technician can find an amazing amount of indications from a straight visual inspection. They do it every week of the year and can find things I sure can't always see, and I consider myself to be above average at finding indications.

One thing I have not seen here is UT, or "ultrasonic testing. And no, we are not checking to see if your damascus tubes are knocked up!!! A good UT technican can tell you loads of information about the indications. UT, especialy "shear wave," makes my brain hurt and eyes cross. you need a very experienced technician to perform this test. But a good one can tell you a lot about your tubes and any indications they may have. The hard part here is finding a technician with a lot of UT experience who you trust. A relatively small number of them in the NDE world.

And there is nothing wrong with good ole' RT, or x-ray. Yes, there will be tons of lines on the film due to all of the welds, but again, a good technician can find indications there.

If you are really worried about the integriy of your tubes and will spend some cash to be warm and fuzzy, RT them and UT them if RT shows an indication that worries you.

Of course, the easiet way to check the tubes is to have the gun proof tested in good proof house. Remember, a pressure test ALWAYS supercedes any NDE/NET findings. Basically, the "proof is in the pudding," or in this case "the pudding is in the proffing!"
_________________________
skunk out

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#7661 - 10/29/06 08:26 AM Re: Damascus barrels and magnafluxing question [Re: Marc Stokeld]
Lowell Glenthorne Offline
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Registered: 04/07/02
Posts: 6250
Loc: Glenthorne Woods
Stop the hocus-pocus, with today's health care costs - send the gun to be re-proofed.

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#7665 - 10/29/06 08:39 AM Re: Damascus barrels and magnafluxing question [Re: Marc Stokeld]
Chuck H Offline
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Registered: 02/19/04
Posts: 13780
Loc: Torrance, CA
There have been some interesting posts on this. Seems like lots of opinions on whether or not Mag Particle inspection would be of any value for inspection of damascus. Marc has some good input based on real experience. Good stuff.

I'm not a NDT tech but have been around it all my 30 yrs in aerospace. My take on Mag Particle inspection is that Fluorescent Mag Particle should be used for this application since is has the capability to resolve small flaws much more readily. This method has the superfine magnetic reactive dust suspended in an oil solution. The oil solution is flushed over the part and then the part is energized and a black light is used to reveal the accumulation of the particles where they collect.

I haven't done this on a damascus barrel but the late Dr Oscar Gaddy related to me that he did indeed use Fluorescent Mag Particle on a set and said the damascus pattern is a very dim background in the visual inspection and that a crack did indeed reveal itself. So, I have only one actual example of someone having done an crack inspection with FMP. But, it was a trusted source.

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#7684 - 10/29/06 09:42 AM Re: Damascus barrels and magnafluxing question [Re: Chuck H]
Dick_dup1 Offline
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Registered: 01/09/03
Posts: 798
Loc: WI
I have set up, staffed and managed Quality Control and NDE Departments in the Nuclear Industry. I assure you that i am familiar with just about any NDE procedure including UT. The one thing that has not been metioned in this discussion is the requirements for 'Passing' an NDE exmaination. These requirements are rigerous and refer to porosity size, number of indications, linear defects among others. A 'Tech' does not give you an opinion, he is not qualified to make a determination of what is safe and what is not safe but tells you what is there and then the code tells you what is acceptable. Interpretations are done by qualifed Welding and NDE inspectors to written criteria.
In all the conjecture I have read, there is no rigerous standard for what is safe and what is not in testing a damascus barrel with NDE. Coupled with the manufacturing methods and materials of the day, there is no way to determine if what you find or don't find is safe. If you think that you can make that determination for yourself simply purchase the NDE materials and do the testing. Dye Penetrant (PT) is very simple, spray on the penetrant, wait, wipe it off and then spray on the developer and look for red indications. As I said in another post, it will be a 'crap shoot'.
I understand the romance with wanting to safely shoot these old shotguns. One of my first doubles was an Ithaca 'Long Range' Double manufactured by Western Arms. I shot a few doves with that gun but research showed the reciever to not tensile steel but a cast type of steel. This type can be subject to brittle fracture. I sold the gun to my dealer. I can not predict the future.
Perhaps it my mathematical and physical science traning but I examin what I am doing and make a determination of what is safe. As the Quality Assurance and Nuclear Safety Manager, that is what I am trained to do i.e make safety decisions which adhere to Code, State and Federal Law and if there are no standards, make them in a controlled and rigerous manner. So I have no problem in making the determination, that you will not obtain any data that will allow you to make any objective determination about your barrel or barrels. -Dick

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#7719 - 10/29/06 01:27 PM Re: Damascus barrels and magnafluxing question [Re: 2-piper]
Chuck H Offline
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Registered: 02/19/04
Posts: 13780
Loc: Torrance, CA
Dick,
While I did work in the QA biz for many years, I've been in the engineering side for the last 10 yrs where our guys set the criteria for inspections or more often I'm involved in evaluating what happened on failed parts and what to do about preventing failures thru inspections.

The studies I've seen suggest that probabilities of detection (POD) at 95% is about a .050" crack/flaw for FMP on most stuff. On most parts we don't allow for any detectable cracks/flaws. That says the minimum detectable crack size is acceptable for strength up to at least twice that size. But, we allow for 2 opportunities to detect. Establishing the inspection interval is at least as important as the type of inspection. The repeated stresses need to be assessed along with the strength of the part in order to intelligently establish intervals. As a NDI pro you're undoubtedly familiar with all of this, I just wanted the crowd here to understand that there's more to it than just inspecting a barrel with a NDI method and declaring it crack free. It ain't necessarily so. It may have a crack below the detectable threshold or may develop a crack right after being inspected. That's why critical components on commercial airplanes get regularly scheduled inspections for cracks.

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#7964 - 10/31/06 05:28 AM Re: Damascus barrels and magnafluxing question [Re: Chuck H]
Dick_dup1 Offline
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Registered: 01/09/03
Posts: 798
Loc: WI
Chuck, you are indeed correct.
What we are responding to is the desire of individuals with Damascus barreled shotguns to assure them selves of the barrels integrity and the ability to function in the future without a catastrophic failure. What I pointed out is that the inspection of a Damascus barrel with MT will not yield any objective evidence and that NDE relies on objective evidence and established criteria to make a determination of safety.
You correctly pointed out that any detection method may not find all indications, the theory then being that the flaw is below a size where it will not grow to a size that will cause catastrophic failure before the next detection interval. In another post I talked about the ability of a homogeneous material to sustain an umilited number of cycles if the stress was below the yeild strenght. This ability is predicated on a homogeneous material i.e. without any defects. In an aircarft the material used is not homogeneous, there are various rivits(holes) and welds that expereince stress cycles every flight. These fastening are sources of cracks because they act as stress risers and any undetected crack/flaw may grow to where if large enough will cause a failure.
Unfortuneatly what we cannot provide is assurance that MT provides a method to assure Damascus barrels are safe to shot. -Dick

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#7989 - 10/31/06 09:07 AM Re: Damascus barrels and magnafluxing question [Re: Dick_dup1]
Chuck H Offline
Sidelock
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Registered: 02/19/04
Posts: 13780
Loc: Torrance, CA
Dick,
I agree with most of what you're saying. A few things you mentioned, I think need a clarification.

I do indeed believe that a good Fluorescent Mag Particle Inspection of a set of damascus barrels (or homog steel) will provide objective evidence. I think what you're saying is; there are no standards to tell either the inspector or the evaluator what is detectable (coupons with engineered flaws) or what to do about indications of various sizes. While this significantly puts the inspection in question as to what it can detect in the barrels, it still has a fairly high level of detectability based on it's history of generic parts. What to do about indications is another matter.

Your understanding of a homogenous material's ability to sustain unlimited cycles if the stress is below the yield strength and no flaws exist is pretty close. But to clarify, this applies to steels (not aluminums) only and my understanding is that the material is said to be able to sustain unlimited stress cycles if stress typically is in the area of 1/2 the ultimate strength and assumes a pre-existing flaw just at or below detectable size (.050" typically). At least this is my passing understanding with my failing memory.

I agree whole heartedly with you that any NDI method will not guarantee any barrel is safe to shoot. It may, however, help a prudent, intellegent person, in adding another piece of information about a set of barrels in his assessment of them along with more conventional methods of inspection such as wall thickness and surface condition.

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#8670 - 11/05/06 12:22 PM Re: Damascus barrels and magnafluxing question [Re: Chuck H]
Zircon Offline
Member
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Registered: 10/01/05
Posts: 142
Loc: Orygun
Dick, in addition to standard codes (how large of an indication is rejectable), there is the issue of standards to set up the inspection process - especially with UT. The instrumentation needs to be calibrated with a standard that has similar metallurgical characteristics to the barrel being tested. For all practical purposes this means the standard needs to be a damascus, twist, or what have you barrel, equivalent in metallurgical condition (chemistry, thermomechanical processing, and final heat treatment) to the barrel being tested. The standard has reference notches, flat bottomed holes or what have you that the instrumentation must "see" and detect at a specified level. Then, and only then, is the test valid. I believe there are way too many variables to conduct NDE and then make a conclusion as to the safety of any given set of barrels.

As far as proofing goes, it's been around a long while, but it isn't the be-all, end-all either. There are some barrels in the "barrel study" that show definite signs of fatigue failure - something that no single overpressure shooting event will be able to detect.

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