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Your Position: Home - Measurement & Analysis Instruments - MT Low L/D ratio Parts

MT Low L/D ratio Parts

Author: becky

Apr. 29, 2024

MT Low L/D ratio Parts

Albert
Other, ASNT NDT Level III (MT, PT, UT and ET ) Aviation, USA, Joined Jun 2012,
140
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140

Other, ASNT NDT Level III (MT, PT, UT and ET )Aviation,USA,Joined Jun 2012

Please visit our website for more information on this topic.

 04:50 Apr-03-2013
MT Low L/D ratio Parts 04:50 Apr-03-2013

Just wondering (Beyond the ASTM 1444 and ASNT MT HNBK) what you guys do in regards to ring shaped parts and gears with low L/D ratios.
The application is aviation, so i'm trying to stay away from direct contact head shots, as all the gears are matched sets and terribly expensive.

Adding pole pieces to increase the L/D sounded good, but if your using the continuous wet method, yes the exposed pieces are preformed that way, but the ends wont be cause they are covered by the pole pieces and then have to be preformed using the residual, which isn't really an option, since i must use the continuous wet.

I haven't really had any success locating much literature that goes into detail about setting up a toroidal field in ring shaped parts.

Any links or info would be greatly appreciated.

Thanks


Tim
Tim
 15:05 Apr-03-2013
Re: MT Low L/D ratio Parts 15:05 Apr-03-2013In Reply to Albert at 04:50 Apr-03-2013 (Opening).

Hello Albert,

Does the geometry preclude the use of a central bar conductor?

Albert
Other, ASNT NDT Level III (MT, PT, UT and ET ) Aviation, USA, Joined Jun 2012,
140
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140

Other, ASNT NDT Level III (MT, PT, UT and ET )Aviation,USA,Joined Jun 2012

 19:28 Apr-03-2013
Re: MT Low L/D ratio Parts 19:28 Apr-03-2013In Reply to Tim at 15:05 Apr-03-2013 .

My apologies, yes the parts are hollow and can have a bar placed thru it.

Tim
Tim
 20:30 Apr-03-2013
Re: MT Low L/D ratio Parts 20:30 Apr-03-2013In Reply to Albert at 19:28 Apr-03-2013 .

My experience has been to use the largest diameter CBC available that "fits" the I.D. of the parts for an Indirect Magnetization. Have also used V channel for small cylindrical parts. Multiple parts can be inspected simultaneously with either method.

Hope that helps!

Albert
Other, ASNT NDT Level III (MT, PT, UT and ET ) Aviation, USA, Joined Jun 2012,
140
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140

Other, ASNT NDT Level III (MT, PT, UT and ET )Aviation,USA,Joined Jun 2012

 00:56 Apr-04-2013
Re: MT Low L/D ratio Parts 00:56 Apr-04-2013In Reply to Tim at 20:30 Apr-03-2013 .

Tim, thank you for the info, the V channel for small parts was actually something I forgot to include in my original post, any recommendation as to what material type and thickness?

Tim
Tim
 16:09 Apr-04-2013
Re: MT Low L/D ratio Parts 16:09 Apr-04-2013In Reply to Albert at 00:56 Apr-04-2013 .

Aluminum or copper (similar to CBC) and a guess of approximately 3/16". Sorry, its been awhile back and of course results will vary and depend on your setup.

Albert
Other, ASNT NDT Level III (MT, PT, UT and ET ) Aviation, USA, Joined Jun 2012,
140
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140

Other, ASNT NDT Level III (MT, PT, UT and ET )Aviation,USA,Joined Jun 2012

 20:08 Apr-04-2013
Re: MT Low L/D ratio Parts 20:08 Apr-04-2013In Reply to Tim at 16:09 Apr-04-2013 .

Thanks Tim, just looking to narrow the selection down, Material isn't cheap.
I do genuinely appreciate the sharing of information.


George Hopman
Consultant,
NDE Solutions,
USA,
Joined Apr 2009
63

Consultant,NDE Solutions,USA,Joined Apr 2009

 04:35 Apr-05-2013
Re: MT Low L/D ratio Parts 04:35 Apr-05-2013In Reply to Albert at 00:56 Apr-04-2013 .

Gentleman, all this talk about a V-Channel. I am not sure what specification or code is driving your inspection. A part nesting in a V-channel for circular magnetism induction is a classic example of "parallel magnetism". Carl Betz in Principles of Magnetic Particle Inspection, ASNT's Handbook of Magnetic Particle Inspection, the Air Forces' TO 33B-1-1 all caution against this practice. ASTM E1444/E1444M specifically disallows it. The field produced is a combination of two fields, circular and transverse.

Rick Lopez
R & D, John Deere - Tech Works Ames, USA, Joined Jul 2011,
214
Rick Lopez
R & D,
John Deere - Tech Works Ames,
USA,
Joined Jul 2011
214

R & D,John Deere - Tech Works Ames,USA,Joined Jul 2011

 14:01 Apr-05-2013
Re: MT Low L/D ratio Parts 14:01 Apr-05-2013In Reply to Albert at 04:50 Apr-03-2013 (Opening).

Albert,
There are a few published resources that either touch on the topic, or discuss toroidal magnetization in detail. One (Morris, 1998) provides a low-cost approach that could be useful for experimentation:
* (journal) Skeie and Hagemeier, Materials Evaluation, May 1988.
* (book) Shull, Nodestructive evaluation: theory, techniques, and applications, 2002.
* (journal) Deutch and Voigt, British Journal of NDT, July 1982.
* (online) Downes, DC or AC magnetizing waveforms in magnetic particle inspection, Insight NDT.
* (magazine) Dunnwald, Quality Magazine, Feb 2006.
* (journal) Morris, Materials Evaluation, June 1998.



Tim
Tim
 15:10 Apr-05-2013
Re: MT Low L/D ratio Parts 15:10 Apr-05-2013In Reply to George Hopman at 04:35 Apr-05-2013 .

George,

With all respect, I have offered information that is in practice. It has been my experience that no NDT method "theory" can not be used for all items that need to be examined.......and no method can be considered 100% accurate. "Real world" testing is not always textbook.

You stated that "ASTM E1444/E1444M specifically disallows it." I disagree and must add that section 6.2.10 states "........unless approved by the Cognizant Engineering Organization."

The information that I provide to anyone, is under the assumption that it must be approved by the proper authority. So again, with all respect I offer this as clarification to my other posts.

Will you please offer Albert and myself a practical technique to inspect small cylindrical parts (plated gears for example) using the fluorescent wet continuous method on a bench?




George Hopman
Consultant,
NDE Solutions,
USA,
Joined Apr 2009
63

Consultant,NDE Solutions,USA,Joined Apr 2009

 17:00 Apr-05-2013
Re: MT Low L/D ratio Parts 17:00 Apr-05-2013In Reply to Tim at 15:10 Apr-05-2013 .

Yes, I understand this technique is being used out there and that "real world" testing is not always textbook. My first day on the job in NDT was wet fluorescent MPI back in 1982 and I have seen many inspectors over the years do the best they can do under the circumstances they have been given and with the tools (or lack of) that they have been given.

As the current owner of E1444/E1444M, I am aware of the caveat of going to the OEM; good luck on that one. Albert is probably not in a position to make that happen. I'm certain he's trying to do the best he can with the tools he's been given. Often times, the Level 2 will approach management for support to buy an additional tool such as a toroidal device and will be rebuffed with a rejoinder of, "Your a certified Level 2, don't you know how to do your job?

Rick Lopez has given some very good sources on toroidal. You can buy these devices from Magwerks in Indianapolis, IN. I provided Albert with a copy of my 2012 ASNT Fall Conf. presentation on "MPI of Challenging Configurations". In that presentation, I make the point that design engineers often throw MPI on the print without understanding that certain geometries do not lend themselves to MPI very well and FPI would be better instead.

I also gave examples of toroidal and inserting a steel central bar through the part and suspending the assembly in the coil. Now the coil acts upon the part as if the L/D is long.
Again, I don't know what the originating requirements are, but if the practice is not prohibited, Albert is free to use it. But I will ask the rhetorical question, why use a technique that the primary references out there caution against?

Albert like the idea of pole pieces/flux extenders, but is concerned with particle application on the ends. In my 2007 ASNT Fall conference paper on "Misconceptions in MPI", I make the point that it is a rare part that we truly get 100% coverage. Think of a simple bar clamped between the heads; then laid in the bottom of the coil. Have we got 100% of the part? Did we inspect the endcaps for cracks in both directions? Absolutely not.

Tim
Tim
 00:57 Apr-06-2013
Re: MT Low L/D ratio Parts 00:57 Apr-06-2013In Reply to George Hopman at 17:00 Apr-05-2013 .

George,

It appears that we are in agreement that it is an imperfect world and this profession is no exception. We face challenges and maybe that's one reason that we enjoy working in this field.

Our experiences are similar and I started radiography training in 1981. Like everyone else here I am attempting to offer some help. "Two heads are better than one" and I am sure Albert appreciates all replies.


Albert
Other, ASNT NDT Level III (MT, PT, UT and ET ) Aviation, USA, Joined Jun 2012,
140
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140

Other, ASNT NDT Level III (MT, PT, UT and ET )Aviation,USA,Joined Jun 2012

 05:03 Apr-06-2013
Re: MT Low L/D ratio Parts 05:03 Apr-06-2013In Reply to Tim at 00:57 Apr-06-2013 .

First I'd like to thank everyone that replied. It’s really a great thing where someone can come to a forum and have access to so many persons more knowledgeable than myself in a field.

I got more information in a few moments than I was originally able to get from days of googling and reading the only books available from the ASNT.

I tried last year to get my employer to let me go to the Orlando conference, but I got some of that benefit from George, I greatly appreciated the lecture you sent me and immediately shared it with my fellow inspectors, all in the spirit of sharing knowledge. You are right, it’s quite the effort to try to explain to an employer that the current inspection procedures could be improved with the purchase of a tool, but I will bring it up till I'm blue in the face or they buy what it takes. Of course anything that I attempted to incorporate I would run by the Responsible Level III.

I just really wanted to increase my knowledge on the subject, as the more I read up on the subject the holes in some of the suggested techniques were becoming more and more apparent (Continuous wet with pole pieces), and the time saving benefits and reduction of the number of total shots required using a laminated central conductor, not to mention improving the overall inspection of the part.

Thank you all for providing your expertise and additional information on this subject.


Tim
Tim
 18:34 Apr-09-2013
Re: MT Low L/D ratio Parts 18:34 Apr-09-2013In Reply to Albert at 05:03 Apr-06-2013 .

Hello Albert,

Your inquiries and initiative are inspiring. They will make you a learned and better inspector as well as Level III (3).

Best of Luck!

Gene Crites
Gene Crites
 16:55 Apr-23-2013
Torodial MT inspection 16:55 Apr-23-2013

Tim
Tim
 15:59 Apr-24-2013
Re: Torodial MT inspection 15:59 Apr-24-2013In Reply to Gene Crites at 16:55 Apr-23-2013 .

Hello Gene,

I assume that you have access to ASTM E 1444. Reference sections 6.2.8 through 6.2.10.

The two methods you mention are not the same. As stated above I have used the Indirect & Parallel methods.

Hopefully someone will offer details of the Induced method.


George Hopman
Consultant,
NDE Solutions,
USA,
Joined Apr 2009
63

Consultant,NDE Solutions,USA,Joined Apr 2009

Recommended article:
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AJR Product Page

 16:59 Apr-24-2013
Re: Torodial MT inspection 16:59 Apr-24-2013In Reply to Gene Crites at 16:55 Apr-23-2013 .

Please allow me to clarify that I did not say that inserting a steel rod through a ring is an example of toroidal; it is not. It is an example of a "flux extender" that modifies the L/D ratio of the part.

One way I created my own toroidal device is to take high permeability welding rod and coat is with plastic. Then group these welding rods together within a plastic tube normally used for plumbing. It worked great as a homemade toroidal device and you can vary the diameter based upon how many rods one packs into what diameter tube.

Thanks!

Gene Crites
Gene Crites
 17:04 Apr-24-2013
Re: Torodial MT inspection 17:04 Apr-24-2013In Reply to Tim at 15:59 Apr-24-2013 .

Hi Tim,

I am sorry if my description of the technique in my post inquiring about laminated versus a Steel rod for the induced field does not in your mind describe the induced method but that is exactly what is taking place in Fig. X5.2 (Figure A) of ASTM E1444/E1444M-11. I am a Level 3 and have been associated with NDT since 1965 and do consulting work presently. I was merely asking if there could be an objection to using a steel rod as the core instead of a laminated core. I understand that different results will occur using different materials as the core. Does a laminated core have to be used to meet the specification intent?

Tim
Tim
 18:18 Apr-24-2013
Re: Torodial MT inspection 18:18 Apr-24-2013In Reply to Gene Crites at 17:04 Apr-24-2013 .

Gene,

It appears that I have insulted your intelligence with my response. That was not my intent and I apologize. You might consider adding to your profile.

I do believe that lamination is a key word. Take care!

Albert
Other, ASNT NDT Level III (MT, PT, UT and ET ) Aviation, USA, Joined Jun 2012,
140
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140

Other, ASNT NDT Level III (MT, PT, UT and ET )Aviation,USA,Joined Jun 2012

 23:11 Apr-24-2013
Re: Torodial MT inspection 23:11 Apr-24-2013In Reply to George Hopman at 16:59 Apr-24-2013 .

George,

Any recommendations on a low cost high permeability steel?

Gene Crites
Gene Crites
 00:13 Apr-25-2013
Re: Torodial MT inspection 00:13 Apr-25-2013In Reply to Tim at 18:18 Apr-24-2013 .

Hi Tim,

No I was not insulted, after all these years in this field I have developed a fairly thick skin. My problem is I am in the Aerospace field and with NADCAP as my overseer. Things get pretty dicey over small stuff at times and I did not want to present a method that they were going to jump on with negative input. I like what George is saying about a flux extender and it makes more sense to me then making up the weld rod cores. I will post a reply to him with my thoughts.

Gene Crites
Gene Crites
 00:31 Apr-25-2013
Re: Torodial MT inspection 00:31 Apr-25-2013In Reply to George Hopman at 16:59 Apr-24-2013 .

Hi George,

You are entering into my world with your words, semantics can kill you with some customers and NADCAP audits. That is why I did not want say I was using a steel rod to comply with the Toroidal method. I have used the method of a steel rod as a flux extender on small hollow parts before and it has worked fine. To me I don't see a huge difference in using a laminated core to serve the same purpose. I have never tried it but I assume the laminated core may provide a larger flux density than a steel rod like I would like to use, hence lower amperages to accomplish the same result. Do you really believe I need to go down the laminated core route to satisfy the toroidal method? The steel rod I am talking about would be the exact same material as the ring I am inspecting. I simply stated that this method is the same thing as inspecting a shaft with a flange on it in the past and never had a problem. QQI Shims validated the technique.


George Hopman
Consultant,
NDE Solutions,
USA,
Joined Apr 2009
63

Consultant,NDE Solutions,USA,Joined Apr 2009

 17:02 Apr-25-2013
Re: Torodial MT inspection 17:02 Apr-25-2013In Reply to Gene Crites at 00:31 Apr-25-2013 .

No, I don't think that the toroidal method is necessary in your situation. If one has a good QQI indication using a flux extender, that is proof of a valid technique. Many Nadcap auditors are very competent. However, there are some that give everyone else a bad name. Having a bully of an auditor who does not understand a technical issue can make ones life miserable. Most people quickly grasp the concept of a flux extender and it is a relatively inexpensive route to pursue. Many overhaul shops would not know the alloy of the parts they are inspecting so your having access to the same alloy for the fixture is an ideal situation.

Thanks!

Gene Crites
Gene Crites
 22:12 Apr-25-2013
Re: Torodial MT inspection 22:12 Apr-25-2013In Reply to George Hopman at 17:02 Apr-25-2013 .

Thanks George for your input.

I think will simply stick with the technique I mentioned and forget the laminated core.

Thanks

Ian
Ian
 09:48 Jan-06-2014
Re: Torodial MT inspection 09:48 Jan-06-2014In Reply to George Hopman at 17:02 Apr-25-2013 .

Intresting article Gentlemen as the subject is something we have been looking at for a while.

I see more Tech Sheets being used where ring/disc shaped objects are being tested flat down in a coil and rotated 90Deg and this never sits right with me.

What are your views on this method?. I would say it goes agaist all my early teachings where the L/D ratio should be at least 3-1.

amy0929a
NDT Inspector, - - USA, Joined Jan 2009,
87
amy0929a
NDT Inspector, - -
USA,
Joined Jan 2009
87

NDT Inspector, - -USA,Joined Jan 2009

 14:36 Jan-06-2014
Re: Torodial MT inspection 14:36 Jan-06-2014In Reply to Ian at 09:48 Jan-06-2014 .

Ian,
It goes against my teaching as well, but it does seem to work. I work in aerospace and quite a few of the standard technique cards have employed this technique. As first I was very weary. The traditional formulas do not hold true (and really are not accurate in most circumstances anyway) and multiple QQI's must be utilized for technique development. We have taken scrap parts and verified the techniques with both QQI's and small artificial defects at the current levels specified, and yes, we were able to prove the techniques. I must mention that these are for inservice parts and mainly looking for cracks and linear indications.


Tim
Tim
 14:37 Jan-06-2014
Re: Torodial MT inspection 14:37 Jan-06-2014In Reply to Ian at 09:48 Jan-06-2014 .

Hello Ian,

I do agree. Added length is beneficial.

Ian
Ian
 15:25 Jan-06-2014
Re: Torodial MT inspection 15:25 Jan-06-2014In Reply to amy0929a at 14:36 Jan-06-2014 .

Thanks for the replies I am certainly going to have to have a look at some of our existing Tech Sheets and see if I can improve them and where possible use Flux extenders or Toroidal methods, especially on some of our larger componets.

Perhaps I can get away with the bottom of the coil for some of our smaller rings.

Albert
Other, ASNT NDT Level III (MT, PT, UT and ET ) Aviation, USA, Joined Jun 2012,
140
Albert
Other, ASNT NDT Level III (MT, PT, UT and ET )
Aviation,
USA,
Joined Jun 2012
140

Other, ASNT NDT Level III (MT, PT, UT and ET )Aviation,USA,Joined Jun 2012

 21:23 Jan-06-2014
Re: Torodial MT inspection 21:23 Jan-06-2014In Reply to Ian at 15:25 Jan-06-2014 .

Ian,

Email me and I can share some of the Technique sheets I generated that were the result of all the information I learned in this thread.

There was a few very large ring shaped parts that I had to lay in the coil, I did verify them with a QQI, You'll find that you have to reduce the rotation to about 72 degrees. You'll start to see the QQI start to fade with distance from the coil.

 

Comparing Nondestructive Testing Methods for Welding

Comparing Nondestructive Testing Methods for Welding

One of the most common uses of nondestructive testing (NDT) is the examination of weld integrity. This is because welds are extraordinarily common in critical industrial applications across the world. The ability to inspect welds nondestructively is essential, as destroying one for testing necessitates replacing it with a new, untested weld. As such, there has been significant technological development in the broad field of nondestructive testing methods for welding.

Many different NDT methods can be used to examine welds. From the most basic visual and somatic tests, techniques increase in speed and effectiveness using a wide array of technologies. Fluid immersion, radioactive waves, electromagnetism, and acoustic techniques all provide means of examining the interior structures of welds. Some techniques, however, are more capable and efficient than others. 

Nondestructive Testing Methods Used for Welding

The aim of each nondestructive testing method used for welding is the same: to detect any internal flaws that could cause weld failure. As the ramifications of weld failure range from minor to extreme, so does the importance of testing. Many weld applications can cause severe harm upon failure, requiring a high level of testing capabilities. At the same time, welds are ubiquitous throughout modern industrial society, demanding efficient testing regimens.

The most common types of nondestructive testing for welds, excluding simple sensory examinations, are liquid penetrant, radiography, magnetic particle, eddy current, and ultrasonic testing.

Liquid Penetrant Testing

While simple in principle, liquid penetrant testing can be difficult to carry out efficiently. This technique isolates a testing area, then attempts to pass fluid through it. If the fluid refuses to pass through the weld, then the weld is secure. However, if cracks or flaws run through the weld, then so will the fluid. This shows technicians not only that a flaw exists, but also where it can be found. While this can be an effective method, partitioning areas for testing, as well as transporting and containing fluids, can make it cumbersome. Further, it does nothing to detect sealed voids within an object, flaws that don’t touch the surface. 

Radiography

Radiographic testing uses X-rays to observe the internal structure of welds (and other objects). This technique can detect sealed internal voids, as well as the cracks and flaws observed by liquid penetrant testing. Without the need for fluid containment, this technique can operate more quickly than liquid penetrant as well. However, the radioactivity inherent in this method poses serious issues. Equipment must be carefully treated. Technicians must take significant safety precautions. Non-essential personnel must be kept away from the testing area while testing is underway. These safety concerns create logistical hurdles diminishing the efficiency of radiographic testing. 

Magnetic Particle Testing

Magnetic particle testing examines the interior of ferromagnetic objects, such as carbon steel welds, by studying their effects on magnetic fields. An induced magnetic field travels through the object, and any flaws or irregularities are observed by how they impede the magnetic field. Unfortunately, paint is not ferromagnetic, requiring it to be removed before inspections and replaced after. Other surface irregularities may also throw off readings. These handicaps inhibit the efficiency of magnetic particle testing, rendering it cost-prohibitive for large-scale testing regimens. 

Eddy Current Testing 

Like magnetic particle testing, eddy current testing relies on electromagnetism to detect flaws in welds. Unlike magnetic particle testing, eddy current techniques typically require no surface preparation—they work effectively, despite coats of paint. This dramatically increases the comparative efficiency of eddy current testing. However, eddy current technology cannot sense flaws deep beneath the surface of larger welds, requiring another method to be used. 

Ultrasonic Testing

For speed and capability, ultrasonic testing is the preferred method of nondestructive testing for welds. High-pitched acoustic waves are introduced into a weld via a transducer. Any internal changes in structure—including cracks, voids, or warps—can alter the transmission of these sound waves through the weld. These alterations can be detected from the same side of the weld that the wave was introduced on, allowing the ultrasonic instrument to interpret their reflectance. Sound waves can also be detected on the far side of the weld and interpreted based on their transmittance. Probes with multiple transducers, using a technique called phased array, can quickly scan a broad swath of a weld’s interior. Powerful software can efficiently analyze images, displaying results for technicians to act on.

The Best NDT Method for Welding

While many methods of nondestructive testing can detect failure-predictive flaws in welds, the most efficient, effective method is phased array ultrasonic testing. Without the safety flaws, labor-intensive set-up, or cumbersome ancillary equipment of earlier methods, ultrasonic allows technicians to perform rapid inspections without sacrificing accuracy.

Zetec has been a cutting edge provider of ultrasonic testing equipment for decades To learn more about using ultrasonic testing on welds, contact us today.

Zetec’s designers are industry-leading experts in ultrasonic and eddy current technologies, and we can help you navigate any of our NDT testing solutions or devices.

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