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16:42 Jan-30-2009
Nathan
Duplex Dag-Nammit...

Does anyone have the acoustic properties for Duplex Steel 2205 (UNS S32205)
Can't find it on any of the tables etc...
Longitudinal and Shear velocity would really sort my headache out...!

 
06:10 Jan-31-2009
Mark
Re: Duplex Dag-Nammit... In Reply to Nathan at 16:42 Jan-30-2009 (Opening).

Why are you measuring velocity? For normal beam flaw detection or thickness gauging?

 
09:29 Feb-04-2009
Nathan
Re: Duplex Dag-Nammit... In Reply to Mark at 06:10 Jan-31-2009 .

Sorry for the tardy reply, been offshore...

for both. I have measured the longitudinal velocity at 5815m/s.

I can't however, measure the shear velocity, as we dont have a test block - and can't get one.

I want the shear velocity, as will be testing for weld erosion, which, doesn't need to be precise, we just need to know if it's happening or not, but I like to be precise as possible.

 
18:22 Feb-04-2009

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1208
Re: Duplex Dag-Nammit... In Reply to Nathan at 09:29 Feb-04-2009 .

Nathan
If you have managed to get a compression mode velocity I assume that you have a sample of known thickness and you identified the pulse-echo transit time. This was perhaps done using a sample with parallel surfaces. Therefore from a known thickness you should also be able identify a reasonable approximation of the transverse mode velocity too. In my old copy of the Krautkramer Ultrasonic Testing of Materials (3rd English edition) there is a useful image in Figure 14.22 showing steel and aluminium plate signals at high gain. You can see the faint transverse mode signals that occur as a result of diffraction from the probe edges.
But an even better signal can be had for shear mode using an SH shearwave probe. For coupling you require a nonNewtonian viscous fluid (honey is the best option) and then you can make a direct reading of the pulse-echo arrival time.

 
03:13 Feb-05-2009

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
818
Re: Duplex Dag-Nammit... In Reply to Ed Ginzel at 18:22 Feb-04-2009 .

Hi Nathan,

This may help you. I asked my nephew at Chrismas if he new a formula that would measure my Skip Distance for curve hollow parts (ring). He's in his third year in mechanical engineering at university. This is what he gave me:


Arc Length = (3.1416 ro / 90) (90 – θ – cos-1 (ro / 90 ri Sin θ))

Theta is your Shearwave Angle, ro is the outer radius of your ring and ri is the inner radius. In this case, the Arc Length will be your Skip Distance. So once you made the calculation, you can calibrate your screen for one or two Skip Distance. At our shop, tone of the code we are working to allow us to put a punch mark in the Outside Diameter of the ring, so we can mark with a pencil our probe location and this way calibrate our screen for the material we are working with.

I hope this will be of help. The formula maybe a little funny, this is probably due to my inability to write formula with the software I have.

Cheerio's

 
10:44 Feb-05-2009
Nathan
Re: Duplex Dag-Nammit... In Reply to Michel Couture at 03:13 Feb-05-2009 .

Thanks Mich & Ed.

Yes, I got the longitudinal velocity by using a machined connecting flange, which was acutally in use along the piping - it was also at the same temperature (reasonably the same anyway). So that's how I worked it out. It was 5615m/s, not 5815m/s that I typed earlier.

SH shearwave probe? Is that one of the rarer ones, with the crystal cut in a different direction, so it only emits shear waves?

 
13:35 Feb-05-2009

J. Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
Re: Duplex Dag-Nammit... In Reply to Nathan at 10:44 Feb-05-2009 .

Nathan,

Many transducers manfuactruers have these special cut 0 Degree shear wave probes. Olympus NDT sells one as well as Sigma Transdcuers, and others. The key is the couplant which the burnt honey.


Have you considered using a 0 Degree Phased Array Probe. Better sensitivity, and the imagery will help you to visibly see the total effect of the corrosion in sector or linear scans.


What is the thickness of the material. What is the pipe diamter?

 
13:37 Feb-05-2009

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1208
Re: Duplex Dag-Nammit... In Reply to Nathan at 10:44 Feb-05-2009 .

zoom image[zoom]

Nathan..yes, an SH shear wave probe is polarised to extend and contract its surface parallel to the plate surface, thereby inducing a strong true "shear" mode.
The other option I referred to, using the tip effects, is not as precise but may be adequate for your use. You can see the formation of the transverse mode off the tips of the probe in modelled beams and on some of my visualisations (like Figure 3 in http://www.ndt.net/article/wcndt2004/pdf/array_transducers/127_ginzel.pdf). With enough gain you can see this signal on the A-scan. I uploaded the image from Krautkramer to illustrate it. You will need to select the correct signal as it is possible that the mode conversion can occur off the backwall resulting in an earlier arriving TL mode. Both may be visible (as they are in the image of the steel plate). Or one may be obscured by the L mode multiple (as in the case of the aluminium plate on the image).
 
08:18 Feb-06-2009

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
158
Re: Duplex Dag-Nammit... In Reply to Nathan at 16:42 Jan-30-2009 (Opening).

I have a couple of straight beam shear wave transducers just for measuring shear wave velocities. They aren't cheap until you compare them with having extra test blocks made. The beam direction is the same as for a longitudinal wave transducer placed on the same spot, so you get two values in the same direction and location. Honey is a good couplant for these transducers. I expect they are made by several transducer manufacturers. Mine came from Ultran. e-mail is sales@ultrangroup.com. They can be used look for anisotropy in a material that could cause shear wave velocity to vary with beam angle. Any type block with a circular segment end can be used with regular angle beam transducers on the reference line and the straight beam shear wave transducer on the circular surface as a receiver. This also determines the actual beam angle by locating the position on the circle of maximum signal amplitude. It's actually fun

 
12:38 Feb-10-2009
Nathan
Re: Duplex Dag-Nammit... In Reply to John Brunk at 08:18 Feb-06-2009 .

Brilliant!

Sorry, I've misunderstood up until now.

Measure the longintudinal velocity of a flange with parallel faces and of a known thickness.

Measure the shear velocity of the same piece with a 0 degree shear wave probe to get the thickness.

So simple!

Now to get the boss to purchase a 0 degree shear wave probe.

 
12:41 Feb-10-2009
Nathan
Re: Duplex Dag-Nammit... In Reply to Nathan at 12:38 Feb-10-2009 .

HONEY:

What is the secret of using honey over other couplants?

 
18:24 Feb-10-2009

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1208
Re: Duplex Dag-Nammit... In Reply to Nathan at 12:41 Feb-10-2009 .

Nathan...the images I pasted back on Feb 5 indicate how you can do this without the SH shearwave probe and monitor the late arriving transverse mode in the multiples.
However, if you prefer to use the SH shearwave probe the purpose of honey is to couple the shear mode! Honey is a nonNewtonian viscous fluid.
In a Newtonian fluid, the relation between the shear stress and the strain rate is linear the constant of proportionality being the coefficient of viscosity. In a non-Newtonian fluid, the relation between the shear stress and the strain rate is nonlinear, and can even be time-dependent. Honey is one of those time-dependent fluids. This accounts for one of the biggest reasons we cannot use SH shearwave probes for contact testing...it is not practical to try to slide along on honey.

 
19:34 Feb-10-2009

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
158
Re: Duplex Dag-Nammit... In Reply to Nathan at 12:41 Feb-10-2009 .

Nathan,

I agree completely with everything Ed Ginzel has posted on this subject. You can buy a tube of special couplant for these transducers, but to me it seems to be no better than honey, or molasses. The only limitation to honey or molasses is the time-dependency. Using contact pressure to squeeze it down to a thin layer, it wll give a stable signal for a couple of minutes, then lose amplitude and disappear. You can clean the surface and repeat with fresh honey if necessary. The reason I suggested honey is that it is cheap and readily available and easy to clean up. It is also delicious if you bring your lunch to the job and include some bread and butter.

 
09:55 Feb-11-2009
Nathan
Re: Duplex Dag-Nammit... In Reply to John Brunk at 19:34 Feb-10-2009 .







Hi Ed!

Using a Carbon Steel UT block, i've took wall thickness on it as you can see from the picture. There are some echo's inbetween the BWE's, are these the echo's you're talking about?
 
15:16 Apr-10-2009
Nathan
Re: Duplex Dag-Nammit... In Reply to Nathan at 09:55 Feb-11-2009 .

Ok...
we have manufactured a 2205 duplex steel step wedge.

I have found out that the acousitic velocity for the duplex steel for compression waves is 5763m/s.

Is there an easy way to find out the shear wave velocity without having to buy anything?

 
00:47 Apr-11-2009

R Duwe

NDT Inspector, API-510, 570, 653
MISTRAS,
USA,
Joined Jan 2009
148
Re: Duplex Dag-Nammit... In Reply to Nathan at 15:16 Apr-10-2009 .

No, there is not. You still need a zero-degree shearwave 'ducer and your block. It always goes back to 'ask the part'. You have to 'ask the part' what its velocity is, by sending a compression wave or shearwave on a calibrated distance. The other option is to have an IIW block fabricated from 2205 and use a standard shearwave 'ducer. Neither option is cheap, sorry.

 
15:52 Apr-11-2009
Ryan Burns
Re: Duplex Dag-Nammit... In Reply to R Duwe at 00:47 Apr-11-2009 .

With your new step wedge, why not turn it on it's side and obtain a corner trap signal with a 45 deg, calibrate for sound path and you should have your velocity. Nathan, I have to ask though, as this is all being done for weld root erosion as per your original comments, why would you not perform 0 degree through the weld? Unless your welds were capped with horizontal stringer beads, you should be able to obtain quality signals without (or with minimal) grinding of the weld cap. When shear wave is done to evaluate this type of damage, it opens the door to many other possibilities, such as excessive penetration geometrical reflectors, lack of fusion (sidewall), root cracks, etc. You may also consider the "Creeping Wave" technique, which would allow for fast scanning to identify anomalous areas and evaluate with 0 degree.

Regards,

Ryan.

 


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