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Career Discussions
Carlos Toledo
NDT Inspector,
Poliend, Brazil, Joined Jun 2014, 1

Carlos Toledo

NDT Inspector,
Poliend,
Brazil,
Joined Jun 2014
1
13:19 Jun-29-2016
creeping wave transducer

Dear all experts,

Someone knows where I can buy creeping wave probe to use with omniscan?

Thanks

 
 Reply 
 
Mark
,
Zambia, Joined Jun 2016, 49

Mark

,
Zambia,
Joined Jun 2016
49
14:48 Jun-29-2016
Re: creeping wave transducer
In Reply to Carlos Toledo at 13:19 Jun-29-2016 (Opening).

Carlos,
Applus RTD has long experience to produce these kind of probes for inspection of coarse grain welds or other propos. You can use creeping wave probe s with any instrument.if you are going to use creeping waves with tofd probes then you will need inter box for more than 6 UT connection.

 
 Reply 
 
Andrew Cunningham
NDT Inspector
Canada, Joined Jun 2008, 239

Andrew Cunningham

NDT Inspector
Canada,
Joined Jun 2008
239
17:02 Jun-29-2016
Re: creeping wave transducer
In Reply to Carlos Toledo at 13:19 Jun-29-2016 (Opening).

Hi Carlos
Before you waste any money, read "proof of creeping wave." Please don't muddle up with High angle compression scan and ID creeping wave. The information on this forum is Free!!!!

All the best
Andrew

 
 Reply 
 
Wieslaw Bicz
Engineering,
PBP Optel sp. z o.o., Poland, Joined Feb 2009, 276

Wieslaw Bicz

Engineering,
PBP Optel sp. z o.o.,
Poland,
Joined Feb 2009
276
17:05 Jun-29-2016
Re: creeping wave transducer
In Reply to Carlos Toledo at 13:19 Jun-29-2016 (Opening).

You do not need special transducer, only the transmission angle must be adjusted- This must be made carefully, since it depends on the material, that you want to investigate it is critical. But it is easier to use such waves with immersed transducer.

We have large experience with this type for waves for testing welds in pipes with small wall thickness and in other applications.

 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 832

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
832
20:27 Jun-29-2016
Re: creeping wave transducer
In Reply to Carlos Toledo at 13:19 Jun-29-2016 (Opening).

As wrongly misunderstood, there is no surface component with these probes. They are 75-80 degree dual L-wave probe.You can get from many other vendors

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1307

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1307
22:45 Jun-29-2016
Re: creeping wave transducer
In Reply to Anmol Birring at 20:27 Jun-29-2016 .

I think some manufacturers have also marketed a single element version. In some applications I have just used the 70° TOFD probes in pulse-echo mode.

 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 255

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
255
23:21 Jun-29-2016
Re: creeping wave transducer
In Reply to Carlos Toledo at 13:19 Jun-29-2016 (Opening).

zoom image

Olympus transducer catalog excerpt

Carlos,

Just call your Olympus rep and ask for a CDS wedge. They are compatible with the single element screw in transducers. As Andrew and Anmol point out, there's no magic and no special wave mode involved.

A little background for those not familiar with CDS...

Below the first critical angle, with a 70 degree longitudinal wave you also get a 30 degree shear wave. Beam spread allows the upper part of the high angle longitudinal wave to brush the upper surface of the part. Due to some complicated boundary condition mathematics which we won't get into, this upper part that brushes the surface generates a secondary shear wave at approximately the same angle as the primary shear wave (i.e. 30 degrees). This secondary shear wave keeps getting generated for as long as the long wave keeps spreading out and brushing the upper surface. The two shear waves kind of blend in with each other, as they're both traveling at the same angle. At the bottom surface, this nifty shear wave reflects (of course), but also mode converts into a 70 degree long wave. Now you have a long wave on the bottom side that behaves just like the top one. It spreads out, brushes the bottom surface, and generates another shear wave which combines with the reflected shear wave. It gets pretty hairy pretty fast.

The idea is that ID connected cracks will reflect the part of the backside longitudinal beam that's brushing the ID surface, which in turn switches the direction that the shear wave is generated at. A reflected shear wave indication is a sign that you have some sort of discrete ID geometry like a crack. There isn't really any "creeping wave" so to speak, it's just referring to the crazy things that longitudinal waves can do when they brush the upper and lower surfaces.

The picture in the Olympus literature is a little misleading. It makes it look like the secondary shear wave is being generated out in front of the wedge at a fixed location.

Since you have an Omniscan, and assuming you have a simple 5L16, is there a reason why you'd prefer to use the CDS technique over simply just hammering a 40-70 sweep and evaluating the crack root, facet, and tip diffracted signals?



Do
 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 832

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
832
02:21 Jun-30-2016
Re: creeping wave transducer
In Reply to Anmol Birring at 20:27 Jun-29-2016 .

Just to clarify the wording in my previous post
"There is no surface wave component produced by the creeping wave probes. These probes are 75 L or 77 refracted L-wave probes".

 
 Reply 
 
Mark
,
Zambia, Joined Jun 2016, 49

Mark

,
Zambia,
Joined Jun 2016
49
10:36 Jun-30-2016
Re: creeping wave transducer
In Reply to Anmol Birring at 02:21 Jun-30-2016 .

Anmol,
Is it possible to explain more about the angle of creeping waves .
As I knew usually the creeping wave probes are dual elements (to increase the S/N ratio)and low frequency (2MHz to get more traveling distance)longitudinal angle beam with 80~85 degree .
I agree with that the creeping wave is coming from beam spread.it is also like lateral waves that generated by beam spread , some how Mr Ginzel has mentioned above.
It is hard to say there is No creeping waves(surface waves) or No lateral waves.

 
 Reply 
 
Mark
,
Zambia, Joined Jun 2016, 49

Mark

,
Zambia,
Joined Jun 2016
49
11:08 Jun-30-2016
Re: creeping wave transducer
In Reply to Mark at 10:36 Jun-30-2016 .

It is hard to achieve to secondary creeping waves at bottom surface with 33 degree shear wave.It is better to replace the secondary creeping waves with other angle beam probe wich easily can detect bottom surface breaking.

 
 Reply 
 
eginzel@mri.on.ca
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1307

eginzel@mri.on.ca

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1307
13:30 Jun-30-2016
Re: creeping wave transducer
In Reply to Mark at 11:08 Jun-30-2016 .

Mark, I think the main point Anmol wants to make here is that; in compression mode the glancing incidence with a boundary does not cause a surface wave. Wieslaw pointed out that is is relatively easy to do generate this shape of compression mode using refraction from water. In a paper (and the associated video) at http://www.ndt.net/article/ndtnet/2013/10_Ginzel.pdf I illustrated the events that occur in the solid as the pulse incident angle from water increases. The transverse mode that people are calling a secondary shear would be considered the shear-headwave by most people using wave propagation. You can see that it is generated at the point of contact of the glancing compression mode and its shape follows the contact geometry. Because it has the same velocity as the bulk shear mode formed according to Snell's Law, we see the headwave connected to the bulk shear wave.

 
 Reply 
 
John Turner
John Turner
14:45 Jun-30-2016
Re: creeping wave transducer
In Reply to Carlos Toledo at 13:19 Jun-29-2016 (Opening).

Dear Carlos,

What application do you wish to use your Creeping wave probe for? If it is for inspection underneath weld caps, I would recommend that you use the twin crystal variety to keep the internal noise down. Use frequencies of 2 to 3.5 MHz, and don't go above 3.5 MHz, because the signal levels will be low. Please be aware of the range you want to use these probes up to. It's very hard to get them to work at much beyond 30 mm from the front of the probe. If you have a wide weld cap, then you will need a probe with a long focal range. It's always best if you discuss you application with the manufacturer. Once someone asked me to produce a creeping wave probe for small-bore pipe inspection, and that meant having to produce a special probe.

I would not recommend single element high angle L-wave probes, unless the internal noise is extremely low, and it is designed for near-surface inspection. The GE (formerly Krautkramer) WSY probes had a well-designed wedge that minimised the noise quite well.

To maximise the benefits from these probes, you need a good flaw detector with low noise at high gains. This is because on a typical flaw detector, the creeping wave signals do not become significant until around 40 to 60 dB of gain is applied.

You must tell the manufacturer exactly what material you are using. If the material is unusual, then the supplier might ask for a sample, or for you to tell them what the compression wave velocity is.

Best regards,

John

 
 Reply 
 
John Pitcher
Consultant,
Sonomatic Ltd, United Kingdom, Joined Apr 2003, 14

John Pitcher

Consultant,
Sonomatic Ltd,
United Kingdom,
Joined Apr 2003
14
16:43 Jun-30-2016
Re: creeping wave transducer
In Reply to Mark at 10:36 Jun-30-2016 .

It is all down to definitions:
Surface wave is not a creeping wave.
A lateral wave (in TOFD is the shortest distance travelled between index points. Can be a creeping wave on flat or concave surfaces.

Also if a creeping wave has limited range then how does a lateral wave exist when using large probe separation of 400mm plus?

 
 Reply 
 
massimo carminati
Consultant, AUT specialist
IMG Ultrasuoni Srl, Italy, Joined Apr 2007, 691

massimo carminati

Consultant, AUT specialist
IMG Ultrasuoni Srl,
Italy,
Joined Apr 2007
691
16:45 Jun-30-2016
Re: creeping wave transducer
In Reply to Carlos Toledo at 13:19 Jun-29-2016 (Opening).

Hello Sir,
We make customizer creeping wave probes since 30 years and many standard creeping wave standard design. As somebody posted already, creeping waves probes functionalit is critical and need applicaton details assestment. Feel free to contact me

 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 832

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
832
17:05 Jun-30-2016
Re: creeping wave transducer
In Reply to Mark at 10:36 Jun-30-2016 .

Mark, When L-waves are refracted, the energy drops with increase in refracted angle and is zero at 90 degrees. There is no L-wave component at 90 degrees. So there is no such thing as creeping wave. See Diagram 5 in the Appendix of Krautkramer and Krautkramer.
These are high angle refracted L-wave probe and all you are seeing is beam spread which picks the bottom of a notch. And the signal is lost if you move the probe 10 mm away from a 2 mm notch. For surface cracks, just use MT

 
 Reply 
 
John Turner
John Turner
17:25 Jun-30-2016
Re: creeping wave transducer
In Reply to John Pitcher at 16:43 Jun-30-2016 .

Dear John,

That's a good question. I tend to view the lateral wave as being the result of the creeping wave plus the high angle longitudinal wave, which is still spreading as travels just under the surface.

In any case, the creeping wave in pulse-echo mode has a short range because very little energy returns from the surface or near-surface defect. Remember the flaw detector has to be at high gain to even detect the signal. This is because the reflected energy from the defect will spread widely owing to the long wavelength, and only a small part of it will be converted into creeping waves / L-waves to return to the sensor.

In the case of lateral waves, the receiving probe has a relatively large area, and picks up a quite a lot of the transmitted energy, hence the ability to receive the signal at long range. Note that if the TOFD probes are facing each other in the circumferential direction on a cylindrical surface, the received energy will be from the direct L-wave, and not so much from the creeping wave.

BR, John

 
 Reply 
 
Mark
,
Zambia, Joined Jun 2016, 49

Mark

,
Zambia,
Joined Jun 2016
49
19:40 Jun-30-2016
Re: creeping wave transducer
In Reply to massimo carminati at 16:45 Jun-30-2016 .

Massimo,
I want to know that how much is the maximum effective sound path achieve able practically with creeping wave probes ?

Regards,

 
 Reply 
 
John Turner
John Turner
14:25 Jul-01-2016
Re: creeping wave transducer
In Reply to Mark at 19:40 Jun-30-2016 .

Dear Mark,

The range of a creeping wave probe depends on several things, assuming you are using the best option, which is a twin crystal probe:
i) The size and, more specifically, the width of the Tx and Rx crystals.
ii) The focal point of the converging beams of the two crystals.
iii) The accuracy with which the wedge angle can be established to optimise the creeping wave in the material. This is important, and makes a big difference to the result!
iv) The size of the defect and how close it is to the surface.

As I said in a previous email, the largest range in most cases is 30 mm max., but a good probe can get up to 40 mm. I once got a signal at 70 mm range from the square edge of V1 block, but this could not have happened if the reflector had been a small defect.

BR, John

 
 Reply 
 
massimo carminati
Consultant, AUT specialist
IMG Ultrasuoni Srl, Italy, Joined Apr 2007, 691

massimo carminati

Consultant, AUT specialist
IMG Ultrasuoni Srl,
Italy,
Joined Apr 2007
691
20:13 Jul-01-2016
Re: creeping wave transducer
In Reply to Mark at 19:40 Jun-30-2016 .

It depends on the reflective height of the surface breaking defect you want to detect. I can give you some practical data for a standard 30x30 creeping wave probe 2 MHz: a 5 mm long notch with 0.5 mm depth can be detected at a probe front distance of 10 to 12 mm with a SNR of 10 dB...same length 1 mm deep can be seen at about 20 mM.

 
 Reply 
 
Mark
,
Zambia, Joined Jun 2016, 49

Mark

,
Zambia,
Joined Jun 2016
49
06:50 Jul-02-2016
Re: creeping wave transducer
In Reply to massimo carminati at 20:13 Jul-01-2016 .

Really thanks Massimo.
What was the angle of creeping wave probe that you have tried?

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1307

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1307
15:42 Jul-02-2016
Re: creeping wave transducer
In Reply to Mark at 06:50 Jul-02-2016 .

I am not sure it is appropriate to refer to a refracted angle when discussing these probes. Steels have compression mode velocities varying from about 5700m/s to almost 6000m/s. A wedge that is designed to produce a nominal 80° refraction on cold rolled steel at 5850m/s would (by Snell's law) produce a totally internally reflected angle on the commonly quoted velocity of 5920m/s. However, even though the Snell's Law calculations indicate that the refraction has reached the first critical angle, there will still be a use-able signal as a result of the spherical shape of the wavefront. At such a high refracted angle, as little as 0.2° change in incident angle could result in the refraction calculated by Snell's Law as changing 4°.
But I am sure Carlos is just looking for a useful probe...so I would suggest he can make a decision based on some of the good guidance provided by John Turner.

 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 832

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
832
20:02 Jul-06-2016
Re: creeping wave transducer
In Reply to John Pitcher at 16:43 Jun-30-2016 .

Answer to John Pitcher:

This is a good question.
First of all, just because we see a signal on the screen does not always mean that it is an elastic wave. There are several phenomenon including mode-conversion, scattering etc. that can cause a signal in addition to reflection.

Here is some information based on measurements taken on Lateral wave
1. the lateral wave signal is half the frequency. the signal was measured 4 MHz frequency when using 10 MHz TOFD probes. That means it is not a direct signal from the probe.
2. the lateral wave signal amplitude drops when you move to finer grains steels. This is in contrast to attenuation, where finer grains would result in higher signal

So what is lateral wave signal that is half the frequency and whose amplitude decreases on finer
grain steels ? This is typical behavior of scattering from grains. Scattering from grains decreases with reduction in grain size.

 
 Reply 
 
john
Consultant,
Sonomatic Ltd, United Kingdom, Joined Apr 2003, 14

john

Consultant,
Sonomatic Ltd,
United Kingdom,
Joined Apr 2003
14
13:25 Jul-07-2016
Re: creeping wave transducer
In Reply to Anmol Birring at 20:02 Jul-06-2016 .

The reason the lateral wave is sometimes at a lower frequency to the main probe frequency can be explained as such: The probes are broadband and have a wide range of frequencies. The low frequencies have a larger beam spread thus creating the LW at a low frequency. See Tim Armitt's presentation 'Refracted Beam Spread of Bi-modal Probes'.
I have never investigated the amplitude versus steel grain size so cannot comment. :)

 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 832

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
832
15:07 Jul-07-2016
Re: creeping wave transducer
In Reply to john at 13:25 Jul-07-2016 .

Based on the boundary conditions, there is no theoretical basis of a L-wave mode on surface. Please see Wave Propagation in elastic media by J.D. Achenbach. The only wave mode on the surface is the shear wave component shown by Rayleigh in 1887

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1307

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1307
15:57 Jul-07-2016
Re: creeping wave transducer
In Reply to Anmol Birring at 15:07 Jul-07-2016 .

This request for information on where to get a probe has spun off some interesting discussion on the so-called creeping wave (again).
I have long been a fan of visualising the mechanics of wave interactions. This was inspired long ago by the work of a Japanese professor, Kasaburo Harumi. In 1982/83 he produced a series of lectures on a film called Educational Film for Ultrasonic Engineers. The authors are Prof. Kasaburo Harumi and Hisao Okada (Gunma University) and Tetsuo Saito and Toshiaki Fujimori (Shimizu Construction Co. Ltd.
It is a 12 part lecture series using lattice and vector representations to illustrate waves. If you can get a copy of this old "film" I am sure it will provide much better insight to the reasons why we rely on boundary interactions for the transverse and Rayleigh waves.
Around the same time a great paper was published by Prof. Leonard Bond that provides insight to the Rayleigh wave; FINITE DIFFERENCE METHODS APPLIED TO ULTRASONIC NON-DESTRUCTIVE TESTING PROBLEMS. http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4654&context=qnde

 
 Reply 
 
Paul Holloway
Consultant,
Holloway NDT & Engineering Inc , Canada, Joined Apr 2010, 255

Paul Holloway

Consultant,
Holloway NDT & Engineering Inc ,
Canada,
Joined Apr 2010
255
22:44 Jul-07-2016
Re: creeping wave transducer
In Reply to Ed Ginzel at 15:57 Jul-07-2016 .

zoom image

Photoelastic pic

Ed,

I found those photoelastic videos you made quite useful. Perhaps you can provide a link to it, or let me know and I'll host it on Dropbox.

-Paul
 
 Reply 
 
BRUNO ZILLI
Engineering, Ndt
Italy, Joined Apr 2018, 15

BRUNO ZILLI

Engineering, Ndt
Italy,
Joined Apr 2018
15
07:32 Jun-15-2018
Re: creeping wave transducer
In Reply to massimo carminati at 20:13 Jul-01-2016 .

dear Massimo.

please I would ask you more on this topic. For instance, a 8X9 double crystal creeping wave probe: which F value could be possible and reliable in your opinion? To be checked: BW-8 mm-AISI316-141-135.

Thank you

Kindest Regards
Bruno Zilli

 
 Reply 
 
J Mark Davis
Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama, USA, Joined Mar 2000, 85

J Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
14:19 Jun-15-2018
Re: creeping wave transducer
In Reply to BRUNO ZILLI at 07:32 Jun-15-2018 .

The FD Focal Depth should be posted on the Creeping Wave Probe. If not, you can physically determine the FD using a depth calibration block with a series of SDHs at depth of .100 inches in depth or at 1 or 2 mm in depth. Look for the highest amplitude for a given SDH. This will get you close to a nominal FD.

 
 Reply 
 

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