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Technical Discussions
Lirin Philip
,
VALDEL , India, Joined Sep 2019, 10

Lirin Philip

,
VALDEL ,
India,
Joined Sep 2019
10
08:37 Sep-13-2019
Quantify porosity by UT

Are we able to quantify porosity of a composite material through UT? I'm using OMNI SCAN SX 16:64 phased array, by olympus. It will be help full if i could refer some good journals on the topic.

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Edward Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Edward Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
13:24 Sep-13-2019
Re: Quantify porosity by UT
In Reply to Lirin Philip at 08:37 Sep-13-2019 (Opening).

There is no useful way to attempt quantification of porosity in a weld by ultrasonic methods. Even radiographic methods rely on projected area and from that try to come up with a volume estimate.

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Rick Lopez
R & D,
John Deere - Moline Technology Innovation Center, USA, Joined Jul 2011, 188

Rick Lopez

R & D,
John Deere - Moline Technology Innovation Center,
USA,
Joined Jul 2011
188
17:11 Sep-13-2019
Re: Quantify porosity by UT
In Reply to Lirin Philip at 08:37 Sep-13-2019 (Opening).

Lirin,
I've never tried it, but I believe that longitudinal wave frequency-dependent attenuation and velocity will both vary with porosity (density; up to ~10% volume percent) in polymer composite materials. My foggy recollection is that velocity was deemed as more straightforward and easier to perform while maintaining precision.

Jeong, H., and D. K. Hsu. "Experimental analysis of porosity-induced ultrasonic attenuation and velocity change in carbon composites." Ultrasonics 33, no. 3 (1995): 195-203.

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Daniel Braun
Daniel Braun
18:55 Sep-13-2019
Re: Quantify porosity by UT
In Reply to Lirin Philip at 08:37 Sep-13-2019 (Opening).

here is the link to the youtube video:
https://www.youtube.com/watch?v=a0x4nAiXpQw&feature=youtu.be&t=312
upon clicking on play it will start at the moment of detection of real porosity in the GFRP: on the B-Scan image it is observed a bulge on the bottom surface however the actual bottom surface is flat - this does occur due to porosity in the resin, which affects the time of flight (TOF) for the back wall echo - it is very easy to quantify and compare TOF values for the clean and porosity areas and reproduce the corresponding A-Scans. For CFRP you will obtain absolutely similar observations

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Edward Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Edward Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
21:45 Sep-13-2019
Re: Quantify porosity by UT
In Reply to Daniel Braun at 18:55 Sep-13-2019 .

Daniel, having watched the video we can see that there is a characterisation difference between the semi-transparent de-bonding and the flaw indicated as "porosity". But there is no indication that the pores were quantified. There appeared to be a small time shift associated with the indication identified as de-bonding and a larger time shift where it was called porosity. Backscatter was present from de-bonding but none from porosity. And although there was a larger time shift in the region called porosity, there was no apparent backscatter from individual pores. Were there no macro photos made of the damage mechanisms showing the size, depths and densities of distribution? These are the parameters I would think of as "quantification" of porosity. And although some people may think that my parallel with attempts to quantify pores in welds was irrelevant, the reality is that the same problems will exist in attempting to quantify pores in composite materials.

1    
 
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Philippe Rioux
R & D, Sonatest
Sonatest, Canada, Joined Jan 2015, 37

Philippe Rioux

R & D, Sonatest
Sonatest,
Canada,
Joined Jan 2015
37
22:46 Sep-15-2019
Re: Quantify porosity by UT
In Reply to Edward Ginzel at 21:45 Sep-13-2019 .

Hello, we worked with one of our customers to quantify porosity level in composite. I can explain to you a little bit what we have found since the technique still belongs to Sonatest. We took a 10 MHz frequency PA probe on known porosity samples. (Other none-UT NDT method.) We successfully correlate the true level vs. the internal noise from the inner composite. On the lowest porosity sample, we put the gain such the internal structure was clearer at 50% average and we measure its std. dev. We compared different mean level and std dev. to the other higher porosity level and it is about 10% precise. One of the other key features was having a very high SNR PA device. So we were not adding instrument-probe SNR to the composite "grain" echoes.

This is the best I can share so far, many hints for you guys!
Regards,

    
 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 746

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
746
04:37 Sep-16-2019
Re: Quantify porosity by UT
In Reply to Lirin Philip at 08:37 Sep-13-2019 (Opening).

Immersion scan using 10 MHz, 19 mm dia F= 25 mm, focused at midwall of composite.

    
 
 Reply 
 
Lirin Philip
,
VALDEL , India, Joined Sep 2019, 10

Lirin Philip

,
VALDEL ,
India,
Joined Sep 2019
10
05:58 Sep-16-2019
Re: Quantify porosity by UT
In Reply to Philippe Rioux at 22:46 Sep-15-2019 .

Sir, are you using immersion method or contact method.

    
 
 Reply 
 
Lirin Philip
,
VALDEL , India, Joined Sep 2019, 10

Lirin Philip

,
VALDEL ,
India,
Joined Sep 2019
10
07:09 Sep-16-2019
Re: Quantify porosity by UT
In Reply to Anmol Birring at 04:37 Sep-16-2019 .

Sir, then shouldn't chose the gate to be as small as possible and placed at the mid point. Also what would be the criteria to select threshold for the gate.

    
 
 Reply 
 
Philippe Rioux
R & D, Sonatest
Sonatest, Canada, Joined Jan 2015, 37

Philippe Rioux

R & D, Sonatest
Sonatest,
Canada,
Joined Jan 2015
37
10:44 Sep-16-2019
Re: Quantify porosity by UT
In Reply to Lirin Philip at 07:09 Sep-16-2019 .

Yes. Gate would be set tight in the midwall.

Thanks Anmol for more hints to Lirin.

Regards,

    
 
 Reply 
 
Edward Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Edward Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
14:53 Sep-16-2019
Re: Quantify porosity by UT
In Reply to Philippe Rioux at 22:46 Sep-15-2019 .

Thank you Philippe. So it would seem that you managed to develop an empirical approach that used a specific set of materials and processes and you carried out destructive tests to do actual quantification analyses on a wide selection of different porosities documented by other NDT methods. For thicker or thinner samples, samples made with different proportions and types of resins, etc,. it would therefore be wise to develop unique techniques with different apertures, delay laws, frequencies, etc. Others attempting to use a similar approach would therefore be advised to customise their technique and document the rationale.

    
 
 Reply 
 
Daniel Braun
Daniel Braun
17:19 Sep-16-2019
Re: Quantify porosity by UT
In Reply to Edward Ginzel at 21:45 Sep-13-2019 .

The video I referred to relates to the inspection of GFRP parts; GFRP is characterized by very coarse structure, the signals from porosity may not be distinguished having in mind the relatively low frequency used; for the customer is important detection of porosity, not evaluation, they do determine the deviation of through-wall velocity ΔV from the normal value based on the measured deviation of time of flight ΔT for the back wall echo received and evaluate the degree of porosity based on ΔV - they have the corresponding procedures for the quick in-service / in-manufacturing inspection, which has been proven by some years of use. The similar procedures are in use by some manufacturers of CFRP parts as well as the porosity is well distinguished in such manner

    
 
 Reply 
 
J.B.
J.B.
16:47 Sep-18-2019
Re: Quantify porosity by UT
In Reply to Daniel Braun at 17:19 Sep-16-2019 .

It is definitely usual to quantify Porosity in FRPs by Ultrasonic Pulse Echo Inspections, just on the fly while doing the usual full area inspections if CFRP structures in aerospace, where this is mandatory.
Porosity causes a loss in ultrasonic back wall echo. Lot of material combinations have been tested at Boeing as well as at Airbus to determine/qualify the necessary parameters. For nearly all combinations of “material type and thickness“ statistical test shows a significant correlation between back wall echo reduction and porosity in Pulse Echo Inspection setup. In case of their proven similarity, different material types can be merged.
So usual not the backscatter of pores is evaluated, but the loss of backwall echo signal.
Some values for a typical threshold of 2.5% Vol Porosity (5Mhz or 3.5MHz array, water column or wheel probe/roto array, typical PAUT equipment like Omniscan but also large scanning machines from PAR, Arreva, GE...)
1mm Thickness – 2 dB Back Wall Echo Reduction
3mm Thickness – 10 dB Back Wall Echo Reduction
10mm Thickness – 16 dB Back Wall Echo Reduction
30mm Thickness – 20 dB Back Wall Echo Reduction

In case of non parallel surfaces / no backwall echo available, also backscatter can be used
- there had been publications on statistical approaches in the 1990ties or earlier, from BASF, but I have no copy available. also Hilger (https://www.hillger-ndt.de) sells a system to deal with such an approach: https://www.dlr.de/fa/Portaldata/17/Resources/dokumente/institut/2002/u2002_2.pdf / https://www.hillger-ndt.de/PDF/Muse_e.pdf

See also my comments in a previous post https://www.ndt.net/forum/thread.php?msgID=74663#74663
Again some links for further reading
• https://patents.google.com/patent/US7617715B2/en
• https://patents.google.com/patent/US6684701 (good old stuff from Lockheed Martin)
• https://patents.google.com/patent/US9002088B2/en US9002088B2 The Boeing Company - Method and apparatus for creating nondestructive inspection porosity standards
• https://patentimages.storage.googleapis.com/fc/03/ae/3bccc4a1fafb64/US7434468.pdf Porosity reference standard for ultrasonic inspection of composite materials
• https://patents.google.com/patent/US9360459B2/en US9360459B2 The Boeing Company - Porosity inspection system for composite structure with non-parallel surfaces
• https://patentimages.storage.googleapis.com/3b/92/96/5484a201002f05/US7712369.pdf US7712369B2 Array-based system and method for inspecting a workpiece with backscattered ultrasonic signals
• From Boeing you may look for a lot of papers & patents from Gary Georgeson like this patents https://patents.google.com/patent/US7617715B2/en
• United States Patent US7823451 https://patents.google.com/patent/US7823451B2/en?oq=US7823451
• https://www.boeing.com/commercial/aeromagazine/articles/2015_q1/pdf/AERO_2015q1.pdf
• some authors of Boeing procedures and patents (can be used for a web search)
o Jeff Kollgaard, Technical Fellow, NDT Maintenance
o Gary Georgeson Technical Fellow, NDT Engineering
o Richard Bossi Technical Fellow, NDT Engineering

Some Airbus and Airbus related papers
• https://hal.inria.fr/hal-01022992/document Phase Statistics And Spectral Analysis Of Ultrasonic Signals For Cfrp Component Assessment
• http://2015.ndt-aerospace.com/Portals/aerospace2015/BB/mo3a1.pdf, https://link.springer.com/chapter/10.1007/978-3-319-29922-8_19
Carsten Brandt (2015) Recurrence Quantification Analysis as an Approach for Ultrasonic Testing of Porous Carbon Fibre Reinforced Polymers
• https://www.ndt.net/article/ecndt2006/doc/Tu.2.1.4.pdf Dominguez, N. & Mascaro, B. 2006, "Ultrasonic Non-Destructive Inspection of Localised Porosity in Composite Materials", ECNDT 2006 - 9th European Conference on NDT 2006, Online-Proceedings on ndt.net, 18./19.09.2006.
• https://www.ndt.net/events/aeroNDT2014/app/content/Paper/10_Barut.pdf / https://www.ndt.net/events/aeroNDT2014/app/content/Slides/10_Barut.pdf ULTIS/NDT-Kit-Software for PAUT Inspection evaluation
• https://www.ndt.net/events/DIR2015/app/content/Paper/53_Kiefel.pdf Reliability Optimization of Quantitative CFRP Porosity Characterization Using µ-CT, https://mediatum.ub.tum.de/doc/1360649/1360649.pdf
• https://www.ndt-aerospace.com/Portals/aerospace2015/BB/mo5a3.pdf
• https://www.ndt.net/article/wcndt2016/papers/we2a2.pdf Kurz/Rabe: “ Porosity determination of carbon fiber reinforced plastics (CFRP) in aviation applications using ultrasound without a back wall echo”
• https://www.ndt.net/article/wcndt2016/papers/fr1d1.pdf / https://www.ndt.net/article/wcndt2016/papers/fr1d2.pdf MAIzfp Project
• https://www.researchgate.net/publication/302233319_Determination_of_Porosity_in_Fiber_Reinforced_Plastics_by_Computer_Aided_Ultrasonic_Signal_Analysis_CAMPUS / https://link.springer.com/chapter/10.1007/978-1-4615-4847-8_112
• https://pdfs.semanticscholar.org/0ac2/8e483d5a3988f208b32ba3006c31e4e27ef1.pdf
• https://www.ndt.net/article/cdcm2006/papers/schnars.pdf
• https://www.dlr.de/fa/Portaldata/17/Resources/dokumente/institut/2002/u2002_2.pdf
• http://iccm-central.org/Proceedings/ICCM16proceedings/contents/pdf/MonI/MoIA1-03ge_olivierp225907p.pdf
• About the ultrasonic testing machines Airbus has installed for A350XWB (capable to determine porosity content of different thickness and complex shauped CFRP) https://www.ndt.net/article/dgzfp2010/Inhalt/mi2c3.pdf
standards:
• Airbus AITM6-0011: Non-Destructive Inspection of Composite Parts
• Airbus AITM6-0012: Reference standards for non-destructive inspection methods on fibre composites
• Airbus AITM6-4005: Ultrasonic pulse-echo inspection of carbon fibre plastics
• Airbus AITM 6-4010: Inspection of fibre composites by ultrasonic phased array technique
• Airbus AITM 6-4022: UT-Insp. around rivet and fastener holes in CFRP
• Airbus AITM6-0014: Probability of detection POD.
• Boeing BAC5980
Other resources:
• http://projects.npl.co.uk/vitcea/docs/20150217-bam-workshop-facc.pdf
• https://www.ingentaconnect.com/content/ben/mats/2012/00000005/00000001/art00004?crawler=true (read with care: not all conclusions are o.k. as it is only a study on patents and papers, no own development results)

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