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- since 1996 -
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Technical Discussions
Sufiyan Mukadam
India, Joined Feb 2020, 3

Sufiyan Mukadam

India,
Joined Feb 2020
3
08:51 Feb-17-2020
Working on coarse grain material.

Dear all,
Greetings for the day!!

I'm currently working on a Nitroglycerin based material which has coarse grains. We do through transmission test. Problem we're facing is high frequency probe can't penetrate the material and low frequency probes aren't able to catch small defects. I'm already working on 90db gain, can I increase the gain upto 200db by any additional support ? If not is there any suggestions for another machines ?

Thanks and regards,
Sufiyan Mukadam

 
 Reply 
 
Wiesław Bicz
Engineering,
PBP Optel sp. z o.o., Poland, Joined Feb 2009, 272

Wiesław Bicz

Engineering,
PBP Optel sp. z o.o.,
Poland,
Joined Feb 2009
272
15:37 Feb-17-2020
Re: Working on coarse grain material.
In Reply to Sufiyan Mukadam at 08:51 Feb-17-2020 (Opening).

There is no simply answer to your question. If you increase the signal amplification, you will also increase signal scattered by grains. 200 dB amplification is theoretically possible only with very narrowband filters and really realistic only with lock-in amplifiers.
I would assume, that only automatic scan (may be confocal scan) with sophisticated signal analysis and frequency that is not to high and not too low can help.

1
 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 786

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
786
18:26 Feb-17-2020
Re: Working on coarse grain material.
In Reply to Sufiyan Mukadam at 08:51 Feb-17-2020 (Opening).

Thru-transmission is based on loss of signal. The loss of signal is ratio area of flaw to area of probe. So a 3 mm dia flaw using a 12 mm probe, the signal drop is only 6 %. This will not be detected. Thru-transmission is only for detection of large flaws that completely block the beam

1
 
 Reply 
 
Wiesław Bicz
Engineering,
PBP Optel sp. z o.o., Poland, Joined Feb 2009, 272

Wiesław Bicz

Engineering,
PBP Optel sp. z o.o.,
Poland,
Joined Feb 2009
272
19:21 Feb-17-2020
Re: Working on coarse grain material.
In Reply to Anmol Birring at 18:26 Feb-17-2020 .

This is not true if you are using focused probes. If the focus is inside the material you can detect also small defects. This can be perfectioned, if you make confocal scan with many layers, but this will naturally take some time, even with phased arrays probes.

1
 
 Reply 
 
Levi Porter
R & D,
Dacon Inspection Technologies, Thailand, Joined Jan 2017, 56

Levi Porter

R & D,
Dacon Inspection Technologies,
Thailand,
Joined Jan 2017
56
05:00 Feb-18-2020
Re: Working on coarse grain material.
In Reply to Sufiyan Mukadam at 08:51 Feb-17-2020 (Opening).

zoom image

Beam Sim.

Hi Sufiyan,
If possible please share more details about your inspection. It may help other who are searching these forums.

Type of ultrasonic inspection: Conventional, Phased Array

Size of transducer:

Frequency of transducer:

Angle beam or normal beam: (I'm sure normal but better to check)

How is the probe coupled?

Delay line?

Thickness of the material being tested:

Velocity of the material:

I'm particularly interested how you are coupling. If you are using conventional or PAUT it may be worth noting that your results could improve if the beam is close to the focal point when entering the part. Please see the attached picture of highly attenuating material simulations on beam formation.

Full article for the picture can be found here:

https://www.ndt.net/article/wcndt2016/papers/th2a4.pdf
 
 Reply 
 
Sufiyan Mukadam
India, Joined Feb 2020, 3

Sufiyan Mukadam

India,
Joined Feb 2020
3
08:55 Feb-18-2020
Re: Working on coarse grain material.
In Reply to Levi Porter at 05:00 Feb-18-2020 .

Hii,

Thanks for your reply.

We're using a conventional Normal beam 0.5Mhz probe with 19mm dia and its coupled.

 
 Reply 
 
Sufiyan Mukadam
India, Joined Feb 2020, 3

Sufiyan Mukadam

India,
Joined Feb 2020
3
13:34 Feb-18-2020
Re: Working on coarse grain material.
In Reply to Wiesław Bicz at 15:37 Feb-17-2020 .

Thanks for your reply.

Suggestions are very helpful and I'll consider your suggestions.

Regards,
Sufiyan

 
 Reply 
 
Ian
Ian
21:28 Feb-18-2020
Re: Working on coarse grain material.
In Reply to Sufiyan Mukadam at 08:55 Feb-18-2020 .

Sufiyan

From the description it sounds as though you might be working with the propellant used in solid rocket motors. This is very attenuating compared with metals, so even 0.5MHz is probably too high a frequency. I worked on rocket motors nearly 40 years ago and to get significant transmission through several cm of propellant needed frequencies below 100kHz.
A quick search on ndt.net found this https://www.ndt.net/article/jrc-nde2009/papers/82.pdf
which suggests something similar in fig 7.

Regards
Ian

 
 Reply 
 
Levi Porter
R & D,
Dacon Inspection Technologies, Thailand, Joined Jan 2017, 56

Levi Porter

R & D,
Dacon Inspection Technologies,
Thailand,
Joined Jan 2017
56
12:36 Feb-19-2020
Re: Working on coarse grain material.
In Reply to Sufiyan Mukadam at 08:55 Feb-18-2020 .

Hi Sufiyan,
How is the probe coupled? Immersion? Contact? Contact through delay line?

 
 Reply 
 

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