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1139 views
03:08 May-24-2004

C. Valdecantos

Engineering
MTORRES, Ing.,
Spain,
Joined May 2001
9
Ultrasonic C-scan image quality. Makes it sense?

Hi everybody.

“Because the purpose of most ultrasonic inspections is to examine a specimen for inhomogeneity, a knowledge of the factors affecting the visibility of detail in the finished C-scan is essential.” (From “Radiography in Modern Industry” by Kodak, "translated" to UT language).

Radiographers are lucky since long time: they have IQI´s (Image Quality Indicators). C-scanners do not have any equivalent IQI at all. It then appears that a general procedure to evaluate the intrinsic quality of an ultrasonic C-scan image is lacking. Unfortunately things may not be so simple, otherwise such a procedure would already be available.

The evaluation of the quality of many high responsibility aerospace composite parts is mostly supported on ultrasonic C-scan images. Makes it sense to claim for Ultrasonic C-scan image quality? Is envisageable an ultrasonic IQI?

Good discussion.

C. Valdecantos




 
03:26 May-24-2004

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1208
Re: Ultrasonic C-scan image quality. Makes it sense? Carlos:
In radiography the purpose of an IQI is to verify sensitivity (but not resolution).
Most ultrasonic C-scan operations require calibration on a reflector of some predefined shape or area to set sensitivity. This is typically a flat bottom hole or a side drilled hole. Often for thick sections of plate or other structures Ultrasonic C-scan systems calibrate on a series of such targets to demonstrate that sensitivity is maintained at varying depths. Distance Amplitude Correction or Time Corrected Gain is used to compensate for dispersion effects as soundpath increases. Since it serves the same function as the radiographic IQI the calibration target is effectively the ultrasonic IQI. Lateral and temporal "resolution" is another issue. This is accomplished by a series of targets at varying depths and lateral separations (description of one such block is found in ASME Section V Article 4 Figure E-460.2) I am not sure if an equivalent resolution method is used in radiography.

Ed

-----------Start Original Message -----------
: Hi everybody.
: “Because the purpose of most ultrasonic inspections is to examine a specimen for inhomogeneity, a knowledge of the factors affecting the visibility of detail in the finished C-scan is essential.” (From “Radiography in Modern Industry” by Kodak, "translated" to UT language).
: Radiographers are lucky since long time: they have IQI´s (Image Quality Indicators). C-scanners do not have any equivalent IQI at all. It then appears that a general procedure to evaluate the intrinsic quality of an ultrasonic C-scan image is lacking. Unfortunately things may not be so simple, otherwise such a procedure would already be available.
: The evaluation of the quality of many high responsibility aerospace composite parts is mostly supported on ultrasonic C-scan images. Makes it sense to claim for Ultrasonic C-scan image quality? Is envisageable an ultrasonic IQI?
: Good discussion.
: C. Valdecantos
------------ End Original Message ------------




 
08:44 May-25-2004

Godfrey Hands

Engineering,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
286
Re: Ultrasonic C-scan image quality. Makes it sense? ----------- Start Original Message -----------
: Hi everybody.
: “Because the purpose of most ultrasonic inspections is to examine a specimen for inhomogeneity, a knowledge of the factors affecting the visibility of detail in the finished C-scan is essential.” (From “Radiography in Modern Industry” by Kodak, "translated" to UT language).
: Radiographers are lucky since long time: they have IQI´s (Image Quality Indicators). C-scanners do not have any equivalent IQI at all. It then appears that a general procedure to evaluate the intrinsic quality of an ultrasonic C-scan image is lacking. Unfortunately things may not be so simple, otherwise such a procedure would already be available.
: The evaluation of the quality of many high responsibility aerospace composite parts is mostly supported on ultrasonic C-scan images. Makes it sense to claim for Ultrasonic C-scan image quality? Is envisageable an ultrasonic IQI?
: Good discussion.
: C. Valdecantos
------------ End Original Message ------------

Hi,
It would be great if we could use a form of IQI with an Ultrasonic C-Scan, but he very principle of ultrasonics precludes the use of an external device with a detection target in it.
With ultrasonics, we need to have the "IQI" integral in the component we are scanning. If we add it afterwards, there will be extra interfaces for the (ultra)sound to reflect from, and it will defeat the objective.
The only way to achieve the status of an IQI in an ultrasonic C-Scan is to produce a component having a defect IN THE COMPONENT. This is frequently achieved either with drilled holes or spark erosion, and there are companies now who can induce thermal fatigue cracking in specified locations and dimensions (see an earlier posting on the forum this month).
Because a C-Sca is frequently computer controlled, or mechanically controlled, the test should be repeatable, so any test results on the reference (or calibration) piece will also be valid for the samples you are testing.
Just as in Radiography, when the exposure conditions and test samples are identical, the detectable feature of the IQI will always be the same.

Hope this helps.

Regards,

Godfrey Hands



 
08:47 May-25-2004

Jean-Louis ARNAUD

Consultant
AIRBUS,
France,
Joined Jan 2002
1
Re: Ultrasonic C-scan image quality. Makes it sense? Bonjour.
Carlos, I really think your idea of ultrasonic IQI is of interest to qualify how good are the thousand of square meters of C-Scans produced each year on metals and composites.
Spatial resolution could be determined by IQI similar to duplex wire IQI like EN462 or EN13068 used in digital X-Rays techniques.
Specific ultrasonic IQI could be designed to determine temporal or attenuation resolution.
The problem is how to proceed? Do we have any starting point both in technical or organisational terms?

----------- Start Original Message -----------
: Carlos:
: In radiography the purpose of an IQI is to verify sensitivity (but not resolution).
: Most ultrasonic C-scan operations require calibration on a reflector of some predefined shape or area to set sensitivity. This is typically a flat bottom hole or a side drilled hole. Often for thick sections of plate or other structures Ultrasonic C-scan systems calibrate on a series of such targets to demonstrate that sensitivity is maintained at varying depths. Distance Amplitude Correction or Time Corrected Gain is used to compensate for dispersion effects as soundpath increases. Since it serves the same function as the radiographic IQI the calibration target is effectively the ultrasonic IQI. Lateral and temporal "resolution" is another issue. This is accomplished by a series of targets at varying depths and lateral separations (description of one such block is found in ASME Section V Article 4 Figure E-460.2) I am not sure if an equivalent resolution method is used in radiography.
: Ed
: : Hi everybody.
: : “Because the purpose of most ultrasonic inspections is to examine a specimen for inhomogeneity, a knowledge of the factors affecting the visibility of detail in the finished C-scan is essential.” (From “Radiography in Modern Industry” by Kodak, "translated" to UT language).
: : Radiographers are lucky since long time: they have IQI´s (Image Quality Indicators). C-scanners do not have any equivalent IQI at all. It thenappears that a general procedure to evaluate the intrinsic quality of an ultrasonic C-scan image is lacking. Unfortunately things may not be so simple, otherwise such a procedure would already be available.
: : The evaluation of the quality of many high responsibility aerospace composite parts is mostly supported on ultrasonic C-scan images. Makes it sense to claim for Ultrasonic C-scan image quality? Is envisageable an ultrasonic IQI?
: : Good discussion.
: : C. Valdecantos
------------ End Original Message ------------




 
03:07 May-25-2004

Carlos Valdecantos

Engineering
MTORRES, Ing.,
Spain,
Joined May 2001
9
Re: Ultrasonic C-scan image quality. Makes it sense? Hi again.
It seems evident that any attempt to find a general solution for a C-scan IQI will fail because the target is so wide: from metals to composites, from through transmission to pulse-echo, from immersion to water jet... This is the reason I pointed to aerospace composite parts, but even in this limited case the goal looks not easy to achieve.
Some systematic work from the practical side is lacking to assess interface and repeatability unknowns. Repeatability of the interface acoustic behaviour may be a major problem, as it happens with lead tabs, sometimes used in USA.
But perhaps the main problem, as pointed by Jean-Louis, comes from the organisational side.

Carlos


 


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