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Tecnatom
Tecnatom has more than 50 years of experience providing services, equipment and systems devoted to NDT testing in several sectors and markets.

536 views
00:43 Mar-08-2001

Mario Belo

NDT Inspection
Trenes Buenos Aires,
Argentina,
Joined Jan 2000
7
Attenuation calculation

Dear experts:

To calculate attenuation with angular probes I have to use the Pitch-Catch technique obtaining two echoes(different measures) of the same piece.

Am I proceeding the right way?

Do I have to do this with the control set for 2 probes?

Kind regards.


Mario bello



 
00:55 Mar-09-2001

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
174
Re: Attenuation calculation reply by Udo Schlengermann
:

Obviously you should use two angle beam probes of same type and angle in separate transmitter receiver mode, i.e. one probe is transmitting, the other is receiving.
Position the probes facing each other on a plate and take an echo at a direct V-path between the probes. Then increase distance till you get a W-path (double V) and take another reading.
The path difference is a single V for the angle used.
So the dB-difference between the two readings give you a measure of attenuation in dB/mm sound travel path.
This technique is not exact, because there are other losses which must be compensated. If both readings are in the farfield of the probes you have to compensate the diffraction losses by 6 dB.
And this technique works only with total reflection, i.e. with angles of 45°. With other angles you get mode conversion and therefore additional losses which are not caused by attenuation.

Kind regards
Udo Schlengermann

: Dear experts:
.
: To calculate attenuation with angular probes I have to use the Pitch-Catch technique obtaining two echoes(different measures) of the same piece.
.
: Am I proceeding the right way?
.
: Do I have to do this with the control set for 2 probes?
.
: Kind regards.
.
:
: Mario bello
.



 


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