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448 views
04:28 Jun-02-2000
Joseph Batt
TOFD

During measurements, is the probes distance so important?
I have found a formula:distance=2/3*2*c*tan a
c=velocity of longitudinal wave
a=angle of the probe

Is that correct?
In some books it is also said that it is better to do measurements
at two different distances between the probes.
Anyway, I find it very difficult to interpret data from the A scan.
I would appreciate if someone could give me some informations.
Thank you.

Joseph Batt



 
02:23 Jun-05-2000

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
174
Re: TOFD ls are weak, and TOFD uses (non rectified) Rf-signals, so interpretation of a single TOFD-A-scan makes no sense.
TOFD results of a lot of A-Scans have to be compiled in a B-Scan image.
In this B-Scan image the human eye can easily detect areas with irregularities.
Because of the wide beams used the images do not show the real shape of the irregularity. The pattern has to be interpreted. Only the points of minimum time-of-flight give some idea of the extension of the irregularity.

Kind regards
Udo Schlengermann

+++++++++++++++++++++++++++++++++++++++
: During measurements, is the probes distance so important?
: I have found a formula:distance=2/3*2*c*tan a
: c=velocity of longitudinal wave
: a=angle of the probe

: Is that correct?
: In some books it is also said that it is better to do measurements
: at two different distances between the probes.
: Anyway, I find it very difficult to interpret data from the A scan.
: I would appreciate if someone could give me some informations.
: Thank you.

: Joseph Batt




 


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