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Re: ASTM E 127 Par. 11
Posted by: Robert (Rocky) A. Day
, E-mail: rocky@xdcr.com, on September 13, 1999 at 19:11:22
:In Reply to: Re: ASTM E 127 Par. 11 posted by : Udo Schlengermann on September 13, 1999 at 15:48:29:
I must disagree with the statement made that all 0.375 inch diameter transducers have the 'required' sound beam. The quartz transducer with a 0.5 inch crystal diameter and a 0.375 inch electrode doesn't produce the same beam as a 0.375 inch diameter crystal of another material, even if the bandwidths are the same. Since quartz is very narrow band one would also be concerned about changes induced in the ASTM E-127 procedure by substituting a piezoceramic with say 80% bandwidth for a quartz crystal with a bandwidth of 5%. Diffraction is effected both by electrode shape (apodizing) and by bandwidth.
The effects are described in Krautkramer P20.
Whether ASTM E-127 results would be influenced by these differences is not obvious to me, but I suspect they would be. It would be interesting to know if anyone has made measurements using wideband pulses and pulse-tones with and without apodized electrodes? It would also be interesting to know what tolerances on transducers might be appropriate for a 'Standard Practice' and why such tolerance are not in Para 11?
Regards,
Robert (Rocky) A. Day
Second Sound
Ultrasonic Systems
220 Gates Street
San Francisco, CA 94110
(415) 647-0625
Fax: (415) 641-4947
: But this beam is generated by a transducer with an effective transducer diameter of 0.375 inches.
: The text of note 6 only tells that during the development of this standard (some decades ago) quartz transducers of 0.5 inch diameter with an 0.375 inch electrode were used.
: Today all narrow band piston type oscillators of 0.375 inch diameter will generate the required sound beam, independent of their material.
: It seems standard E127 has to be revised again to be consistent in clauses 8.4, 8.5 and 11.3.5.
: Kind regards
: Udo Schlengermann