Re: Contact transducers with paper?? : Hi, folks,
: I am developing a research project related with treatment of paper with ultrasonic waves. I am trying to determine the elastic constants in paper. To doing this, I would need to excite some longitudinal and shear ultrasonic waves in the in-plane of the paper and measure the velocity of the sound in it, which is directly related with these elastic constants.
: To exciting these ultrasonic waves I have not decided totally the ultrasonic transducer that I am going to use, and I am in the doubt between to use air-coupled transducers and measure the Leaky Lamb wave travelling in the plate (paper), or to use contact transducers, but I think that the latter option would be more reliable.
: I would like to know if anybody has excited some ultrasonic waves in the plane of paper and how what transducer did you use. What about to use air-coupled transducers, and get the signal from the Leaky wave along the paper??? Would it be a enough energetic signal or the mismatch between paper and air, and attenuation of paper would avoid any travel of ultrasound inside the paper???
: I would be very grateful if anybody comment to me his experience or idea about this question.
: My data are:
: Adolfo Rodriguez Miguelez
: E-mail: firstname.lastname@example.org
: Address: 20 Perth Road, flat 1, door 1
: Dundee - Scotland
: DD1 4LN
: Fax: (01382) 227664
: Thanks in advance and sorry for my bad English.
I have seen a number of recent publications concerning inspection of paper with laser ultrasonics.
Most of the stuff is theoretical (modelling) but there are some experimental measurements reported also.
Laser Ultrasonics in copy paper
Y.H. Berthelot and M.A. Johnson
Optical Engineering 36(2) p.408-416 Feb. 1997
Theory of laser-generated transient lamb waves in orthotropic plates
J.C. Cheng and Y.H. Berthelot
J. Appl. Phys. D: Appl. Phys. 29 (1996) p.1857-1867
Good papers on Lamb waves in plates:
A laser study of transient Lamb waves in thin materials
D.A. Hutchins and K. Lundgren and S.B. Palmer
J.Acoust. Soc. Am. 85(4) April 1989 p. 1441
Mechanisms of laser-generated ultrasound in plates
L. Wu and JC Cheng and S Zhang
J. Phys. D: Appl. Phys. 28(1997) p.957-964
Also worth checking out are papers by Alleyne and Cawley
of Imperial College London, R. Dewhurst of UMIST, and D.A. Hutchins, Warwick
Most of the principles discussed in these papers are
applicable to all types of transduction.
Hope this is of help