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Technical Discussions
Adolfo Rodriguez Miguelez
Adolfo Rodriguez Miguelez
06:14 May-20-1998
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 andair, 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: pelly69@hotmail.com
a.rodriguezmiguelez@dundee.ac.uk

Address: 20 Perth Road, flat 1, door 1
Dundee - Scotland
DD1 4LN

Fax: (01382) 227664

Thanks in advance and sorry for my bad English.

Adolfo.


    
 
 
Udo Schlengermann
Consultant, -
Standards Consulting, Germany, Joined Nov 1998, 176

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
176
05:11 Jun-01-1998
Re: Contact transducers with paper??
answer by Udo Schlengermann (uschlengermann@krautkramer.de)
to Adolfo Rodriguez Miguelez (pelly69@hotmail.com)

Dear Sir,

To determine the elastic moduli of paper you obviously want to use the theoretical relations between density, sound velocities for transverse
and longitudinal waves and bulk, rep. shear modulus.
But these equations only hold for an ideal elastic half space and not for thin plates or foils as paper.
Within these sheet material there are no pure longitudinal or transverse waves but the body is vibrating as a whole (plate waves) or only
surface waves are generated.
I think you have to find a correlation between paper strength and these guided waves by experiment, possibly in the low frequency range
(acousto-ultrasonics) using separate transmitter and receiver.

- Coupling to paper using fluids makes not much sense. Perhaps air-coupled transducers are better.

- I heard about some research on ultrasonic methods on paper from Finland, but unfortunately I do not know publications.

Kind regards

Udo Schlengermann



    
 
 
Colm Flannery
Colm Flannery
06:55 Jun-26-1998
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: pelly69@hotmail.com
: a.rodriguezmiguelez@dundee.ac.uk

: Address: 20 Perth Road, flat 1, door 1
: Dundee - Scotland
: DD1 4LN

: Fax: (01382) 227664

: Thanks in advance and sorry for my bad English.

: Adolfo.

Hello,

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.

Try:

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

Colm Flannery


    
 
 
Alex Bancroft
Alex Bancroft
08:01 Dec-14-1998
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: pelly69@hotmail.com
: a.rodriguezmiguelez@dundee.ac.uk

: Address: 20 Perth Road, flat 1, door 1
: Dundee - Scotland
: DD1 4LN

: Fax: (01382) 227664

: Thanks in advance and sorry for my bad English.

: Adolfo.




    
 
 

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