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Technical Discussions
sachin shinde
sachin shinde
07:21 Feb-03-2001
Re: Use of Ultrasonic Velocities for Materials Characterization
:
: 'Nondestructive Characterization of State and Properties of Aluminium Structures'
: In this article Eckhardt Schneider writes:
: 'It is common practice to evaluate the elastic constants Young`s- and shear
: moduli using the material density and the propagation velocities of ultrasonic
: longitudinal and shear waves. The velocities can be determined with an accuracy
: better than 0.1%.'

: I would like to know more about the time of flight measurement principle
: which is used to measure the velocities.

: Is the ultrasonic birefringence effect used? And how does this work?
: What kind of ultrasonic signals are evaluated? Is a backwall echo needed
: to measure the sound path travel time?

: I have the article Ultrasonic Birefringence Effect
: - Its Appplication for Materials Characterization.
: E. Schneider in Optics and Laser Engineering 22 (1995) pp 305-323 (Elsevier) on
: my desk, unfortunately it does not helps me much to understand this technique.

:Especially from Mr. Schneider I would appreciate if he could bring some light
: in this matter. Please contact me if I can help in supplying any image for
: the explanation.

: Rolf Diederichs




    
 
 Reply 
 
Rolf Diederichs
Director,
NDT.net, Germany, Joined Nov 1998, 608

Rolf Diederichs

Director,
NDT.net,
Germany,
Joined Nov 1998
608
05:33 Nov-05-1998
Use of Ultrasonic Velocities for Materials Characterization


'Nondestructive Characterization of State and Properties of Aluminium Structures'
In this article Eckhardt Schneider writes:
'It is common practice to evaluate the elastic constants Young`s- and shear
moduli using the material density and the propagation velocities of ultrasonic
longitudinal and shear waves. The velocities can be determined with an accuracy
better than 0.1%.'

I would like to know more about the time of flight measurement principle
which is used to measure the velocities.

Is the ultrasonic birefringence effect used? And how does this work?
What kind of ultrasonic signals are evaluated? Is a backwall echo needed
to measure the sound path travel time?

I have the article Ultrasonic Birefringence Effect
- Its Appplication for Materials Characterization.
E. Schneider in Optics and Laser Engineering 22 (1995) pp 305-323 (Elsevier) on
my desk, unfortunately it does not helps me much to understand this technique.

Especially from Mr. Schneider I would appreciate if he could bring some light
in this matter. Please contact me if I can help in supplying any image for
the explanation.

Rolf Diederichs



    
 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 301

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
301
08:56 Nov-07-1998
Re: Use of Ultrasonic Velocities for Materials Characterization

:
: 'Nondestructive Characterization of State and Properties of Aluminium Structures'
: In this article Eckhardt Schneider writes:
: 'It is common practice to evaluate the elastic constants Young`s- and shear
: moduli using the material density and the propagation velocities of ultrasonic
: longitudinal and shear waves. The velocities can be determined with an accuracy
: better than 0.1%.'

: I would like to know more about the time of flight measurement principle
: which is used to measure the velocities.

: Is the ultrasonic birefringence effect used? And how does this work?
: What kind of ultrasonic signals are evaluated? Is a backwall echo needed
: to measure the sound path travel time?

: I have the article Ultrasonic Birefringence Effect
: - Its Appplication for Materials Characterization.
: E. Schneider in Optics and Laser Engineering 22 (1995) pp 305-323 (Elsevier) on
: my desk, unfortunately it does not helps me much to understand this technique.

: Especially from Mr. Schneider I would appreciate if he could bring some light
: in this matter. Please contact me if I can help in supplying any image for
: the explanation.

: Rolf Diederichs

In reply to Rlof's enquiry, I can advise you that Resonance techniques are able to analyse the material characteristics of structures and also of small samples of structures.
These techniques use either a broad band (impulse) excitation and fourier transform to generate the spectrum, or else operate with a swept sine wave excitation principle.

You all know that the Elastic Properties affect the ultrasound velocities, so these techniques can compare the ultrasonic velocities from one component or structure to the next.
All modes of wave propagation can be generated with these techniques.

For more information, please feel free to contact me.

Regards,

Godfrey Hands


    
 
 Reply 
 
Eckhardt Schneider
Eckhardt Schneider
03:39 Nov-09-1998
Youngs Modulus and time-of-flight measurements

Dear Mr. Diederichs,

There are two possibilities to evaluate the elastic moduli by ultrasonic techniques.
a) the resonance technique,
b) the time-of flight technique.

I would like to concentrate on the time-of flight technique. The ultrasonic velocities are in first approximation given by the elastic constants Lambda and Mü (called the LAME-Constants) and/or the Shear and Young`s moduli and the density of the material.

Knowing the density and determining the velocities, the shear and the Young`s modulus can be evaluated according to well known formulas. The velocity is calculated from time-of-flight and path length data. There are some possibilities to measure the time-of-flight. The most often used ones are described in the attached copy from my contribution to V. HAUK: STRUCTURAL AND RESIDUAL STRESS ANALYSIS BY NONDESTRUCTIVE METHODS, ELSEVIER Amsterdam (1997) 522-563. (available through this message at http://www.ndt.net/wshop/forum/forum.htm or go direct to http://www.ndt.net/article/1198/forum/eschneid.htm)

Very precise velocity data can also be determined by the measurement of the time-of-flight of a longitudinal or shear wave propagating from the transmitter to the receiver in a surface layer.The time-of-flight is measured as function of the systematic change of the transmitter/receiver distance. The slope of the measured linear dependence gives you a very precise value for the velocity.

The birefringence occurs in materials with an elastic anisotropy. A linearely polarized shear wave vibrates linearely only if the directions of propagation and vibration are in the principal directions of the anisotropy. In all other cases, the wave vibrates elliptically, which can be described by the superposition of two wave parts, propagation in the same direction, but vibrating in one principal direction each. Different velocities of the wave parts result in a phase shift and in a more or less pronounced destructive interference.
The effect is named birefringence since there is the same effect in the optics.

Kind regards
Eckhardt



    
 
 Reply 
 
lauriston
lauriston
06:12 Sep-21-1999
Re: Use of Ultrasonic Velocities for Materials Characterization
:
: 'Nondestructive Characterization of State and Properties of Aluminium Structures'
: In this article Eckhardt Schneider writes:
: 'It is common practice to evaluate the elastic constants Young`s- and shear
: moduli using the material density and the propagation velocities of ultrasonic
: longitudinal and shear waves. The velocities can be determined with an accuracy
: better than 0.1%.'

: I would like to know more about the ultrasonic velocity in several types of rocks

: Is the ultrasonic birefringence effect used? And how does this work?
: What kind of ultrasonic signals are evaluated? Is a backwall echo needed
: to measure the sound path travel time?

: I have the article Ultrasonic Birefringence Effect
: - Its Appplication for Materials Characterization.
: E. Schneider in Optics and Laser Engineering 22 (1995) pp 305-323 (Elsevier) on
: my desk, unfortunately it does not helps me much to understand this technique.

: Especially from Mr. Schneider I would appreciate if he could bring some light
: in this matter. Please contact me if I can help in supplying any image for
: the explanation.

: Rolf Diederichs





    
 
 Reply 
 
Rolando Gonzalez-Peña
Rolando Gonzalez-Peña
04:40 Dec-08-2000
Asking for information
Dear Mr. Diederichs

I would want to ask you some questions can help me to find answers related to my PhD thesis. The main subject of my thesis is to prove possibilities of speckle interferometry technique as a non-destructive method to measure the displacement field in structural element such as shearwalls and building model. For this purpose I need to know if have you seen the modeling of structural elements such as shearwalls by optical techniques.

I also used an electronic speckle pattern interferometry to measure dynamic Young modulus in cementitious materials. In this experiment interferometry technique was combined with longitudinal resonance method to measure resonance frequency by using the quantities of fringe that appear over the specimen. Have American Concrete Institute and other committees reported the Young modulus measurements by optical techniques, for example: holographic technique and speckle interferometry technique? Could you comment the most important advantages and drawbacks that the ultrasonic method has when is used to measure the elastic modulus?

I will appreciate any opinion you can suggest me

Best regards

Prof. Rolando Gonzalez-Peña
Instituto Superior Politecnico Jose A Echeverria
Calle 127 s/n, Marianao CP 19390
Ciudad de La Habana, Cuba
e-mail:rglezp@electrica.ispjae.edu.cu
fax:53 7 272964




    
 
 Reply 
 

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