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Technical Discussions
Nathan
Nathan
11:40 Jan-27-2009
ULTRASONICS: Shear/Longitudinal Velocity Calculation...

Hi Guys...

What is the calculation to work out the shear wave velocity of a material, if you know the transverse velocity? I know it's approximately half, but is there a formula(e) to work it out?

Hope you can help?

Nathan

    
 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 847

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
847
12:56 Jan-27-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Nathan at 11:40 Jan-27-2009 (Opening).

Nathan,

The link below will bring you the Table of Materials Properties for UT inspection. Another source is the Metal's Handbook from the American Society of Materials.

http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/Reference%20Information/UT/ut_matlprop_metals.htm

Cheerio's

    
 
 Reply 
 
Thomas Vogt
R & D, - -
Guided Ultrasonics Ltd, United Kingdom, Joined Apr 2007, 22

Thomas Vogt

R & D, - -
Guided Ultrasonics Ltd,
United Kingdom,
Joined Apr 2007
22
14:38 Jan-27-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Nathan at 11:40 Jan-27-2009 (Opening).

Nathan,

I think you mean longitudinal instead of transverse, but nevertheless, the first thing to realize is that the shear and longitudinal velocities of a material are entirely independent. Together with the density they define the elastic properties of a material, so you cannot work one out purely from the other. You have to look it up in the table as Michel suggested.

However, you can derive a lower (theoretical) limit for the longitudinal velocity: The longitudinal velocity must be greater than the shear velocity times the square root of 2 [in a formula: v_l > v_s*sqrt(2)].

Hope this helps,
Tom

    
 
 Reply 
 
Richard Freemantle
NDT Inspector, Consultant, R&D
Wavelength NDT Limited, United Kingdom, Joined Nov 1998, 16

Richard Freemantle

NDT Inspector, Consultant, R&D
Wavelength NDT Limited,
United Kingdom,
Joined Nov 1998
16
15:09 Jan-27-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Thomas Vogt at 14:38 Jan-27-2009 .

Hi,

Just to add to Tom's comments, as far as I remember the longitudinal velocity can be directly related to the shear velocity provided you know the Poisson's ratio for the material. Do you have this value for the materials you are interested in ? If so I can try and dig out the equation for you !

Hope this helps,

Regards,

Richard

    
 
 Reply 
 
James Barshinger
Engineering
General Electric Global Research Center, USA, Joined Aug 2000, 8

James Barshinger

Engineering
General Electric Global Research Center,
USA,
Joined Aug 2000
8
17:58 Jan-27-2009
Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation...
In Reply to Richard Freemantle at 15:09 Jan-27-2009 .

The equation relating shear velocity to longitudinal velocity is CT=CL*sqrt((1-2u)/(2(1-u))) where u=Poisson's ratio.

-Jim

    
 
 Reply 
 

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