
1646 views  Technical Discussions   Nathan
 Nathan
 11:40 Jan272009 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  
   Michel Couture NDT Inspector, consultant, Canada, Joined Sep 2006, ^{893}   12:56 Jan272009 Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation... In Reply to Nathan at 11:40 Jan272009 (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.ndted.org/EducationResources/CommunityCollege/Ultrasonics/Reference%20Information/UT/ut_matlprop_metals.htm
Cheerio's  
   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 Jan272009 Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation... In Reply to Nathan at 11:40 Jan272009 (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  
   Richard Freemantle NDT Inspector, Consultant, R&D Wavelength NDT Limited, United Kingdom, Joined Nov 1998, ^{16}   15:09 Jan272009 Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation... In Reply to Thomas Vogt at 14:38 Jan272009 .
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  
   James Barshinger Engineering General Electric Global Research Center, USA, Joined Aug 2000, ^{8}   17:58 Jan272009 Re: ULTRASONICS: Shear/Longitudinal Velocity Calculation... In Reply to Richard Freemantle at 15:09 Jan272009 .
The equation relating shear velocity to longitudinal velocity is CT=CL*sqrt((12u)/(2(1u))) where u=Poisson's ratio.
Jim  
  
