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00:48 Sep-11-2001
Rayleigh waves

I want to establish a system that can measure grain size by rayleigh waves.
Is there anybody that help me, how can I measure grain size by this way and
how can establish that experiment setup.
thanks for your helps.

01:00 Sep-11-2001
Re: Rayleigh waves

Very interesting. Rayleigh waves are very popular in geophysical/geotechnical testing
(SASW method).
Grain size: R. Chammas (of French streets and bridges authority)
has done FE modelling on the influence of inclusions
on surface waves (rabih.chammas@lcps.fr).
Please keep me informed!

01:24 Sep-12-2001
Re: Rayleigh waves

I have been working with Fallon Ultrasonics, Inc. on methods to deduce residual stresses from elastic wave velocity measurements. As part of this work, I have used Rayleigh wave ( relatively insensitive to stress) and critically refracted longitudinal wave (much more sensitive to stress) velocities (actually, travel times). These waves have been generated using focused ultrasonic beams like those generated by spherically and cylindrically focused ultrasonic transducers, by plastic wedges of an appropriate angle and by plane waves at an angle to the specimen surface in a water bath. Each of these methods has one or more advantages over the others. In all cases of practical alloys that we have studied, grain scattering is the material parameter that limits the highest frequency that can be used. We have not yet done much quantitative work with respect to determining grain size but it is very clear that the attenuation of these waves is strongly influenced by grain scattering at higher frequencies (as expected) and that this attenuation can be measured with relative ease. There are several corrections that must be made to the measured attenuation in order to obtain the grain scattering term which can be used to deduce the "mean" grain diameter in the region of material being sampled by the elastic wave. If you care to let me know the material and grain size range that is of interest to you, I can give you some general idea of the magnitude of effort that will be required.