Difference between revisions of "SRAS for materials characterisation"

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To measure the acoustic spectrum at each point on the sample a fixed grating is illuminated with a short laser pulse (typically ~1ns). As the laser pulse contains a broad range of frequencies, only the frequencies which match the grating spacing and acoustic velocity of that sample point will be generated. We measure the waves that have been generated close to the excitation region (see top figure). We can then calculate the frequencies generated and with the knowledge of the grating spacing we can obtain the acoustic velocity using v = fλ. If the sample is raster scanned we build up a detailed image of the sample velocity for that propagation direction. These images show the grain structure of the material and are very useful for material scientists for assessing the properties of the material.
 
To measure the acoustic spectrum at each point on the sample a fixed grating is illuminated with a short laser pulse (typically ~1ns). As the laser pulse contains a broad range of frequencies, only the frequencies which match the grating spacing and acoustic velocity of that sample point will be generated. We measure the waves that have been generated close to the excitation region (see top figure). We can then calculate the frequencies generated and with the knowledge of the grating spacing we can obtain the acoustic velocity using v = fλ. If the sample is raster scanned we build up a detailed image of the sample velocity for that propagation direction. These images show the grain structure of the material and are very useful for material scientists for assessing the properties of the material.
  
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==EMDA Sponsored Instrument==
 
==EMDA Sponsored Instrument==
  
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==From Velocity to Orientation==
 
==From Velocity to Orientation==
  

Revision as of 08:36, 5 April 2011

Whats is SRAS

SRAS System.PNG

SRAS stands for Spatially Resolved Acoustic Spectroscopy, it is a technique for mapping the surface acoustic wave velocity of a material. The technique is analogous to optical spectroscopy techniques where analysis of the optical spectrum and the wavelengths that are most readily transmitted or absorbed tells us some properties of the sample being examined. In the acoustic sense we monitor the spectrum of sound waves emitted from a grating source. The technique can be performed two ways, the first is to use a fixed frequency source and sweep the grating spacing or the grating period can be fixed and the frequency is swept.

SRAS 300dpi emda sras.png
SRAS 300dpi sras austenitic ss.png

To measure the acoustic spectrum at each point on the sample a fixed grating is illuminated with a short laser pulse (typically ~1ns). As the laser pulse contains a broad range of frequencies, only the frequencies which match the grating spacing and acoustic velocity of that sample point will be generated. We measure the waves that have been generated close to the excitation region (see top figure). We can then calculate the frequencies generated and with the knowledge of the grating spacing we can obtain the acoustic velocity using v = fλ. If the sample is raster scanned we build up a detailed image of the sample velocity for that propagation direction. These images show the grain structure of the material and are very useful for material scientists for assessing the properties of the material.


EMDA Sponsored Instrument

SRAS 300dpi al 011 111.png
SRAS 300dpi nickel 001 011 111.png



From Velocity to Orientation

History of the technique

Related publications