Some Optical Methods of Characterizing Solid and Particulate Materials During Manufacturing Processes

  • F. Alan Wedgwood


Non destructive Testing is usually seen as an end-of-process quality control step. It is becoming apparent however that inspection should be carried out as early as possible in the process. In this paper two methods of non-invasive measurement using lasers will be described. Since they are non-invasive these measurements can be made on hot or fast moving materials and hence at an early stage in some manufacturing processes.

The first method is generation and detection of ultrasound in solids. This can be used for measuring grain scattering and attenuation of ultrasound using lasers of moderate power. Applications include measurement of grain size in metals during rolling operations and monitoring during welding.

The second method is optical sizing of particles or droplets in a gas stream. Instrumentation has been refined so that a wide range of particle sizes and types can be measured. Applications to powder metallurgy, plasma spraying, spray drying and paint spraying will be described. In the last example the philosophy of this sort of measurement is discussed. In application to paint spray quality control it was found that the economical solution in practice is to develop an accurate model using the optical measurements for validation and use the model, with cheaper on-line measurements, for process control.


Laser Doppler Anemometry Ultrasonic Attenuation Quality Control Step Spray Booth Paint Finish 
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Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • F. Alan Wedgwood
    • 1
  1. 1.AERE Harwell, DidcotNational NDT CentreOxonEngland

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