Description: The Naval Research Laboratory (NRL) has developed a metrology workbench for the measurement and visualization of displacement and strain fields in three dimensions. The NRL workbench uses two or more cameras to image a specimen and includes custom software the implements the 3D Meshless Random Grid method. A random pattern of optically distinct dots is applied on the specimen surface. This procedure greatly reduces specimen preparation time compared to other optical methods. With the help of the software, the dots are indentified, tracked, and their displacement is computed as the specimen deforms under various loads. Additionally, optically distinct intrinsic features of the specimen surface can be tracked, allowing for remote measurement of deforming objects in various length scales including the nanoscale. In contrast to the Pure Grid Method (PGM), a uniform grid on the surface of the sample is not required, simplifying set-up and allowing the test and measurement of irregularly shaped objects. The NRL method is both faster and more accurate when compared to Digital Image Correlation (DIC) techniques. Other features of the software include: choice of any number of gauge points, optional calculation of advanced deformation measures, automated detection of convex and non-convex domain geometries, time-domain filtering, import/export capabilities, scripting interface, and multi-operating system capability.

Advantages/Features Include:

  • Greatly increased speed and accuracy in measurements compared to DIC and PGM
  • Ability to measure displacement and strain on any scale, including nanoscale
  • Uses ordinary digital cameras with no requirements for additional hardware or complicated set-up

Applications Include:

  • Experimental mechanics applications
  • Material characterization
  • Remote sensing
  • Reverse engineering
  • Quality Control
  • Nanoscale engineering
  • Non-contact metrology
  • Finite Element Analysis validation

References:

  • "A Computational Workbench for Remote Full Field 2D Displacement and Strain Measurements," ASME, IDETC/CIE, August 30 - September 2, 2009, San Diego, CA, USA.
  • "Performance Sensitivity Analysis of the Mesh-Free Random Grid Method for Whole Field Strain Measurements," ASME, IDETC/CIE, August 3 - 6, 2008, Brooklyn, NY, USA.
  • "A Computational Workbench for Remote Full Field 3D Displacement and Strain Measurements," ASME, August 28 - 31, 2011, Washington, DC, USA.

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