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August 2017 Newsletter

Identifying Foreign Object Debris

In the Metallurgical Laboratory, we often receive inquiries regarding our capability to identify FOD (Foreign Object Debris). FOD may be any foreign material introduced into an operating system which may cause damage during use. This article will attempt to clarify the small size capability and the methodology used for identification using Scanning Electron Microscopy (SEM), in conjunction with Energy Dispersive Spectroscopy (EDS). The example to the right shows a sample collected by a client and taped to a standard microscope glass slide. As can be seen, the collected particle is not clearly visible when examined using the unaided eye.

When examined at higher magnification using the Stereo Microscope the particle is now visible. Dimensional checks show the particle measures approximately 0.004 inches in width and is 0.015 inches in length. (Original magnification 15X).

 

 

 

In most cases the suspect particle is transferred to a special sample holder for examination using the Scanning Electron Microscope. Silver, conductive paint, is often used to attach the particle to the specimen holder. The particle can be analyzed using several methods. In the example at right, a reduced raster, free hand area was inscribed within the particle field of view. The resulting spectrographic analysis, shown below, indicates that this particular particle is composed of Aluminum. The high aluminum content would indicate the particle is a commercially pure aluminum grade, such as Aluminum Alloy 3003.

Another useful tool in the identification and evaluation of unknown particles is the production of a spectral map, which is shown below for the analyzed aluminum FOD sample.  This analytical feature uses collected spectral data to be transformed into color coded maps which show how each element is distributed within the field of view. This is helpful when a group of collected debris samples is composed of several different materials.

If you have concerns about foreign object debris, call our Metallurgical staff at 937-298-9390.  They would be happy to discuss your situation and help you devise a solution.