• Question: What kind of damage is visible under a microscope?

    Asked by anon-74126 to Martin on 27 Apr 2020.
    • Photo: Martin Jones

      Martin Jones answered on 27 Apr 2020:

      Hi Daisy

      We have different types of microscope for looking at different types of damage. Normally, we use a simple one which can magnify from 0.8 times normal size to around 16 times normal size. This microscope has a camera attached to it. We use it to take photos of any damage we see.

      The parts that we look at are similar in size to small lego pieces, about 1cm. It could be a spring, a screw, ball or other small parts.

      The damage we would look for with this microscope is wear, from parts moving against each other (one part will normally be harder than the other that it is moving against, and generally the softer one wears). We want to see what the wear looks like, how much material has been removed, whether there are any deep scratches (by deep I’m talking about 0.01mm)

      We also have some more complex microscopes that are computer controlled, and can take measurements of any damage that is seen. One of them can magnify up to 1000 times. These are used for more detailed analysis, when we can to see the exact size and shape of any wear, normally if that wear is unusual, we can then take measurement and figure out how it has happened, to help decide how to fix it.

      Other types of damage (apart from wear) that we would use the more complex microscopes for would be:
      – cracks in the surface of the parts
      – rust/corrosion
      – small bits of material being removed from the surface

Comments

  • Photo: anon-74126

    anon-74126 commented on :

    How interesting! Do the microscopes you use have a high resolution?

  • Photo: Martin

    Martin commented on :

    Hi Daisy
    The basic one with the camera on it has a 3 mega pixel camera: https://www.leica-microsystems.com/products/microscope-cameras/p/leica-dfc295/gallery/
    The last photo here is similar to how we have it set up. We’ll use the eye pieces to inspect the parts first, then the camera/computer to take some photos.

    For the more specialised ones the way they work is a bit different. https://www.alicona.com/en/products/infinitefocus/

    They use software to take pictures from above at different distances, and build up a 3D model.
    The focus of the picture is always at the same distance from the lens, so if you have something that is flat, with a dent in it, and focus on the bottom of the dent, then the rest of the surface will not be in focus. So the microscope will take lots of pictures at different heights, and automatically build up the picture so all of the in-focus parts are stitched together.
    I would set the top and bottom limits for the pictures, and set how high each step should be, for example a standard set-up would have a range of about 0.5mm, with a resolution of 100-200nm (nanometres), so 5000-10000 pictures stiched together.