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Crack width in mortar sample


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 I am researching crack width in reinforce mortar with carbon fiber samples.  I'm straggling mapping the thickness of the cracks. It microscopic cracks.  I wonder if with the photo resolution I use is enough? I have attached an enlargement of the crack in the software GOM. I would really appreciate if someone can answer me. I attached one the original photo that im import to the analysis and enlargement with "zoom in" for you to see the quality of the crack and if I can measure the width.

DIC zoom crack.JPG

IMG_0003.JPG

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Hi Yarden,

the resolution of your surface could be higher to measure more detail. You are losing a lot of pixel because you also measuring the area wide next to your specimen. I would recommend to rotate the camera through 90° and get closer. You are increasing the amount of pixel on your surface and so you can be more precise during the inspection. 

The next point you can improve is the stochastic pattern itself. If you get closer to your surface with your camera you need a finer pattern. You do have a good pattern style on the left side slightly under the middle space (s.attachment). 

I hope this input can help you to reach your measuring goal. 

Greetings, Ivan

 

IMG_0003.JPG.6c9485b7b6016fa1280e37ad31944ac5.jpg

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 already mentioned some ideas, how to improve your measurement in general.

But as much as I see, you are interested in crack width evaluation, too. So I just want to add a possible workflow for that.

The strain values will only provide an idea where cracks are and do represent the crack width only indirectly by the strain reference length. So if you assume there is no strain left in the mortar material itself after cracks happened, you can get an estimation about crack width by these two workflows:

  1. Check the surface component for "Displacement Y".
    1. Apply a "Rigid Body Motion Compensation" (RBMC) to the lower part of the specimen where no crack happened.
      1. Select such an area of your surface component.
      2. Create as Component Region ("OPERATIONS -> Component -> Component Region...")
      3. Apply the RBMC to this Component Region ("OPERATIONS -> Alignement -> Rigid Body Motion Compensation -> Transform By Component..." and select the Component Region).
    2. Create a Section perpendicular to the X-Axis through the Surface Component (Select all points of the Surface Component, "CONSTRUCT -> Section -> Single Section... -> Reference plane: Plane X, Position: ...").
    3. Check this section for "Displacement Y".
    4. Switch on the diagram
    5. Interpret the step height as crack width. / Relate it to the noise and average height of the values in the "undeformed" areas.
  2. Check the distance changes of the "undeformed" areas between cracks.
    1. Create two sections perpendicular to the Y-Axis through the Surface Component in "undeformed" areas between cracks - one on each side of a crack. (Select all points of the Surface Component, "CONSTRUCT -> Section -> Single Section... -> Reference plane: Plane Y, Position: ...")
    2. Create a Continuous Curve Distance element ("CONSTRUCT -> Distance -> Continuous Curve Distance..." and select the two sections on both sides of the crack)
    3. Check this element for Distance (or Distance Y).
    4. Switch on the diagram
    5. Interpret the Distance values as crack width. / Relate it to the noise and average height of the values.

I would expect an crack width accuracy of 0.1 Pixel with your images. So as the cracks are visible in the images I suggest they have an overall width in the range of 1-2 Pixel. With the improvements suggested by

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you can reach an accuracy in the range of 0.02..0.05 Pixel.

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