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Will my PA66 (Nylon) beam plastic deform?

  1. Dec 7, 2016 #1
    I have this model that required to be pressed vertically 1mm.
    I successfully displaced 1mm vertically with 30N of force.
    Unluckily, Von mises stress goes way beyond the yield strength.
    However, the strain is below the yield strain of 5%.
    I do not understand how ductile/flexible material like Nylon will plastic deform with 30N of force applied.
    Can someone explain to me if my model will plastic deform or not?
    Please help,
    Thank you
    Included the x_b file of the part model.
    model.PNG Displacement.PNG stress.PNG Strain.PNG

    Attached Files:

    Last edited: Dec 7, 2016
  2. jcsd
  3. Dec 7, 2016 #2


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    Have you done any evaluation of your problem using the classical analysis methods?
  4. Dec 7, 2016 #3
    I was not able to. I can only do evaluation of the straight beams....
  5. Dec 7, 2016 #4


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    your primary concern is the bending moment tensile stress at the base of the angle cantilevered section. For a start , resolve your force vector and treat the problem as a cantilever beam connected to the base.

    FEA is subject to a number of issues in its modelling, so it is important that you understand the basic principle elements of the force vectors and stress analysis that apply to the problem you are analyzing in order to evaluate the accuracy or its solutions.
  6. Dec 7, 2016 #5
    Two words.

    Fillet radius.
  7. Dec 8, 2016 #6


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    Gold Member

    I am with Chris. Add fillet radii wherever possible but particularly around the high stress areas and re-analyse it. I would go for a radius of 25% of the wall section to start with.
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