General Mechanical

General Mechanical

Large plastic strain during collapse in 3 point bending simulation

    • DanielLavayen

      Hello everyone,


      I am having some troubles analyzing the collapse of a hollow square tube in a 3 point bending test simulation. Even though I obtain a F-u curve quite close to the expected curve (theoretical and experimental). I have found some points that suffer from excesive plastic strain. Some of them have 1.1 and even -1.1 plastic strain in all directions. Those points are the ones in contact with the rigid force applicator. Also, the point where the collapse occurs, also suffers this large plastic deformations. 

      I used solid185 elements for the tube, with little fillets (if i dont use fillets, the problem is more severe) and conta174 elements for contacts and targe169 elements to model the supports and force applicator (as cylinders). 

      I tried the ERESX,NO option to avoid stress above the limit, I have also tried changing to enhanced strain formulation and simplified enhanced strain formulation (however this two last options have problems converging). 

      How can i decrease this extremely high plastic deformations? I tried several mesh sizes but have the same issues at the end. Below there are some screenshots of the problem at hand.

      Here is the general scheme of the test

      General scheme of the test, the central cylinder is the force applicator

      A detail of the mesh used

      detailed mesh

      A cross section of the mesh

      cross section of the mesh

      Plastic deformation in the x-direction. Notice the point with high plastic deformation

      x richtung dehnung

      von Mises plastic deformation... excesive in one point in the middle

      vm dehnung


      Thanks in advance for your help!

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