General Mechanical

General Mechanical

Contact normal and FKT value

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    • alen_malagic

      I am modelling a pull-out test of the self-tapping screw, Figure 1. The wood is modelled with SHELL 181 elements and screw with BEAM 188 elements. The contact is defined as bonded with CONTA 175 and TARGET 170. Contact-force based model of the connection is defined.

      I calibrated the deformation of the screw in Y direction with the test result by modifying the value of FKT (tangential spring stiffness) and I obtained satisfactory results. However I need to define for some other analyses the stiffness between wood and screw in X-direction at that value is different to one in Y direction.

      This is where it starts to be complicated. I would like to define different connection stiffnesses between wood and screw in X and Y direction, however both directions are in Ansys regarded as tangential directions and therefore only one value of FKT can be used leading to same stiffnesses in X and Y which I don’t want. The normal direction doesn’t help as FKN is out of the plane in Z-axis where I don’t have any deformations.

      My question is following: If it is possible somehow to define the different FKT values for different directions in my case? Alternatively, is it possible to reorient the normal of the contact so the normal is for example in X-direction and then the FKN value defines stiffness in X-direction, while FKT value is defined in that case for Y-direction, leading to different stiffnesses.

      Thank You very much!!

      Best regards,


    • TomPhemmy
      what you are looking for is called orthotropic friction. ANSYS has this. and it allows you to define two tangential contact stiffness. You should have a look at the Mechanical APDL Theory Reference under the section on Contact Algorithms. I have not used this before so I cannot say more. Hopefully, someone who has can give you precise details.

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