General Mechanical

General Mechanical

Recommendations on the behaviour of my simulated data

    • kirstenbraun
      Subscriber

      Hello all,

      My thesis is based on the modelling a light agricultural tyre. In my simulations I am subjecting the inside of the tyre to either a 2Bar or 0.8Bar as well as am applying a remote displacement to a road surface which is moved towards the tyre to cause tyre deformation.

      I am trying to understand what the smulation is doing but cannot understand where I am going wrong. Below I have attached my results, the solid lines represent the exisitng data that I am trying to match, and the dotted lines represent some of the simulations I have run. At this point in time I have only simulated a 2Bar, 0 camber as well as a 0.8Bar, 0camber case.

      I have two issues:

      1. As the stiffness of the tyre is determined by the slope of the lins in the figure below, I tried adjusting the Young's Modulus to relax the stiffness of the tyre however found that with a decrease in the Young's Modulus the stiffness increases which is the opposite effect that is expected
      2. The model fairly estimates the tyres behavour for 20mm for the 2Bar case and around 30mm for the 0.8Bar case, however there after for both simulations the data points exponentially increase.

      Can anyone make sence of these behaviours?

      Thank you in advance

    • Karthik R
      Administrator
      Hello,nCould you please clarify the tool you are using? Is it Ansys Mechanical?nThanks.nKarthikn
    • kirstenbraun
      Subscriber
      As you can see in the figure, when removing the belt of the tyre and making it the same material as the tyre tread, the stiffness of the tyre increases which indects that something is happening in the physics that is causing the opposite expected behaviour.nThe following are the connections. The frictional contact has a friction coefficient of 0.64 which is the frictional coefficient between rubber (tyre tread) and stainless steel (road).nThe origin of the model sits at [x, y, z] = [0, 0, 0]mm and is at the center of the tyre:nTo ensure that the tyre rim is treated as static the displacement [x, y, z] = [0, 0, 0]mm as follows is applied to the faces of the sidewalls which come in contact with the rim:nThe internal pressure as said before is applied to the internal surface of the tyre. The image below is a section of the tyre, just so you can see on which surfaces the pressure is applied to.nAnd a remote displacement is applied to the road surface along the tyre-road interface:nAs I have the vertial force-displacement curve of the experimentally tested tyre I can input the vertical displacement value and thoguh using a force reaction probe and a deformation probe I can collect the vertical force and displacement that my model experiences.nThe force reaction probe:nwhere the Coordinate System is as follows:nThe defomration probe then sits at the same point as the force reaction probe:nPlease let me know if there is any other information that you might need.n
    • kirstenbraun
      Subscriber
      Appologies, yes it is ANSYS Mechanical Karthikn
    • Karthik R
      Administrator
      Thank you for the quick response. I'm moving your post to the 'Structures' Category for better alignment.nKarthikn
    • SaiD
      Ansys Employee
      Hi,nBased on your description, it looks like the simulation results are stiffer than the experimental results. I can think of a couple possible reasons:nThe mesh may not be fine enough. Have you tried to do mesh refinement studies to see whether the mesh is actually fine enough?nThe boundary condition of (0,0,0) on the surfaces that come in contact with the rim might be somewhat of an overconstraint. May be a cylindrical support would be a better boundary condition?nI am still not sure why decreasing the Young's modulus of the material would lead to a stiffer response, but may be trying out the above two things would provide some clues.nnSai n
    • kirstenbraun
      Subscriber
      HelloArray, nThank you for the recommendations, I have implemented them both and found the following:nMesh refinement:Though refining the mesh, the simulation was able to solve in around the same amount of time, but had almost no affect on the results.nCylindrical support:As the region of the sidewall which is in contact with the rim is not a cylinder (as shown in the image below) no matter what my selection (face or line) the support does not work. I have tried replacing the displacement [x, y, z] = [0, 0, 0], as previously mentioned, with a remote displacement where all X, Y and Z components and X, Y and Z rotations are set to zero (as shown in image below). Changing to a remote displacement just increased the solving time and ended up not solving.nI have also tried setting the integration method to Reduced but found that the results were exactly the same. nDo you have any other recommendations?nThank youn
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