General Mechanical

General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

Static structural problem in Hip implant simulation.. “Internal solution… “

    • Abhijeet Chilwirwar
      Subscriber

      I have been trying to simulate a hip implant in Ansys WB but I am constantly getting same errors. I have many similar discussions on this portal, some were relevant I tried them but nothing worked. I am applying compressive load of 2.3 kN on a hip implant placed inside an acrylic cement everything supported by a SS holder. No meshing error is been shown but solution is the same "An Internal solution magnitude limit wasexceeded. Please check your environment for inapppropriate load values or insufficient supports." And point to note is that when I am applying load using global co-ordinate axis then position of force arrow is corrrect but when I am using a different co-ordinate system (which is required) then the location of force arrow gets changed(since I am using the same face to define the remote force in both the co-ordinate axis the point of location of arrow should be same). Because of this reason I had to use pressure as a load.

      Help me with this. Attaching some relevant photos. Thanking you.

    • Akshay Maniyar
      Ansys Employee

      Hi Abhijeet,

      As per the error message you are getting, it looks like you are facing rigid body motion. Can you check the initial contact information by inserting the contact tool and see if any contact status is near open or far open. If you have contact with some gap, try using a small contact stabilization factor(0.05 or 0.1) or change the interface treatment to 'Adjust to touch'. Also, check the below AIC course for more details on preventing rigid body motion.

      https://courses.ansys.com/index.php/courses/prevent-rigid-body-motion-in-contact/

      Thank you,

      Akshay Maniyar

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    • Abhijeet Chilwirwar
      Subscriber

      I had already used the 'Adjust to touch'.. but the simulation was running when I constrained the upper plate and restricted its movement in X AND Z direction. But I saw that the femoral head was penetrating into the upper curved plate. Only one error was there which read:

       

      Then I did what was given in the error. I switched the large deformation as 'OFF' then I rerun the simulation but there was no change, the penetration between curved plate and femoral head is still there. It seems that the results are fine but can you confirm that.

    • Akshay Maniyar
      Ansys Employee

      Hi Abhijeet,

      For more details about the warning message, you can refer to the below link.

      https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/wb_sim/ds_Large_Deformation_Effects.html?q=large%20deformation%20effects%20are%20active

      As per the deformation plots, it looks like the penetration is because of the scale factor which you have used. You can change it to 'True scale' and then check if it looks correct or not.

      Thank you,

      Akshay Maniyar

      How to access Ansys help links

      Guidelines for Posting on Ansys Learning Forum

       

    • Abhijeet Chilwirwar
      Subscriber

      Hi Akshay,

      Thanks for the swift reply. I used the 'True scale' option and the penetration problem is solved. The deformation is in limits now.

      Actually I am trying to topology optimize the implant. I am getting these error about non-linearity in the problem so it's not running the optimization problem. The curved plate and femoral head have a frictional value of 0.3. The geometries are non linear and large deformations is turned off. I feel the frictional contact is making the problem non-linear.

      Below is my optimization region:

    • Akshay Maniyar
      Ansys Employee

      Hi Abhijeet,

      Thanks for the update. It is great that your initial issue got solved. Can you start a new post for the topology optimization problem? So it will be helpful for other users with similar issues. 

      Thank you,

      Akshay Maniyar

      How to access Ansys help links

      Guidelines for Posting on Ansys Learning Forum

       

    • Abhijeet Chilwirwar
      Subscriber

      Thanks Akshay. Yes I will do the same. 

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