General Mechanical

General Mechanical

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no convergence due to screw preload

    • Julian Frankl
      Subscriber

      Hello,

      I want to analyze an aluminum casting housing for my thesis that is subjected to internal pressure. The assembly consists of seven components, all connected through a cylindrical surface and an end face. All fasteners are designed as blind holes, so there are no nuts involved.

       

      The geometry was created in Inventor and imported into Ansys as a STEP file. The cast parts are connected to each other through cylindrical and end surfaces and defined as frictional. The screws are simplified as cylinders (screw head, shaft, and thread). The threaded surface is connected to the housing as a bonded contact, and the screw head surface is also bonded to the casting part. The housing is fixed using a cylindrical support and a rigid support at the attachment points.

       

      I applied the preload force on the shaft, without any contacts or constraints on the surface. When I apply pressure to the inside of the housing, I obtain a solution. However, when I add the preload to the screws, the calculation stops at 17% and restarts. Ansys aborts the calculation after about 45 minutes. It doesn't make a difference whether I apply the preload in one load step or two load steps (first step: preload, second step: pressure with preload locked).

       

      Thank you!

       

    • Akshay Maniyar
      Ansys Employee

      Hi Julian,

      Can you share the error message that you are getting? Also, check for initial contact information and paste the screenshot of it.

      Thank you,

      Akshay Maniyar

    • Julian Frankl
      Subscriber

      Hello,

      thank you very much for the response.

    • Akshay Maniyar
      Ansys Employee

      Hi Julian,

      Thanks for the screenshots. Can you check the Newton-Raphson residual plots and find out which are the problematic locations? Also, from the above screenshots it looks like you have some contacts with far open status. Please check those contacts and make sure that the pinball radius is big enough so that contact is detected.

      Thanks,

      Akshay Maniyar

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