General Mechanical

General Mechanical

The stress on F&D head is extremely high in ANSYS Workbench as compared to ASME VIII Div-1.

    • Sachinpdl
      Subscriber

      Issue: The stress on F&D head is extremely high in ANSYS Workbench as compared to ASME VIII Div-1 calculation.

      Vessel OD: 96”, 106” Seam-Seam

      Thickness: 0.4375”

      Pressure: 105 psi

      Material: SA-24 316L

      I did ANSYS analysis for F&D (ASME 80:10) head. The obtained Eq. stress was 35,000 psi (Membrane stress: 25k) which is extremely high as compared to code calculation. Code calculation gives 14,000 psi.

      I performed a similar comparison with the 2:1 Ellipsoidal head. The ANSYS Eq. Stress was 18,000 psi (Membrane Stress: 12,000 psi). This is close to code calculation, code calculation gives 11,500 psi stress.

      Also, there was high stress (30k psi) in SUPPORT LEG for the F&D head and just 9k in the ellipsoidal head.

      The setup and procedure of analysis were the same for F&D and Ellipsoidal head but there was a high deviation from the code calculation in the case of F&D head while analysis of Ellipsoidal head is in line with code calculation.

      PS: I have ignored stress concentrated at a point due to singularity.

    • 1shan
      Ansys Employee
      Have you done a mesh convergence study for both the cases? Not sure but there seems to be a discontinuity in the the stress contour (marked below)? Could you check the mesh connectivity in this region? you could use a virtual topology object to make sure that the mesh is conformal.
      Regards Ishan.
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