Spring 2008, MET 415 - FEA Applications I

Prof. Dave Johnson, dhj1@psu.edu, Penn State - Erie, The Behrend College

3D SHELL ELEMENTS

HW-8B Summary: 

What is the BEST model ? [2D Plane Stress (PLANE183 w/thickness)]

Imprint Faces or Cut/Slice Bodies to create features for loading (load patch) AND for reporting results

If ½ symmetry 3D model is used – must cut load in half.

Need selecting/scoping to exclude singularity (point load) 

HW-9A Summary:

Physically, a shell element is a surface with no thickness (like a Pro/E “quilt” ?).  We define the thickness as a constant data value, not as a measurable distance between “top” and “bottom” faces.

 We see apparent thickness as a graphical feature – PowerGraphics makes the mesh seem thick using the thickness value we defined.  We see the maximum stress on each apparent face of the shell.

 When PowerGraphics is NOT used – the model shows NO thickness – stress results are shown based on the SHELL command setting (TOP / MID / BOTTOM).  We cannot see both the TOP and BOTTOM face stress in the same plot because the graphical thickness is not available.

 MESH ERROR: Is 10% OK ?

• [NO - high stress occurs at high error location]
• Shells meet at an angle.  Could be “warped” slightly in rounds.

HW-9B Concepts:

 2D planar or 3D Solid or 3D shell ?

• [2D plane stress or 3D shell, not 3D solid]
• S.A./t = (125mm)(50mm)/2mm = 3215

 A rectangle split into 2 bodies, but still one part ?  (Cut or Imprint Faces)

Use of a coordinate system ? (placement & reference for results)