Picking an element type for FEA

  • #1

Main Question or Discussion Point

When choosing between a 2D 4-node quadrilateral element and 8-node for FEA stress analysis, why is the 8 node option preferred? I understand it has much more flexibility with different shapes due to the central mid node but are there any other reasons?
 

Answers and Replies

  • #2
Mech_Engineer
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This article gives a useful practical overview of mid-side node elements for stress calculation in ANSYS: http://www.padtinc.com/blog/the-focus/mid-side-nodes-do-they-really-help

The advantages of elements with mid-side nodes are two fold:
  1. The sides of the element can better follow curved or non-uniform surface geometries
  2. Straight-sided (a.k.a. linear) elements only have two elements along any edge, so only linear interpolation is available between the nodes; if mesh density is limited, this can become a problem. FEA elements with mid-side nodes along each side allow for order (n-1) interpolation, so in the case of an element with single mid-side nodes (3 nodes per edge), 2nd-order quadratic interpolation is possible between nodes which in some cases results in smoother stress calculations.
 
  • #3
Thank you
 

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