Picking an element type for FEA

[mattyboson12]

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?

 

[Mech_Engineer]

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.

 

[mattyboson12]

Thank you