Define a Simple 3D Element

Description

• This example explains Continuity’s convention for interpreting element definitions and then guides the user through a simple exercise to check understanding.

• The cont6 file contains all data and parameters for this problem.3delem.cont6

Understanding the Continuity Element Definition Convention

• An element definition tells Continuity how to connect nodes to one another to form elements

• The element definition is entered into the Elements Form as global node numbers separated by commas

  • A 1D element consists of 2 nodes, so an example of a 1D element definition is: 11,14

  • A 2D element consists of 4 nodes, so an example of a 2D element definition is: 11,14,18,19

  • A 3D element consists of 8 nodes, so an example of a 3D element definition is: 11,14,18,19,21,23,27,29

• The order in which the global node numbers are listed determines how nodes are connected

• The significance of this order is explained by the convention below, which is specific to Continuity and has no particular meaning outside of it.

  

• Study the following example:
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Try it for yourself

• Now that you’ve seen a few examples, try it for yourself in Continuity. A set of eight nodes has already been set up for you with GLOBAL element numbering that looks like this:

• Follow the step-by-step instructions below to load the nodes into Continuity, then try your hand at defining an element

Start Continuity

• Launch the Continuity 6.3 Client

• On the About Continuity 6.3 startup screen

  • check the Mesh module box under Use Modules:

Create Mesh

• Mesh→Edit→Coordinates…

  • Select rectangular cartesian in the Global Coordinates: pop-up menu

  • Click OK to submit Coordinate Form

• Mesh→Edit→Basis…

  • Choose Lagrange Basis Function→3D→Linear-Linear-Linear with 3 integration/collocation points for Xi 1, Xi 2, and Xi 3

  • Click Add

  • Click OK to submit Basis Form

• Mesh→Edit→Nodes…

  • Click Import/Export/Graph button to open Continuity Table Manager

    • Continuity Table Manager→File→Open…

      • Select tab-delimited nodes file attachment:nodes.xls

      • Continuity Table Manager→File→Close and update form

  • Select Linear-Linear-Linear Lagrange 3*3*3 under Coordinate 1, Coordinate 2, and Coordinate 3

  • Click OK to submit Node Form

• Mesh→Edit→Elements…

  • At this point, follow the step-by-step example at the top of this page for defining an element, BUT note that the global element numbering is different.

    • Note that for step 1, you may choose ANY node to be your element origin
    • Also note that for step 2, you may choose ANY of the nodes connected to your element origin to define Xi 1

  • Click OK to submit Element Form

Render the Result

• File→Send

• Mesh→Calculate Mesh…

• Mesh→Render→Elements…

  • Click the lines radio button

  • Click Render to display mesh lines

• The rendered element should look something like this (after zooming and rotating appropriately):

• If the element lines look jumbled or wrong, you’ve made a mistake in your ordering. Re-open the elements form and try it again.

  • Once you’ve clicked OK in the elements form, you’ll have to repeat the steps under Render Results to see the change.