How and When to Use Midside Nodes
Some element types have optional configurations that include midside nodes. Using midside nodes
provides greater accuracy at the cost of increased processing time and resources.
Midside nodes are available with the following element types:
- linear brick elements
- linear tetrahedral elements
- nonlinear 2-D elements
- nonlinear brick elements
- nonlinear shell elements
- nonlinear 2-D hydrodynamic elements
- nonlinear 3-D hydrodynamic elements
- nonlinear tetrahedral elements
- nonlinear 2-D kinematic elements
- nonlinear 3-D kinematic elements
- nonlinear membrane elements
- heat transfer tetrahedral elements
- electrostatic tetrahedral elements
In general, midside nodes should be used when results can vary significantly over a single element.
Some applications where midside nodes can be beneficial include the following:
- Flexible-element models (made of 2-D, brick, shell or
tetrahedral elements) that are expected to experience bending require midside nodes.
- For hydrodynamic elements, midside nodes can be used to better simulate large-scale motion
of fluid.
- For kinematic elements, midside nodes are rarely needed, except for when kinematic elements
share boundaries with flexible or hydrodynamic elements that have midside nodes.
- When performing a Mechanical Event Simulation analysis with surface-to-surface contact, midside
nodes can enhance the solver's ability to converge on a solution.
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The option to include midside nodes in the element configuration is specified on the
"Element Definition" screen as follows:
- In the FEA Editor environment, select a part and then right click to access a pop-up menu of options.
- Use the "Modify:Element Definition..." command sequence to access the "Element Definition"
screen.
- In the "Midside Nodes" field, choose the "Included" option (see Figure 1).
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Figure 1: Specifying that midside nodes will be included in the element configuration.
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When higher-order shell elements (elements with midside nodes) are used, computing a consistent
pressure loading may cause convergence difficulties. In such cases, you can do the following:
- In the FEA Editor environment, use the "Analysis:Parameters..." command sequence to access the
"Analysis Parameters" screen.
- On the "Shell Loads" tab in the "Global Shell Parameters" section, set the "Smooth shell pressure"
field to "Yes" (see Figure 2). Specifying this option will instruct the software to smooth out the
consistent pressure loading by redistributing the loads on the midside nodes to the corner locations, which
should help to obtain a convergent solution.
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| Figure 2: Activating the option for smooth shell pressure
loading. |
For more information about midside nodes, see the ALGOR User's Guide.
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