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Documentation

Element Technology

Element technology refers to the numerical formulation for the solid finite element used in the simulation. This includes the mesh order, reduced integration, and mass lumping.

element technology setup window simscale
Figure 1. Modal window for element technology setup

The available parameters are:

  • Definition: By default, Automatic is selected, allowing the solver to use the recommended default values, based on the simulation type and physical setup. By switching to Custom, the user has the option to manually select the different options, explained below.
  • Mechanical or Thermal mesh order: Select between First order (linear interpolation) or Second order (parabolic interpolation) finite elements, as used for the mechanical or thermal models, respectively.
  • Reduced integration: Used in second order mechanical elements, it implements a reduced number of Gauss integration points in the finite elements. The aim is to compensate for the typical over-estimation in the stiffness of the finite elements, with a side effect of slightly reducing computational time. The downside of this technique is that it can create artificial deformations related to the lower stiffness (with zero strain and no stress), also known as hour-glass modes.
  • Lumped mass: For thermal elements, it allows to reduce the thermal mass to only one component, thus achieving a diagonal thermal mass matrix. This allows a faster convergence and reduction of memory consumption.

Element Definitions

It is possible to select particular reduced integration and lumped mass configurations for the different parts of the model by creating different Element definitions in the simulation tree, just below the Element technology element. Please be aware that this option is only available when using the Custom definition.

Advice on Element Technology

First-order elements are less expensive to use in terms of computational resources but require a finer mesh to properly capture the variations in the fields across the geometrical features. In thin-walled parts, we recommend the use of second-order elements. Using reduced integration second-order elements will reduce computation time, but some artificial deformations can be obtained, due to numerical errors (hour-glassing of elements).

What is an hour-glass deformation mode?

Hour-glass deformation of elements is a numerical error phenomenon that can arise in reduced integration, second-order mesh elements. The error causes the elements to deform under no stress condition, creating a lack of precision in the results. If you detect strange, irregular deformations in your results, try changing back to standard (full integration) second-order elements and compare.

For thermal simulations, it is always recommended to use first-order elements. This condition becomes relevant for thermomechanical simulations using second-order mechanical elements.

Last updated: August 15th, 2022

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