RFEM – Online Manual

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RFEM – Online Manual

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9.7.1 Work Window

Work Window

The Display navigator controls the results smoothing that influences the work window.

Figure 9.29 Display navigator: Results → Surfaces or Solids → Distribution of Internal Forces/Stresses
Example

The following example illustrates the effects of the different smoothing options.

A steel plate with the dimensions 3 m ⋅ 3 m and a thickness of 3 cm is supported on two lines with pinned supports facing each other. The plate is not modeled with one complete surface, but with two surfaces with the same properties lying side by side. The local z-axes of both surfaces are oriented in opposite directions.

Figure 9.30 Steel plate – modeled with two surfaces

The FE length is 1 m. This element size cannot provide precise results; it is only used to demonstrate the result displays of the different smoothing modes.

The steel surface is stressed only by its self-weight.

Distribution of internal forces Constant on Elements
Figure 9.31 Distribution of internal forces Constant on Elements, values On FE mesh points

The values of the FE nodes are averaged and the result is displayed in the middle of the elements. The distribution in each finite element is constant. This type of results display is recommended for plastic material models (see Chapter 4.3).

Distribution of internal forces Non Continuous
Figure 9.32 Distribution of internal forces Non Continuous, values On FE mesh points

The display shows the FE node values that result from the displacements and rotations of each single element. Several values are therefore displayed for each FE node. A dotted line on the node value indicates the element to which the value belongs.

For the graphic display, a plane is defined by the corner values of every element. As the results of adjacent elements are not taken into account, there is a discontinuous distribution.

Distribution of internal forces Continuous within Surfaces
Figure 9.33 Distribution of internal forces Continuous within Surfaces, values On FE mesh points

The values on the FE nodes are averaged. The averaging stops on the surface boundary, which may result in discontinuities between adjacent surfaces. This is quite correct in our example. At the boundary line, two FE node values are displayed.

This smoothing option is preset because it provides the best results in most cases.

Distribution of internal forces Continuous Total
Figure 9.34 Distribution of internal forces Continuous Total, values On FE mesh points

The average values are determined by considering the FE values beyond the surface boundaries. This leads to a continuous distribution between adjoining surfaces, which is not correct for our example.

The following requirements must be met for the Continuous Total display option:

    • The orientation of the surface axis systems is congruent.
    • Only two surfaces concur.
    • The surfaces lie in one plane.
    • No line release is defined on the boundary line.

If one of these conditions is not met, incorrect result distributions are displayed.

Distribution of internal forces Continuously by Groups

It is also possible to smooth results by groups. RFEM provides Generated groups with similar material properties.

You can create user-defined groups of surfaces or solids by using the navigator shortcut menu (right-click User Groups).

Figure 9.35 Creating a New Averaging Group via the navigator shortcut menu

Then, a dialog box opens where you can define the objects that you want to examine as a group.