Solids

Solids describe the geometry of spatial objects. When generating the FE mesh, 3D elements are created on solids. Solids can also be used to represent orthotropic and contact properties, or to perform analyses for gas models.

Normally, the 'Boundary Surfaces' of a solid must be defined using the Without Thickness stiffness type (see the Surfaces chapter). However, if no solid is connected in a model representing the contact between two surfaces, both contact surfaces must be provided with a stiffness.

Main

The Main tab manages the basic solid parameters.

Solid Type

The solid type controls the way internal forces and moments are absorbed, or which properties are applied to the solid. Various types are available for selection in the list.

Standard

The standard model is represented by a 3D object with the solid-specific properties of a homogeneous and isotropic material. Therefore, the boundary surfaces should be defined by the 'Without Thickness' stiffness type .

If the solid has orthotropic properties, stiffnesses are also derived from the material characteristics. You can check the elastic stiffnesses of the three-dimensional material model in the Orthotropic - Linear Elastic (Solids) tab of the Material dialog box.

Gas

This type allows you to represent solids that have the properties of an ideal gas, such as pneumatic cushions, pressure vessels, or insulating glass. You can assign the pressure and temperature properties of the gas or define new ones in the 'Gas' tab (see the Gas Solids chapter).

Contact

This solid type is useful for modeling the contact between two surfaces. You can define the contact properties in the 'Contact Solid' tab.

Select the contact solid type in the list or create a new contact with appropriate properties (see the Contact Solids chapter).

If the structure's geometry is adequate, two opposite contact surfaces are preset. You can modify the '1st Surface' via the list or define it graphically with the button. RFEM determines the '2nd Surface' automatically as the solid surface that is parallel to the first surface.

Hole

With this solid type, you can create openings and holes for bolts and so on. The solid type is also appropriate for modeling construction pits for the Geotechnical Analysis add-on for special solutions.

Intersection

When two solids intersect, you can create the intersection by assigning the 'Intersection' type to one of these solids. After answering the query, RFEM creates the intersection lines and the intersection. In the navigator, the components of the (other) 'Standard' solid are added as generated objects.

Soil

The solid type is used for the Geotechnical Analysis add-on for special solutions.

Material

Select the appropriate type in the list of available materials, or define a new material (see the Materials chapter).

Mesh refinement

The mesh size of the FE mesh can be adjusted to the geometry of the solid (see the Surface Mesh Refinements chapter). Thus, it is independent of the general mesh settings.

In the 'Mesh Refinement' tab, you can select a solid mesh refinement or define a new one. In the 'Layered Mesh' dialog section, there is an alternative option to arrange a solid's FE division by layers that are generated between two parallel and opposite surfaces. The function is briefly presented in a video.

Specific direction

Each solid has a local coordinate system. Usually, it is aligned parallel to the global axes. However, the coordinate system can also be user-defined.

The list in the 'Direction Type' dialog section provides various options for adjusting the axis orientation of the solid:

• Rotated via 3 Angles: rotation of xyz-axes about angles α_X', α_Y', and α_Z' in relation to global axes
• Directed to Node: orientation of '1st axis' (x-axis) and '2nd axis' (y-axis) each to one node
• Parallel to Two Nodes: orientation of '1st axis' (option) parallel to two nodes, and '2nd axis' (option) to one node
• Parallel to CS of Line: Alignment of x-axis parallel to x-axis of a line
• Parallel to CS of Member: Alignment of x-axis parallel to x-axis of a member

You can define the reference objects graphically with the button.

The axis system is also used for the output of results.

Stiffness matrix

This feature is still in preparation. The check box will allow you to define the stiffness matrix of the solid manually in a separate tab.

Deactivate for calculation

With this check box you have the possibility not to consider the solid for the calculation; for example, in order to simulate construction stages or to analyze varying modeling versions. In this case, the stiffness, properties, and loads of the solid are not applied.

Information | Analytical & Mesh

This dialog section provides an overview of important properties of the solid, such as area, volume, mass, and center position.