Load Definition

  NASTRAN load data is included as part of the model history data which is in turn divided into steps (see chapter 6). The association of a FEMGEN load with an NASTRAN step is achieved via the FEMGEN loadcase number argument in the 'PROPERTY LOAD' command. All loads with loadcase number 1 will be associated with the first NASTRAN step and so on.

All FEMGEN load commands have the following form:

PROPERTY LOAD load_type [load_name] [loadcase_no] part_name/ALL args

Argument Meaning

load_type Load type (e.g. PRESSURE).

load_name Optional load name identifier (for reference purposes).

loadcase_no Optional FEMGEN loadcase No.

part_name/ALL Geometric part to which load is applied.

args Varying arguments depending on load_type

Notes:

1.

The part name may be either a single part in the model geometry or a set of such parts. In either case the interface expands the geometry-based load definition into a series of nodal, element face, or whole element loads. The user does not need to consider node/element numbers or element face identifiers; the interface derives these automatically.

2.

The use of ALL for the part name is only valid in circumstances where all parts of the model have a valid geometry for the load in question. For example a pressure load applied to ALL of a model which contains FEMGEN bodies would be invalid. A temperature load applied to the same model would be valid.

3.

The command arguments vary with the load type and are described in the following sections. For all loads types, the actual load values (be it per unit depth, area, or circumference) must be entered correctly by the user. The interface, for example, does not attempt to multiply load values by element thicknesses or areas.

Notes on advanced loading:

• Load Masks, Local Coordinate Systems, Space Curves, defined with the FEMGEN 'CONSTRUCT' command, can be attached to loads using the FEMGEN command 'PROPERTY ATTACH'. The interface program supports some of these new features for most loads. Please note that Time Curves are not supported by this interface program . More detailed information on advanced loading may be found in the FEMGV User Manual.

The following load types are supported:

Generic Load Type FEMGEN Load Type Application

Uniform Pressure PRESSURE Element faces.

Concentrated Force FORCE Nodes.

Prescribed Displacement DISPLACE Nodes.

Gravity GRAVITY Whole elements.

Temperature TEMPERAT Nodes.

Hydrostatic Pressure HYDROSTA Element faces.

Centrifugal Force CENTRIFU Whole elements.