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*DLOAD

Keyword type: step

This option allows the specification of distributed loads. These include constant pressure loading on element faces and volume loading either by gravity forces or by centrifugal forces.

For surface loading the faces of the elements are numbered as follows (for the node numbering of the elements see Figure 1 and 2, section 2.1): C3D20R and C3D8:

- face 1: 1-2-3-4
- face 2: 5-8-7-6
- face 3: 1-5-6-2
- face 4: 2-6-7-3
- face 5: 3-7-8-4
- face 6: 4-8-5-1

The surface loading is entered as a uniform pressure with distributed load type label Px where x is the number of the face. Thus, for pressure loading the magnitude of the load is positive, for tension loading it is negative. Optional parameters are OP and AMPLITUDE. OP is used for surface loading only, taking the value NEW or MOD. OP=MOD is default and implies that the surface loads on different faces are kept over all steps starting from the last perturbation step. Specifying a distributed load on a face for which such a load was defined in a previous step replaces this value. OP=NEW implies that all previous surface loading is removed. If multiple *DLOAD cards are present in a step this parameter takes effect for the first *DLOAD card only.

For centrifugal loading the rotational speed square () and two points on the rotation axis are required, for gravity loading the size and direction of the gravity vector are to be given. Although both formats call for an element number or element set the load applies to, in the present implementation centrifugal and gravity loading apply to ALL elements. Respecifying either of them replaces the old value. The parameter OP has no effect.

The AMPLITUDE parameter allows for the specification of an amplitude by which the force values are scaled (mainly used for dynamic calculations). Thus, in that case the values entered on the *DLOAD card are interpreted as reference values to be multiplied with the (time dependent) amplitude value to obtain the actual value. At the end of the step the reference value is replaced by the actual value at that time, for use in subsequent steps.

First line:

- *DLOAD
- Enter any needed parameters and their value

Following line for surface loading:

- Element number or element set label.
- Distributed load type label.
- Actual magnitude of the load.

Repeat this line if needed.

    Example:

    *DLOAD,AMPLITUDE=A1
    Se1,P3,10.

assigns a pressure loading with magnitude 10. times the amplitude curve of amplitude A1 to face number three of all elements belonging to set Se1.

Example files: beamd.

Following line for centrifugal loading:

- Element number or element set label.
- CENTRIF
- rotational speed square ()
- Coordinate 1 of a point on the rotation axis
- Coordinate 2 of a point on the rotation axis
- Coordinate 3 of a point on the rotation axis
- Component 1 of the normalized direction of the rotation axis
- Component 2 of the normalized direction of the rotation axis
- Component 3 of the normalized direction of the rotation axis

Repeat this line if needed. In the present version, centrifugal loading always applies to the whole structure and the element number or element set label is not used.

    Example:

    *DLOAD
    Eall,CENTRIF,100000.,0.,0.,0.,1.,0.,0.

Example files: achtelc.

assigns a centrifugal loading with about an axis through the points (0.,0.,0.) and (1.,0.,0.) to all elements.

Following line for gravity loading:

- Element number or element set label.
- GRAV
- Actual magnitude of the gravity vector.
- Coordinate 1 of the normalized gravity vector
- Coordinate 2 of the normalized gravity vector
- Coordinate 3 of the normalized gravity vector

Repeat this line if needed. Here "gravity" really stands for any acceleration vector. In the present version gravity loading always applies to the whole structure and the element number or element label is not used.

    Example:

    *DLOAD
    Eall,GRAV,9810.,0.,0.,-1.

assigns gravity loading in the negative z-direction with magnitude 9810. to all elements.

Example files: achtelg.

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