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*MASS ADJUST
Adjust and/or redistribute the mass of an element set.

This option is used to increase or decrease the mass of the elements in an element set uniformly so that the total mass for that set matches a specified value. It can also be used to redistribute the mass among the elements in the element set to raise the minimum stable time increment for that set to a specified target value.

The total mass of an element set can also be increased or decreased using a scale factor. When using a scale factor, the total mass of the elements in the element set can be redistributed to reach the maximum time target for the set or only the added mass can be redistributed (the pre-adjusted mass of the elements is preserved).

Mass can be adjusted for multiple element sets; the mass is adjusted in the order in which the element sets are specified. This behavior influences the final outcome for element sets that share elements.

This option can appear only once in an analysis.

Product: Abaqus/Explicit  

Type: Model data

Level: Assembly  

Reference:

Optional parameter:

TARGET DT

Set this parameter equal to a value to define a default minimum element stable time increment for all of the mass-adjusted element sets. Target time increments can be specified for selected sets on the data lines, if needed. A nonzero target value causes redistribution of mass within the element sets.

Set TARGET DT=MAXIMIZE to indicate that a maximum possible time increment for the elements in the sets is desired. The mass redistribution to maximize the time increment can be done for the total mass or for only the added mass. Maximizing the time increment can be specified for selected sets on the data lines, if needed.

If this parameter is omitted, the third field in the data lines specifies the redistribution behavior.

Data lines to adjust and/or redistribute the mass of element sets: 

First line:

  1. Element set label.

  2. Total mass of the element set. Enter the mass value, or enter CURRENT to redistribute the mass to achieve a target time increment without altering the total mass.

  3. Enter the minimum element stable time increment value for the element set. If using a scale factor, enter MAXIMIZE to maximize the minimum stable time increment in the initial configuration or enter UNIFORM to distribute the mass in proportion with the pre-adjusted mass. If omitted, the default value is the setting of the TARGET DT parameter if it is used; otherwise, the default value for the minimum element stable time increment is 0.0 or, if using a scale factor, the default behavior is to distribute the mass in proportion with the pre-adjusted mass. When both the TARGET DT parameter and a data line entry for the element set are specified, the data line entry for the element set is used for that set.

  4. Mass scale factor for the element set. Only relevant for redistributing mass to achieve a maximum possible time increment in the element set and distributing the mass in proportion with the pre-adjusted mass. If omitted, a default value of one is used to maximize the time increment.

  5. Enter REDIST to indicate that the total element mass (the pre-adjusted mass plus the added mass) should be redistributed. Enter ADD to indicate that only the added mass should be redistributed. Only relevant for redistributing mass to achieve a maximum possible time increment in the element set. If omitted, the default behavior is to redistribute the total element mass.

Repeat this data line as often as necessary to adjust the mass for different element sets. The same element set label cannot be entered more than once. The mass is adjusted in the order the element sets are specified on the data lines.