This record specifies a multi linear time-load diagram for the bounda_unknown or bounda_force record with the same index. Between to time points in the diagram, the load is interpolated linearly (ramp function between the two points).
At all times that an unknown is not prescribed in such way, it is free and determined with the governing differential equations. For a specific index only one of bounda_time, bounda_time_file, bounda_sine and bounda_time_user can be specified.
As a special option, you can specify only one value in the bounda_time record if the load is constant over time (so not time-load sets but directly the constant load value).
As a further special option, you can specify no bounda_time and no bounda_sine at all; then a 0 value is assumed.