rblock configure bbm command

Syntax

rblock configure bbm keyword ... <range>

Primary keywords:

facet-total    relative    remap-interval

Configure rigid blocks for bonded block (BBM) modeling. This command performs a number of operations that can be accomplished individually with other commands. It represents the preferred way to perform BBM simulations using rigid blocks.

One should not use the rblock contact-resolution command with this command. This command should be given before any contacts are created. Though BBM modeling can be undertaken without automatic timestep scaling (see the model mechanical timestep scale command), this commands is primarily designed for quasi-static analyses in either small or large strain. Also note that neither the rblock dilate nor rblock erode commands should be used with this command.

The following operations are undertaken by default:

1. The stress is accumulated, meaning that a stress tensor is created for each rigid block and updated during each cycle. This is equivalent to the rblock contact-resolution accumulate-stress true command. This slows performance by ~15% but allows the current stress state to be queried and used in contact models during force-displacement computations.

2. Contacts are not created between rigid blocks unless the contact area is greater than 0.01 multiplied by the minimum of the total facet area of the two rigid blocks. This condition is checked whenever new rblock-rblock contacts are detected. This is equivalent to the rblock contact-resolution facet-total 0.01 check-on-remap true.

3. The rigid blocks are dilated by the relative amount of 1e-5 the first time that contacts are detected. In addition, the inertial properties are kept unchanged. This is equivalent to the rblock dilate expand 1e-5 relative keep-inertial command.

4. By default, contacts are detected between rigid blocks every 100 cycles regardless of displacement. This can be changed with the remap-interval keyword.

5. Accumulated contact stiffnesses are adjusted, that are used to scaled the rigid block masses and velocities when in automatic timestep scaling mode, to account for potential contacts with adjacent rigid blocks where the areas fall below the facet-total criteria. This provides additional stability for quasi-static simulations in situations where a large contrast in adjacent rigid block sizes exists.

facet-total f

Specify that rblock-rblock contacts with area less than f multiplied by the minimum of the total facet area of the two rigid blocks in contact should not be created. The default value is 0.01. This check happens whenever there is a new contact detection event.

relative f

The amount of expansion is computed as the product of f and the radius of a {circle in 2D; sphere in 3D} with the same size as the rigid block. Thus the expansion varies per rigid block. The default value is 1e-5. The inertial properties are also unchanged as a result of dilation.

remap-interval i

Contacts are detected between rigid blocks every i cycles regardless of the amount of displacement. This is necessary to ensure that