# rblock erode command

Syntax

rblock erode keyword ... <range>

Primary keywords:

Change the rigid block rounding by erosion. A rigid block is represented by a core shape that is composed of {linear facets in 2D; triangular facets in 3D}. The core shape is convex, closed and manifold. When rounding is nonzero, the core shape is expanded in all directions by a {circle in 2D; sphere in 3D} of a specified radius with center passing along all points on the exterior of the core shape. The value of the rounding corresponds to the radius of this expansion {circle in 2D; sphere in 3D}. Rounding can result in fewer contacts for highly packed models and in faster contact resolution.

Erosion attempts to produce a new core shape such that the rounded rigid block has essentially the same dimensions as the previous core shape. This process generally results in a rounded rigid block where the facet planes are unchanged but the {corners in 2D; edges and corners in 3D} are rounded. This can be highly advantageous computationally for highly packed assemblies of rigid blocks, culling many active contacts. Erosion is accomplished by translating all facets of the core shape inward (i.e., toward the centroid) in the facet-normal direction by the rounding distance. If the original core shape has a fair degree of radial symmetry and the rounding is small compared with the distance from the facets to the centroid, erosion will result in a core shape with the same surface topology (i.e., facet number and connectivity) as the original core shape. In some cases, though, erosion can produce a different topology. In such cases, in order to keep the surface topology unchanged, the principal aspect ratios of the new core shape are computed and the old core shape is stretched in the principal aspect-ratio directions to match the new core shape aspect ratio. In either case, the inertial properties are not changed when eroding a rigid block. If the specified rounding distance is too great, erosion cannot occur as a negative volume rigid block would be created (i.e., a facet would be translated past the centroid). In this case an error occurs unless the skip-errors keyword is given, in which case a warning is issued instead. If the rigid block was previously rounded the core shape is eroded and the old rounding is added to the new rounding.

minimum-distance f

The degree of rounding is computed as the product of f and the minimum distance from a facet to the rigid block centroid. This can be more effective than using the relative option for very thin rigid blocks.

relative f

The degree of rounding 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.

skip-errors

If the specified rounding distance is too great, erosion cannot occur as a negative volume rigid block would be created (i.e., a facet would be translated past the centroid). This keyword specifies that a warning is issued instead of an error.

Usage Examples

Erode all rigid blocks. Set limit of rounding to 0.05 × the size of the rigid block and issue a warning instead of an error if eroding a rigid block fails.

rblock erode relative 0.05 skip-errors


from “specimen.dat” in Simple Rigid Block Bonded-Block Modeling (BBM)

Erode all rigid blocks. Erosion (edge rounding) should be 0.1 × the size of the rigid block.

rblock erode relative 0.1