Main Help → All Commands → Multimaterial MPM → MultimaterialMode
The Multimaterial
command turns on use of multimaterial MPM calculations and selects various options used by the mode:
MultimaterialMode 0.0,1,<(normals)>,<(rigidBiasOrAzimuth)>,<(polar)>
where
(normals)
determines the method used to find surface normals during contact calculations. The options are:
"logreg"
(or 6) - the normal is found using logistic regression. This is the default option and preferred option of all material contact simulations (except maybe when you can "specify"
the normal)."linreg"
(or 5) - the normal is found linear regression. It is slightly faster than "logreg"
, but less accurate."avggrad"
(or 2) - the normal is found from the volume-weighted mean volume gradient. When contact is all non-rigid materials, it averages the gradient of one material with the net gradient of all other materials. When a rigid material is involved, it averages each material with the one rigid material (this is the default option)."specify"
(or 4) - use a single, specified normal defined by the azimuth and polar angles in the following two parameters. The specified normal is used for all contact calculations and it should point from the lower-numbered material into the higher-numbered material. The material number is the order the materials appear in the output file. For contact with rigid materials, the normal vector should point from the non-rigid material into the rigid material."maxgrad"
(or 0) - the normal is found from the one material at the node that has the largest magnitude of its volume gradient."maxvol"
(or 1) - the normal is found from the one material at the node that has the largest magnitude of its volume."owngrad"
(or 3) - each material uses its own normal. In contact or interface calculations, the calculations are done separately for the two sides for the surface. If the normals are not equal and opposite, this method (unlike the other three) will not conserve momentum. It is the method originally proposed in MPM contact methods (e.g., Bardenhagen, et al. (2001)), before the importance of the normal was established."logreg"
(or 6). See the OSUPDocs wiki for more details and references.
(rigidBiasOrAzimuth)
- when (normals)
is "maxgrad" (0), "avggrad" (2), "linreg" (5), or "logreg" (6), this parameter sets a bias for rigid material volume gradients. When a problem has contact with rigid materials (with direction=8
), the normals from the rigid material may be more reliable (especially if those particles are stationary). This parameter says to determine the normal from the volume gradient of the rigid material unless the volume gradient calculated by the "maxgrad" or "avggrad" method is this factor larger. Values around 100 will almost always use the rigid material. For "linreg" (5) or "logreg" (6), values greater than 10 will use rigid material normal instead of the regression normal.(rigidBiasOrAzimuth)
or (polar)
- when (normals)
is "specify"
(4), these two parameters set the azimuth angle (or φ) and polar angle (θ) in degrees for the specified normal vector. The resulting normal is (cos φ sin θ, sin φ sin θ, cos θ). For 2D calculations, the (polar)
setting is ignored (and automatically set to 90 degrees).Multimaterial
command is only allowed for MPM analyses.