Lagrange Multiplier Method

Block Format Keyword Lagrange Multiplier Method is one of the contact treatments used in Radioss and is purely mathematical and does not require physical elements (springs) to model contact. The Lagrange multiplier matrix has to be reversed at each cycle of computation and; therefore, takes more CPU time during computation, but there is no time step collapse, due to high interface stiffness.

Table 1. Interface Types with Lagrange Multiplier

Contact Treatment		Types	Application	Description
Lagrange multiplier method	Tied	/INTER/LAGMUL/TYPE2	Change of mesh density (solid)	Tied contact between main and secondary nodes.
	Slide / Void	/INTER/LAGMUL/TYPE7	Solid contact impact at all speeds	Multi-usage impact interface between a main surface and a list of secondary nodes.
	Slide / Void	/INTER/LAGMUL/TYPE16	Meshes with 8-node or 16-node thick-shell or 20 bricks	Contact of impact between nodes and external surfaces.
	Slide / Void	/INTER/LAGMUL/TYPE17	Meshes with 8-node or 16-node thick-shell or 20 bricks	Contact of impact between external surface of two brick groups.

Comments

1. Lagrange multiplier interfaces are compatible with all Lagrange multiplier kinematic conditions.
2. Lagrange multiplier interfaces are not compatible with other kinematic conditions.
3. Lagrange multiplier interfaces are not compatible with SPMD parallel version.