SHSD

SHSD, RID, Action, CHCH_Opt, CGAP, CPEN
Creates or deletes a shell-solid interface to be used in shell-to-solid assemblies.

PREP7: Elements

RID

The real constant set ID that identifies the contact pair on which a shell-to-solid assembly is defined. If ALL, all selected contact pairs will be considered for assembly.

Action

Action to be performed:

EDGE	—	Create virtual shell elements based on the shell edge (default).
SURFACE	—	Create virtual shell elements based on the solid element surface.
DELETE	—	Delete the nodes and elements created during a previous execution of SHSD for the real constant set identified by `RID`.

CNCH_Opt

CNCHECK option to close initial penetration or gap:

NONE	—	No adjustment of initial penetration or gap (default).
ADJUST	—	Use CNCHECK,ADJUST logic internally to close the initial gap or penetration (see the CNCHECK command for detail). `CGAP` or `CPEN` must be specified.

CGAP

Control parameter for opening gap; must be greater than or equal to zero. Close the gap if the gap distance is smaller than the CGAP value. CGAP defaults to 0.25*PINB (where PINB is the pinball radius) for bonded and no-separation contact. Otherwise, it defaults to the value of real constant ICONT.

CPEN

Control parameter for initial penetration; must be greater than or equal to zero. Close the penetration if the penetration distance is smaller than the CPEN value. CPEN defaults to 0.25*PINB (where PINB is the pinball radius) for any type of interface behavior (either bonded or standard contact).

Notes

The SHSD command creates a shell-solid interface to be used in shell-to-solid assemblies, or deletes a previously-created shell-solid interface. Virtual shell elements and additional CONTA175 or CONTA177 elements are created at the contact pair identified by RID when Action = EDGE or SURFACE. Set Action = DELETE to remove the generated nodes and elements at the contact pair identified by RID.

The SHSD command is active only when the following element KEYOPTs of associated CONTA175 or CONTA177 element types are predefined:

Element	KEYOPT	Detail
CONTA175 or CONTA177	KEYOPT(2) = 2	MPC algorithm
	KEYOPT(12) = 5, 6	Bonded contact
	KEYOPT(4) = 0	Contact normal perpendicular to target surface

When ACTION = EDGE, the virtual shell elements are built perpendicular to the pre-existing shell elements attached to the contact elements. They geometrically follow the contact interface edge and are built on both sides of this interface in such a way that each new shell element (SHELL181) has two nodes that belong to the associated pre-existing shell element in the shell edge. (See Figure 28: Virtual Shell Elements Following the Contact Interface Edge.) The width of the new shell elements is half the thickness of the pre-existing shell element. If CONTA175 is used at the shell nodes, the CONTA175 elements are then created at each node of the virtual shell elements where no CONTA175 element exists. If CONTA177 is used at the shell edge, new CONTA174 elements are created and overlayed on the virtual shell. The new contact elements are identified by the same contact pair ID as the pre-existing contact elements. The virtual shell elements are assigned the next available element type number and material number.

Figure 28: Virtual Shell Elements Following the Contact Interface Edge

When ACTION = SURFACE, the virtual shell elements (SHELL181 - low order; SHELL281 - high order) overlap the existing low or high order target elements identified with the RID argument, and share their nodes. Only those target elements close enough to the contact interface (identified using the PINB real constant) are overlapped. The program uses the FTOLN real constant (defaults to half the shell element thickness) to define an influence distance. The associated virtual shell elements are created only for target elements that lie partially inside the influence distance region (see Figure 29: Virtual Shell Elements Overlapping Target Elements).

Figure 29: Virtual Shell Elements Overlapping Target Elements

For the bonded always option (KEYOPT(12) = 5), any contact node inside the pinball region (gap < PINB) is included in the KEYOPT(5) = 2 process. A relatively small PINB value may be used to prevent false contact. PINB defaults to 25% of the contact depth for small deformation analyses.

For the bonded initial option (KEYOPT(12) = 6), only those contact nodes which initially lie inside the adjustment zone (gap < ICONT) are always included in the KEYOPT(5) = 2 process. ICONT defaults to 5% of the contact depth.

For both processes, the new nodes and elements are stored in internally-named components. The internal naming convention is based on the real constant set ID specified by RID, as illustrated in the following table.

Nodes	SHSD_ND_`RID`
Contact Elements	SHSD_CN_`RID`
Shell Elements	SHSD_SH_`RID`

Issuing SHSD,RID,DELETE deletes components based on their generated names. Only components whose names match the internal naming convention will be deleted.

Caution: Do not rename or manually delete generated components. Use the SHSD command to delete generated components.

Renaming or manually deleting generated components will cause these components to be ignored when SHSD,RID,DELETE is executed and when the program searches for these components to verify if SHSD,RID,EDGE or SURFACE can be safely executed. Manually renaming or deleting generated components and reissuing SHSD,RID,EDGE or SURFACE may result in erroneous generation of virtual shell or contact elements.

SHSD does not support assemblies that contain a preintegrated shell section (SECTYPE,,GENS).

See Modeling a Shell-Solid Assembly in the Contact Technology Guide for more information.

Menu Paths

This command cannot be accessed from a menu.