SECJOINT

SECJOINT, DataType, Val1, Val2, Val3, Val4, Val5, Val6
Defines local coordinate systems at joint element nodes and other data for joint elements.

PREP7: Cross Sections

DataType

The type of joint element data being defined:

LSYS	—	Define local coordinate systems at the nodes that form the MPC184 joint element (default).
RDOF	—	Define the relative degrees of freedom to be fixed for an MPC184-General or MPC184-Genb joint element.
PITC	—	Define the pitch of an MPC184-Screw joint element.
FRIC	—	Define the geometric quantities required for Coulomb frictional behavior in the MPC184-Revolute, MPC184-Slot, MPC184-Translational, or MPC184-Spherical joint element.
PNLT	—	Define the penalty factors for the penalty-based joint element formulation.
SPWE	—	Define the spring-damper location for the MPC184-Spotweld joint element.

Val1, Val2, Val3, Val4, Val5, Val6

The values of Val1 through Val6 vary according to the specified DataType:

If DataType = LSYS (or blank), Val1 and Val2 are defined as follows:

Val1 = Local coordinate system at node I.

Val2 = Local coordinate system at node J.

(Val3 through Val6 are not used.)

Alternatively, a local coordinate system based on the vector from node I to node J of the joint element can be defined as follows:

Val1 = IJX (or IJY or IJZ), where:

IJX = vector from node I to node J is considered as the local X-axis at node I.

IJY = vector from node I to node J is considered as the local Y-axis at node I.

IJZ = vector from node I to node J is considered as the local Z-axis at node I.

(Val2 through Val6 are not used.)

A local coordinate system is constructed internally based on this vector from node I to J. The program selects the other two axes such that an orthonormal coordinate system is generated. This local coordinate system is used at both the nodes of the joint element in subsequent calculations.

If DataType = RDOF, Val1 through Val6 are the relative degrees of freedom to be fixed for a general joint element:

1 = UX

2 = UY

3 = UZ

4 = ROTX

5 = ROTY

6 = ROTZ

You can input the degrees of freedom in any order.

If DataType = RDOF, Val1 through Val6 are the relative degrees of freedom to be fixed for a Genb joint element:

1 = UX

2 = UY

3 = UZ

4 = ROTX (first local Z direction)

5 = ROTY (intermediate local X direction)

6 = ROTZ (final local Z direction)

You can input the degrees of freedom in any order.

If DataType = PITC, Val1 is the pitch of the screw joint element. The pitch is defined as the ratio of relative axial displacement (length units) to relative rotation (in radians). (Val2 through Val6 are not used.)

If DataType = FRIC, Val1 through Val3 are defined as follows (and Val4 through Val6 are not used):

For Revolute Joint:

Val1 = Outer radius

Val2 = Inner radius

Val3 = Effective length

For Translational Joint:

Val1 = Effective length

Val2 = Effective radius

For Spherical Joint:

Val1 = Effective radius

If DataType = PNLT, Val1 and Val2 are defined as follows (and Val3 through Val6 are not used):

Val1

—

Constraint type:

DISP - Displacement-based constraint

ROT - Rotation-based constraint

Val2

—

Scaling factor (positive number) or penalty factor (negative number) used with the penalty-based joint element formulation:

> 0 -- The number is used as a scaling factor to scale the internally calculated penalty values.

< 0 -- The absolute value of the number is used as the penalty factor in calculations.

If DataType = SPWE, Val1, Val2, Val3, and Val4 are defined as follows:

Val1

—

Spring-damper location:

RATIO -- Specify only Val2 (0 <= Val2 <=1), indicating the spring-damper location between nodes I and J. (Val3 through Val6 are not used.)

COORD -- Specify Val2, Val3, and Val4. The values represent the global (X,Y,Z) coordinates, respectively, of the spring-damper location. (Val5 and Val6 are not used.)

If Val1 is not specified, the default is RATIO with Val2 = 0.5.

Notes

This command defines additional section data for MPC184 joint elements. The values that you input are interpreted based on the most recently issued SECTYPE command. To overwrite current values, issue another SECJOINT command with the same DataType value.

SECJOINT,LSYS,IJX (or IJY or IJZ) is typically used in spotweld applications. The joint element nodes should not be coincidental when this command is used. If the nodes are coincidental, the default global coordinate system applies. Specify axes to conform to the type of joint element used; otherwise, unexpected behavior may occur as the local coordinate system was not properly selected.

SECJOINT,PNLT applies to penalty-based joints only (KEYOPT(2) = 1 on most joint elements) and overwrites the default penalty factor. The default penalty factor (common to all constraints of the joint element) is of the order of 10*E_avg, where E_avg is the average Young’s modulus of the elements attached to the joint element or deduced from the connections to other elements. The penalty factor can affect the constraint satisfaction as well as overall solution convergence.

Menu Paths

Main Menu>Preprocessor>Sections>Joints>Add / Edit