MPC184-General
## MPC184 General Joint Element Description

## MPC184 General Joint Input Data

### MPC184 General Joint Input Summary

## MPC184 General Joint Output Data

## MPC184 General Joint Assumptions and Restrictions

**Multipoint
Constraint Element: General Joint**

Compatible Products: – | Pro | Premium | Enterprise | Ent PP | Ent Solver | –

The MPC184 general joint is a two-node element. By default, no relative degrees of freedom are fixed. However, you can specify which relative degrees of freedom need to be constrained. By specifying as many relative degrees of freedom to be constrained as needed, you can simulate different joint elements.

By default, a general joint has both displacement and rotational degrees of freedom activated at the nodes of the element. In some cases only displacement degrees of freedom are needed (as in a model consisting of only continuum elements). In such cases, you can specify a general joint with only displacement degrees of freedom activated by setting KEYOPT(4) = 1.

Set KEYOPT(1) = 16 to define a two-node general joint element.

Use KEYOPT(4) to specify the active degree-of-freedom set:

KEYOPT(4) = 0 (default) - both displacement and rotational degrees of freedom are activated. |

KEYOPT(4) = 1 - only displacement degrees of freedom are activated. |

For this element, you can specify which relative degrees of
freedom need to be constrained. First, define the section type (**SECTYPE** command) for this joint. Then define the **SECJOINT** command as follows:

SECJ,LSYS,local cs1,local cs2 ! Defines the local coordinate systems for the joints. SECJ,RDOF,dof1,dof2,…,dof6 ! Defines the relative DOFs to be constrained.

Note that the **SECJOINT** command is issued
twice when the general joint is used with some degrees of freedom
constrained. The first **SECJOINT** command defines
the local coordinate systems for the joint. In the second **SECJOINT** command, specify as many relative degrees of freedom
as needed (a maximum of 6 may be specified). The general joint element
allows you to simulate different joint elements by specifying different
relative degrees of freedom to be constrained. The following examples
highlight the different joint elements that can be simulated:

SECJ,RDOF,dof1,dof2,dof3,dof5,dof6 ! Simulates a revolute joint with local e_1 axis as the axis of revolute. SECJ,RDOF,dof2,dof3,dof5,dof6 ! Simulates a cylindrical joint with local e_1 axis as the axis of rotation. SECJ,RDOF,dof1,dof2,dof3,dof4,dof5,dof6 ! Simulates a weld joint.

When KEYOPT(4) = 1, the local coordinate systems specified at nodes I and J remain fixed in their initial orientation. The rotation at the nodes, if any, is ignored.

When KEYOPT(4) = 0, the local coordinate systems specified at nodes I and J are assumed to evolve with the rotations at the nodes.

For an unconstrained general joint (KEYOPT(4) = 0 or 1), the relative displacements between nodes I and J are as follows:

The relative rotations between nodes I and J are characterized by the Cardan (or Bryant) angles as follows (only if KEYOPT(4) = 0):

The relative displacements and rotations are suitably constrained when some or all of the relative degrees of freedom are fixed.

Note that the relative angular positions for the general joint
are characterized by the Cardan (or Bryant) angles. This requires
that the rotations about the local e_{2} axis
be restricted between –PI/2 to +PI/2. Thus, the local e_{2} axis should not be used to simulate the axis of rotation.

For an unconstrained general joint, the constitutive calculations use the following definitions for relative displacement:

where:

,
, and
= reference lengths, length1, length2, and length3, specified on
the SECDATA command. |

The following definitions are for relative rotations:

where:

,
, and
= reference angle specifications, angle1, angle2, and angle3 on
the SECDATA command. |

Other input data that are common to all joint elements (material behavior, stops and limits, locks, etc.) are described in "Joint Input Data" in the MPC184 element description.

This input summary applies to the general joint element option of MPC184: KEYOPT(1) = 16.

**Nodes**I, J

**Note:**For a grounded joint element, specify either node I or node J in the element definition and leave the other node (the grounded node) blank.**Degrees of Freedom**UX, UY, UZ, ROTX, ROTY, ROTZ (KEYOPT(4) = 0)

UX, UY, UZ (KEYOPT(4) = 1)

**Real Constants**None

**Material Properties**Use the JOIN label on the

**TB**command to define stiffness and damping behavior. (See MPC184 Joint in the*Material Reference*for detailed information on defining joint materials.)**Surface Loads**None

**Body Loads****Temperatures --**T(I), T(J)

**Element Loads**For an unconstrained general joint:

**Displacement (KEYOPT(4) = 0 or 1) --**UX, UY, UZ

**Rotation (KEYOPT(4) = 0) --**ROTX, ROTY, ROTZ

For a constrained general joint, loads are based on the free relative degrees of freedom in the joint.

**Special Features**Large deflection Linear perturbation **KEYOPT(1)**Element behavior:

**16 --**General joint element

**KEYOPT(4)**Element configuration:

**0 --**General joint with both displacement and rotational degrees of freedom activated.

**1 --**General joint with only displacement degrees of freedom activated.

The solution output associated with the element is in two forms:

Nodal displacements included in the overall nodal solution

Additional element output as shown in Table 184gen.1: MPC184 General Joint Element Output Definitions and Table 184gen.2: MPC184 General Joint Element - NMISC Output.

These tables use the following notation:

A colon (:) in the Name column indicates the item can be accessed
by the Component Name method [**ETABLE**, **ESOL**]. The O column indicates the availability of the
items in the file **Jobname.OUT**. The R column indicates
the availability of the items in the results file.

In either the O or R columns, Y indicates that the item is *always* available, a number refers to a table
footnote that describes when the item is *conditionally* available, and a - indicates that the item is *not* available.

**Table 184gen.1: MPC184 General Joint Element Output Definitions**

Name | Definition | O | R |
---|---|---|---|

General joint with displacement and rotation DOF (KEYOPT(4)
= 0)
| |||

EL | Element number | - | Y |

NODES | Element node numbers (I, J) | - | Y |

The constraint force and moment output depends on which of the relative DOFs are constrained. | |||

FX | Constraint force in X direction | - | Y |

FY | Constraint force in Y direction | - | Y |

FZ | Constraint force in Z direction | - | Y |

MX | Constraint moment in X direction | - | Y |

MY | Constraint moment in Y direction | - | Y |

MZ | Constraint moment in Z direction | - | Y |

The following output depends on which of the relative DOFs are unconstrained. | |||

CSTOP1-6 | Constraint force/moment if stop is specified on DOFs 1-6 | - | Y |

CLOCK1-6 | Constraint force/moment if lock is specified on DOFs 1-6 | - | Y |

CSST1-6 | Constraint stop status on relative DOFs 1-6[1] | - | Y |

CLST1-6 | Constraint lock status on relative DOFs 1-6[2] | - | Y |

JRP1-6 | Joint relative position of DOFs 1-6 | - | Y |

JCD1-6 | Joint constitutive displacement/rotation of DOFs 1-6 | - | Y |

JEF1-6 | Joint elastic force/moment 1-6 | - | Y |

JDF1-6 | Joint damping force/moment 1-6 | - | Y |

JRU1-6 | Joint relative displacement/rotation 1-6 | - | Y |

JRV1-6 | Joint relative velocity (or rotational velocity) 1-6 | - | Y |

JRA1-6 | Joint relative acceleration (or rotational acceleration) 1-6 | - | Y |

JTEMP | Average temperature in the element[3] | - | Y |

General joint with displacement DOF (KEYOPT(4)
=1)
| |||

EL | Element number | - | Y |

NODES | Element node numbers (I, J) | - | Y |

The constraint force and moment output depends on which of the relative DOFs are constrained. | |||

FX | Constraint force in X direction | - | Y |

FY | Constraint force in Y direction | - | Y |

FZ | Constraint force in Z direction | - | Y |

The following output depends on which of the relative DOFs are unconstrained. | |||

CSTOP1-3 | Constraint force if stop is specified on DOFs 1-3 | - | Y |

CLOCK1-3 | Constraint force if lock is specified on DOFs 1-3 | - | Y |

CSST1-3 | Constraint stop status on relative DOFs 1-3[1] | - | Y |

CLST1-3 | Constraint lock status on relative DOFs 1-3[2] | - | Y |

JRP1-3 | Joint relative position of DOFs 1-3 | - | Y |

JCD1-3 | Joint constitutive displacement of DOFs 1-3 | - | Y |

JEF1-3 | Joint elastic force 1-3 | - | Y |

JDF1-3 | Joint damping force 1-3 | - | Y |

JRU1-3 | Joint relative displacement 1-3 | - | Y |

JRV1-3 | Joint relative velocity 1-3 | - | Y |

JRA1-3 | Joint relative acceleration 1-3 | - | Y |

JTEMP | Average temperature in the element[3] | - | Y |

0 = stop not active, or deactivated 1 = stopped at minimum value 2 = stopped at maximum value 0 = lock not active 1 = locked at minimum value 2 = locked at maximum value Average temperature in the element when temperatures are applied on the nodes of the element using the

**BF**command, or when temperature are applied on the element using the**BFE**command.

The following table shows additional non-summable miscellaneous (NMISC) output available for all forms of the general joint element.

**Note:** This output is intended for use in the ANSYS Workbench program
to track the evolution of local coordinate systems specified at the
nodes of joint elements.

**Table 184gen.2: MPC184 General Joint Element - NMISC Output**

Name | Definition | O | R |
---|---|---|---|

The following output is available for all general joint
elements (KEYOPT(4) = 0 and 1)
| |||

E1X-I, E1Y-I, E1Z-I | X, Y, Z components of the evolved
e_{1} axis at node I | - | Y |

E2X-I, E2Y-I, E2Z-I | X, Y,
Z components of the evolved e_{2} axis at node
I | - | Y |

E3X-I, E3Y-I, E3Z-I | X, Y, Z components of the evolved e_{3} axis at node I | - | Y |

E1X-J, E1Y-J, E1Z-J | X, Y, Z components
of the evolved e_{1} axis at node J | - | Y |

E2X-J, E2Y-J, E2Z-J | X, Y, Z components of the evolved e_{2} axis at node J | - | Y |

E3X-J, E3Y-J, E3Z-J | X, Y, Z components of the
evolved e_{3} axis at node J | - | Y |

JFX, JFY, JFZ | Constraint forces expressed in the evolved coordinate system specified at node I | - | Y |

JMX, JMY, JMZ | Constraint moments expressed in the evolved coordinate system specified at node I | - | Y |

Table 184gen.3: MPC184 General Joint Item and Sequence Numbers - SMISC Items and Table 184gen.4: MPC184 General Joint Item and Sequence Numbers - NMISC Items list output available via the **ETABLE** command using the Sequence Number method. See The General Postprocessor (POST1) in the *Basic Analysis Guide* and The Item and Sequence Number Table for further information.
The tables use the following notation:

**Name**output quantity as defined in the Element Output Definitions table.

**Item**predetermined Item label for

**ETABLE**command**E**sequence number for single-valued or constant element data

**Table 184gen.3: MPC184 General Joint Item and Sequence Numbers - SMISC Items**

Output Quantity Name |
ETABLE and ESOL Command Input | |
---|---|---|

Item | E | |

| ||

FX | SMISC | 1 |

FY | SMISC | 2 |

FZ | SMISC | 3 |

MX | SMISC | 4 |

MY | SMISC | 5 |

MZ | SMISC | 6 |

CSTOP1-6 | SMISC | 7-12 |

CLOCK1-6 | SMISC | 13-18 |

CSST1-6 | SMISC | 19-24 |

CLST1-6 | SMISC | 25-30 |

JRP1-6 | SMISC | 31-36 |

JCD1-6 | SMISC | 37-42 |

JEF1-6 | SMISC | 43-48 |

JDF1-6 | SMISC | 49-54 |

JRU1-6 | SMISC | 61-66 |

JRV1-6 | SMISC | 67-72 |

JRA1-6 | SMISC | 73-78 |

JTEMP | SMISC | 79 |

| ||

FX | SMISC | 1 |

FY | SMISC | 2 |

FZ | SMISC | 3 |

CSTOP1-3 | SMISC | 7-9 |

CLOCK1-3 | SMISC | 13-15 |

CSST1-3 | SMISC | 19–21 |

CLST1-3 | SMISC | 25-27 |

JRP1-3 | SMISC | 31-33 |

JCD1-3 | SMISC | 37-39 |

JEF1-3 | SMISC | 43-45 |

JDF1-3 | SMISC | 49-51 |

JRU1-3 | SMISC | 61-63 |

JRV1-3 | SMISC | 67-69 |

JRA1-3 | SMISC | 73-78 |

JTEMP | SMISC | 79 |

**Table 184gen.4: MPC184 General Joint Item and Sequence Numbers - NMISC Items**

Output Quantity Name |
ETABLE and ESOL Command Input | |
---|---|---|

Item | E | |

The following output is available for all general joint
elements (KEYOPT(4) = 0 and 1)
| ||

E1X-I | NMISC | 1 |

E1Y-I | NMISC | 2 |

E1Z-I | NMISC | 3 |

E2X-I | NMISC | 4 |

E2Y-I | NMISC | 5 |

E2Z-I | NMISC | 6 |

E3X-I | NMISC | 7 |

E3Y-I | NMISC | 8 |

E3Z-I | NMISC | 9 |

E1X-J | NMISC | 10 |

E1Y-J | NMISC | 11 |

E1Z-J | NMISC | 12 |

E2X-J | NMISC | 13 |

E2Y-J | NMISC | 14 |

E2Z-J | NMISC | 15 |

E3X-J | NMISC | 16 |

E3Y-J | NMISC | 17 |

E3Z-J | NMISC | 18 |

JFX | NMISC | 19 |

JFY | NMISC | 20 |

JFZ | NMISC | 21 |

JMX | NMISC | 22 |

JMY | NMISC | 23 |

JMZ | NMISC | 24 |

Boundary conditions cannot be applied on the nodes forming the general joint.

Rotational degrees of freedom are activated at the nodes forming the element. When these elements are used in conjunction with solid elements, the rotational degrees of freedom must be suitably constrained. Since boundary conditions cannot be applied to the nodes of the general joint, a beam or shell element with very weak stiffness may be used with the underlying solid elements at the nodes forming the joint element to avoid any rigid body modes.

If both stops and locks are specified, then lock specification takes precedence. That is, if the degree of freedom is locked at a given value, then it will remain locked for the rest of the analysis.

In a nonlinear analysis, the components of relative motion are accumulated over all the substeps. It is essential that the substep size be restricted such that these rotations in a given substep are less than π for the values to be accumulated correctly.

The element currently does not support birth or death options.

The equation solver (

**EQSLV**) must be the sparse solver or the PCG solver. The command**PCGOPT**,,,,,,,ON is also required in order to use the PCG solver.The element coordinate system (

**/PSYMB**,ESYS) is not relevant.