MPC184-Point

Multipoint Constraint Element: Point-in-plane Joint

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

## MPC184 Point-in-plane Joint Element Description

The MPC184 point-in-plane joint element is a two-node element that has two relative displacement degrees of freedom. The relative rotational degrees of freedom are not considered and cannot be controlled.

## MPC184 Point-in-plane Joint Input Data

Set KEYOPT(1) = 9 to define a two-node point-in-plane joint element.

Figure 184poin.1: MPC184 Point-in-plane Joint Geometry shows the geometry and node locations for this element. Two nodes (I and J) define the element.

A local Cartesian coordinate system must be specified at the first node, I, of the element. The second node, J, is constrained such that it remains on a plane defined by the local and axes. The normal distance from this plane containing node J to node I is held fixed. The local coordinate system specified at node I evolves with the rotations at node I. Use the SECJOINT command to specify the identifiers of the local coordinate systems.

The constraints imposed on a point-in-plane joint element are easily described by referring to Figure 184poin.1: MPC184 Point-in-plane Joint Geometry. At any given instant of time, the constraint imposed is as follows:

Where, xI and xJ are the positional vectors of nodes I and J in the current configuration, and XI and XJ are the position vectors of nodes I and J in the reference configuration. eI are in the current configuration, while EI are specified in the initial configuration.

The changes in the relative position of the nodes I and J are given by:

The constitutive calculations use the following definition of the joint displacement:

where:

 = reference length specified on the SECDATA command = reference length specified on the SECDATA command

If the reference lengths are not specified, the initial offsets are used.

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.

### MPC184 Point-in-plane Joint Input Summary

This input summary applies to the point-in-plane joint element option of MPC184: KEYOPT(1) = 9.

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

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.)

None

Temperatures --

T(I), T(J)

None

Special Features
 Large deflection Linear perturbation
KEYOPT(1)

Element behavior:

9  --

Point-in-plane joint element

## MPC184 Point-in-plane Joint Output Data

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

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 184poin.1:  MPC184 Point-in-plane Joint Element Output Definitions

NameDefinitionOR
ELElement Number-Y
NODESElement node numbers (I, J)-Y
FXConstraint Force in X direction-Y
CSTOP2Constraint force if stop is specified on DOF 2-Y
CSTOP3Constraint force if stop is specified on DOF 3-Y
CLOCK2Constraint force if lock is specified on DOF 2-Y
CLOCK3Constraint force if lock is specified on DOF 3-Y
CSST2Constraint stop status on DOF 2[1]-Y
CLST2Constraint lock status on DOF 2[2]-Y
CSST3Constraint stop status on DOF 3[1]-Y
CLST3Constraint lock status on DOF 3[2]-Y
JRP2Joint relative position of DOF2-Y
JRP3Joint relative position of DOF3-Y
JCD2Joint constitutive displacement on DOF2-Y
JCD3Joint constitutive displacement on DOF3-Y
JEF2Joint elastic force in direction -2-Y
JEF3Joint elastic force in direction -3-Y
JDF2Joint damping force in direction -2-Y
JDF3Joint damping force in direction -3-Y
JRU2Joint relative displacement in direction -2-Y
JRU3Joint relative displacement in direction -3-Y
JRV2Joint relative velocity in direction -2-Y
JRV3Joint relative velocity in direction -3-Y
JRA2Joint relative acceleration in direction -2-Y
JRA3Joint relative acceleration in direction -3-Y
JTEMPAverage temperature in the element[3]-Y

1. Constraint stop status:

 0 = stop not active, or deactivated 1 = stopped at minimum value 2 = stopped at maximum value
2. Constraint lock status:

 0 = lock not active 1 = locked at minimum value 2 = locked at maximum value
3. 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 the point-in-plane 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 184poin.2:  MPC184 Point-in-plane Joint Element - NMISC Output

NameDefinitionOR
E1X-I, E1Y-I, E1Z-IX, Y, Z components of the evolved e1 axis at node I-Y
E2X-I, E2Y-I, E2Z-IX, Y, Z components of the evolved e2 axis at node I-Y
E3X-I, E3Y-I, E3Z-IX, Y, Z components of the evolved e3 axis at node I-Y
E1X-J, E1Y-J, E1Z-JX, Y, Z components of the evolved e1 axis at node J-Y
E2X-J, E2Y-J, E2Z-JX, Y, Z components of the evolved e2 axis at node J-Y
E3X-J, E3Y-J, E3Z-JX, Y, Z components of the evolved e3 axis at node J-Y
JFX, JFY, JFZConstraint forces expressed in the evolved coordinate system specified at node I-Y
JMX, JMY, JMZConstraint moments expressed in the evolved coordinate system specified at node I-Y

Table 184poin.3: MPC184 Point-in-plane Joint Item and Sequence Numbers - SMISC Items and Table 184poin.4: MPC184 Point-in-plane 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 table uses 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 184poin.3:  MPC184 Point-in-plane Joint Item and Sequence Numbers - SMISC Items

Output Quantity Name ETABLE and ESOL Command Input
ItemE
FXSMISC1
CSTOP2SMISC8
CSTOP3SMISC9
CLOCK2SMISC14
CLOCK3SMISC15
CSST2SMISC20
CLST2SMISC26
CSST3SMISC21
CLST3SMISC27
JRP2SMISC32
JRP3SMISC33
JCD2SMISC38
JCD3SMISC39
JEF2SMISC44
JEF3SMISC45
JDF2SMISC50
JDF3SMISC51
JRU2SMISC62
JRU3SMISC63
JRV2SMISC68
JRV3SMISC69
JRA2SMISC74
JRA3SMISC75
JTEMPSMISC79

Table 184poin.4:  MPC184 Point-in-plane Joint Item and Sequence Numbers - NMISC Items

Output Quantity Name ETABLE and ESOL Command Input
ItemE
E1X-INMISC1
E1Y-INMISC2
E1Z-INMISC3
E2X-INMISC4
E2Y-INMISC5
E2Z-INMISC6
E3X-INMISC7
E3Y-INMISC8
E3Z-INMISC9
E1X-JNMISC10
E1Y-JNMISC11
E1Z-JNMISC12
E2X-JNMISC13
E2Y-JNMISC14
E2Z-JNMISC15
E3X-JNMISC16
E3Y-JNMISC17
E3Z-JNMISC18
JFXNMISC19
JFYNMISC20
JFZNMISC21
JMXNMISC22
JMYNMISC23
JMZNMISC24

## MPC184 Point-in-plane Joint Assumptions and Restrictions

• Boundary conditions cannot be applied on the nodes forming the point-in-plane 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 point-in-plane 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.

## MPC184 Point-in-plane Joint Product Restrictions

When used in the product(s) listed below, the stated product-specific restrictions apply to this element in addition to the general assumptions and restrictions given in the previous section.

ANSYS Mechanical Pro

• Linear perturbation is not available.