MPC184-Point

Multipoint Constraint Element: Point-in-plane Joint

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.

Figure 184poin.1: MPC184 Point-in-plane Joint Geometry

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, x^I and x^J are the positional vectors of nodes I and J in the current configuration, and X^I and X^J are the position vectors of nodes I and J in the reference configuration. e^I are in the current configuration, while E^I 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

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.)

Surface Loads

None

Body Loads

Temperatures --: T(I), T(J)

Element Loads

None

Special Features

Large deflection

Linear perturbation

KEYOPT(1)

Element behavior:

9 --: Point-in-plane joint element

KEYOPT(2)

Element constraint imposition method:

0 --: Lagrange multiplier method (default)
1 --: Penalty-based method

MPC184 Point-in-plane Joint Output Data

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 184poin.1: MPC184 Point-in-plane Joint Element Output Definitions and Table 184poin.2: MPC184 Point-in-plane 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 184poin.1: MPC184 Point-in-plane Joint Element Output Definitions

Name	Definition	O	R
EL	Element Number	-	Y
NODES	Element node numbers (I, J)	-	Y
FX	Constraint Force in X direction	-	Y
CSTOP2	Constraint force if stop is specified on DOF 2	-	Y
CSTOP3	Constraint force if stop is specified on DOF 3	-	Y
CLOCK2	Constraint force if lock is specified on DOF 2	-	Y
CLOCK3	Constraint force if lock is specified on DOF 3	-	Y
CSST2	Constraint stop status on DOF 2[1]	-	Y
CLST2	Constraint lock status on DOF 2[2]	-	Y
CSST3	Constraint stop status on DOF 3[1]	-	Y
CLST3	Constraint lock status on DOF 3[2]	-	Y
JRP2	Joint relative position of DOF2	-	Y
JRP3	Joint relative position of DOF3	-	Y
JCD2	Joint constitutive displacement on DOF2	-	Y
JCD3	Joint constitutive displacement on DOF3	-	Y
JEF2	Joint elastic force in direction -2	-	Y
JEF3	Joint elastic force in direction -3	-	Y
JDF2	Joint damping force in direction -2	-	Y
JDF3	Joint damping force in direction -3	-	Y
JRU2	Joint relative displacement in direction -2	-	Y
JRU3	Joint relative displacement in direction -3	-	Y
JRV2	Joint relative velocity in direction -2	-	Y
JRV3	Joint relative velocity in direction -3	-	Y
JRA2	Joint relative acceleration in direction -2	-	Y
JRA3	Joint relative acceleration in direction -3	-	Y
JTEMP	Average temperature in the element[3]	-	Y

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

Name	Definition	O	R
E1X-I, E1Y-I, E1Z-I	X, Y, Z components of the evolved e₁ axis at node I	-	Y
E2X-I, E2Y-I, E2Z-I	X, Y, Z components of the evolved e₂ axis at node I	-	Y
E3X-I, E3Y-I, E3Z-I	X, Y, Z components of the evolved e₃ axis at node I	-	Y
E1X-J, E1Y-J, E1Z-J	X, Y, Z components of the evolved e₁ axis at node J	-	Y
E2X-J, E2Y-J, E2Z-J	X, Y, Z components of the evolved e₂ axis at node J	-	Y
E3X-J, E3Y-J, E3Z-J	X, Y, Z components of the evolved e₃ 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 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
Output Quantity Name	Item	E
FX	SMISC	1
CSTOP2	SMISC	8
CSTOP3	SMISC	9
CLOCK2	SMISC	14
CLOCK3	SMISC	15
CSST2	SMISC	20
CLST2	SMISC	26
CSST3	SMISC	21
CLST3	SMISC	27
JRP2	SMISC	32
JRP3	SMISC	33
JCD2	SMISC	38
JCD3	SMISC	39
JEF2	SMISC	44
JEF3	SMISC	45
JDF2	SMISC	50
JDF3	SMISC	51
JRU2	SMISC	62
JRU3	SMISC	63
JRV2	SMISC	68
JRV3	SMISC	69
JRA2	SMISC	74
JRA3	SMISC	75
JTEMP	SMISC	79

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

Output Quantity Name	ETABLE and ESOL Command Input
Output Quantity Name	Item	E
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

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.
For the Lagrange multiplier element formulation (KEYOPT(2) = 0), the equation solver (EQSLV) must be the sparse solver. Either the sparse or the PCG solver can be used with penalty based element formulation (KEYOPT(2)=1).
Lagrange multiplier-based joint elements (KEYOPT(2) = 0) and penalty-based joint elements (KEYOPT(2) = 1) cannot be connected to each other.
The element coordinate system (/PSYMB,ESYS) is not relevant.

MPC184 Point-in-plane Joint Product Restrictions

None.