MPC184-Translational

Multipoint Constraint Element: Translational Joint

MPC184 Translational Joint Element Description

The MPC184 translational joint element is a two-node element that has one relative displacement degree of freedom. All other relative degrees of freedom are fixed.

Figure 184tran.1: MPC184 Translational Joint Geometry

MPC184 Translational Joint Input Data

Set KEYOPT(1) = 10 to define a two-node translational joint element.

Figure 184tran.1: MPC184 Translational 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 local coordinate system specification at the second node is optional. The second node J is constrained to move along the e₁ axis specified at node I. 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 translational joint element are easily described by referring to Figure 184tran.1: MPC184 Translational Joint Geometry. At any given instant of time, the constraints imposed are 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. Essentially these constraints force the node J to move along the e₁ axis of the local coordinate system specified at node I. e^I are in the current configuration, while E^I are specified in the initial configuration.

The change in the relative position of the nodes I and J is given by:

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

where:

= reference length, length1, specified on SECDATA command

If the reference length is not specified, the initial offset is 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 Translational Joint Input Summary

This input summary applies to the translational joint element option of MPC184: KEYOPT(1) = 10.

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, damping, and Coulomb friction 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:

10 --: Translational joint element

MPC184 Translational 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 184tran.1: MPC184 Translational Joint Element Output Definitions and Table 184tran.2: MPC184 Translational 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 184tran.1: MPC184 Translational Joint Element Output Definitions

Name	Definition	O	R
EL	Element number	-	Y
NODES	Element node numbers (I, J)	-	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
CSTOP1	Constraint force if stop is specified on DOF 1	-	Y
CLOCK1	Constraint force if lock is specified on DOF 1	-	Y
CSST1	Constraint stop status[1]	-	Y
CLST1	Constraint lock status[2]	-	Y
JRP1	Joint relative position	-	Y
JCD1	Joint constitutive displacement	-	Y
JEF1	Joint elastic force	-	Y
JDF1	Joint damping force	-	Y
JFF1	Joint friction force	-	Y
JRU1	Joint relative displacement	-	Y
JRV1	Joint relative velocity	-	Y
JRA1	Joint relative acceleration	-	Y
JTEMP	Average temperature in the element[3]	-	Y
JFST1	Slip/stick status when friction is specified[4]	-	Y
JFNF1	Normal moment in friction calculations	-	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.
Stick/slip status when friction is active:
0 = friction is not activated
1 = sticking
2 = slipping or sliding

The following table shows additional non-summable miscellaneous (NMISC) output available for the translational 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 184tran.2: MPC184 Translational 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 184tran.3: MPC184 Translational Joint Item and Sequence Numbers - SMISC Items and Table 184tran.4: MPC184 Translational 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 184tran.3: MPC184 Translational Joint Item and Sequence Numbers - SMISC Items

Output Quantity Name	ETABLE and ESOL Command Input
Output Quantity Name	Item	E
FY	SMISC	2
FZ	SMISC	3
MX	SMISC	4
MY	SMISC	5
MZ	SMISC	6
CSTOP1	SMISC	7
CLOCK1	SMISC	13
CSST1	SMISC	19
CLST1	SMISC	25
JRP1	SMISC	31
JCD1	SMISC	37
JEF1	SMISC	43
JDF1	SMISC	49
JFF1	SMISC	55
JRU1	SMISC	61
JRV1	SMISC	67
JRA1	SMISC	73
JTEMP	SMISC	79
JFST1	SMISC	80
JFNF1	SMISC	81

Table 184tran.4: MPC184 Translational 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 Translational Joint Assumptions and Restrictions

Boundary conditions cannot be applied on the nodes forming the translational 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 translational 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 Translational 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.