MPC184-Spotweld


Multipoint Constraint Element: Spotweld Joint

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MPC184 Spotweld Joint Element Description

The MPC184 Spotweld joint is a two-node element used primarily for modeling spotweld behavior. The element requires a specified stiffness and/or damping at the element center. The relative degrees of freedom are unconstrained.

Figure 184spwd.1: MPC184 Spotweld Joint Geometry

MPC184 Spotweld Joint Geometry

MPC184 Spotweld Joint Input Data

Set KEYOPT(1) = 18 to define a two-node spotweld joint element.

Figure 184spwd.1: MPC184 Spotweld Joint Geometry shows the geometry and node locations for this element. The local coordinate systems can be specified in either of the following ways:

  • Issue SECJOINT,LSYS,Val1,Val2 to specify the local coordinate system IDs (Val1 and Val2).

  • Issue SECJOINT,LSYS,IJX (or IJY or IJZ) to construct the local coordinate system based on the vector joining the nodes I to J of the spotweld joint element.

The specified local coordinate systems are used in the spring/damping calculations.

By default, the location of the center (where the spring or damping behavior is active) is located midway between nodes I and J. The center location can be changed as follows:

  • Issue SECJOINT,SPWE,RATIO,Val2 (where 0≤ Val2 ≤ 1). The location of the center is determined based on the locations of nodes I and J and the specified value.

  • Issue SECJOINT,SPWE,COORD,Val2,Val3,Val4 (where Val2, Val3, Val4 represent the global X,Y,Z coordinates of the center). This option enables you to offset the center away from the line joining nodes I and J.

The relative displacements and rotations between nodes I and J are determined in the same way as for general joints.

The reference lengths and angles   are not used in spotweld joint calculations.

MPC184 Spotweld Joint Input Summary

This input summary applies to the spotweld joint element form of MPC184: KEYOPT(1) = 18.

Nodes

I, J

Degrees of Freedom

UX, UY, UZ, ROTX, ROTY, ROTZ

Real Constants

None

Material Properties

Issue TB,JOIN to define stiffness and damping behavior. (See MPC184 Joint in the Material Reference for information about defining joint materials.)

Surface Loads

None

Body Loads
Temperatures -- 

T(I), T(J)

Element Loads
Displacements/Rotations -- 

UX, UY, UZ, ROTX, ROTY, ROTZ

Velocities  -- 

VELX, VELY, VELZ, OMGX, OMGY, OMGZ

Accelerations  -- 

ACCX, ACCY, ACCZ, DMGX, DMGY, DMGZ

Forces/Moments  -- 

FX, FY, FZ, MX, MY, MZ

Special Features
KEYOPT(1)

Element behavior:

18  -- 

Spotweld joint element

KEYOPT(2)

Element constraint-imposition method:

0 -- 

Lagrange multiplier method (default)

1  -- 

Penalty-based method

MPC184 Spotweld 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 184spwd.1: MPC184 Spotweld Joint Element Output Definitions

NameDefinitionOR
ELElement number-Y
NODESElement node numbers (I, J)-Y
The constraint force and moment output depends on which of the relative degrees of freedom are constrained:
FXConstraint force in X direction-Y
FYConstraint force in Y direction-Y
FZConstraint force in Z direction-Y
MXConstraint moment in X direction-Y
MYConstraint moment in Y direction-Y
MZConstraint moment in Z direction-Y
The following output depends on which of the relative degrees of freedom are unconstrained:
JRP1-6Joint relative position of DOFs 1-6-Y
JCD1-6Joint relative position of DOFs 1-6 Joint constitutive displacement/rotation of DOFs 1-6-Y
JEF1-6 Joint elastic force/moment 1-6-Y
JDF1-6Joint damping force/moment 1-6 -Y
JRU1-6Joint relative displacement/rotation 1-6 -Y
JRV1-6Joint relative velocity (or rotational velocity) 1-6-Y
JRA1-6Joint relative acceleration (or rotational acceleration) 1-6-Y
JTEMPAverage temperature in the element[a] -Y

[a] Average temperature in the element when temperatures are applied on the element (BFE) or on element nodes (BF).


The following table shows additional non-summable miscellaneous (NMISC) output available for the spotweld 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 joint element nodes.

Table 184spwd.2: MPC184 Spotweld 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 184spwd.3: MPC184 Spotweld Joint Item and Sequence Numbers - SMISC Items and Table 184spwd.4: MPC184 Spotweld Joint Item and Sequence Numbers - NMISC Items list output available via ETABLE 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 184spwd.3: MPC184 Spotweld Joint Item and Sequence Numbers - SMISC Items

Output Quantity NameETABLE and ESOL Command Input
ItemE
FXSMISC1
FYSMISC2
FZSMISC3
MXSMISC4
MYSMISC5
MZSMISC6
JRP1-6SMISC31-36
JCD1-6SMISC37-42
JEF1-6SMISC43-48
JDF1-6SMISC49-54
JRU1-6SMISC61-66
JRV1-6SMISC67-72
JRA1-6SMISC73-78
JTEMPSMISC79

Table 184spwd.4: MPC184 Spotweld Joint Item and Sequence Numbers - NMISC Items

Output Quantity NameETABLE 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 Spotweld Joint Assumptions and Restrictions

  • Boundary conditions cannot be applied on the nodes forming the spotweld joint.

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

  • In a nonlinear analysis, the components of relative motion are accumulated over all 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.

  • Element birth and death options are not available.

  • For the Lagrange multiplier element formulation (KEYOPT(2) = 0) and the penalty-based element formulation (KEYOPT(2) = 1), the equation solver (EQSLV) must be the sparse or PCG solver.

  • 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 Spotweld Joint Product Restrictions

None.