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As always, you must associate the contact pair with a contact interaction property definition. The tied contact formulation constrains only translational degrees of freedom in mechanical simulations. Tied contact has not been implemented with self-contact. Self-contact is designed for finite-sliding situations in which it is not obvious from the original geometry which parts of the surface will come into contact during the deformation.

Defining tie constraints

Any slave nodes not precisely in contact at the start of the analysis—e. In mechanical simulations an unconstrained slave node can penetrate the master surface freely. In a thermal, electrical, or pore pressure simulation an unconstrained slave node will not exchange heat, electrical current, or pore fluid with the master surface. It is intended only for nodes that are close to the master surface and is not intended to correct large errors in the mesh geometry.

Defining tied contact for a contact pair. The tied contact formulation. Limitations of tied contact in mechanical simulations. Use of tied contact in nonmechanical simulations.

How can I get contact force in abaqus?

Unconstrained nodes in tied contact pairs. Checking that slave nodes are constrained.It is preferable to use the surface-based tie constraint capability instead of tied contact see Mesh tie constraints for details. As always, you must associate the contact pair with a contact interaction property definition.

tie contact in abaqus

The traditional node-to-surface approach is used by default for tied contact. The tied contact formulation constrains only translational degrees of freedom in mechanical simulations. Self-contact is not supported with tied contact. Self-contact is designed for finite-sliding situations in which it is not obvious from the original geometry which parts of the surface will come into contact during the deformation. Mechanical constraints for tied contact are strictly enforced with a direct Lagrange multiplier method by default.

The constraint enforcement method specified will be applied to the tangential constraints in addition to the normal constraints. Softened contact pressure-overclosure relationships exponential, tabular, or linear—see Contact pressure-overclosure relationships are ignored for tied contact. Any slave nodes not precisely in contact at the start of the analysis—e. In mechanical simulations an unconstrained slave node can penetrate the master surface freely.

In a thermal, electrical, or pore pressure simulation an unconstrained slave node will not exchange heat, electrical current, or pore fluid with the master surface.

It is intended only for nodes that are close to the master surface and is not intended to correct large errors in the mesh geometry. Use of tied contact in mechanical simulations The tied contact formulation constrains only translational degrees of freedom in mechanical simulations. The following topics are discussed: Defining tied contact for a contact pair The tied contact formulation Unconstrained nodes in tied contact pairs.

Related Topics. Defining surface-to-surface contact. Using contact and constraint detection.A tie constraint ties two separate surfaces together so that there is no relative motion between them.

This type of constraint allows you to fuse together two regions even though the meshes created on the surfaces of the regions may be dissimilar.

You can define a tie constraint between edges of a wire or between faces of a solid or shell. For more information, see Understanding constraintsand Mesh tie constraints. If you are creating multiple tie constraints, you may want to use the automatic contact detection tool. This tool automates the process of selecting surfaces and allows you to create multiple constraints simultaneously. For more information, see Using contact and constraint detection. From the main menu bar, select Constraint Create.

Tip: You can also create a tie constraint using the tool in the Interaction module toolbox. In the Create Constraint dialog box that appears, do the following: Name the constraint. For more information about naming objects, see Using basic dialog box components. From the Type list, select Tiethen click Continue.

Select the master surface. In the prompt area, select one of the following: Select Surface if you want to select a named surface. Select Node Region if you want to select a region from which to create a node-based surface.

Use an existing surface to define the region. On the right side of the prompt area, click Surfaces. Select an existing surface name from the Region Selection dialog box that appears, and click Continue. Note: The default selection method is based on the selection method you most recently employed. To revert to the other method, click Select in Viewport or Surfaces on the right side of the prompt area. Use the mouse to select a region in the viewport. For more information, see Selecting objects within the current viewport.

Click mouse button 2 to indicate that you have finished selecting. If the model contains a combination of mesh and geometry, click one of the following from the prompt area:. Click Geometry if you want to select the surface or vertex from a geometry region. Click Mesh if you want to select the surface or node from a native or orphan mesh selection. You can use the angle method to select a group of faces or edges from geometry or a group of element faces from a mesh. For more information, see Using the angle and feature edge method to select multiple objects.

Select the slave surface. In the prompt area, select one of the following: Select Surface if you want to select a surface.

The Switch Surfaces option allows you to interchange your master and slave surface selections without having to start over. The Switch Surfaces icon is available only when the master and slave regions are the same type—both surfaces or both node-based regions. From the editor, select the Discretization method.

Select Node to surface to generate the tie coefficients according to the interpolation functions at the point where the slave node projects onto the master surface. Select Surface to surface to generate the tie coefficients such that stress accuracy is optimized for the specified surface pairing. Toggle on Exclude shell element thickness if you want to ignore shell thickness effects in calculations involving position tolerances and adjustments for initial gaps.

tie contact in abaqus

Choose one of the following Position Tolerance methods: Use computed default. Abaqus determines the nodes to be tied using the default position tolerance.A surface-based tie constraint can be used to make the translational and rotational motion as well as all other active degrees of freedom equal for a pair of surfaces. By default, as discussed below, nodes are tied only where the surfaces are close to one another. One surface in the constraint is designated to be the slave surface; the other surface is the master surface.

Either element-based or node-based surfaces can be used as the slave surface. Any surface type element-based, node-based, or analytical can be used as the master surface.

tie contact in abaqus

Table 1 and Table 2 provide comparisons of surface restrictions for the different formulations and analysis codes. The surface-to-surface formulation generally avoids stress noise at tied interfaces.

As indicated in Table 1 and Table 2only a few surface restrictions apply to the surface-to-surface formulation: this formulation reverts to the node-to-surface formulation if a node-based or edge-based surface is used. The surface-to-surface formulation does not allow for a mixture of rigid and deformable portions of a surface, and the master surface must not contain T-intersections.

Any nodes shared between the slave and master surfaces will not be tied with the surface-to-surface formulation. Nodes and faces that are shared between the master and slave surfaces are eliminated automatically from the master surface in this case if the paired surfaces are either both element-based or both node-based, enabling the possibility of tying multiple slave surfaces defined over various regions of the model to a common master surface defined over the entire model.

tie contact in abaqus

This is a convenient way to define tie constraints in large models, as it eliminates the need for defining specialized master surfaces for each surface pairing; however, you must still take care that slave surfaces do not include portions of the opposing surface to which they should be tied for example, no tie constraints will be generated if the master and slave surfaces are identical.

Sometimes when meshes are transitioned from one type of element to another type or from one element size to another element size, common nodes may exist at the interface of the two regions. Typically, a tie constraint is defined at the interface of the two zones to stitch the two meshes together.

In a situation like this common nodes may get tied to a neighboring facet on the interface and may cause undesirable mesh distortion due to the tie adjustment. One possible way to avoid the undesirable mesh distortion is to specify a very small position tolerance for the tie pair. Another situation that may arise when common nodes occur between the slave and master surfaces at the interface of mesh transition zones is that slave nodes in the vicinity of the common node may not get tied.

This happens due to the exclusion of master facets attached to the common nodes. Therefore, care must be taken to ensure that elements in different mesh zones do not share common nodes at the interface. For all such common nodes, duplicate nodes occupying the same physical location should be defined. In addition, you can define surfaces as collections of faces and edges using the Surface toolset.

By default, Abaqus uses a position tolerance criterion to determine the constrained nodes based on the distance between the slave nodes and the master surface. Alternatively, you can specify a node set containing the slave nodes to be constrained regardless of their distance to the master surface.

The default position tolerance criterion ensures that nodes are tied only where the slave and master surfaces are close to one another in the initial configuration.A tie constraint ties two separate surfaces together so that there is no relative motion between them. This type of constraint allows you to fuse together two regions even though the meshes created on the surfaces of the regions may be dissimilar.

You can define a tie constraint between edges of a wire or between faces of a solid or shell. From the main menu bar, select Constraint Create. In the Create Constraint dialog box that appears, do the following:.

Name the constraint. From the Type list, select Tiethen click Continue. Use one of the following methods to select the master surface: Use an existing surface to define the region.

On the right side of the prompt area, click Surfaces. Select an existing surface from the Region Selection dialog box that appears, and click Continue. To revert to the other method, click Select in Viewport or Surfaces on the right side of the prompt area.

Use the mouse to select a region in the viewport. Click mouse button 2 to indicate that you have finished selecting. You must select a region from only one part instance; the region that you select cannot span multiple part instances. If the model contains a combination of orphan mesh instances and native geometric part instances, click one of the following from the prompt area: Click Geometry if you want to select the surface or vertex from a native geometric part instance.

Click Mesh if you want to select the surface or node from an orphan mesh instance. In the prompt area, click the arrow next to the text field and select one of the following: Select Surface if you want to select a surface. Select Node Region if you want to select a region from which to create a node-based surface. After you select the slave surface, the constraint editor appears. The Switch button allows you to interchange your master and slave surface selections without having to start over.

The Switch button is available only if you selected Surface in the previous step. From the editor, select the Constraint enforcement method. Select Node to surface to generate the tie coefficients according to the interpolation functions at the point where the slave node projects onto the master surface.

Select Surface to surface to generate the tie coefficients such that stress accuracy is optimized for the specified surface pairing. Toggle on Exclude shell element thickness if you want to ignore shell thickness effects in calculations involving position tolerances and adjustments for initial gaps.

Choose one of the following Position Tolerance methods: Use computed default. Specify distance.The order in which the two surfaces are specified is critical because of the manner in which surface interactions are discretized. The interaction is then discretized between the point on the master surface and the slave node. Figure The slave nodes are constrained not to penetrate into the master surface; however, the nodes of the master surface can, in principle, penetrate into the slave surface see Figure Generally, contact interactions occur between two surfaces.

Thus, a slave surface can be defined as a group of nodes—a node-based surface. Slave surfaces must always be attached to deformable bodies or deformable bodies defined as rigid. Analytical and rigid-element-based surfaces must always be the master surface in the contact pair. Both surfaces in a contact pair cannot be rigid surfaces with the exception of deformable surfaces defined as rigid.

A node-based surface must always be the slave surface. When both surfaces in a contact pair are deformable surfaces, you have to choose which surface will be the slave surface and which will be the master surface.

Abaqus Tutorial Videos - Contact Analysis of 3D Shell Parts in Abaqus 6.14

Generally, the master surface should be chosen as the surface of the stiffer body or as the surface with the coarser mesh if the two surfaces are on structures with comparable stiffnesses. The stiffness of the structure and not just the material should be considered when choosing the master and slave surface. For example, a thin sheet of metal may be less stiff than a larger block of rubber even though the steel has a larger modulus than the rubber material.

If the stiffness and mesh density are the same on both surfaces, the preferred choice is not always obvious. A master surface must have a consistent orientation. The direction of the master surface's outward normal is critical for the proper detection of contact. Except for initial interference fit problems, the slave surface should be on the same side of the master surface as the outward normal. In most of these cases the analysis will immediately fail to converge.

It is easy to create a surface with the wrong orientation when using structural beam and shellmembrane, truss, or rigid elements; therefore, check any surfaces created on these elements carefully. A master surface cannot be made up of two or more disconnected regions—it must be continuous across element edges in three-dimensional models or through nodes in two-dimensional models. The continuity requirement has several implications for what constitutes a valid or invalid master surface definition.

In two dimensions the surface must be either a simple, nonintersecting curve with two terminal ends or a closed loop. In three dimensions an edge of an element face belonging to a valid surface may be either on the perimeter of the surface or shared by one other face. Two element faces forming a contact surface cannot be joined just at a shared node; they must be joined across a common element edge.

An element edge cannot be shared by more than two surface facets.See About contact interactions for a comparison of the two algorithms. The general contact algorithm allows for very general characteristics in the surfaces that it uses, as discussed in About contact interactions.

Two-dimensional surfaces cannot be used with the general contact algorithm. A convenient method of specifying the contact domain is using cropped surfaces.

For more information, see Operating on surfaces. The all-inclusive automatically defined surface includes all element-based surface facets as well as all analytical rigid surfaces and surfaces on all Eulerian materials. The general contact algorithm generates contact forces to resist node-into-face, node-into-analytical rigid surface, and edge-into-edge contact penetrations.

The primary mechanism for enforcing contact is node-to-face contact the only mechanism used in the contact pair algorithm. If analytical rigid surfaces are present in the contact domain, the general contact algorithm also enforces node-to-analytical rigid surface contact. The general contact algorithm also considers edge-to-edge contact, which is very effective in enforcing contact that cannot be detected as penetrations of nodes into faces.

For example, contact between beam segments and shell perimeter edges see Figure 1 usually is detected only as edge-to-edge contact. The contact edges representing beam and truss elements have a circular cross-section, regardless of the actual cross-section of the beam or truss element.

The radius of a contact edge representing a truss element is derived from the cross-sectional area specified on the truss section definition it is equal to the radius of a solid circular section with an equivalent cross-sectional area. For beams with circular cross-sections, the radius of the contact edge is equivalent to the section radius. For beams with non-circular cross-sections, the radius of the contact edge is equal to the radius of a circumscribed circle around the section.

If connected edges have different radii, a nodal radius is first computed as the minimum radius of the adjacent contact edges, and the radius of the edge cross-section is interpolated linearly over the length of the contact edge from the nodal values. Shell element edges reflect the shell thickness in the normal direction and do not extend past the perimeter similar to shell nodes and facets. Some numerical rounding of features occurs for both node-to-facet and edge-to-edge contact.

To model contact between edges that are not cylindrical in shape, surface elements can be attached to the edge nodes using surface-based tie constraints and node-to-face contact can be defined between the surface elements see Surface elements. This technique is useful for modeling geometric details important to the contact definition that are not modeled with the underlying element geometry.

Surface elements can also be defined around shell elements in which Abaqus has reduced the contact thickness i. However, using surface elements with general contact requires a physically reasonable mass to be associated with the surface element nodes, and care must be taken not to alter the bulk mass properties when transferring mass to the surface elements from the underlying elements.

By default, when a surface is used in a general contact interaction, all applicable facets, analytical rigid surfaces, nodes, perimeter edges, and beam and truss segments are included in the contact definition.

Geometric feature edges and perimeter edges do not have to be included explicitly in a surface definition by using edge identifiers for them to be considered for edge-to-edge contact. The general contact algorithm also enforces contact between Eulerian materials and Lagrangian surfaces.

Mesh tie constraints

This algorithm automatically compensates for mesh size discrepancies to prevent penetration of Eulerian material through the Lagrangian surface. Eulerian-Lagrangian contact is enforced only for Lagrangian surfaces defined on solid and shell elements.

Other surface types, such as beam edges and analytical rigid surfaces, are ignored. Contact interactions between Eulerian materials and interactions due to Eulerian material self-contact are handled naturally by the Eulerian formulation; these interactions do not require a general contact definition.

See Interactions for more information. If a general contact definition does not appear in a step, any general contact definition active in the previous step will be propagated to the current step.

For convenience, general contact can be defined as model data. Alternatively, you can make changes to an existing general contact definition. In this case the existing general contact definition remains active and any additional information specified is appended to the general contact definition.

Contact state information such as the proper contact normal orientation for double-sided surfaces is transferred across step boundaries even if the contact domain is modified. Each part of a general contact definition is considered independently when it is modified.

For example, the following contact definition is specified in Step 1 the individual options are discussed later in this section :.