INTER194 Element Description

INTER194 is a 3D 16-node quadratic interface element. When used with 3D quadratic structural elements (SOLID186, and SOLID187), INTER194 simulates gasket joints (KEYOPT(2) = 0 or 1). It is defined by 16 nodes having three degrees of freedom at each node: translations in the nodal x, y, and z directions.

INTER194 is also suitable for modeling thin-solid structures with linear elastic materials (KEYOPT(2) = 2 or 3) or nonlinear von Mises plasticity (KEYOPT(2)=2). Element behavior through-the-thickness is assumed to be uniform. To properly capture the bending stiffness of a thin-solid structure, consider using standard structural solid elements (such as SOLID185 and SOLSH190).

See Gasket Material and INTER194 in the Mechanical APDL Theory Reference for more details about this element.

Also see Gasket Joints Simulation in the Structural Analysis Guide for more details about gasket simulation.

Figure 194.1: INTER194 Geometry

INTER194 Input Data

The element geometry, node locations, connectivity, and the nodal coordinate system are shown in Figure 194.1: INTER194 Geometry. The element geometry is defined by 16 nodes, which form bottom and top surfaces of the element. The bottom surface is defined by nodes, I, J, K, L, Q, R, S, T; and the top surface is defined by nodes, M, N, O, P, U, V, W, X. As shown, the element connectivity is defined as I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X. The element is degenerated to a wedge (prism) element, when K=L=S and O=P=W, as shown in Figure 194.2: INTER194 3D 16-Node Degenerated Quadratic Interface.

Figure 194.2: INTER194 3D 16-Node Degenerated Quadratic Interface

For the degenerated element, 3 integration points are used for numerical integration. The degenerated element can be used in conjunction with 10-node solid tetrahedral elements (such as SOLID187). Dropping any or some of midside nodes, Q, R, S, T, U, V, W, X is not permitted.

Temperatures can be input as element body loads at the nodes. The node I temperature T(I), defaults to TUNIF. If all other temperatures are unspecified, they default to T(I). For any other input pattern, unspecified temperatures default to TUNIF.

Gasket Joint Behavior (KEYOPT(2) = 0 or 1)

When used as a gasket joint, the element uses a full-integration scheme (KEYOPT(4) = 2) and is capable of both through-the-thickness and transverse-shear deformations (KEYOPT(2) = 1) by default. For through-the-thickness deformation only, set KEYOPT(2) = 0.

The full-integration scheme and the inclusion of transverse-shear stiffness are generally required when the interfaces between the gasket and the mating parts are modeled as sliding contact; however, if the interfaces are modeled with a matching mesh method (that is, with coincident nodes), Ansys, Inc. recommends using the reduced-integration scheme (KEYOPT(4) = 0) and through-the-thickness deformation only (KEYOPT(2) = 0) for better efficiency and to avoid unnecessary in-plane interaction between the gasket and the mating parts.

Thin-Solid Element Behavior (KEYOPT(2) = 2 or 3)

To include both membrane and transverse stiffnesses, set KEYOPT(2) = 2. To account for transverse stiffness (thickness normal and transverse shear) only, set KEYOPT(2) = 3.

Because the element behaviors through-the-thickness are assumed to be uniform, the program uses a reduced-integration scheme (one integration point though the thickness).

If the element is not adequately constrained via either matching nodes or bonded contact with other mating parts, include a small stabilization stiffness to suppress the hourglass modes resulting from the reduced-integration rule. The stable stiffness can be added by specifying a positive stiffness scaling factor HGSTIF via the third real constant (C3). The stable stiffness is equal to HGSTIF*K, where K is the representative native stiffness of the thin-solid.

Only the linear elastic material properties, and standard stress and strain outputs, are supported by the thin-solid option without membrane stiffness (KEYOPT(2) = 3). Additionally, nonlinear material behavior based on von Mises plasticity is supported by the thin-solid behavior with membrane and transverse shear stiffness (KEYOPT(2) = 2). Corresponding plasticity related outputs, such as plastic strain, are available in this case.

By default, the element thickness is equal to the distance between the element top and bottom faces. By setting KEYOPT(7) = 1, you can provide a user-defined element thickness THKE via the second real constant (C2).

Element Orientation

You can define element orientation (ESYS) as described in Coordinate Systems. If you do so, the program compares the x axis of the local Cartesian coordinate system with the element normal direction. Proceed as follows:

The new element z axis is obtained by the cross product of the element normal and the new element y axis according to the right-hand rule.

Figure 194.3: INTER194 Element Orientation

INTER194 Output Data

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

The output directions for element items are parallel to the local element coordinate system based on the element midplane as illustrated in Figure 194.4: INTER194 Stress Output. See Gasket Material in the Mechanical APDL Theory Reference for details.

A general description of solution output is given in Solution Output. See the Basic Analysis Guide for ways to review results.

Figure 194.4: INTER194 Stress Output

The Element Output Definitions table uses the following notation:

A colon (:) in the Name column indicates that the item can be accessed by the Component Name method (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 “-” indicates that the item is not available.

INTER194 Assumptions and Restrictions

INTER194 Product Restrictions

There are no product-specific restrictions for this element.