Analysis

Published on July 28th, 2018 | by ozgun

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Contact Types and Behaviours in Ansys

Choosing the appropriate contact type depends on the type of problem you are trying to solve. If modeling the ability of bodies to separate or open slightly is important and/or obtaining the stresses very near a contact interface is important, consider using one of the nonlinear contact types (FrictionlessRoughFrictional), which can model gaps and more accurately model the true area of contact. However, using these contact types usually results in longer solution times and can have possible convergence problems due to the contact nonlinearity. If convergence problems arise or if determining the exact area of contact is critical, consider using a finer mesh on the contact faces or edges.

The available contact types are listed below. Most of the types apply to Contact Regions made up of faces only.

Bonded

This is the default configuration and applies to all contact regions (surfaces, solids, lines, faces, edges). If contact regions are bonded, then no sliding or separation between faces or edges is allowed. Think of the region as glued. This type of contact allows for a linear solution since the contact length/area will not change during the application of the load. If contact is determined on the mathematical model, any gaps will be closed and any initial penetration will be ignored. [Not supported for Rigid Dynamics. Fixed joint can be used instead.]

No Separation

This contact setting is similar to the Bonded case. It only applies to regions of faces (for 3D solids) or edges (for 2D plates). Separation of the geometries in contact is not allowed.

Frictionless

This setting models standard unilateral contact; that is, normal pressure equals zero if separation occurs. Thus gaps can form in the model between bodies depending on the loading. This solution is nonlinear because the area of contact may change as the load is applied. A zero coefficient of friction is assumed, thus allowing free sliding. The model should be well constrained when using this contact setting. Weak springs are added to the assembly to help stabilize the model in order to achieve a reasonable solution.

Rough

Similar to the frictionless setting, these setting models perfectly rough frictional contact where there is no sliding. It only applies to regions of faces (for 3D solids) or edges (for 2D plates). By default, no automatic closing of gaps is performed. This case corresponds to an infinite friction coefficient between the contacting bodies. [Not supported for Explicit Dynamics analyses.]

Frictional

In this setting, the two contacting geometries can carry shear stresses up to a certain magnitude across their interface before they start sliding relative to each other. This state is known as “sticking.” The model defines an equivalent shear stress at which sliding on the geometry begins as a fraction of the contact pressure. Once the shear stress is exceeded, the two geometries will slide relative to each other. The coefficient of friction can be any nonnegative value. [Not supported for Rigid Dynamics. Forced Frictional Sliding should be used instead.]

Forced Frictional Sliding

In this setting, a tangent resisting force is applied at each contact point. The tangent force is proportional to the normal contact force. This settings is similar to Frictional except that there is no “sticking” state. [Supported only for Rigid Dynamics]

By default the friction is not applied during collision. Collisions are treated as if the contact is frictionless regardless the friction coefficient. The following commands override this behavior and include friction in shock resolution (see Rigid Dynamics Command Objects Library in the ANSYS Mechanical User’s Guide for more information).

Note that shock resolution assumes permanent sliding during shock, which may lead to unrealistic results when the friction coefficient is greater than 0.5.

Friction Coefficient

Allows you to enter a friction coefficient. Displayed only for frictional contact applications.

If you want to read more about contact behaviours in Ansys Workbech, you can have a look at the tutorial below;

http://inside.mines.edu/~apetrell/ENME442/Labs/1301_ENME442_lab6_lecture.pdf

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Solid Mechanics, Finite Element and Material Science

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Researcher Solid Mechanics, Finite Element and Material Science



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