The *CONTACT CONTROLS option with the MAXCHP, PERRMX, and UERRMX parameters provides the user with control over the contact logic by allowing the contact criteria to be violated to prescribed tolerances at any number of contact points. The *CONTACT CONTROLS option with the AUTOMATIC TOLERANCES parameter works in a similar fashion, but the values of the tolerance parameters are calculated automatically. The controls specified with this option remain in effect until they are either changed by another *CONTACT CONTROLS option or reset to their default values by the *CONTACT CONTROLS, RESET option. Tolerance controls can be defined for a specific contact pair or for the entire model. Further description of the tolerance controls can be found in “Adjusting contact controls in ABAQUS/Standard,” Section 29.2.12 of the ABAQUS Analysis User's Manual. In this test various combinations of tolerance controls are tested in a multistep analysis with multiple contact pairs.

The model consists of eight contact surfaces (some of which have interface properties defined with the *SURFACE BEHAVIOR option) and a slider block arrangement. There are 13 steps in which the tolerance controls are applied either to the entire model, to individual contact surfaces, or to both. The surfaces are repeatedly brought together and separated to verify the normal contact constraints. The slider block arrangement tests the tangential contact constraints.

The *CONTACT CONTROLS option with the STABILIZE parameter can be used to control rigid body motions that may exist in a model before contact is fully developed. The option adds viscous damping in both the normal and tangential directions. By default, the damping is calculated automatically, but it is possible to modify the damping coefficient, the variation of the damping coefficient over the step, the range over which the damping works, and the ratio between normal and tangential damping. The controls specified with this option remain in effect until they are either changed by another *CONTACT CONTROLS option or reset to their default values by the *CONTACT CONTROLS, RESET option. Contact stabilization can be defined for a specific contact pair or for the entire model. Further description of the stabilization controls can be found in “Adjusting contact controls in ABAQUS/Standard,” Section 29.2.12 of the ABAQUS Analysis User's Manual. In these tests various combinations of stabilization controls are tested in multistep analyses with multiple contact pairs.

The first group of analyses consists of six pairs of blocks that are pushed together in Step 1, subjected to tangential sliding in Step 2, and pulled apart in Step 3. The blocks are elastic, and the motion of the blocks is controlled with boundary conditions. Contact stabilization parameters are specified for the whole model and are overridden by different parameters for several individual contact pairs. The stabilization parameters vary from step to step. A restart file is written, and some restarts are made to test the restart functionality.

The second group of analyses consists of three blocks that are pushed together in Step 1, subjected to tangential sliding in Step 2, and pulled apart in Step 3. The blocks are elastic; and the top and bottom blocks are controlled with boundary conditions, whereas the middle block is completely free and held in place by contact stabilization. Different contact stabilization parameters are used for each contact pair. In addition, frictional properties are prescribed for one contact pair. This group contains two-dimensional and three-dimensional static analyses as well as a dynamic analysis.