Description: Intra-increment adaptivity of specific contact controls for Abaqus/Standard is provided based on the philosophy that the early iterations for a nonlinear implicit simulation increment should robustly find an approximate solution and subsequent iterations should fine-tune the solution to provide a high degree of accuracy. These objectives sometimes call for different controls settings for the early and late iterations of an increment, because applying the same control settings for all iterations of an increment may sacrifice accuracy for robustness.

For example, the existing contact stabilization feature has often helped to robustly find converged solutions, but the associated stabilization forces occasionally significantly affect the reported solution. In previous releases a common modeling practice was to reduce contact stabilization across increments of a simulation step; however, in Abaqus 6.13 contact stabilization can also be reduced across iterations of an increment. With the new intra-increment adaptive approach for contact stabilization, a significant amount of contact stabilization can be in effect during the early iterations of an increment to more robustly find an approximate solution (and, for example, allow some contact to be established), and the final iterations of the same increment can use less or no contact stabilization so that the reported solution has little or no effects of artificial stabilization forces.

Intra-increment adaptivity can also be applied to the penalty stiffness in the first increment of an analysis. Using a reduced penalty stiffness in the early iterations often helps convergence behavior when large portions of the surface come into or out of contact during the first increment. Once an approximate solution is found with a reduced penalty stiffness, additional iterations with the default penalty stiffness in effect are able to converge to a more accurate solution.

The intra-increment adaptive contact controls are intended for advanced users and will likely undergo changes in subsequent releases of Abaqus/Standard.