Initial Stresses for Contact
Initial stresses for contact are derived from initial stresses that you specify for elements underlying contact surfaces. This involves estimating both normal and shear contact traction such that they are approximately in equilibrium with the element initial stresses. The procedure for estimating initial stresses matches the true distribution very well for cases where underlying element stress distributions result in either uniform or linearly varying contact stresses. For example, linearly varying underlying element stresses result in linearly varying contact stresses on flat contact surfaces. For more complex spatial variations of contact stress, the initial contact stress distribution may only be approximate. In situations where the underlying element stress distribution is an equilibrium stress distribution, nonzero initial contact stresses are meant to ensure that the overall system that includes both contact and user elements is close to an overall equilibrium state with respect to initial loads and boundary conditions. Consequently, an initial static or geostatic equilibration step with no changes to loads and boundary conditions is likely to converge more easily.
In cases where initial element stresses are different across the contact interface, the secondary side of the element stresses is used to estimate the initial contact stresses. These stresses can be visualized in the zero-increment frame of an analysis or after a data check analysis. You can control whether initial contact stresses are to be calculated and reported.