Projection based reduction methods utilize a reduction basis of selected displacement shapes which determine the ability of the linear elastic structure to deform. In case of the approach proposed by Craig and Bampton, this basis typically holds so called constraint modes representing static displacements and boundary fixed normal modes representing the internal dynamics.
Both types of displacement shapes do not explicitly consider the local displacements within the contact interfaces. Thus the computed contact stresses would not be trustworthy as well. But for contact influenced structures a meaningful exploration of the dynamics requires to take into account the occurring contact stresses, either in interface normal direction only or, if necessary, in interface normal and tangential direction.
The MAMBA simulation process core feature is a projection based model order reduction step which preserves the nonlinear behavior due to the nonlinear contact conditions. This is achieved by an extension of the classical reduction basis and an extension of the reduced equations of motion. The latter one introduces the reduced nonlinear relations originating from the contact interfaces.
This way the reduced order model is capable of computing meaningful contact stresses.