Product: Abaqus/Standard
Benefits: Quadratic smoothness of contact force redistribution often improves convergence and provides better resolution of contact stresses within regions with high contact stress gradients.
Description: Key advantages of the surface-to-surface contact formulation in Abaqus/Standard over traditional node-to-surface formulations include enhanced convergence behavior and better contact stress predictions. Further enhancements to these characteristics are now available for many models due to smoother redistributions of contact forces upon sliding. This enhanced smoothing is activated for general contact and surface-to-surface contact pairs by default if the slave surface is based on second-order elements. A user control is provided such that you can directly specify linear or quadratic smoothness regardless of the underlying element types.
The surface-to-surface formulation is able to represent linear variations in contact stress with a higher degree of accuracy with the new default smoothness setting if the underlying elements are quadratic. Consider the case shown in Figure 11–6 of a bending load applied to two blocks that are joined by “tied” contact.
The two blocks are modeled with non-matching meshes of second-order tetrahedral (C3D10) elements and linear elastic material behavior. The analytical solution has the same variation of constraint pressure as that of the applied load, which varies linearly from compressive stress of unity at the top edge of the interface to tensile stress of unity at the bottom edge of the interface. Numerical predictions of constraint pressures are shown in Figure 11–7: the maximum and minimum predictions for the contact pressure deviate from the analytical solution by less than 1% with Abaqus/Standard 6.10 using the new default quadratic smoothing, whereas this deviation is 5 to 6% with Abaqus/Standard 6.9-EF (which uses linear smoothing). The numerical predictions will become more accurate as the mesh is refined, so it is interesting to consider the deviation of numerical results from the analytical solution as a fraction of the variation of contact pressure over individual surface faces: in this example this fraction is about 1/50 with Abaqus/Standard 6.10 and about 1/7 with Abaqus/Standard 6.9-EF.References:
